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Volume 67 (2018): Issue 3 (September 2018)

Volume 67 (2018): Issue 2 (June 2018)

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Journal Details
Format
Journal
eISSN
2544-4646
First Published
04 Mar 1952
Publication timeframe
4 times per year
Languages
English

Search

Volume 67 (2018): Issue 3 (September 2018)

Journal Details
Format
Journal
eISSN
2544-4646
First Published
04 Mar 1952
Publication timeframe
4 times per year
Languages
English

Search

16 Articles

original-paper

Open Access

Exopolysaccharides Produced by Lactobacillus rhamnosus KL 53A and Lactobacillus casei Fyos Affect Their Adhesion to Enterocytes

Published Online: 04 Sep 2018
Page range: 273 - 281

Abstract

Abstract

Probiotics promote and help to maintain beneficial microbiota composition of the gastrointestinal tract ecosystem and have a positive impact on the host’s health. Production of exopolysaccharides is an important feature of probiotic lactobacilli. It increases the chance of their survival in the gastrointestinal tract and promotes adhesion to the epithelium; therefore, exopolysaccharides are important for the process of colonization. Two lactic acid bacteria strains were used in this study: Lactobacillus rhamnosus KL 53A and Lactobacillus casei Fyos. Exopolysaccharides were isolated from bacterial cells and their monosaccharide composition was examined using liquid chromatography. The influence of exopolysaccharides on lactobacilli adhesion to enterocytes was studied after deglycosylation of the bacterial cells and incubation with the selected intestinal microbiota strains that metabolize polysaccharides – Faecalibacterium prausnitzii DSM 17677 and Blautia luti DSM 14534. Both deglycosylation and incubation with polysaccharide metabolizing strains influenced the ability of probiotic strains to adhere to enterocytes. Enzymatic deglycosylation decreased adhesion efficiency of L. rhamnosus KL 53A; however, co-incubation of both lactobacillus strains with F. prausnitzii DSM 17677 resulted in an increase of their adhesion efficiency. Exopolysaccharides are important adhesins of Lactobacillus spp. that influence their ability to colonize gut epithelium. Other members of gut microbiota can modify the adhesion property in situ; therefore the composition and metabolic state of commensal bacteria may influence their probiotic action.

Keywords

  • bacteria
  • adhesion
  • deglycosylation
  • polysaccharides
  • Caco-2 cells
Open Access

Biohydrogen Production by Antarctic Psychrotolerant Klebsiella sp. ABZ11

Published Online: 04 Sep 2018
Page range: 283 - 290

Abstract

Abstract

Lower temperature biohydrogen production has always been attractive, due to the lower energy requirements. However, the slow metabolic rate of psychrotolerant biohydrogen-producing bacteria is a common problem that affects their biohydrogen yield. This study reports on the improved substrate synthesis and biohydrogen productivity by the psychrotolerant Klebsiella sp. strain ABZ11, isolated from Antarctic seawater sample. The isolate was screened for biohydrogen production at 30°C, under facultative anaerobic condition. The isolate is able to ferment glucose, fructose and sucrose with biohydrogen production rate and yield of 0.8 mol/l/h and 3.8 mol/g, respectively at 10 g/l glucose concentration. It also showed 74% carbohydrate uptake and 95% oxygen uptake ability, and a wide growth temperature range with optimum at 37°C. Klebsiella sp. ABZ11 has a short biohydrogen production lag phase, fast substrate uptake and is able to tolerate the presence of oxygen in the culture medium. Thus, the isolate has a potential to be used for lower temperature biohydrogen production process.

Keyword

  • sp.
  • biohydrogen
  • facultative psychrotolerant
  • oxygen uptake
  • carbohydrate consumption
Open Access

Evaluation of Modified Hodge Test as a Non-molecular Assay for Accurate Detection of KPC-producing Klebsiella pneumoniae

Published Online: 04 Sep 2018
Page range: 291 - 295

Abstract

Abstract

Klebsiella pneumoniae carbapenemase (KPC) have become a major therapeutic challenge because of its increasingly fast dissemination throughout the world. Accurate detection of KPC is essential for optimal treatment. The Clinical and Laboratory Standards Institutes (CLSI) for fast detection of KPC producers currently recommend Modified Hodge Test (MHT) and Carba NP test. MHT can directly detect carbapenemase production in Enterobacteriaceae isolates. The current study was conducted to evaluate the capacity of MHT with two carbapenem disks for accurate detection of KPC. MHT was performed according to guidelines of CLSI to identify isolates with carbapenem resistance. In doing so, two substrates of MHT were assigned into two groups for examination: meropenem and ertapenem groups. A total of 96 non-repetitive clinical isolates of Klebsiella pneumoniae were tested. The presence of the blaKPC gene in each MHT-positive isolate was examined by PCR. A total of 54 isolates exhibited reduced susceptibility or resistance to carbapenems. Sensitivity of MHT with two carbapenem disks was similar. Specificity of the MHT with meropenem disk was 64% and with ertapenem disk was 53%. Detection of KPC by MHT with meropenem disk was found to be more effective than with ertapenem disk. Based on our results, the presence of KPC does not in itself influence the categorization of resistance. Therefore, the use of MHT with ertapenem disk for the rapid detection of KPC among K. pneumoniae for infection control should not be recommended.

Keywords

  • carbapenem disks
  • detection method
  • Modified Hodge Test
  • KPC
Open Access

Optimization of Mixed Solid-state Fermentation of Soybean Meal by Lactobacillus Species and Clostridium butyricum

Published Online: 04 Sep 2018
Page range: 297 - 305

Abstract

Abstract

Soybean meal is the main vegetable protein source in animal feed. Soybean meal contains several anti-nutritional factors, which directly affect digestion and absorption of soy protein, thereby reducing growth performance and value in animals. Fermented soybean meal is rich in probiotics and functional metabolites, which facilitates soybean protein digestion, absorption and utilization in piglets. However, the mixed solid-state fermentation (SSF) conditions of soybean meal remain to be optimized. In this study, we investigated the optimal parameters for SSF of soybean meal by Lactobacillus species and Clostridium butyricum. The results showed that two days of fermentation was sufficient to increase the viable count of bacteria, lactic acid levels and degradation of soybean protein in fermented soybean meal at the initial moisture content of 50%. The pH value, lowering sugar content and oligosaccharides in fermented soybean meal, was significantly reduced at the initial moisture content of 50% after two days of fermentation. Furthermore, the exogenous proteases used in combination with probiotics supplementation were further able to enhance the viable count of bacteria, degradation of soybean protein and lactic acid level in the fermented soybean meal. In addition, the pH value and sugar content in fermented soybean meal were considerably reduced in the presence of both proteases and probiotics. Furthermore, the fermented soybean meal also showed antibacterial activity against Staphylococcus aureus and Escherichia coli. These results together suggest that supplementation of both proteases and probiotics in SSF improves the nutritional value of fermented soybean meal and this is suitable as a protein source in animal feed.

Keywords

  • probiotics
  • proteases
  • soybean meal
  • solid-state fermentation
Open Access

Broad Prebiotic Potential of Non-starch Polysaccharides from Oats (Avena sativa L.): an in vitro Study

Published Online: 04 Sep 2018
Page range: 307 - 313

Abstract

Abstract

Prebiotics inducing the growth or activity of beneficial intestinal bacteria – probiotics producing short-chain fatty acids (SCFA) have lately received wide recognition for their beneficial influence on host intestinal microbiota and metabolic health. Some non-starch polysaccharides (NSP) are defined as prebiotics and oats being one of richest sources of NSP in grains are considered as potentially having prebiotic effect. However, information on fermentation of specific NSP of oats is limited. Moreover, bacterial cross-feeding interactions in which fermentation of prebiotics is involved is poorly characterized. Here, we report the exploration of new candidates for the syntrophic bacterial interactions and fermentability of oat non-starch polysaccharides (NSP). The results obtained by differentiating composition, viscosity and concentration of oats NSP in fermentation medium showed that Bacillus licheniformis pre-digests oat NSP, degrades high viscosity of oat β-glucan and makes hemicellulose easier to access for other bacteria. Because of fermentation, B. licheniformis produces lactic and succinic acids, which further can be used by other bacteria for cross-feeding and SCFA production.

Keywords

  • Oat NSP
  • prebiotics
Open Access

The Effect of Silver Nanoparticles on Listeria monocytogenes PCM2191 Peptidoglycan Metabolism and Cell Permeability

Published Online: 04 Sep 2018
Page range: 315 - 320

Abstract

Abstract

Listeria monocytogenes is Gram-positive bacterial pathogen, a causative agent of food poisoning and systemic disease – listeriosis. This species is still susceptible to several conventionally used antibiotics but an increase in its resistance has been reported. For this reason the search for new, alternative therapies is an urgent task. Silver nanoparticles seem to be the promising antibacterial agent. Minimal inhibitory concentration of silver nanoparticles was determined. Sublethal concentrations were used in study of nanosilver effect on cells lysis by estimation of the number of cells surviving the treatment with 0.25 or 0.5 of minimal inhibitory concentrations of silver nanoparticles. Autolysis of isolated peptidoglycan was studied by measuring the absorbance of preparation subjected to nanosilver treatment. Silver nanoparticles effect on L. monocytogenes envelopes permeability was determined by measuring the efflux of cF, DNA and proteins. It was demonstrated that nanosilver enhanced the lysis of L. monocytogenes cells and, to the lesser extent, autolysis of isolated peptidoglycan. The increase in the efflux of carboxyfluoresceine, DNA and proteins was also noted. The obtained results allow to postulate that L. monocytogenes peptidoglycan, constituting the main component of cell wall, is the target of silver nanoparticles activity against this pathogen.

Keywords

  • autolysis
  • peptidoglycan
  • permeability
  • silver nanoparticles
Open Access

Isolation of Bacterial Endophytes from Phalaris arundinacea and their Potential in Diclofenac and Sulfamethoxazole Degradation

Published Online: 04 Sep 2018
Page range: 321 - 331

Abstract

Abstract

Diclofenac (DCF), a non-steroidal anti-inflammatory drug (NSAID) and sulfamethoxazole (SMX), an antimicrobial agent, are in common use and can be often detected in the environment. The constructed wetland systems (CWs) are one of the technologies to remove them from the aquatic environment. The final effect of the treatment processes depends on many factors, including the interaction between plants and the plant-associated microorganisms present in the system. Bacteria living inside the plant as endophytes are exposed to secondary metabolites in the tissues. Therefore, they can possess the potential to degrade aromatic structures, including residues of pharmaceuticals. The endophytic strain MG7 identified as Microbacterium sp., obtained from root tissues of Phalaris arundinacea exposed to DCF and SMX was tested for the ability to remove 2 mg/l of SMX and DCF in monosubstrate cultures and in the presence of phenol as an additional carbon source. The MG7 strain was able to remove approximately 15% of DCF and 9% of SMX after 20 days of monosubstrate culture. However, a decrease in the optical density of the MG7 strain cultures was observed, caused by an insufficient carbon source for bacterial growth and proliferation. The adsorption of pharmaceuticals onto autoclaved cells was negligible, which confirmed that the tested strain was directly involved in the removal of DCF and SMX. In the presence of phenol as the additional carbon source, the MG7 strain was able to remove approximately 35% of DCF and 61% of SMX, while an increase in the optical density of the cultures was noted. The higher removal efficiency can be explained by adaptive mechanisms in microorganisms exposed to phenol (i.e. changes in the composition of membrane lipids) and by a co-metabolic mechanism, where non-growth substrates can be transformed by non-specific enzymes. The presence of both DCF and SMX and the influence of the supply frequency of CWs with the contaminated wastewater on the diversity of whole endophytic bacterial communities were demonstrated. The results of this study suggest the capability of the MG7 strain to degrade DCF and SMX. This finding deserves further investigations to improve wastewater treatment in CWs with the possible use of pharmaceuticals-degrading endophytes.

Keywords

  • endophytic bacteria
  • constructed wetlands
  • diclofenac
  • sulfamethoxazole
  • biodegradation
Open Access

Carbapenem-resistant Acinetobacter baumannii from Air and Patients of Intensive Care Units

Published Online: 04 Sep 2018
Page range: 333 - 338

Abstract

Abstract

To understand the molecular epidemiology and antibiotic resistance of air and clinical isolates of Acinetobacter baumannii, the intensive care unit settings of a hospital in Northern China were surveyed in 2014. Twenty non-duplicate A. baumannii isolates were obtained from patients and five isolates of airborne A. baumannii were obtained from the wards’ corridors. Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to analyze the homology relationships of isolates. Resistance and resistance genes were detected by drug susceptibility test and PCR. The results demonstrated that all isolates can be classified into eight PFGE types and four sequence types (ST208, ST195, ST369 and ST530). A pair of isolates from patients (TAaba004) and from the air (TAaba012) that share 100% similarity in PFGE was identified, indicating that air might be a potential and important transmission route for A. baumannii. More than 80% of the isolates were resistant to carbapenems and aminoglycoside antibiotics. Twenty-four isolates, which were resistant to carbapenems, carried the blaOXA-23-like gene. The data indicated that air might be an alternative way for the transmission of A. baumannii. Hospitals should pay more attention to this route, and design new measures accordingly.

Keywords

  • molecular epidemiology
  • antibiotic resistance
  • airborne
  • nosocomial infection
Open Access

Bacterial Microbiota and Fatty Acids in the Faeces of Overweight and Obese Children

Published Online: 04 Sep 2018
Page range: 339 - 345

Abstract

Abstract

The growing number of children with overweight and obesity constitutes a major health problem of the modern world and it has been suggested that intestinal microbiota may influence energy intake from food. The objectives of this study were to determine quantity and proportions of dominant genera of Bacteroides, Prevotella (phylum Bacteroidetes); Clostridium, Lactobacillus (phylum Firmicutes) and Bifidobacterium (phylum Actinobacteria) in the intestines and to determine the content of short-chain fatty acids (SCFAs) and branched-chain fatty acids (BCFAs) in the stool of 20 obese children and 20 children with normal body weight. Strains classified as Firmicutes (Clostridium and Lactobacillus) predominated in stool microbiota of obese children, while those of Bacteroidetes (Prevotella and Bacteroides) were in minority (p < 0.001). Concentration of SCFAs in the stool of obese children was lower in comparison to the stool of normal weight children (p = 0.04). However, these differences were significant only in obese children, not in overweight children in comparison with the lean ones. Therefore, in our study obesity was associated with intestinal dysbiosis and a predominance of phylum Firmicutes. Secondly, stool of obese children contained lower amounts of SCFAs.

Keywords

  • BCFAs
  • obesity
  • SCFAs
Open Access

RNA Quality Control Using External Standard RNA

Published Online: 04 Sep 2018
Page range: 347 - 353

Abstract

Abstract

In this paper, we propose a new evaluation method using external standard RNA for quality control of the extracted RNA. RNA Integrity Number and UV absorption are generally used as a basis for RNA quality control; however, these methods do not always reflect the quality of mRNA. While standard RNA is supposedly designed on the basis of mRNA, it has the potential to be used to evaluate the quality of the mRNA. In this study, we took into consideration the three essential factors, viz., yield of mRNA, inhibition to DNA polymerase, and degradation of mRNA for determining the RNA quality using standard RNA. It would be possible to know yield of mRNA and inhibition of the enzyme reaction by adding standard RNA before RNA extraction and looking at standard RNA loss. Degradation was evaluated by comparing the differences in the 3’ and 5’ regions of the RNA. In our study, it was demonstrated that in the crude extract of Saccharomyces cerevisiae, degradation was comparatively higher at the 3’ end of RNA than at the 5’ end. Hence, the degree of RNA degradation can be evaluated by comparing the ratio of degradation from the 3’ and 5’ end.

Keywords

  • RNA degradation
  • RNA quality control
  • Standard RNA
Open Access

Improved Production of Recombinant Human β-NGF in Escherichia coli – a Bioreactor Scale Study

Published Online: 04 Sep 2018
Page range: 355 - 363

Abstract

Abstract

Human nerve growth factor β (β-NGF) is considered a major therapeutic agent for treatment of neurodegenerative diseases. We have previously reported the optimized conditions for β-NGF overproduction in Escherichia coli in a shake-flask culture. In this study the optimal %DO (dissolved oxygen) and post induction temperature values for improved production of β-NGF were found in the bioreactor scale using response surface methodology (RSM) as the most common statistical method. Also, for further enhancement of the yield, different post-induction periods of time were selected for testing. In all experiments, the productivity level and bacterial cell growth were evaluated by western blotting technique and monitoring of absorbance at 600 nm, respectively. Our results indicated that %DO, the post-induction time and temperature have significant effects on the production of β-NGF. After 2 hours of induction, the low post induction temperature of 32°C and 20% DO were used to increase the production of β-NGF in a 5-l bioreactor. Another important result obtained in this study was that the improved β-NGF production was not achieved at highest dry cell weigh or highest cell growth. These results are definitely of importance for industrial β-NGF production.

Keywords

  • bioreactor
  • RSM
  • β-NGF over production
Open Access

The Emergence of Different Functionally Equivalent PAH Degrading Microbial Communities from a Single Soil in Liquid PAH Enrichment Cultures and Soil Microcosms Receiving PAHs with and without Bioaugmentation

Published Online: 04 Sep 2018
Page range: 365 - 375

Abstract

Abstract

Polycyclic aromatic hydrocarbon (PAHs) are common soil contaminants of concern due to their toxicity toward plants, animals and microorganisms. The use of indigenous or added microbes (bioaugmentation) is commonly used for bioremediation of PAHs. In this work, the biodegradation rates and changes in the bacterial community structure were evaluated. The enrichment culture was useful for unambiguously identifying members of the soil bacterial community associated with PAH degradation and yielded a low diversity community. No significant difference in the rate of PAH degradation was observed between the microcosm receiving only PAHs or PAHs and bioaugmentation. Moreover, identical matches to the bioaugmentation inoculum were only observed at the initial stages of PAH degradation on day 8. After 22 days of incubation, the substantial degradation of all PAHs had occurred in both microcosms and the PAH contaminated soil had statistically significant increases in Alphaproteobacteria. There were also increases in Betaproteobacteria. In contrast, the PAH contaminated and bioaugmented soil was not enriched in PAH degrading Proteobacteria genera and, instead, an increase from 1.6% to 8% of the population occurred in the phylum Bacteroidetes class Flavobacteria, with Flavobacterium being the only identified genus. In addition, the newly discovered genus Ohtaekwangia increased from 0% to 3.2% of the total clones. These results indicate that the same soil microbial community can give rise to different PAH degrading consortia that are equally effective in PAH degradation efficiency. Moreover, these results suggest that the lack of efficacy of bioaugmentation in soils can be attributed to a lack of persistence of the introduced microbes, yet nonetheless may alter the microbial community that arises in response to PAH contamination in unexpected ways.

Keywords

  • polycyclic aromatic hydrocarbon
  • PAH
  • soil microbial community
  • biodegradation
  • bioaugmentation
Open Access

Biochemical and Molecular Characterization of a Native Haloalkalophilic Tolerant Strain from the Texcoco Lake

Published Online: 04 Sep 2018
Page range: 377 - 382

Abstract

Abstract

In the last decade several new genera have been isolated in alkaline and halophile growth conditions. The studies conducted in the Texcoco Lake soils have shown a generalized microbial adaptation to the specific conditions. In this research work, morphological and phylogenetic characterization of the HN31(22) strain that was isolated from the cited soil is presented. The strain was identified as a Gram-positive halophile and alkaline tolerant bacteria from the Nesterenkonia genus, which uses different substrates in metabolic processes.

Keywords

  • halophile
  • alkalophile
  • adaptation
  • phylogeny

short-communication

Open Access

Gut Microbial Compositions in Four Age Groups of Tibetan Minipigs

Published Online: 04 Sep 2018
Page range: 383 - 388

Abstract

Abstract

In this study, the gut microbiota was characterized in four age strata of Tibetan minipigs. Results indicated that the fecal bacteria of 7-, 28-, 56-, and 180-day-old minipigs did not significantly differ in terms of phylogenetic diversity (i.e., PD whole tree) or the Shannon index (both, p > 0.05). Findings of a principal coordinate analysis demonstrated that fecal bacteria of 180-day-old minipigs were discernable from those of the other three age groups. From ages seven to 56 days, the abundance of Bacteroidetes or Firmicutes appeared to vary. Regarding genera, the populations of Bacteroides and Akkermansia decreased with increasing age.

Keywords

  • Tibetan minipig
  • gut microbiota
  • age
  • 16S rRNA gene

mini-review

Open Access

Are Probiotic Really Safe for Humans?

Published Online: 04 Sep 2018
Page range: 251 - 258

Abstract

Abstract

Probiotic bacteria have been used as a health-promoting factor for a very long time. Nowadays, products containing probiotic bacteria are becoming more and more popular on the market. The term probiotics refers to the products belonging to the following groups: probiotic drugs (medicinal products – live biotherapeutic products for human use), medical devices, probiotic foods (e.g. foods, food ingredients, dietary supplements or food for special medical purposes), directly fed microorganisms (for animal use) and designer probiotics (genetically modified probiotics). Safety assessment of bacterial strains used as probiotics should be carefully studied. Even though probiotic bacteria have the generally recognized as safe (GRAS status), there are several reports about side effects triggered by the presence of these organisms. Microorganisms used as probiotics may cause systemic infections, stimulate the immune system, disturb metabolism and participate in horizontal gene transfer.

Keywords

  • bacteremia
  • gene transfer
  • probiotic bacteria
  • probiotic side effect
  • safety of probiotics
Open Access

Secondary Metabolites of Actinomycetes and their Antibacterial, Antifungal and Antiviral Properties

Published Online: 04 Sep 2018
Page range: 259 - 272

Abstract

Abstract

The growing resistance of microorganisms towards antibiotics has become a serious global problem. Therapeutics with novel chemical scaffolds and/or mechanisms of action are urgently needed to combat infections caused by multidrug resistant pathogens, including bacteria, fungi and viruses. Development of novel antimicrobial agents is still highly dependent on the discovery of new natural products. At present, most antimicrobial drugs used in medicine are of natural origin. Among the natural producers of bioactive substances, Actinobacteria continue to be an important source of novel secondary metabolites for drug application. In this review, the authors report on the bioactive antimicrobial secondary metabolites of Actinobacteria that were described between 2011 and April 2018. Special attention is paid to the chemical scaffolds, biological activities and origin of these novel antibacterial, antifungal and antiviral compounds. Arenimycin C, chromopeptide lactone RSP 01, kocurin, macrolactins A1 and B1, chaxamycin D as well as anthracimycin are regarded as the most effective compounds with antibacterial activity. In turn, the highest potency among selected antifungal compounds is exhibited by enduspeptide B, neomaclafungins A-I and kribelloside D, while ahmpatinin iBu, antimycin A1a, and pentapeptide 4862F are recognized as the strongest antiviral agents.

Keywords

  • bioactive
  • secondary metabolites
  • actinomycetes
  • antibacterial activity
  • sp.
16 Articles

original-paper

Open Access

Exopolysaccharides Produced by Lactobacillus rhamnosus KL 53A and Lactobacillus casei Fyos Affect Their Adhesion to Enterocytes

Published Online: 04 Sep 2018
Page range: 273 - 281

Abstract

Abstract

Probiotics promote and help to maintain beneficial microbiota composition of the gastrointestinal tract ecosystem and have a positive impact on the host’s health. Production of exopolysaccharides is an important feature of probiotic lactobacilli. It increases the chance of their survival in the gastrointestinal tract and promotes adhesion to the epithelium; therefore, exopolysaccharides are important for the process of colonization. Two lactic acid bacteria strains were used in this study: Lactobacillus rhamnosus KL 53A and Lactobacillus casei Fyos. Exopolysaccharides were isolated from bacterial cells and their monosaccharide composition was examined using liquid chromatography. The influence of exopolysaccharides on lactobacilli adhesion to enterocytes was studied after deglycosylation of the bacterial cells and incubation with the selected intestinal microbiota strains that metabolize polysaccharides – Faecalibacterium prausnitzii DSM 17677 and Blautia luti DSM 14534. Both deglycosylation and incubation with polysaccharide metabolizing strains influenced the ability of probiotic strains to adhere to enterocytes. Enzymatic deglycosylation decreased adhesion efficiency of L. rhamnosus KL 53A; however, co-incubation of both lactobacillus strains with F. prausnitzii DSM 17677 resulted in an increase of their adhesion efficiency. Exopolysaccharides are important adhesins of Lactobacillus spp. that influence their ability to colonize gut epithelium. Other members of gut microbiota can modify the adhesion property in situ; therefore the composition and metabolic state of commensal bacteria may influence their probiotic action.

Keywords

  • bacteria
  • adhesion
  • deglycosylation
  • polysaccharides
  • Caco-2 cells
Open Access

Biohydrogen Production by Antarctic Psychrotolerant Klebsiella sp. ABZ11

Published Online: 04 Sep 2018
Page range: 283 - 290

Abstract

Abstract

Lower temperature biohydrogen production has always been attractive, due to the lower energy requirements. However, the slow metabolic rate of psychrotolerant biohydrogen-producing bacteria is a common problem that affects their biohydrogen yield. This study reports on the improved substrate synthesis and biohydrogen productivity by the psychrotolerant Klebsiella sp. strain ABZ11, isolated from Antarctic seawater sample. The isolate was screened for biohydrogen production at 30°C, under facultative anaerobic condition. The isolate is able to ferment glucose, fructose and sucrose with biohydrogen production rate and yield of 0.8 mol/l/h and 3.8 mol/g, respectively at 10 g/l glucose concentration. It also showed 74% carbohydrate uptake and 95% oxygen uptake ability, and a wide growth temperature range with optimum at 37°C. Klebsiella sp. ABZ11 has a short biohydrogen production lag phase, fast substrate uptake and is able to tolerate the presence of oxygen in the culture medium. Thus, the isolate has a potential to be used for lower temperature biohydrogen production process.

Keyword

  • sp.
  • biohydrogen
  • facultative psychrotolerant
  • oxygen uptake
  • carbohydrate consumption
Open Access

Evaluation of Modified Hodge Test as a Non-molecular Assay for Accurate Detection of KPC-producing Klebsiella pneumoniae

Published Online: 04 Sep 2018
Page range: 291 - 295

Abstract

Abstract

Klebsiella pneumoniae carbapenemase (KPC) have become a major therapeutic challenge because of its increasingly fast dissemination throughout the world. Accurate detection of KPC is essential for optimal treatment. The Clinical and Laboratory Standards Institutes (CLSI) for fast detection of KPC producers currently recommend Modified Hodge Test (MHT) and Carba NP test. MHT can directly detect carbapenemase production in Enterobacteriaceae isolates. The current study was conducted to evaluate the capacity of MHT with two carbapenem disks for accurate detection of KPC. MHT was performed according to guidelines of CLSI to identify isolates with carbapenem resistance. In doing so, two substrates of MHT were assigned into two groups for examination: meropenem and ertapenem groups. A total of 96 non-repetitive clinical isolates of Klebsiella pneumoniae were tested. The presence of the blaKPC gene in each MHT-positive isolate was examined by PCR. A total of 54 isolates exhibited reduced susceptibility or resistance to carbapenems. Sensitivity of MHT with two carbapenem disks was similar. Specificity of the MHT with meropenem disk was 64% and with ertapenem disk was 53%. Detection of KPC by MHT with meropenem disk was found to be more effective than with ertapenem disk. Based on our results, the presence of KPC does not in itself influence the categorization of resistance. Therefore, the use of MHT with ertapenem disk for the rapid detection of KPC among K. pneumoniae for infection control should not be recommended.

Keywords

  • carbapenem disks
  • detection method
  • Modified Hodge Test
  • KPC
Open Access

Optimization of Mixed Solid-state Fermentation of Soybean Meal by Lactobacillus Species and Clostridium butyricum

Published Online: 04 Sep 2018
Page range: 297 - 305

Abstract

Abstract

Soybean meal is the main vegetable protein source in animal feed. Soybean meal contains several anti-nutritional factors, which directly affect digestion and absorption of soy protein, thereby reducing growth performance and value in animals. Fermented soybean meal is rich in probiotics and functional metabolites, which facilitates soybean protein digestion, absorption and utilization in piglets. However, the mixed solid-state fermentation (SSF) conditions of soybean meal remain to be optimized. In this study, we investigated the optimal parameters for SSF of soybean meal by Lactobacillus species and Clostridium butyricum. The results showed that two days of fermentation was sufficient to increase the viable count of bacteria, lactic acid levels and degradation of soybean protein in fermented soybean meal at the initial moisture content of 50%. The pH value, lowering sugar content and oligosaccharides in fermented soybean meal, was significantly reduced at the initial moisture content of 50% after two days of fermentation. Furthermore, the exogenous proteases used in combination with probiotics supplementation were further able to enhance the viable count of bacteria, degradation of soybean protein and lactic acid level in the fermented soybean meal. In addition, the pH value and sugar content in fermented soybean meal were considerably reduced in the presence of both proteases and probiotics. Furthermore, the fermented soybean meal also showed antibacterial activity against Staphylococcus aureus and Escherichia coli. These results together suggest that supplementation of both proteases and probiotics in SSF improves the nutritional value of fermented soybean meal and this is suitable as a protein source in animal feed.

Keywords

  • probiotics
  • proteases
  • soybean meal
  • solid-state fermentation
Open Access

Broad Prebiotic Potential of Non-starch Polysaccharides from Oats (Avena sativa L.): an in vitro Study

Published Online: 04 Sep 2018
Page range: 307 - 313

Abstract

Abstract

Prebiotics inducing the growth or activity of beneficial intestinal bacteria – probiotics producing short-chain fatty acids (SCFA) have lately received wide recognition for their beneficial influence on host intestinal microbiota and metabolic health. Some non-starch polysaccharides (NSP) are defined as prebiotics and oats being one of richest sources of NSP in grains are considered as potentially having prebiotic effect. However, information on fermentation of specific NSP of oats is limited. Moreover, bacterial cross-feeding interactions in which fermentation of prebiotics is involved is poorly characterized. Here, we report the exploration of new candidates for the syntrophic bacterial interactions and fermentability of oat non-starch polysaccharides (NSP). The results obtained by differentiating composition, viscosity and concentration of oats NSP in fermentation medium showed that Bacillus licheniformis pre-digests oat NSP, degrades high viscosity of oat β-glucan and makes hemicellulose easier to access for other bacteria. Because of fermentation, B. licheniformis produces lactic and succinic acids, which further can be used by other bacteria for cross-feeding and SCFA production.

Keywords

  • Oat NSP
  • prebiotics
Open Access

The Effect of Silver Nanoparticles on Listeria monocytogenes PCM2191 Peptidoglycan Metabolism and Cell Permeability

Published Online: 04 Sep 2018
Page range: 315 - 320

Abstract

Abstract

Listeria monocytogenes is Gram-positive bacterial pathogen, a causative agent of food poisoning and systemic disease – listeriosis. This species is still susceptible to several conventionally used antibiotics but an increase in its resistance has been reported. For this reason the search for new, alternative therapies is an urgent task. Silver nanoparticles seem to be the promising antibacterial agent. Minimal inhibitory concentration of silver nanoparticles was determined. Sublethal concentrations were used in study of nanosilver effect on cells lysis by estimation of the number of cells surviving the treatment with 0.25 or 0.5 of minimal inhibitory concentrations of silver nanoparticles. Autolysis of isolated peptidoglycan was studied by measuring the absorbance of preparation subjected to nanosilver treatment. Silver nanoparticles effect on L. monocytogenes envelopes permeability was determined by measuring the efflux of cF, DNA and proteins. It was demonstrated that nanosilver enhanced the lysis of L. monocytogenes cells and, to the lesser extent, autolysis of isolated peptidoglycan. The increase in the efflux of carboxyfluoresceine, DNA and proteins was also noted. The obtained results allow to postulate that L. monocytogenes peptidoglycan, constituting the main component of cell wall, is the target of silver nanoparticles activity against this pathogen.

Keywords

  • autolysis
  • peptidoglycan
  • permeability
  • silver nanoparticles
Open Access

Isolation of Bacterial Endophytes from Phalaris arundinacea and their Potential in Diclofenac and Sulfamethoxazole Degradation

Published Online: 04 Sep 2018
Page range: 321 - 331

Abstract

Abstract

Diclofenac (DCF), a non-steroidal anti-inflammatory drug (NSAID) and sulfamethoxazole (SMX), an antimicrobial agent, are in common use and can be often detected in the environment. The constructed wetland systems (CWs) are one of the technologies to remove them from the aquatic environment. The final effect of the treatment processes depends on many factors, including the interaction between plants and the plant-associated microorganisms present in the system. Bacteria living inside the plant as endophytes are exposed to secondary metabolites in the tissues. Therefore, they can possess the potential to degrade aromatic structures, including residues of pharmaceuticals. The endophytic strain MG7 identified as Microbacterium sp., obtained from root tissues of Phalaris arundinacea exposed to DCF and SMX was tested for the ability to remove 2 mg/l of SMX and DCF in monosubstrate cultures and in the presence of phenol as an additional carbon source. The MG7 strain was able to remove approximately 15% of DCF and 9% of SMX after 20 days of monosubstrate culture. However, a decrease in the optical density of the MG7 strain cultures was observed, caused by an insufficient carbon source for bacterial growth and proliferation. The adsorption of pharmaceuticals onto autoclaved cells was negligible, which confirmed that the tested strain was directly involved in the removal of DCF and SMX. In the presence of phenol as the additional carbon source, the MG7 strain was able to remove approximately 35% of DCF and 61% of SMX, while an increase in the optical density of the cultures was noted. The higher removal efficiency can be explained by adaptive mechanisms in microorganisms exposed to phenol (i.e. changes in the composition of membrane lipids) and by a co-metabolic mechanism, where non-growth substrates can be transformed by non-specific enzymes. The presence of both DCF and SMX and the influence of the supply frequency of CWs with the contaminated wastewater on the diversity of whole endophytic bacterial communities were demonstrated. The results of this study suggest the capability of the MG7 strain to degrade DCF and SMX. This finding deserves further investigations to improve wastewater treatment in CWs with the possible use of pharmaceuticals-degrading endophytes.

Keywords

  • endophytic bacteria
  • constructed wetlands
  • diclofenac
  • sulfamethoxazole
  • biodegradation
Open Access

Carbapenem-resistant Acinetobacter baumannii from Air and Patients of Intensive Care Units

Published Online: 04 Sep 2018
Page range: 333 - 338

Abstract

Abstract

To understand the molecular epidemiology and antibiotic resistance of air and clinical isolates of Acinetobacter baumannii, the intensive care unit settings of a hospital in Northern China were surveyed in 2014. Twenty non-duplicate A. baumannii isolates were obtained from patients and five isolates of airborne A. baumannii were obtained from the wards’ corridors. Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to analyze the homology relationships of isolates. Resistance and resistance genes were detected by drug susceptibility test and PCR. The results demonstrated that all isolates can be classified into eight PFGE types and four sequence types (ST208, ST195, ST369 and ST530). A pair of isolates from patients (TAaba004) and from the air (TAaba012) that share 100% similarity in PFGE was identified, indicating that air might be a potential and important transmission route for A. baumannii. More than 80% of the isolates were resistant to carbapenems and aminoglycoside antibiotics. Twenty-four isolates, which were resistant to carbapenems, carried the blaOXA-23-like gene. The data indicated that air might be an alternative way for the transmission of A. baumannii. Hospitals should pay more attention to this route, and design new measures accordingly.

Keywords

  • molecular epidemiology
  • antibiotic resistance
  • airborne
  • nosocomial infection
Open Access

Bacterial Microbiota and Fatty Acids in the Faeces of Overweight and Obese Children

Published Online: 04 Sep 2018
Page range: 339 - 345

Abstract

Abstract

The growing number of children with overweight and obesity constitutes a major health problem of the modern world and it has been suggested that intestinal microbiota may influence energy intake from food. The objectives of this study were to determine quantity and proportions of dominant genera of Bacteroides, Prevotella (phylum Bacteroidetes); Clostridium, Lactobacillus (phylum Firmicutes) and Bifidobacterium (phylum Actinobacteria) in the intestines and to determine the content of short-chain fatty acids (SCFAs) and branched-chain fatty acids (BCFAs) in the stool of 20 obese children and 20 children with normal body weight. Strains classified as Firmicutes (Clostridium and Lactobacillus) predominated in stool microbiota of obese children, while those of Bacteroidetes (Prevotella and Bacteroides) were in minority (p < 0.001). Concentration of SCFAs in the stool of obese children was lower in comparison to the stool of normal weight children (p = 0.04). However, these differences were significant only in obese children, not in overweight children in comparison with the lean ones. Therefore, in our study obesity was associated with intestinal dysbiosis and a predominance of phylum Firmicutes. Secondly, stool of obese children contained lower amounts of SCFAs.

Keywords

  • BCFAs
  • obesity
  • SCFAs
Open Access

RNA Quality Control Using External Standard RNA

Published Online: 04 Sep 2018
Page range: 347 - 353

Abstract

Abstract

In this paper, we propose a new evaluation method using external standard RNA for quality control of the extracted RNA. RNA Integrity Number and UV absorption are generally used as a basis for RNA quality control; however, these methods do not always reflect the quality of mRNA. While standard RNA is supposedly designed on the basis of mRNA, it has the potential to be used to evaluate the quality of the mRNA. In this study, we took into consideration the three essential factors, viz., yield of mRNA, inhibition to DNA polymerase, and degradation of mRNA for determining the RNA quality using standard RNA. It would be possible to know yield of mRNA and inhibition of the enzyme reaction by adding standard RNA before RNA extraction and looking at standard RNA loss. Degradation was evaluated by comparing the differences in the 3’ and 5’ regions of the RNA. In our study, it was demonstrated that in the crude extract of Saccharomyces cerevisiae, degradation was comparatively higher at the 3’ end of RNA than at the 5’ end. Hence, the degree of RNA degradation can be evaluated by comparing the ratio of degradation from the 3’ and 5’ end.

Keywords

  • RNA degradation
  • RNA quality control
  • Standard RNA
Open Access

Improved Production of Recombinant Human β-NGF in Escherichia coli – a Bioreactor Scale Study

Published Online: 04 Sep 2018
Page range: 355 - 363

Abstract

Abstract

Human nerve growth factor β (β-NGF) is considered a major therapeutic agent for treatment of neurodegenerative diseases. We have previously reported the optimized conditions for β-NGF overproduction in Escherichia coli in a shake-flask culture. In this study the optimal %DO (dissolved oxygen) and post induction temperature values for improved production of β-NGF were found in the bioreactor scale using response surface methodology (RSM) as the most common statistical method. Also, for further enhancement of the yield, different post-induction periods of time were selected for testing. In all experiments, the productivity level and bacterial cell growth were evaluated by western blotting technique and monitoring of absorbance at 600 nm, respectively. Our results indicated that %DO, the post-induction time and temperature have significant effects on the production of β-NGF. After 2 hours of induction, the low post induction temperature of 32°C and 20% DO were used to increase the production of β-NGF in a 5-l bioreactor. Another important result obtained in this study was that the improved β-NGF production was not achieved at highest dry cell weigh or highest cell growth. These results are definitely of importance for industrial β-NGF production.

Keywords

  • bioreactor
  • RSM
  • β-NGF over production
Open Access

The Emergence of Different Functionally Equivalent PAH Degrading Microbial Communities from a Single Soil in Liquid PAH Enrichment Cultures and Soil Microcosms Receiving PAHs with and without Bioaugmentation

Published Online: 04 Sep 2018
Page range: 365 - 375

Abstract

Abstract

Polycyclic aromatic hydrocarbon (PAHs) are common soil contaminants of concern due to their toxicity toward plants, animals and microorganisms. The use of indigenous or added microbes (bioaugmentation) is commonly used for bioremediation of PAHs. In this work, the biodegradation rates and changes in the bacterial community structure were evaluated. The enrichment culture was useful for unambiguously identifying members of the soil bacterial community associated with PAH degradation and yielded a low diversity community. No significant difference in the rate of PAH degradation was observed between the microcosm receiving only PAHs or PAHs and bioaugmentation. Moreover, identical matches to the bioaugmentation inoculum were only observed at the initial stages of PAH degradation on day 8. After 22 days of incubation, the substantial degradation of all PAHs had occurred in both microcosms and the PAH contaminated soil had statistically significant increases in Alphaproteobacteria. There were also increases in Betaproteobacteria. In contrast, the PAH contaminated and bioaugmented soil was not enriched in PAH degrading Proteobacteria genera and, instead, an increase from 1.6% to 8% of the population occurred in the phylum Bacteroidetes class Flavobacteria, with Flavobacterium being the only identified genus. In addition, the newly discovered genus Ohtaekwangia increased from 0% to 3.2% of the total clones. These results indicate that the same soil microbial community can give rise to different PAH degrading consortia that are equally effective in PAH degradation efficiency. Moreover, these results suggest that the lack of efficacy of bioaugmentation in soils can be attributed to a lack of persistence of the introduced microbes, yet nonetheless may alter the microbial community that arises in response to PAH contamination in unexpected ways.

Keywords

  • polycyclic aromatic hydrocarbon
  • PAH
  • soil microbial community
  • biodegradation
  • bioaugmentation
Open Access

Biochemical and Molecular Characterization of a Native Haloalkalophilic Tolerant Strain from the Texcoco Lake

Published Online: 04 Sep 2018
Page range: 377 - 382

Abstract

Abstract

In the last decade several new genera have been isolated in alkaline and halophile growth conditions. The studies conducted in the Texcoco Lake soils have shown a generalized microbial adaptation to the specific conditions. In this research work, morphological and phylogenetic characterization of the HN31(22) strain that was isolated from the cited soil is presented. The strain was identified as a Gram-positive halophile and alkaline tolerant bacteria from the Nesterenkonia genus, which uses different substrates in metabolic processes.

Keywords

  • halophile
  • alkalophile
  • adaptation
  • phylogeny

short-communication

Open Access

Gut Microbial Compositions in Four Age Groups of Tibetan Minipigs

Published Online: 04 Sep 2018
Page range: 383 - 388

Abstract

Abstract

In this study, the gut microbiota was characterized in four age strata of Tibetan minipigs. Results indicated that the fecal bacteria of 7-, 28-, 56-, and 180-day-old minipigs did not significantly differ in terms of phylogenetic diversity (i.e., PD whole tree) or the Shannon index (both, p > 0.05). Findings of a principal coordinate analysis demonstrated that fecal bacteria of 180-day-old minipigs were discernable from those of the other three age groups. From ages seven to 56 days, the abundance of Bacteroidetes or Firmicutes appeared to vary. Regarding genera, the populations of Bacteroides and Akkermansia decreased with increasing age.

Keywords

  • Tibetan minipig
  • gut microbiota
  • age
  • 16S rRNA gene

mini-review

Open Access

Are Probiotic Really Safe for Humans?

Published Online: 04 Sep 2018
Page range: 251 - 258

Abstract

Abstract

Probiotic bacteria have been used as a health-promoting factor for a very long time. Nowadays, products containing probiotic bacteria are becoming more and more popular on the market. The term probiotics refers to the products belonging to the following groups: probiotic drugs (medicinal products – live biotherapeutic products for human use), medical devices, probiotic foods (e.g. foods, food ingredients, dietary supplements or food for special medical purposes), directly fed microorganisms (for animal use) and designer probiotics (genetically modified probiotics). Safety assessment of bacterial strains used as probiotics should be carefully studied. Even though probiotic bacteria have the generally recognized as safe (GRAS status), there are several reports about side effects triggered by the presence of these organisms. Microorganisms used as probiotics may cause systemic infections, stimulate the immune system, disturb metabolism and participate in horizontal gene transfer.

Keywords

  • bacteremia
  • gene transfer
  • probiotic bacteria
  • probiotic side effect
  • safety of probiotics
Open Access

Secondary Metabolites of Actinomycetes and their Antibacterial, Antifungal and Antiviral Properties

Published Online: 04 Sep 2018
Page range: 259 - 272

Abstract

Abstract

The growing resistance of microorganisms towards antibiotics has become a serious global problem. Therapeutics with novel chemical scaffolds and/or mechanisms of action are urgently needed to combat infections caused by multidrug resistant pathogens, including bacteria, fungi and viruses. Development of novel antimicrobial agents is still highly dependent on the discovery of new natural products. At present, most antimicrobial drugs used in medicine are of natural origin. Among the natural producers of bioactive substances, Actinobacteria continue to be an important source of novel secondary metabolites for drug application. In this review, the authors report on the bioactive antimicrobial secondary metabolites of Actinobacteria that were described between 2011 and April 2018. Special attention is paid to the chemical scaffolds, biological activities and origin of these novel antibacterial, antifungal and antiviral compounds. Arenimycin C, chromopeptide lactone RSP 01, kocurin, macrolactins A1 and B1, chaxamycin D as well as anthracimycin are regarded as the most effective compounds with antibacterial activity. In turn, the highest potency among selected antifungal compounds is exhibited by enduspeptide B, neomaclafungins A-I and kribelloside D, while ahmpatinin iBu, antimycin A1a, and pentapeptide 4862F are recognized as the strongest antiviral agents.

Keywords

  • bioactive
  • secondary metabolites
  • actinomycetes
  • antibacterial activity
  • sp.

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