Enterobacter spp. isolates from an underground coal mine reveal ligninolytic activity.

Lignin, the second most abundant renewable carbon source on earth, holds significant potential for producing biobased specialty chemicals. However, its complex, highly branched structure, consisting of phenylpropanoic units and strong carbon-carbon and ether bonds, makes it highly resistant to depolymerisation. This recalcitrancy highlights the need to search for robust lignin-degrading microorganisms with potential for use as industrial strains. Bioprospecting for microorganisms from lignin-rich niches is an attractive approach among others. Here, we explored the ligninolytic potential of bacteria isolated from a lignin-rich underground coalmine, the Morupule Coal Mine, in Botswana. Using a culture-dependent approach, we screened for the presence of bacteria that could grow on 2.5% kraft lignin-supplemented media and identified them using 16 S rRNA sequencing. The potential ligninolytic isolates were evaluated for their ability to tolerate industry-associated stressors. We report the isolation of twelve isolates with ligninolytic abilities. Of these, 25% (3) isolates exhibited varying robust ligninolytic ability and tolerance to various industrial stressors. The molecular identification revealed that the isolates belonged to the Enterobacter genus. Two of three isolates had a 16 S rRNA sequence lower than the identity threshold indicating potentially novel species pending further taxonomic review. ATR-FTIR analysis revealed the ligninolytic properties of the isolates by demonstrating structural alterations in lignin, indicating potential KL degradation, while Py-GC/MS identified the resulting biochemicals. These isolates produced chemicals of diverse functional groups and monomers as revealed by both methods. The use of coalmine-associated ligninolytic bacteria in biorefineries has potential.

Comparative genomics of plant growth promoting phosphobacteria isolated from acidic soils.

Despite being one of the most abundant elements in soil, phosphorus (P) often becomes a limiting macronutrient for plants due to its low bioavailability, primarily locked away in insoluble organic and inorganic forms. Phosphate solubilizing and mineralizing bacteria, also called phosphobacteria, isolated from P-deficient soils have emerged as a promising biofertilizer alternative, capable of converting these recalcitrant P forms into plant-available phosphates. Three such phosphobacteria strains-Serratia sp. RJAL6, Klebsiella sp. RCJ4, and Enterobacter sp. 198-previously demonstrated their particular strength as plant growth promoters for wheat, ryegrass, or avocado under abiotic stresses and P deficiency. Comparative genomic analysis of their draft genomes revealed several genes encoding key functionalities, including alkaline phosphatases, isonitrile secondary metabolites, enterobactin biosynthesis and genes associated to the production of indole-3-acetic acid (IAA) and gluconic acid. Moreover, overall genome relatedness indexes (OGRIs) revealed substantial divergence between Serratia sp. RJAL6 and its closest phylogenetic neighbours, Serratia nematodiphila and Serratia bockelmanii. This compelling evidence suggests that RJAL6 merits classification as a novel species. This in silico genomic analysis provides vital insights into the plant growth-promoting capabilities and provenance of these promising PSRB strains. Notably, it paves the way for further characterization and potential application of the newly identified Serratia species as a powerful bioinoculant in future agricultural settings.

Bacterial Swarmers Enriched During Intestinal Stress Ameliorate Damage.

BACKGROUND AND AIMS: Bacterial swarming, a collective movement on a surface, has rarely been associated with human pathophysiology. This study aims to define a role for bacterial swarmers in amelioration of intestinal stress. METHODS: We developed a polymicrobial plate agar assay to detect swarming and screened mice and humans with intestinal stress and inflammation. From chemically induced colitis in mice, as well as humans with inflammatory bowel disease, we developed techniques to isolate the dominant swarmers. We developed swarm-deficient but growth and swim-competent mutant bacteria as isogenic controls. We performed bacterial reinoculation studies in mice with colitis, fecal 16S, and meta-transcriptomic analyses, as well as in vitro microbial interaction studies. RESULTS: We show that bacterial swarmers are highly predictive of intestinal stress in mice and humans. We isolated a novel Enterobacter swarming strain, SM3, from mouse feces. SM3 and other known commensal swarmers, in contrast to their mutant strains, abrogated intestinal inflammation in mice. Treatment of colitic mice with SM3, but not its mutants, enriched beneficial fecal anaerobes belonging to the family of Bacteroidales S24-7. We observed SM3 swarming associated pathways in the in vivo fecal meta-transcriptomes. In vitro growth of S24-7 was enriched in presence of SM3 or its mutants; however, because SM3, but not mutants, induced S24-7 in vivo, we concluded that swarming plays an essential role in disseminating SM3 in vivo. CONCLUSIONS: Overall, our work identified a new but counterintuitive paradigm in which intestinal stress allows for the emergence of swarming bacteria; however, these bacteria act to heal intestinal inflammation.

Community Structure of Nitrifying and Denitrifying Bacteria from Effluents Discharged into Lake Victoria, Kenya.

An active microbial community of nitrifying and denitrifying bacteria is needed for efficient utilization of nitrogenous compounds from wastewater. In this study, we explored the bacterial community diversity and structure within rivers, treated and untreated wastewater treatment plants (WWTPs) discharging into Lake Victoria. Water samples were collected from rivers and WWTPs that drain into Lake Victoria. Physicochemical analysis was done to determine the level of nutrients or pollutant loading in the samples. Total community DNA was extracted, followed by Illumina high throughput sequencing to determine the total microbial community and abundance. Enrichment and isolation were then done to recover potential nitrifiers and denitrifiers. Physicochemical analysis pointed to high levels total nitrogen and ammonia in both treated and untreated WWTPs as compared to the samples from the lake and rivers. A total of 1,763 operational taxonomic units (OTUs) spread across 26 bacterial phyla were observed with the most dominant phylum being Proteobacteria. We observed a decreasing trend in diversity from the lake, rivers to WWTPs. The genus Planktothrix constituted 19% of the sequence reads in sample J2 collected from the lagoon. All the isolates recovered in this study were affiliated to three genera: Pseudomonas, Klebsiella and Enterobacter in the phylum Proteobacteria. A combination of metagenomic analysis and a culture-dependent approach helped us understand the relative abundance as well as potential nitrifiers and denitrifiers present in different samples. The recovered isolates could be used for in situ removal of nitrogenous compounds from contaminated wastewater.

Bacterial contaminants and their antibiotic susceptibility patterns in ready-to-eat foods vended in Ogun state, Nigeria.

Contamination of ready-to-eat (RTE) foods by pathogenic bacteria may predispose consumers to foodborne diseases. This study investigated the presence of bacterial contaminants and their antibiotic susceptibility patterns in three locally processed RTE foods (eko, fufu and zobo) vended in urban markets in Ogun state, Nigeria. Bacteria isolated from a total of 120 RTE food samples were identified by 16S rRNA gene phylogeny while susceptibility patterns to eight classes of antibiotics were determined by the disc diffusion method. Species belonging to the genera Acinetobacter and Enterobacter were recovered from all RTE food types investigated, Klebsiella and Staphylococcus were recovered from eko and fufu samples, while those of Shigella were recovered from eko samples. Enterobacter hormaechei was the most prevalent species in all three RTE food types. Precisely 99% of 149 isolates were multidrug-resistant, suggesting a high risk for RTE food handlers and consumers. Co-resistance to ampicillin and cephalothin was the most frequently observed resistance phenotype. Results demonstrate that improved hygiene practices by food processors and vendors are urgently required during RTE processing and retail. Also, adequate food safety guidelines, regulation and enforcement by relevant government agencies are needed to improve the safety of RTE foods and ensure the protection of consumer health.

Enterobacter spp.: Update on Taxonomy, Clinical Aspects, and Emerging Antimicrobial Resistance.

The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. First described in 1960, this group member has proven to be more complex as a result of the exponential evolution of phenotypic and genotypic methods. Today, 22 species belong to the Enterobacter genus. These species are described in the environment and have been reported as opportunistic pathogens in plants, animals, and humans. The pathogenicity/virulence of this bacterium remains rather unclear due to the limited amount of work performed to date in this field. In contrast, its resistance against antibacterial agents has been extensively studied. In the face of antibiotic treatment, it is able to manage different mechanisms of resistance via various local and global regulator genes and the modulation of the expression of different proteins, including enzymes (ß-lactamases, etc.) or membrane transporters, such as porins and efflux pumps. During various hospital outbreaks, the Enterobacter aerogenes and E. cloacae complex exhibited a multidrug-resistant phenotype, which has stimulated questions about the role of cascade regulation in the emergence of these well-adapted clones.

Genome analysis-based reclassification of Enterobacter tabaci Duan et al. 2016 as a later heterotypic synonym of Enterobacter mori Zhu et al. 2011.

We performed a comparative genomic analysis to clarify the taxonomic relationship between the two Enterobacter species, Enterobacter tabaci and Enterobacter mori. Whole genome sequences of types strains of the two species became available recently. Average nucleotide identity (ANI) and in silico DNA-DNA hybridization (isDDH) between the two type strains were determined. Type strains of the two species had a 97.25 % ANI and an 80.4 % isDDH value, which are above the well-recognized cutoffs (≥95-96 % ANI and ≥70 % isDDH) for bacterial species delineation. The two strains have similar overall phenotypic characteristics and are clustered together with high bootstrap values in the multi-locus sequence analysis on rpoB, gyrB, infB and atpD housekeeping genes. It therefore becomes evident that the two species actually belong to the same species. E. mori has priority over E. tabaci, therefore we proposed that E. tabaci Duan et al. 2016 is a later heterotypic synonym of E. mori [15].

Enterobacter wuhouensis sp. nov. and Enterobacter quasihormaechei sp. nov. recovered from human sputum.

Two novel strains of members of the genus Enterobacter, WCHEs120002T and WCHEs120003T, were recovered from the sputum of two patients at a hospital in PR China in 2017. The strains were Gram-stain-negative, facultatively anaerobic, motile and non-spore-forming. The two strains were subjected to whole-genome sequencing. Phylogenetic analysis based on core genes of type strains of species of the family Enterobacteriaceae revealed that the two strains belonged to the genus Enterobacter but were distinct from any previously known species of the genus. Both average nucleotide identity and in silico DNA-DNA hybridization values between strains WCHEs120002T and WCHEs120003T and type strains of all known species of the genus Enterobacter were lower than the recommended thresholds of 95 and 70  %, respectively, for species delineation. The major fatty acids of the two strains were C16 : 0, C17 : 0 cyclo and C18:1ω7c, which are similar to those of other species of the genus Enterobacter. Genomic DNA G+C contents of strains WCHEs120002T and WCHEs120003T were 56.09 and 55.91 mol%, respectively. WCHEs120002T ferments melibiose and sucrose but is negative for d-sorbitol and methyl-α-d-mannopyranoside reactions, which distinguish it from all other species of the genus Enterobacter. WCHEs120003T can be differentiated from other species of the genus Enterobacter by its ability to ferment potassium gluconate and its negative reactions for d-sorbitol and l-fucose. Genotypic and phenotypic characteristics indicate that strains WCHEs120002T and WCHEs120003T represent two novel species of the genus Enterobacter, for which the names Enterobacter wuhouensis sp. nov. and Enterobacter quasihormaechei sp. nov. are proposed, respectively. The type strain of E. wuhouensis sp. nov. is WCHEs120002T (=GDMCC1.1569T=NCTC 14273T) and the type strain of E. quasihormaechei sp. nov. is WCHEs120003T (=GDMCC1.1568T=NCTC 14274T).

Biodegradation of bis(2-hydroxyethyl) terephthalate by a newly isolated Enterobacter sp. HY1 and characterization of its esterase properties.

Bis(2-hydroxyethyl) terephthalate (BHET) is an important compound produced from poly(ethylene terephthalate) (PET) cleavage. It was selected as the representative substance for the study of PET degradation. A bacterial strain HY1 that could degrade BHET was isolated and identified as Enterobacter sp. The optimal temperature and pH for BHET biodegradation were determined to be 30°C and 8.0, respectively. The half-life of degradation was 70.20 h at an initial BHET concentration of 1,000 mg/L. The results of metabolites' analysis by liquid chromatograph-mass spectrometer revealed that BHET was first converted to mono-(2-hydroxyethyl) terephthalate (MHET) and then to terephthalic acid. Furthermore, an esterase-encoding gene, estB, was cloned from strain HY1, and the expressed enzyme EstB was characterized. The esterase has a molecular mass of approximately 25.13 kDa, with an isoelectric point of 4.68. Its optimal pH and temperature were pH 8.0 and 40°C, respectively. The analysis of the enzymatic products showed that EstB could hydrolyze one ester bond of BHET to MHET. To the best of authors' knowledge, this is the first report on the biodegradation characteristics of BHET by a member of the Enterobacter genus.

Efficacy of soil-borne Enterobacter sp. for carbofuran degradation: HPLC quantitation of degradation rate.

Excessive use of pesticides in agricultural fields is a matter of great concern for living beings as well as the environment across the world, in particular, the third world countries. Therefore, there is an urgent need to find out an effective way to degrade these hazardous chemicals from the soil in an environment-friendly way. In the current project, a bacterial species were isolated through enrichment culture from carbofuran-supplemented rice-field soil and identified as a carbofuran degrader. The rate of carbofuran degradation by this bacterial species was evaluated using reverse-phase high-performance liquid chromatography (RP-HPLC), which confirmed the ability to utilize as a carbon source up to 4 µg/ml of 99% technical grade carbofuran. The morphological, physiological, biochemical characteristics and phylogenetic analysis of the 16S rRNA sequence showed that this strain belongs to the genus of Enterobacter sp. (sequence accession number LC368285 in DDBJ), and the optimum growth condition for the isolated strain was 37°C at pH 7.0. Moreover, an antibiotic sensitivity test showed that it was susceptible to azithromycin, penicillin, ceftazidime, ciprofloxacin, and gentamycin, and the minimal inhibitory concentration value of gentamycin was 400 µg/ml against the bacteria. It shows beyond doubt from the RP-HPLC quantification that the isolated bacterium has the ability to detoxify carbofuran (99% pure). Finally, the obtained results imply that the isolated strain of Enterobacter can be used as a potential and effective carbofuran degrader for bioremediation of contaminated sites through bioaugmentation.

Rice-Associated Rhizobacteria as a Source of Secondary Metabolites against Burkholderia glumae.

Various diseases, including bacterial panicle blight (BPB) and sheath rot, threaten rice production. It has been established that Burkholderia glumae (B. glumae) is the causative agent of the above mentioned pathologies. In the present study, antagonistic activity, growth promotion, and the metabolite profiles of two rhizobacteria, isolated in different paddy fields, were assessed against B. glumae. Strains were identified based on 16S rRNA gene sequences, and the phylogenetic analyses showed that both strains belong to the genus Enterobacter, with high similarity to the strain Enterobacter tabaci NR146667.2 (99%). The antagonistic activity was assessed with the disc diffusion method. Active fractions were isolated through a liquid/liquid extraction with ethyl acetate (EtOAc) from the fermentation media, and their antibacterial activities were evaluated following the Clinical and Laboratory Standards Institute (CLSI) guidelines. The Pikovskaya modified medium was used to test the ability of in vitro inorganic phosphorus solubilization, and BSB1 proved to be the best inorganic phosphorus solubilizer, with a solubilization index (SI) of 4.5 ± 0.2. The glass-column fractionation of the EtOAc extracted from BCB11 produced an active fraction (25.9 mg) that inhibited the growth of five B. glumae strains by 85-95%. Further, metabolomic analysis, based on GC-MS, showed 3-phenylpropanoic acid (3-PPA) to be the main compound both in this fraction (46.7%), and in the BSB1 extract (28.6%). This compound showed antibacterial activity against all five strains of B. glumae with a minimum inhibitory concentration (MIC) of 1000 mg/L towards all of them. The results showed that rice rhizosphere microorganisms are a source of compounds that inhibit B. glumae growth and are promising plant growth promoters (PGP).

Enterobacter huaxiensis sp. nov. and Enterobacter chuandaensis sp. nov., recovered from human blood.

Enterobacter strains 090008T and 090028T were recovered from the blood of two different patients at West China Hospital, Chengdu, PR China in 2017. Phylogenetic analysis based on the 16S rRNA gene and multi-locus sequence analysis of the rpoB, gyrB, infB and atpD housekeeping genes revealed that the two strains were distinct from any previously known species of the genus Enterobacter. Both average nucleotide identity (ANI) and in silico DNA-DNA hybridization (isDDH) values between strains 090008T, 090028T and type strains of all known Enterobacter species were lower than the cut-off (≥95-96 % for ANI and ≥70 % for isDDH) to define a bacterial species. The major cellular fatty acids of strains 090008T and 090028T are C16 : 0, C17 : 0cyclo and C18 : 1ω7c, which are similar to other Enterobacter species, and the genomic DNA G+C content was 55.73 and 55.68 mol%, respectively. Strain 090008T can be differentiated from other Enterobacter species by its ability to ferment sucrose, melibiose and d-arabitol, but with a negative methyl α-d-mannopyranoside reaction. Strain 090028T can ferment potassium gluconate, but is negative for l-fucose, mdecarboxylase, deaminase aelibiose and d-sorbitol, which distinguishes it from all other Enterobacter species. Genotypic and phenotypic characteristics indicate that strains 090008T and 090028T represent two novel species of the genus Enterobacter, for which the names Enterobacter huaxiensissp. nov. and Enterobacter chuandaensis sp. nov. are proposed, respectively. The type strain of Enterobacter huaxiensissp. nov. is 090008T (=GDMCC1.1426T=CCTCC AB 2018174T=CNCTC 7648T) and the type strain of Enterobacter chuandaensissp. nov. is 090028T (=GDMCC1.1427T=CCTCC AB 2018173T=CNCTC 7649T).

Characterization of a strain representing a new Enterobacter species, Enterobacter chengduensis sp. nov.

An Enterobacter strain, WCHECl-C4, was recovered from a human blood sample in China in 2015. Phylogenetic analysis based on multi-locus sequence analysis of the rpoB, gyrB, infB and atpD housekeeping genes revealed that the strain is distinct from any previously described species of the genus Enterobacter. The whole genome sequence of strain WCHECl-C4 has an 80.48-93.34% average nucleotide identity with those of type strains of all known Enterobacter species. In silico DNA-DNA hybridization (isDDH) values between strain WCHECl-C4 and type strains of all known Enterobacter species range from 23.2 to 52.4%. The major cellular fatty acids of strain WCHECl-C4 are C16:0, C17:0 cyclo and C18:1ω7c, which are in the range of Enterobacter species. The genomic DNA G + C content was 55.7 mol%. Strain WCHECl-C4 can be distinguished from all known Enterobacter species by its ability to ferment D-sorbitol, L-rhamnose and melibiose but with a negative Voges-Proskauer reaction. Genotypic and phenotypic characteristics from this study indicate that strain WCHECl-C4 represents a novel species of the genus Enterobacter, for which the name Enterobacter chengduensis sp. nov. is proposed. The type strain is WCHECl-C4T (= GDMCC1.1216T = CCTCC AB 2017105T = KCTC 52993T).

Genomic Epidemiology of Global Carbapenemase-Producing Enterobacter spp., 2008-2014.

We performed whole-genome sequencing on 170 clinical carbapenemase-producing Enterobacter spp. isolates collected globally during 2008-2014. The most common carbapenemase was VIM, followed by New Delhi metallo-ß-lactamase (NDM), Klebsiella pneumoniae carbapenemase, oxacillin 48, and IMP. The isolates were of predominantly 2 species (E. xiangfangensis and E. hormaechei subsp. steigerwaltii) and 4 global clones (sequence type [ST] 114, ST93, ST90, and ST78) with different clades within ST114 and ST90. Particular genetic structures surrounding carbapenemase genes were circulating locally in various institutions within the same or between different STs in Greece, Guatemala, Italy, Spain, Serbia, and Vietnam. We found a common NDM genetic structure (NDM-GE-U.S.), previously described on pNDM-U.S. from Klebsiella pneumoniae ATCC BAA-214, in 14 different clones obtained from 6 countries spanning 4 continents. Our study highlights the importance of surveillance programs using whole-genome sequencing in providing insight into the molecular epidemiology of carbapenemase-producing Enterobacter spp.

Molecular Characterization of IMP-1-Producing Enterobacter cloacae Complex Isolates in Tokyo.

Although KPC enzymes are most common among carbapenemases produced by Enterobacter cloacae complex globally, the epidemiology varies from one country to another. While previous studies have suggested that IMP enzymes are most common in Japan, detailed analysis has been scarce thus far. Here, we carried out a molecular epidemiological study and plasmid analysis of IMP-1-producing E. cloacae complex isolates collected from three hospitals in central Tokyo using whole-genome sequencing. Seventy-one isolates were classified into several sequence types (STs), and 49 isolates were identified as Enterobacter hormaechei ST78. Isolates of ST78 were divided into three clades by core-genome single nucleotide polymorphism (SNP)-based phylogenetic analysis. Whereas isolates of clade 3 were isolated from only one hospital, isolates of clade 1 and 2 were identified from multiple hospitals. Ten of 12 clade 1 isolates and 1 of 4 clade 2 isolates carried blaIMP-1 on IncHI2 plasmids, with high similarity of genetic structures. In addition, these plasmids shared backbone structures with IncHI2 plasmids carrying blaIMP reported from other countries of the Asia-Pacific region. All isolates of clade 3 except one carried blaIMP-1 in In1426 on IncW plasmids. An isolate of clade 3, which lacked IncW plasmids, carried blaIMP-1 in In1426 on an IncFIB plasmid. These observations suggest that IMP-producing E. cloacae complex isolates with a diversity of host genomic backgrounds have spread in central Tokyo, and they indicate the possible contribution of IncHI2 plasmids toward this phenomenon.

Multi-drug resistant Enterobacter bugandensis species isolated from the International Space Station and comparative genomic analyses with human pathogenic strains.

BACKGROUND: The antimicrobial resistance (AMR) phenotypic properties, multiple drug resistance (MDR) gene profiles, and genes related to potential virulence and pathogenic properties of five Enterobacter bugandensis strains isolated from the International Space Station (ISS) were carried out and compared with genomes of three clinical strains. Whole genome sequences of ISS strains were characterized using the hybrid de novo assembly of Nanopore and Illumina reads. In addition to traditional microbial taxonomic approaches, multilocus sequence typing (MLST) analysis was performed to classify the phylogenetic lineage. Agar diffusion discs assay was performed to test antibiotics susceptibility. The draft genomes after assembly and scaffolding were annotated with the Rapid Annotations using Subsystems Technology and RNAmmer servers for downstream analysis. RESULTS: Molecular phylogeny and whole genome analysis of the ISS strains with all publicly available Enterobacter genomes revealed that ISS strains were E. bugandensis and similar to the type strain EB-247T and two clinical isolates (153_ECLO and MBRL 1077). Comparative genomic analyses of all eight E. bungandensis strains showed, a total of 4733 genes were associated with carbohydrate metabolism (635 genes), amino acid and derivatives (496 genes), protein metabolism (291 genes), cofactors, vitamins, prosthetic groups, pigments (275 genes), membrane transport (247 genes), and RNA metabolism (239 genes). In addition, 112 genes identified in the ISS strains were involved in virulence, disease, and defense. Genes associated with resistance to antibiotics and toxic compounds, including the MDR tripartite system were also identified in the ISS strains. A multiple antibiotic resistance (MAR) locus or MAR operon encoding MarA, MarB, MarC, and MarR, which regulate more than 60 genes, including upregulation of drug efflux systems that have been reported in Escherichia coli K12, was also observed in the ISS strains. CONCLUSION: Given the MDR results for these ISS Enterobacter genomes and increased chance of pathogenicity (PathogenFinder algorithm with > 79% probability), these species pose important health considerations for future missions. Thorough genomic characterization of the strains isolated from ISS can help to understand the pathogenic potential, and inform future missions, but analyzing them in in-vivo systems is required to discern the influence of microgravity on their pathogenicity.

Enterobacter sichuanensis sp. nov., recovered from human urine.

An Enterobacter strain, WCHECL1597T, was recovered from the urine of a patient in China in 2016. Phylogenetic analysis based on its 16S rRNA gene sequence indicated the strain belongs to the genus Enterobacter, while multi-locus sequence analysis of the rpoB, gyrB, infB and atpD housekeeping genes revealed that the strain was distinct from any previously described Enterobacter species. The whole genome sequence of strain WCHECL1597T had a 79.81-91.49 % average nucleotide identity to those of type strains of all known Enterobacter species. In silico DNA-DNA hybridization values between strain WCHECL1597T and the type strains of all known Enterobacter species ranged from 22.8 to 45.2 %. The major cellular fatty acids of strain WCHECL1597T were C16 : 0, C17 : 0cyclo and C18 : 1ω7c, which are in the quantitative range of other Enterobacter species while differentiated by the relatively higher amount (12.3 %) of iso-c16 : 1 I/C14 : 0 3-OH. The genomic DNA G+C content was 55.2 mol%. Strain WCHECL1597T could be distinguished from all known Enterobacter species by its ability to ferment inositol but with a negative l-rhamnose and d-mannitol reaction. Genotypic and phenotypic characteristics from this study indicate that strain WCHECL1597T represents a novel species of the genus Enterobacter, for which the name Enterobactersichuanensis sp. nov. is proposed. The type strain is WCHECL1597T (=GDMCC1.1217T=CCTCC AB 2017104T=KCTC 52994T).

Lelliottia jeotgali sp. nov., isolated from a traditional Korean fermented clam.

Strain PFL01T was isolated from traditional Korean fermented clam, jogae-jeotgal, and characterized. The strain was a facultative anaerobic, Gram-stain-negative bacterium that was rod-shaped, motile and beige-pigmented. The phylogenetic sequence analysis based on the 16S rRNA gene from PFL01T revealed that it was closely related to Lelliottia nimipressuralis LMG 10245T and Lelliottia amnigena LMG 2784T with 99.3 and 99.3 % sequence identities, respectively. Multilocus sequence type analysis of concatenated partial aptD, gyrB, infB and rpoB gene sequences showed a clear distinction of strain PFL01T from its closest related type strains. The discrimination was also supported by unique repetitive extragenic palindromic PCR (Rep-PCR, ERIC-PCR) fingerprint patterns. In addition, results from average nucleotide identity analyses with other species were less than 85 %. vitek and API analyses revealed distinct characteristics from other species of Lelliottia. The cellular fatty acid profile of the strain consisted of C16 : 0, cyclo-C17 : 0, C16 : 1ω7c/C16 : 1ω6c and C18 : 1ω7c/C18 : 1ω6c as major components. The whole genome of PFL01T was 4.6 Mb with a G+C content of 55.3 mol%. Based on these results, strain PFL01T was classified as a novel species of the genus Lelliottia, for which the name Lelliottia jeotgali sp. nov. is proposed. The type strain in PFL01T (=KCCM 43247T=JCM 31901T).

Auto-aggregation properties of a novel aerobic denitrifier Enterobacter sp. strain FL.

Enterobacter sp. strain FL was newly isolated from activated sludge and exhibited significant capability of auto-aggregation as well as aerobic denitrification. The removal efficiencies of NO3--N, total nitrogen (TN), and TOC by strain FL in batch culture reached 94.6, 63.9, and 72.5% in 24 h, respectively. The production of N2O and N2 in the presence of oxygen demonstrated the occurrence of aerobic denitrification. The auto-aggregation index of strain FL reached 54.3%, suggesting a high tendency that the cells would agglomerate into aggregates. The production of extracellular polymeric substances (EPSs), which were mainly composed of proteins followed by polysaccharides, was considered to be related to the cell aggregation according to Fourier transform infrared (FT-IR) and confocal laser scanning microscopy (CLSM). The proteins in EPS were evenly and tightly combined to cells and altered the protein secondary structures of cell surface from random coils to ß-sheets and three-turn helices. The alteration of protein secondary structures of cell surface caused by the proteins in EPS might play a dominant role in the auto-aggregation of strain FL. To further assess the feasibility of strain FL for synthetic wastewater treatment, a sequencing batch reactor (SBR), solely inoculated with strain FL, was conducted. During the 16 running cycles, the removal efficiency of NO3--N was 90.2-99.7% and the auto-aggregation index was stabilized at 35.0-41.5%. The EPS promoted the biomass of strain FL to aggregate in the SBR.

Screening of plant growth promotion ability among bacteria isolated from field-grown sorghum under different managements in Brazilian drylands.

Sorghum [Sorghum bicolor (L.) Moench] is a multipurpose grass cultivated in drylands due to its adaptation to drought. However the characteristics of sorghum-associated bacteria are not known in the Brazilian drylands. The aim of this study was to isolate and evaluate the plant growth promotion potential bacteria from field-grown sorghum under two irrigation and manure application levels in a Brazilian semi-arid reagion. Sorghum was irrigated with 3 or 1 mm day-1 and fertilized or not with liquid goat manure. Bacteria were obtained from surface-disinfected roots applying two nitrogen-free semi-solid media. The bacteria were evaluated for the presence of nifH gene, 16S rRNA sequences, calcium-phosphate solubilization, production of auxins and siderophores and for sorghum growth promotion. We obtained 20 out of 24 positive bacteria for nifH. The isolates were classified as in six different genera. All isolates produced auxins "in vitro", six bacteria produced siderophores and three Enterobacteriaceae solubilized calcium-phosphate. At least ten bacteria resulted in the increased total N content in the sorghum shoots, comparable to fertilization with 50 mg N plant-1 week-1 and to inoculation with Azospirillum brasilense Ab-V5. Enterobacter sp. ESA 57 was the best sorghum plant-growth promoting bacteria isolated in this study.