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Meyer M.,Institute of Microbiology and Biotechnology | Schweiger P.,Missouri State University | Deppenmeier U.,Institute of Microbiology and Biotechnology
Applied Microbiology and Biotechnology | Year: 2015

Gluconobacter oxydans is an industrially important bacterium that possesses many uncharacterized oxidoreductases, which might be exploited for novel biotechnological applications. In this study, gene gox1801 was homologously overexpressed in G. oxydans and it was found that the relative expression of gox1801 was 13-fold higher than that in the control strain. Gox1801 was predicted to belong to the 3-hydroxyisobutyrate dehydrogenase-type proteins. The purified enzyme had a native molecular mass of 134 kDa and forms a homotetramer. Analysis of the enzymatic activity revealed that Gox1801 is a succinic semialdehyde reductase that used NADH and NADPH as electron donors. Lower activities were observed with glyoxal, methylglyoxal, and phenylglyoxal. The enzyme was compared to the succinic semialdehyde reductase GsSSAR from Geobacter sulfurreducens and the γ-hydroxybutyrate dehydrogenase YihU from Escherichia coli K-12. The comparison revealed that Gox1801 is the first enzyme from an aerobic bacterium reducing succinic semialdehyde with high catalytic efficiency. As a novel succinic semialdehyde reductase, Gox1801 has the potential to be used in the biotechnological production of γ-hydroxybutyrate. © 2014, Springer-Verlag Berlin Heidelberg.


Hoyles L.,University College Cork | McCartney A.L.,University of Reading | Neve H.,Institute of Microbiology and Biotechnology | Gibson G.R.,University of Reading | And 4 more authors.
Research in Microbiology | Year: 2014

This work represents an investigation into the presence, abundance and diversity of virus-like particles (VLPs) associated with human faecal and caecal samples. Various methodologies for the recovery of VLPs from faeces were tested and optimized, including successful down-stream processing of such samples for the purpose of an in-depth electron microscopic analysis, pulsed-field gel electrophoresis and efficient DNA recovery. The applicability of the developed VLP characterization method beyond the use of faecal samples was then verified using samples obtained from human caecal fluid. © 2014 Institut Pasteur.


Zahid N.,Institute of Microbiology and Biotechnology | Schweiger P.,Missouri State University | Galinski E.,Institute of Microbiology and Biotechnology | Deppenmeier U.,Institute of Microbiology and Biotechnology
Applied Microbiology and Biotechnology | Year: 2015

Gluconobacter oxydans is an industrially important bacterium owing to its regio- and enantio-selective incomplete oxidation of various sugars, alcohols, and polyols. The complete genome sequence is available, but it is still unknown how the organism adapts to highly osmotic sugar-rich environments. Therefore, the mechanisms of osmoprotection in G. oxydans were investigated. The accumulation and transport of solutes are hallmarks of osmoadaptation. To identify potential osmoprotectants, G. oxydans was grown on a yeast glucose medium in the presence of 100 mM potassium phosphate (pH 7.0) along with various concentrations of sucrose (0–600 mM final concentration), which was not metabolized. Intracellular metabolites were analyzed by HPLC and 13C NMR spectroscopy under stress conditions. Both of these analytical techniques highlighted the accumulation of mannitol as a potent osmoprotectant inside the stressed cells. This intracellular mannitol accumulation correlated with increased extracellular osmolarity of the medium. For further confirmation, the growth behavior of G. oxydans was analyzed in the presence of small amounts of mannitol (2.5–10 mM) and 300 mM sucrose. Growth under sucrose-induced osmotic stress conditions was almost identical to control growth when exogenous mannitol was added in low amounts. Thus, mannitol alleviates the osmotic stress of sucrose on cellular growth. Moreover, the positive effect of exogenous mannitol on the rate of glucose consumption and gluconate formation was also monitored. These results may be helpful to optimize the processes of industrial product formation in highly concentrated sugar solutions. © 2015, Springer-Verlag Berlin Heidelberg.


Mihatsch W.A.,Deaconry Hospital | Vossbeck S.,Section of Neonatology and Pediatric Critical Care | Eikmanns B.,Institute of Microbiology and Biotechnology | Hoegel J.,University of Ulm | Pohlandt F.,Section of Neonatology and Pediatric Critical Care
Neonatology | Year: 2010

Background: Nosocomial infections endanger preterm infants. Objective: The aim of the present controlled randomized trial was to investigate whether Bifidobacterium lactis reduces the incidence of nosocomial infections in infants with very low birth weight (VLBW; <1,500 g) <30 weeks of gestation. Patients and Methods: In a randomized controlled trial, 183 VLBW infants <30 weeks of gestation were stratified according to gestational age (23-26 and 27-29 weeks) and early antibiotic therapy (days 1-3, yes or no) and randomly assigned to have their milk feedings supplemented with B. lactis (6 × 2.0 × 109 CFU/kg/day, 12 billion CFU/kg/day) or placebo for the first 6 weeks of life. Primary outcome was the 'incidence density' of nosocomial infections defined as periods of elevated C-reactive protein (>10 mg/l) from day 7 after initiation of milk feedings until the 42nd day of life (number of nosocomial infections/total number of patient days). The main secondary outcome was necrotizing enterocolitis (NEC; ≥stage 2). Results: There were 93 infants in the B. lactis group and 90 in the placebo group. There was no significant difference between the two groups with regard to the incidence density of nosocomial infections (0.021 vs. 0.016; p = 0.9, χ2 test). There were 2 cases of NEC in the B. lactis group and 4 in the placebo group. None of the blood cultures grew B. lactis. Conclusion: In the present setting, B. lactis at a dosage of 6 × 2.0 × 109 CFU/kg/day (12 billion CFU/kg/day) did not reduce the incidence density of nosocomial infections in VLBW infants. No adverse effect of B. lactis was observed. Copyright © 2010 S. Karger AG, Basel.


Pham T.L.,International University | Trinh T.T.,Institute of Microbiology and Biotechnology | Nguyen H.T.,International University
IFMBE Proceedings | Year: 2015

This study aimed to evaluate the antimicrobial activity of Senna alata (L.), Rhinacanthus nasutus and Chromolaena odorata against antibiotic resistant Staphylococcus aureus, Pseudomonas aeruginosa clinical strains; vitro – induced antibiotic resistant S. aureus strains; S. aureus ATCC 25213 and P. aeruginosa ATCC 9027. Plant samples were extracted with different solvents including ethanol, ethyl acetate and n-hexane. Disc diffusion method was used to evaluate the antimicrobial activity of extracts. In general, most of extracts showed good antimicrobial activity against both antibiotic resistant and sensitive S. aureus but no activity against P. aeruginosa. To clinical S. aureus strains, C. odorata and R. nasutus extracts using ethyl acetate showed better inhibitory zones (17.17 ± 0.29 mm; 16.67 ± 0.58 mm) than the ones extracted using ethanol (14.17 ± 0.58mm, 11.67 ± 1.53 mm) and n- hexane (12.17 ± 0.58 mm; 13.67 ± 0.58 mm, respectively). To other S. aureus strains, S. alata (L.) extract using ethanol showed the greatest inhibition zone (22.33 ± 0.58 mm). This result suggested that these traditional herbs should be further investigated to serve as alternative treatment for multidrug- resistant S. aureus infections and probably also for other gram positive pathogenic bacteria. © Springer International Publishing Switzerland 2015.


PubMed | Institute of Microbiology and Biotechnology and National Institute of Nutrition
Type: Journal Article | Journal: Asia Pacific journal of clinical nutrition | Year: 2017

To demonstrate the gastrointestinal survival of Lactobacillus casei strain Shirota (LcS) in healthy Vietnamese adults, a fermented milk drink containing LcS was administered daily for 14 days. Twenty-six healthy Vietnamese adults took part in the study. Each participant consumed 65 mL of a fermented milk drink containing LcS daily for 14 days. The drink contained a dose of 10 8 CFU/mL LcS. Fecal samples were collected before, during and after consuming the fermented milk drink. LcS was confirmed by culture and ELISA. After 7 and 14 days of ingesting fermented milk drink, LcS was recovered from fecal samples at average of 5.010 7 CFU/g feces (n=26) and 5.410 7 CFU/g feces (n=26), respectively. LcS persisted in 8 voluteers until day 42 (after 14 days stopping fermented milk drink) at 0.003310 7 CFU/g feces (n=8). We confirmed survival of LcS after passage through the gastrointestinal tract of Vietnamese adults.


Singh T.P.,National Dairy Research Institute | Kaur G.,National Dairy Research Institute | Malik R.K.,National Dairy Research Institute | Schillinger U.,Institute of Microbiology and Biotechnology | And 2 more authors.
Probiotics and Antimicrobial Proteins | Year: 2012

This study was conducted to evaluate the probiotic properties of Lactobacillus reuteri isolated from human infant feces (less than 3 months). Out of thirty-two representative L. reuteri strains isolated from the infant human feces, nine isolates (i.e. LR5, LR6, LR9, LR11, LR19, LR20, LR25, LR26 and LR34) showed survival in acid, bile and simulated stomach-duodenum passage conditions, indicating their high tolerance to gastric juice, duodenal juice and bile environments. The nine isolates did not show strong hydrophobic properties because the percentages of adhesion to the apolar solvent, n-hexadecane, did not exceed 40%, showing that their surfaces were rather hydrophilic. Functionality of these nine probiotic isolates was supported by their antagonistic activity and their ability to deconjugate bile salts. The safety of the nine indigenous L. reuteri isolates was supported by the absence of transferable antibiotic resistance determinants, DNase activity, gelatinase activity and hemolysis. The results obtained so far suggest that the nine strains are resistant to low pH, bile salts and duodenum juice, so they could survive when passing through the upper part of the gastrointestinal tract and fulfill their potential probiotic action in the host organism. According to these results, the L. reuteri strains isolated from human infant feces possess interesting probiotic properties that make them potentially good candidates for probiotics. © 2012 Springer Science + Business Media, LLC.


Refai S.,Institute of Microbiology and Biotechnology | Berger S.,Institute of Microbiology and Biotechnology | Wassmann K.,Institute of Microbiology and Biotechnology | Deppenmeier U.,Institute of Microbiology and Biotechnology
Journal of Biotechnology | Year: 2014

Methanogenic archaea are essential for the production of methane in biogas plants. Here we present enzymatic test systems for the analysis of the metabolic activity of methanogens based on the heterodisulfide reductase reaction. The first rapid test shows that heterodisulfide reductase can be detected in 1. g of biogas sludge after sonication and centrifugation. The resulting cell lysate used reduced methylviologen for heterodisulfide reduction, a reaction that is specifically catalyzed by methanogenic heterodisulfide reductase. In the second test cell lysate from 60. g of biogas sludge was separated by ultracentrifugation. Both, cytoplasmic membrane and cytoplasmic fractions revealed heterodisulfide reductase activity, indicating the presence of hydrogenotrophic and aceticlastic methanogens, respectively. © 2014 Elsevier B.V.


Zahid N.,Institute of Microbiology and Biotechnology | Deppenmeier U.,Institute of Microbiology and Biotechnology
Applied Microbiology and Biotechnology | Year: 2016

Gluconobacter (G.) oxydans is able to incompletely oxidize various sugars and polyols for the production of biotechnologically important compound. Recently, we have shown that the organism produces and accumulates mannitol as compatible solute under osmotic stress conditions. The present study describes the role of two cytoplasmic mannitol dehydrogenases for osmotolerance of G. oxydans. It was shown that Gox1432 is a NADP+-dependent mannitol dehydrogenase (EC 1.1.1.138), while Gox0849 uses NAD+ as cofactor (EC 1.1.1.67). The corresponding genes were deleted and the mutants were analyzed for growth under osmotic stress and non-stress conditions. A severe growth defect was detected for Δgox1432 when grown in high osmotic media, while the deletion of gox0849 had no effect when cells were exposed to 450 mM sucrose in the medium. Furthermore, the intracellular mannitol content was reduced in the mutant lacking the NADP+-dependent enzyme Gox1432 in comparison to the parental strain and the Δgox0849 mutant under stress conditions. In addition, transcriptional analysis revealed that Gox1432 is more important for mannitol production in G. oxydans than Gox0849 as the transcript abundance of gene gox1432 was 30-fold higher than of gox0849. In accordance, the activity of the NADH-dependent enzyme Gox0849 in the cell cytoplasm was 10-fold lower in comparison to the NADPH-dependent mannitol dehydrogenase Gox1432. Overexpression of gox1432 in the corresponding deletion mutant restored growth of the cells under osmotic stress, further strengthening the importance of the NADP+-dependent mannitol dehydrogenase for osmotolerance in G. oxydans. These findings provide detailed insights into the molecular mechanism of mannitol-mediated osmoprotection in G. oxydans and are helpful engineering strains with improved osmotolerance for biotechnological applications. © 2016 Springer-Verlag Berlin Heidelberg


PubMed | Institute of Microbiology and Biotechnology
Type: Journal Article | Journal: Applied microbiology and biotechnology | Year: 2016

Gluconobacter (G.) oxydans is able to incompletely oxidize various sugars and polyols for the production of biotechnologically important compound. Recently, we have shown that the organism produces and accumulates mannitol as compatible solute under osmotic stress conditions. The present study describes the role of two cytoplasmic mannitol dehydrogenases for osmotolerance of G. oxydans. It was shown that Gox1432 is a NADP

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