Aerogenes Strains Research Articles

Antibacterial activity of chensinin-1b, a peptide with a random coil conformation, against multiple-drug-resistant Pseudomonas aeruginosa

Nosocomial infections caused by Pseudomonas aeruginosa are difficult to treat due to the low permeability of its outer membrane as well as to its remarkable ability to acquire further resistance to antibiotics. Chensinin-1b exhibited antibacterial activity against the tested multiple-drug-resistant bacteria with a MIC ranging between 1.56 and 50μM, except E. cloacae strain 0320 (MREC0320), P. fluorescens strain 0322 (MRPF0322) and E. aerogenes strain 0320 (MREA0320). However, the MIC (25μM) of chensinin-1b to multiple-drug-resistant P. aeruginosa strain (MRPA 0108) was 16-fold higher than that observed to P. aeruginosa susceptible strain CGMCC 1.860 (PA1860). Chensinin-1b was able to disturb the integration of the cytoplasmic membrane of PA1860 and MRPA0108 cells similarly, but the outer membrane permeability of MRPA0108 cells was significantly lower. This low permeability was associated with increased expression of lipopolysaccharide (LPS) in the outer membrane and a decrease in negatively charged phospholipids in the outer membrane leaflet. In addition, the biofilm of MRPA0108 was responsible for the reduced susceptibility to chensinin-1b. A higher concentration of chensinin-1b (12.5µM) was required to maximally inhibit the formation of MRPA0108 biofilm. Notably, chensinin-1b inhibited the formation of MRPA0108 biofilm at concentrations below its MIC value by down-regulating the level of PelA, algD, and PslA gene transcription. Importantly, chensinin-1b had a significant antibacterial effect against MRPA0108 in vivo. Administration of chensinin-1b to mice infected with MRPA 0108 significantly increased survival by 50–70%. Moreover, chensinin-1b reduced the production of pro-inflammatory mediators and correspondingly reduced lung and liver tissue damage in the mouse model of septic shock induced by MRPA 0108. Collectively, these results suggest that chensinin-1b could be an effective antibiotic against multiple-drug-resistant bacterial strains.

Detection of New Delhi Metallo-β-Lactamase Variants NDM-4, NDM-5, and NDM-7 in Enterobacter aerogenes Isolated from a Neonatal Intensive Care Unit of a North India Hospital: A First Report

A total 402 Enterobacteriaceae isolates were recovered from blood and rectal swabs of 1,000 infants admitted to the Neonatal Intensive Care Unit (NICU) of the Jawaharlal Medical College and Hospital Aligarh, India. Carbapenamase producers were determined by Carba NP phenotype biochemical assay. Out of 402 isolates, it was the first time three of the isolates were identified as Enterobacter aerogenes carrying blaNDM-4, blaNDM-5, and blaNDM-7 genes. These genes were identified by polymerase chain reaction (PCR) and sequence analysis. The isolates were further characterized to know the plasmid type and genetic environment features, including integron and IS elements. All the three E. aerogenes isolates (AK-93, AK-95, and AK-96) were resistant to all β-lactams, including carbapenems. The β-lactamase genes blaOXA-1, blaOXA-9, blaSHV-1, and blaVIM-2 were also found to be coassociated with blaNDM-4 in AK-93, blaOXA-1, blaOXA-9, and blaCMY-149 were found to be coexisted with blaNDM-5 in AK-95, and blaOXA-1; blaOXA-9, and blaCMY-145 were also found to be coassociated with blaNDM-7 in AK-96, identified by PCR analysis. Plasmid-based replicon typing revealed plasmids of different incompatibility in E. aerogenes in each of the isolates, AK-93 AK-95, and AK-96, respectively. ERIC-PCR was performed for the analysis of genetic relatedness of the strains. We found blaNDM-4, blaNDM-5, and blaNDM-7 producing three E. aerogenes strains, which were not clonally related. Genetic environment analysis revealed the presence of bleomycin resistance gene (bleMBL) to downstream of blaNDM and complete ISAba125 sequence were found upstream of blaNDM in all the three variants of these isolates. This is the first time we have identified blaNDM-4, blaNDM-5, and blaNDM-7 in E. aerogenes species, isolated from the NICU of a tertiary care hospital in India.

Production and Characterization of Halo Tolerant Alkaline Protease of Enterobacter aerogenes Strain ZB and Its Application

Production and Characterization of Halo Tolerant Alkaline Protease of Enterobacter aerogenes Strain ZB and Its Application

Physiological and molecular characteristics of carbapenem resistance in Klebsiella pneumoniae and Enterobacter aerogenes.

Bacterial resistance is a growing concern in the nosocomial environment in which Klebsiella pneumoniae and Enterobacter aerogenes play an important role due to their opportunism and carbapenemase-production. This work aimed to evaluate physiological and molecular characteristics of carbapenem-resistant K. pneumoniae and E. aerogenes isolated in a Brazilian tertiary hospital. In total, 42 carbapenem-resistant bacteria isolated from clinical specimens were included (21 K. pneumoniae and 21 E. aerogenes). Drug-sensitive K. pneumoniae (n = 27) were also included. Antimicrobial susceptibility and biocide tolerance patterns, hemolytic activity, tolerance to oxidative stress, and aggregative ability were assessed. Genetic markers related to carbapenem resistance, or ESBL-production were screened by PCR. Compared to drug-sensitive strains, carbapenem-resistant K. pneumoniae were more tolerant to biocides and to oxidative stress, and they displayed an increase in biofilm formation. The genetic markers blaKPC (95.2%) and blaTEM (90.5%) were the most frequent. Among the carbapenem-resistant E. aerogenes strains, blaKPC, and blaTEM were detected in all bacteria. Drug-sensitive E. aerogenes were not isolated in the same period. blaSHV, blaVIM, and blaCTX markers were also observed among carbapenem-resistant bacteria. Results suggest that carbapenemase-producing enterobacteria might show peculiar characteristics regarding their physiology associated with their environmental persistency, virulence, and multidrug resistance. The observed phenomenon may have implications not only for antimicrobial chemotherapy, but also for the prognosis of infectious diseases and infection control.

Isolation and characterization of a bacteriophage phiEap-2 infecting multidrug resistant Enterobacter aerogenes.

Enterobacter aerogenes (Enterobacteriaceae) is an important opportunistic pathogen that causes hospital-acquired pneumonia, bacteremia, and urinary tract infections. Recently, multidrug-resistant E. aerogenes have been a public health problem. To develop an effective antimicrobial agent, bacteriophage phiEap-2 was isolated from sewage and its genome was sequenced because of its ability to lyse the multidrug-resistant clinical E. aerogenes strain 3-SP. Morphological observations suggested that the phage belongs to the Siphoviridae family. Comparative genome analysis revealed that phage phiEap-2 is related to the Salmonella phage FSL SP-031 (KC139518). All of the structural gene products (except capsid protein) encoded by phiEap-2 had orthologous gene products in FSL SP-031 and Serratia phage Eta (KC460990). Here, we report the complete genome sequence of phiEap-2 and major findings from the genomic analysis. Knowledge of this phage might be helpful for developing therapeutic strategies against E. aerogenes.

NDM-1 encoded by a pNDM-BJ01-like plasmid p3SP-NDM in clinical Enterobacter aerogenes.

A carbapenem-nonsusceptible Enterobacter aerogenes strain named 3-SP was isolated from a human case of pneumonia in a Chinese teaching hospital. NDM-1 carbapenemase is produced by a pNDM-BJ01-like conjugative plasmid designated p3SP-NDM to account for carbapenem resistance of 3-SP. p3SP-NDM was fully sequenced and compared with all publically available pNDM-BJ01-like plasmids. The genetic differences between p3SP-NDM and pNDM-BJ01 include only 18 single nucleotide polymorphisms, a 1 bp deletion and a 706 bp deletion. p3SP-NDM and pNDM-BJ01 harbor an identical Tn125 element organized as ISAba125, blaNDM−1, bleMBL, ΔtrpF, dsbC, cutA, ΔgroES, groEL, ISCR27, and ISAba125. The blaNDM−1 surrounding regions in these pNDM-BJ01-like plasmids have a conserved linear organization ISAba14-aphA6-Tn125-unknown IS, with considerable genetic differences identified within or immediately downstream of Tn125. All reported pNDM-BJ01-like plasmids are exclusively found in Acinetobacter, whereas this is the first report of identification of a pNDM-BJ01-like plasmid in Enterobacteriaceae.

Evaluation of Antibiogram, Genotype and Phylogenetic Analysis of Biofield Treated Nocardia otitidis

Nocardiosis is a soil-borne aerobic infection caused by Nocardia species commonly affects the respiratory tract. Nocardia otitidis (N. otitidis) is the key organism for non-mycobacterial tuberculosis. The current study was attempted to investigate the effect of Mr. Trivedi’s biofield energy treatment on N. otitidis and analyzed for antimicrobial susceptibility pattern, minimum inhibitory concentration (MIC), DNA polymorphism by Random Amplified Polymorphic DNA (RAPD) and 16S rDNA sequencing. The strain of N. otitidis (ATCC 14630) was divided into two parts, control and treated. Antimicrobial susceptibility was studied using the broth microdilution technique. Overall, the MIC values of 16.67% antimicrobials were changed in the treated group of N. otitidis as compared to the control. Moreover, MIC value of trimethoprim/sulfamethoxazole was reduced by two-fold (0.5/9.5 to 0.25/4.75 μg/mL) in the biofield energy treated sample as compared to the control without alteration in the sensitivity spectrum. The 16S rDNA analysis showed that the treated sample was detected as Enterobacter aerogenes strain NCTC10006T (GenBank Accession No: AJ251468) with 98% identity of gene sequencing data. However, the nearest homolog genus-species was found as Kluyvera cryocrescens (GenBank Accession No: AM184245). Using RAPD biomarkers, the sample showed an average range of 34 to 53% of polymorphism among treated samples as compared to the control. The 16S rDNA sequencing of treated sample was carried out to correlate the phylogenetic relationship of N. otitidis with other bacterial species. These results suggested that Mr. Trivedi’s biofield energy treatment has a significant impact on N. otitidis.

Characterization of Phenotype and Genotype of Biofield Treated Enterobacter aerogenes

Enterobacter aerogenes (E. aerogenes) has been commonly described as a versatile opportunistic pathogen in hospital infections. The aim of the present work was to evaluate the impact of biofield treatment on E. aerogenes for its phenotypic and genotypic characteristics. E. aerogenes bearing ATCC 13048 (American Type Culture Collection) was procured from Bangalore Genei, in sealed pack and divided into control and treated groups. Treated group was subjected to Mr. Trivedi’s biofield treatment and analyzed for antimicrobial susceptibility, minimum inhibitory concentration (MIC), biochemical reactions, and biotype using automated MicroScan Walk-Away® system. In addition, treated group of E. aerogenes was evaluated for DNA polymorphism by Random Amplified Polymorphic DNA (RAPD) and 16S rDNA sequencing to establish the phylogenetic relationship of E. aerogenes with different closely related bacterial species. Antimicrobial susceptibility results showed an alteration of 14.28% among twenty-eight tested antimicrobials. Similarly, 15.65% tested antimicrobials showed an alteration in MIC values. Chloramphenicol showed improved sensitivity i.e. resistant to susceptible after biofield treatment, with the support of decreased MIC by two folds (i.e. >16 to ≤8 μg/mL). Norfloxacin also showed decrease MIC by two folds (i.e. 8 to ≤4 μg/mL) as compared to control. Biofield treatment showed an impact on biochemical reactions (9.09%) followed by a change in biotype number (7770 5272) in treated group with respect to control (7770 5372). Using RAPD analysis, sample showed an average range of 4 to 42% of polymorphism, while 16S rDNA study showed that treated sample was detected as Kluyvera cryocrescens (GenBank Accession Number: AM184245) with 97% identity of gene sequencing data, which was nearest homolog species to Enterobacter aerogenes strain: C1111 (Accession No. AB244467). These results suggest that Mr. Trivedi’s unique biofield treatment can alter the antimicrobial sensitivity pattern, thus it can be used as alternate energy medicine in future.

Study of the role of anaerobic metabolism in succinate production by Enterobacter aerogenes.

Succinate is a core biochemical building block; optimizing succinate production from biomass by microbial fermentation is a focus of basic and applied biotechnology research. Lowering pH in anaerobic succinate fermentation culture is a cost-effective and environmentally friendly approach to reducing the use of sub-raw materials such as alkali, which are needed for neutralization. To evaluate the potential of bacteria-based succinate fermentation under weak acidic (pH <6.2) and anaerobic conditions, we characterized the anaerobic metabolism of Enterobacter aerogenes AJ110637, which rapidly assimilates glucose at pH 5.0. Based on the profile of anaerobic products, we constructed single-gene knockout mutants to eliminate the main anaerobic metabolic pathways involved in NADH re-oxidation. These single-gene knockout studies showed that the ethanol synthesis pathway serves as the dominant NADH re-oxidation pathway in this organism. To generate a metabolically engineered strain for succinate production, we eliminated ethanol formation and introduced a heterogeneous carboxylation enzyme, yielding E. aerogenes strain ΔadhE/PCK. The strain produced succinate from glucose with a 60.5% yield (grams of succinate produced per gram of glucose consumed) at pH <6.2 and anaerobic conditions. Thus, we showed the potential of bacteria-based succinate fermentation under weak acidic conditions.

Characterization of KPC-2-Producing Escherichia coli, Citrobacter freundii, Enterobacter cloacae, Enterobacter aerogenes, and Klebsiella oxytoca Isolates from a Chinese Hospital

Twelve nonduplicated KPC-2-producing enterobacterial isolates, including three Escherichia coli, two Citrobacter freundii, two Enterobacter cloacae, four Enterobacter aerogenes, and one Klebsiella oxytoca, were collected from various clinical samples within 18 months (March 2011 to September 2012). Two of the 12 patients died from infections caused by KPC-2-producing pathogens, while the rest of the patients with KPC-2-producing pathogens improved or were cured. The majority of the clinical isolates exhibited a high-level of resistance to oxyimino-cephalosporins and carbapenems, and possessed self-transferable bla(KPC-2)-carrying plasmids with sizes ranging from 20 to 120 kb. Most isolates carried bla(CTX-M) and plasmid-mediated quinolone resistance genes, while some isolates produced 16S rRNA methylases (ArmA or RmtB). The genetic environment of bla(KPC-2) of most clinical strains was consistent with the genetic structure surrounding bla(KPC-2) on the plasmid pKP048, which contains an integration structure of a Tn3-based transposon and partial Tn4401 segment. Inserted fragments (truncated bla(TEM)) were detected upstream of the bla(KPC-2) gene for two E. aerogenes strains. In conclusion, the enterobacterial isolates exhibited sporadic emergence and did not arise by clonal spread at our hospital. The outcome of infections caused by KPC-producing enterobacterial isolates and their mortality were closely associated with the baseline condition of patients. The spread of bla(KPC-2) gene between different enterobacterial species in China was mainly mediated by horizontal transfer of the Tn3-based transposons and not the bla(KPC-2)-carrying plasmids.

Hospital clonal dissemination of Enterobacter aerogenes producing carbapenemase KPC-2 in a Chinese teaching hospital

Carbapenems are first-line agents for the treatment of serious nosocomial infections caused by multidrug-resistant Enterobacteriaceae. However, resistance to carbapenems has increased dramatically among Enterobacteriaceae in our hospital. In this study, we report clonal dissemination caused by carbapenem-resistant Enterobacter aerogenes (CREA). In 2011, CREA was identified from 12 patients admitted to the neurosurgical ward. All 12 clinical isolates were non-susceptible to cefotaxime, ceftazidime, cefoxitin, ertapenem, imipenem or meropenem. All isolates carried the gene encoding Klebsiella pneumoniae carbapenemase-2 (KPC-2), except for the isolate E4. However, a remarkably lower expression level of the porin OmpF was detected in the non-KPC-2-producing isolate E4 on SDS-PAGE compared with the carbapenem-susceptible isolate. Epidemiological and molecular investigations showed that a single E. aerogenes strain (PFGE type A), including seven KPC-2-producing clinical isolates, was primarily responsible for the first isolation and subsequent dissemination. In a case-control study, we identified risk factors for infection/colonization with CREA. Mechanical ventilation, the changing of sickbeds and previous use of broad-spectrum antibiotics were identified as potential risk factors. Our findings suggest that further studies should focus on judicious use of available antibiotics, implementation of active antibiotic resistance surveillance and strict implementation of infection-control measures to avoid the rapid spread or clonal dissemination caused by carbapenem-resistant Enterobacteriaceae in healthcare facilities.

Monitoring in vitro antibacterial efficacy of Terminalia alata Heyne ex. Roth, against MDR enteropathogenic bacteria isolated from clinical samples

The employed antibiotic could be ineffective against acute health effect causing multidrug resistant enteropathogenic bacteria. Thus, phytodrugs could be used for its control. Leaf and bark extracts of Terminalia alata, an ethnomedicinal plant used for ailments of the human gastrointestinal tract, were assessed for antibacterial efficacy in vitro, against eight enteropathogenic, extended spectrum β-lactamase enzyme producing multidrug resistant bacteria. Pathogenic bacteria were typified with serial biochemical steps. The double-disc diffusion–synergy test was used for the determination of extended spectrum β-lactamase producers. Sixteen antibiotics were used for determining antibiograms of eight isolated bacteria, using the disc-diffusion method. Antibacterial efficacies, of plant-extracts obtained using eight solvents, were monitored by the agar-well diffusion method. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of plant-extracts using solvents, methanol, ethanol, and acetone were determined by the micro-broth dilution method. Seven qualitative phytochemical tests were done with plant extracts. Of 16 antibiotics, resistant patterns were recorded with 14 antibiotics for Enterobacter aerogenes strains, 13 for Escherichia coli, 14 for Klebsiella sp., seven for Salmonella paratyphi, 15 for Salmonella typhi, 14 for two species of Shigella, and four for Vibrio cholerae. It was found that plant extracts using petroleum ether and n-hexane had the least antibacterial activity. Leaf and bark extracts using methanol, ethanol, and acetone registered the highest antibacterial activities with all these bacteria. The methanolic bark extract recorded MIC values, of 1.56 mg/mL against E. coli, Klebsiella sp., S. paratyphi, Shigella dysenteriae, and Shigella sonnei; 3.13 mg/mL against E. aerogenes and S. typhi; and 12.5 mg/mL against V. cholerae. The MBC values of the methanolic bark extract were: 12.5 mg/mL against E. coli, Klebsiella sp., S. dysenteriae, and S. sonnei; 25 mg/mL against E. aerogenes, S. typhi, and S. paratyphi; and 50 mg/mL against V. cholerae. Phytochemical analyses of methanolic leaf and bark extracts of T. alata confirmed the presence of alkaloids, terpenoids, reducing sugars, tannins, and flavonoids. The antibacterial efficacy of methanolic crude extracts revealed that leaves and bark of T. alata could serve as complementary/supplementary medicines to control multidrug resistant enteropathogenic bacteria.

OMICS OF asnA GENE FROM Enterobactor aerogenes KCTC2190

Background &amp; Aim: The present study was carried out to evaluate the omics of asnA gene fromEnterobactor aerogenes strain KCTC2190. Methods: This was achieved by using various onlinecomputational tools for both genomic and proteomic analysis. Results: Genomic studies states that thepyramidine rich gene codes for 388 aminoacid peptide with approximately 37KD (ss DNA) containingboth left &amp; right primers, a hybridization probe and several restriction sites for restriction enzymes. Thecorresponding peptide primary structure reveals that it is an acidic, stable protein. Secondary structuredefines that it mainly contains the random coils &amp; alpha helix. The protein has a total of tenphosphorylation sites along with net N &amp; O-Glycosylation sites. Conclusion: The present study statesthat the pyramidine rich gene has both left &amp; right primers, Hybridization probe with sufficient GCcontent. The encoded acidic, stable peptide ahs the multiple sites for phosphorylation, glycosylation.Above results shows that the asnA from Enterobactor aerogenes strain KCTC2190 is much suitable forthe experiments to enhance the L-Asparginase enzyme.

Emergence of extended-spectrum β-lactamase producing Enterobacter spp. in patients with bacteremia in a tertiary hospital in southern Brazil

BackgroundExtended-spectrum β-lactamases (ESBLs) are increasingly prevalent in Enterobacter spp., posing a challenge to the treatment of infections caused by this microorganism. The purpose of this retrospective study was to evaluate the prevalence, risk factors, and clinical outcomes of inpatients with bacteremia caused by ESBL and non ESBL-producing Enterobacter spp. in a tertiary hospital over the period 2004–2008. MethodsThe presence of blaCTX-M, blaTEM, blaSHV, and blaPER genes was detected by polymerase chain reaction (PCR) and nucleotide sequence analysis. Genetic similarity between strains was defined by pulsed-field gel electrophoresis (PFGE). ResultsEnterobacter spp. was identified in 205 of 4907 of the patients who had positive blood cultures during hospitalization. Of those cases, 41 (20%) were ESBL-producing Enterobacter spp. Nosocomial pneumonia was the main source of bacteremia caused by ESBL-producing Enterobacter spp. The presence of this microorganism was associated with longer hospital stays. The ESBL genes detected were: CTX-M-2 (23), CTX-M-59 (10), CTX-M-15 (1), SHV-12 (5), and PER-2 (2). While Enterobacter aerogenes strains showed mainly a clonal profile, Enterobacter cloacae strains were polyclonal. ConclusionAlthough no difference in clinical outcomes was observed between patients with infections by ESBL-producing and non-ESBL-producing strains, the detection of ESBL in Enterobacter spp. resulted in the change of antimicrobials in 75% of cases, having important implications in the decision-making regarding adequate antimicrobial therapy.

In vivo transmission of a plasmid containing the KPC-2 gene in a single patient.

Here we describe a case of in vivo horizontal interspecies transmission of a KPC-2-producing plasmid from a Klebsiella pneumoniae to an Enterobacter aerogenes strain in the same patient. The patient's gut flora initially contained a carbapenem-susceptible E. aerogenes strain and 10 days after admission a KPC-2-positive K. pneumoniae. Three months after admission, a KPC-2-positive E. aerogenes was identified in fecal surveillance cultures. This isolate was isogenic with the initial E. aerogenes and contained a KPC-2-coding plasmid identical to that of the K. pneumoniae. The patient developed bacteraemia by the KPC-2-positive K. pneumoniae 17 days after her first colonization. In vivo horizontal transmission of blaKPC-carrying plasmids between bacterial species underscores the importance of antibiotic stewardship along with implementation of infection control measures for the containment of KPC-producers.

Genetic characterization of tigecycline resistance in clinical isolates of Enterobacter cloacae and Enterobacter aerogenes

The intrinsically encoded ramA gene has been linked to tigecycline resistance through the up-regulation of efflux pump AcrAB in Enterobacter cloacae. The molecular basis for increased ramA expression in E. cloacae and Enterobacter aerogenes, as well as the role of AraC regulator rarA, has not yet been shown. To ascertain the intrinsic molecular mechanism(s) involved in tigecycline resistance in Enterobacter spp., we analysed the expression levels of ramA and rarA and corresponding efflux pump genes acrAB and oqxAB in Enterobacter spp. clinical isolates. The expression levels of ramA, rarA, oqxA and acrA were tested by quantitative real-time RT-PCR. The ramR open reading frames of the ramA-overexpressing strains were sequenced; strains harbouring mutations were transformed with wild-type ramR to study altered ramA expression and tigecycline susceptibility. Tigecycline resistance was mediated primarily by increased ramA expression in E. cloacae and E. aerogenes. Only the ramA-overexpressing E. cloacae isolates showed increased rarA and oqxA expression. Upon complementation with wild-type ramR, all Enterobacter spp. containing ramR mutations exhibited decreased ramA and acrA expression and increased tigecycline susceptibility. Exceptions were one E. cloacae strain and one E. aerogenes strain, where a decrease in ramA levels was not accompanied by lower acrA expression. Increased ramA expression due to ramR deregulation is the primary mediator of tigecycline resistance in clinical isolates of E. cloacae and E. aerogenes. However, some ramA-overexpressing isolates do not show changes in ramR, suggesting alternate pathways of ramA regulation; the rarA regulator and the oqxAB efflux pump may also play a role in tigecycline resistance in E. cloacae.

Alleviation of Salt Stress in Eggplant (Solanum melongena L.) by Plant-Growth-Promoting Rhizobacteria

This study was conducted to elucidate the effects of inoculation with plant-growth-promoting rhizobacteria (PGPR) on eggplant growth, yield, and mineral content under salt stress [0, 25, and 50 mM sodium chloride (NaCl)]. The PGPR strains Xanthobacter autotrophicus BM13, Enterobacter aerogenes BM10, and Bacillus brevis FK2 were isolated from the salt-affected maize and kidney bean fields. The increase in salinity decreased the growth and yield and increased the sodium (Na+) uptake of eggplant. However, inoculation with PGPR strains reduced the negative effects at each level of salinity tested. The E. aerogenes strain was capable of promoting eggplant growth and yield when compared to an uninoculated control. The B. brevis was the most effective strain for reducing the negative effects of salinity, and its effects occurred through increasing the potassium (K+)/Na+ ratio and K+-Na+ selectivity in the eggplant shoots. Inoculation of the eggplant seedlings with PGPR could alleviate the negative effects of salt stress.

Bioengineering of the Enterobacter aerogenes strain for biohydrogen production

Enterobacter aerogenes is one of the most widely-studied model strains for fermentative hydrogen production. To improve the hydrogen yield of E. aerogenes, the bioengineering on a biomolecular level and metabolic network level is of importance. In this review, the fermentative technology of E. aerogenes for hydrogen production will be first briefly summarized. And then the bioengineering of E. aerogenes for the improvement of hydrogen yield will be thoroughly reviewed, including the anaerobic metabolic networks for hydrogen evolution in E. aerogenes, metabolic engineering for improving hydrogen production in E. aerogenes and mixed culture of E. aerogenes with other hydrogen-producing bacteria to enhance the overall yield in anaerobic cultivation. Finally, a perspective on E. aerogenes as a hydrogen producer including systems bioengineering approach for improving the hydrogen yield and application of the engineered E. aerogenes in mixed culture will be presented.

Improved hydrogen production under microaerophilic conditions by overexpression of polyphosphate kinase in Enterobacter aerogenes

Effects of different microaerophilic conditions on cell growth, glucose consumption, hydrogen production and cellular metabolism of wild Enterobacter aerogenes strain and polyphosphate kinase (PPK) overexpressing strain were systematically studied in this paper, using NaH 2PO 4 as the phosphate sources. Under different microaerophilic conditions, PPK-overexpressing strain showed better cell growth, glucose consumption and hydrogen production than the wild strain. In the presence of limited oxygen (2.1%) and by PPK overexpression, the hydrogen production per liter of culture, the hydrogen production per cell and the hydrogen yield per mol of glucose increased by 20.1%, 12.3% and 10.8%, respectively, compared with the wild strain under strict anaerobic conditions. Metabolic analysis showed that the increase of the total hydrogen yield was attributed to the improvement of NADH pathway. The result of more reductive cellular oxidation state balance also further demonstrated that, under proper initial microaerophilic conditions and by PPK overexpression, the cell could adjust the cellular redox states and make more energy flow into hydrogen production pathways.

IDENTIFICATION OF CELLULOLYTIC BACTERIA ISOLATED FROM THE TERMITE COPTOTERMES CURVIGNATHUS (HOLMGREN)

ABSTRACT The aim of the present research was to isolate and identify cellulolytic bacteria from the gut of the local termite Coptotermes curvignathus (Holmgren) present in the vicinity of the University of Putra Malaysia. The isolates were cultured in a medium containing carboxymethyl‐cellulose and cellobiose. The bacterial species were tentatively identified by using the Biolog reader as well as the Bergey's manual and later confirmed by 16S rRNA sequence homology. The species were all novel strains and identified as Bacillus cereus strain Razmin A, Enterobacter aerogenes strain Razmin B, Enterobacter cloacae strain Razmin C, Chryseobacterium kwangyangense strain Cb and Acinetobacter strain Raminalimon. Biolog reader was not able to identify one of the bacterial species in which it was identified as C. kwangyangense strain Cb by 16S rRNA sequence homology. The GenBank NCBI/EMBL accession numbers for the bacterial strains are EU294508, EU305608, EU305609, EU169201 and EU332791 for B. cereus Razmin A, E. aerogenes strain Razmin B, E. cloacae strain Razmin C, C. kwangyangense strain Cb and Acinetobacter strain Raminalimon, respectively.PRACTICAL APPLICATIONSThe experiment describes the isolation and identification of cellulolytic bacteria from termites, using Biolog reader and polymerase chain reaction technique. Termites are common insects in tropical regions and thrive on wood and cellulolytic materials. Hence, the bacteria isolated may be useful in the degradation of cellulosic materials to increase their digestibility and possibly production of metabolites and enzymes.