The Intermucosal Connection between the Mouth and Gut in Commensal Pathobiont-Driven Colitis.

The precise mechanism by which oral infection contributes to the pathogenesis of extra-oral diseases remains unclear. Here, we report that periodontal inflammation exacerbates gut inflammation in vivo. Periodontitis leads to expansion of oral pathobionts, including Klebsiella and Enterobacter species, in the oral cavity. Amassed oral pathobionts are ingested and translocate to the gut, where they activate the inflammasome in colonic mononuclear phagocytes, triggering inflammation. In parallel, periodontitis results in generation of oral pathobiont-reactive Th17 cells in the oral cavity. Oral pathobiont-reactive Th17 cells are imprinted with gut tropism and migrate to the inflamed gut. When in the gut, Th17 cells of oral origin can be activated by translocated oral pathobionts and cause development of colitis, but they are not activated by gut-resident microbes. Thus, oral inflammation, such as periodontitis, exacerbates gut inflammation by supplying the gut with both colitogenic pathobionts and pathogenic T cells.

TnpB homologues exapted from transposons are RNA-guided transcription factors.

Transposon-encoded tnpB and iscB genes encode RNA-guided DNA nucleases that promote their own selfish spread through targeted DNA cleavage and homologous recombination1-4. These widespread gene families were repeatedly domesticated over evolutionary timescales, leading to the emergence of diverse CRISPR-associated nucleases including Cas9 and Cas12 (refs. 5,6). We set out to test the hypothesis that TnpB nucleases may have also been repurposed for novel, unexpected functions other than CRISPR-Cas adaptive immunity. Here, using phylogenetics, structural predictions, comparative genomics and functional assays, we uncover multiple independent genesis events of programmable transcription factors, which we name TnpB-like nuclease-dead repressors (TldRs). These proteins use naturally occurring guide RNAs to specifically target conserved promoter regions of the genome, leading to potent gene repression in a mechanism akin to CRISPR interference technologies invented by humans7. Focusing on a TldR clade found broadly in Enterobacteriaceae, we discover that bacteriophages exploit the combined action of TldR and an adjacently encoded phage gene to alter the expression and composition of the host flagellar assembly, a transformation with the potential to impact motility8, phage susceptibility9, and host immunity10. Collectively, this work showcases the diverse molecular innovations that were enabled through repeated exaptation of transposon-encoded genes, and reveals the evolutionary trajectory of diverse RNA-guided transcription factors.

Revisiting host identification of bacteriophage Enc34: from biochemical to molecular.

In our 2012 genome announcement (J Virol 86:11403-11404, 2012, https://doi.org/10.1128/JVI.01954-12), we initially identified the host bacterium of bacteriophage Enc34 as Enterobacter cancerogenus using biochemical tests. However, later in-house DNA sequencing revealed that the true host is a strain of Hafnia alvei. Capitalizing on our new DNA-sequencing capabilities, we also refined the genomic termini of Enc34, confirming a 60,496-bp genome with 12-nucleotide 5' cohesive ends. IMPORTANCE: Our correction reflects the evolving landscape of bacterial identification, where molecular methods have supplanted traditional biochemical tests. This case underscores the significance of revisiting past identifications, as seemingly known bacterial strains may yield unexpected discoveries, necessitating essential updates to the scientific record. Despite the host identity correction, our genome announcement retains importance as the first complete genome sequence of a Hafnia alvei bacteriophage.

VIM-1-producing Enterobacter asburiae with mobile colistin resistance genes from wastewaters.

BACKGROUND: Wastewaters are considered as important players in the spread of antimicrobial resistance, thus affecting the health of humans and animals. Here, we focused on wastewaters as a possible source of carbapenemase-producing Enterobacterales for the environment. METHODS: A total of 180 presumptive coliforms from hospital and municipal wastewaters, and a river in the Czech Republic were obtained by selective cultivation on meropenem-supplemented media and tested for presence of carbapenemase-encoding genes by PCR. Strains carrying genes of interest were characterized by testing antimicrobial susceptibility, carbapenemase production and combination of short- and long- read whole-genome sequencing. The phylogenetic tree including publicly available genomes of Enterobacter asburiae was conducted using Prokka, Roary and RAxML. RESULTS: Three VIM-producing Enterobacter asburiae isolates, members of the Enterobacter cloacae complex, were detected from hospital and municipal wastewaters, and the river. The blaVIM-1 gene was located within a class 1 integron that was carried by different F-type plasmids and one non-typeable plasmid. Furthermore, one of the isolates carried plasmid-borne colistin-resistance gene mcr-10, while in another isolate chromosomally located mcr-9 without colistin resistance phenotype was detected. In addition, the analysis of 685 publicly available E. asburiae genomes showed they frequently carry carbapenemase genes, highlighting the importance of this species in the emergence of resistance to last-line antibiotics. CONCLUSION: Our findings pointed out the important contribution of hospital and community wastewaters in transmission of multi-drug resistant pathogens.

Green-synthesized zinc oxide nanoparticles by Enterobacter sp.: unveiling characterization, antimicrobial potency, and alleviation of copper stress in Vicia faba (L.) plants.

BACKGROUND: The biosynthesis of zinc oxide nanoparticles (ZnO NPs) using Enterobacter sp. and the evaluation of their antimicrobial and copper stress (Cu+ 2)-reducing capabilities in Vicia faba (L.) plants. The green-synthesized ZnO NPs were validated using X-ray powder diffraction (XRD); Fourier transformed infrared (FTIR), Ultraviolet-Visible spectroscopy (UV-Vis), Transmission electron microscope (TEM) and scanning electron microscopy (SEM) techniques. ZnO NPs could serve as an improved bactericidal agent for various biological applications. as well as these nanoparticles used in alleviating the hazardous effects of copper stress on the morphological and physiological traits of 21-day-old Vicia faba (L.) plants. RESULTS: The results revealed that different concentrations of ZnO NPs (250, 500, or 1000 mg L-1) significantly alleviated the toxic effects of copper stress (100 mM CuSO4) and increased the growth parameters, photosynthetic efficiency (Fv/Fm), and pigments (Chlorophyll a and b) contents in Cu-stressed Vicia faba (L.) seedlings. Furthermore, applying high concentration of ZnO NPs (1000 mg L-1) was the best dose in maintaining the levels of antioxidant enzymes (CAT, SOD, and POX), total soluble carbohydrates, total soluble proteins, phenolic and flavonoid in all Cu-stressed Vicia faba (L.) seedlings. Additionally, contents of Malondialdehyde (MDA) and hydrogen peroxide (H2O2) were significantly suppressed in response to high concentrations of ZnO NPs (1000 mg L-1) in all Cu-stressed Vicia faba (L.) seedlings. Also, it demonstrates strong antibacterial action (0.9 mg/ml) against various pathogenic microorganisms. CONCLUSIONS: The ZnO NPs produced in this study demonstrated the potential to enhance plant detoxification and tolerance mechanisms, enabling plants to better cope with environmental stress. Furthermore, these nanoparticles could serve as an improved bactericidal agent for various biological applications.

Distribution and expression of the aac(6')-Im (aacA16) aminoglycoside resistance gene.

BACKGROUND: The aac(6')-Im (aacA16) amikacin, netilmicin and tobramycin resistance gene cassette had been circulating globally undetected for many years in a sublineage of Acinetobacter baumannii global clone 2. OBJECTIVES: To identify sources for the aac(6')-Im fragment found in A. baumannii. METHODS: MinION long-read sequencing and Unicycler hybrid assemblies were used to determine the genetic context of the aac(6')-Im gene. Quantitative reverse transcriptase PCR was used to measure expression. RESULTS: Among >60 000 non-Acinetobacter draft genomes in the MRSN collection, the aac(6')-Im gene was detected in Pseudomonas putida and Enterobacter hormaechei isolates recovered from patients in Thailand between 2016 and 2019. Genomes of multiply resistant P. putida MRSN365855 and E. hormaechei MRSN791417 were completed. The class 1 integron containing the aac(6')-Im cassette was in the chromosome in MRSN365855, and in an HI2 plasmid in MRSN791417. However, MRSN791417 was amikacin susceptible and the gene was not expressed due to loss of the Pc promoter of the integron. Further examples of aac(6')-Im in plasmids from or the chromosome of various Gram-negative species were found in the GenBank nucleotide database. The aac(6')-Im context in integrons in pMRSN791417-8 and a Klebsiella plasmid pAMR200031 shared similarities with the aac(6')-Im region of AbGRI2-Im islands in A. baumannii. In other cases, the cassette array including the aac(6')-Im cassette was different. CONCLUSIONS: The aac(6')-Im gene is widespread, being found so far in several different species and in several different gene cassette arrays. The lack of amikacin resistance in E. hormaechei highlights the importance of correlating resistance gene content and antibiotic resistance phenotype.

Genome analysis and hyphal movement characterization of the hitchhiker endohyphal Enterobacter sp. from Rhizoctonia solani.

Bacterial-fungal interactions are pervasive in the rhizosphere. While an increasing number of endohyphal bacteria have been identified, little is known about their ecology and impact on the associated fungal hosts and the surrounding environment. In this study, we characterized the genome of an Enterobacter sp. Crenshaw (En-Cren), which was isolated from the generalist fungal pathogen Rhizoctonia solani, and examined the genetic potential of the bacterium with regard to the phenotypic traits associated with the fungus. Overall, the En-Cren genome size was typical for members of the genus and was capable of free-living growth. The genome was 4.6 MB in size, and no plasmids were detected. Several prophage regions and genomic islands were identified that harbor unique genes in comparison with phylogenetically closely related Enterobacter spp. Type VI secretion system and cyanate assimilation genes were identified from the bacterium, while some common heavy metal resistance genes were absent. En-Cren contains the key genes for indole-3-acetic acid (IAA) and phenylacetic acid (PAA) biosynthesis, and produces IAA and PAA in vitro, which may impact the ecology or pathogenicity of the fungal pathogen in vivo. En-Cren was observed to move along hyphae of R. solani and on other basidiomycetes and ascomycetes in culture. The bacterial flagellum is essential for hyphal movement, while other pathways and genes may also be involved.IMPORTANCEThe genome characterization and comparative genomics analysis of Enterobacter sp. Crenshaw provided the foundation and resources for a better understanding of the ecology and evolution of this endohyphal bacteria in the rhizosphere. The ability to produce indole-3-acetic acid and phenylacetic acid may provide new angles to study the impact of phytohormones during the plant-pathogen interactions. The hitchhiking behavior of the bacterium on a diverse group of fungi, while inhibiting the growth of some others, revealed new areas of bacterial-fungal signaling and interaction, which have yet to be explored.

Citrobacter spp. and Enterobacter spp. as reservoirs of carbapenemase blaNDM and blaKPC resistance genes in hospital wastewater.

Antibiotic resistance has emerged as a global threat to public health, generating a growing interest in investigating the presence of antibiotic-resistant bacteria in environments influenced by anthropogenic activities. Wastewater treatment plants in hospital serve as significant reservoirs of antimicrobial-resistant bacteria, where a favorable environment is established, promoting the proliferation and transfer of resistance genes among different bacterial species. In our study, we isolated a total of 243 strains from 5 hospital wastewater sites in Mexico, belonging to 21 distinct Gram-negative bacterial species. The presence of ß-lactamase was detected in 46.9% (114/243) of the isolates, which belonging to the Enterobacteriaceae family. We identified a total of 169 ß-lactamase genes; blaTEM in 33.1%, blaCTX-M in 25.4%, blaKPC in 25.4%, blaNDM 8.8%, blaSHV in 5.3%, and blaOXA-48 in 1.1% distributed in 12 different bacteria species. Among the 114 of the isolates, 50.8% were found to harbor at least one carbapenemase and were discharged into the environment. The carbapenemase blaKPC was found in six Citrobacter spp. and E. coli, while blaNDM was detected in two distinct Enterobacter spp. and E. coli. Notably, blaNDM-1 was identified in a 110 Kb IncFII conjugative plasmid in E. cloacae, E. xiangfangensis, and E. coli within the same hospital wastewater. In conclusion, hospital wastewater showed the presence of Enterobacteriaceae carrying a high frequency of carbapenemase blaKPC and blaNDM. We propose that hospital wastewater serves as reservoirs for resistance mechanism within bacterial communities and creates an optimal environment for the exchange of this resistance mechanism among different bacterial strains. IMPORTANCE: The significance of this study lies in its findings regarding the prevalence and diversity of antibiotic-resistant bacteria and genes identified in hospital wastewater in Mexico. The research underscores the urgent need for enhanced surveillance and prevention strategies to tackle the escalating challenge of antibiotic resistance, particularly evident through the elevated frequencies of carbapenemase genes such as blaKPC and blaNDM within the Enterobacteriaceae family. Moreover, the identification of these resistance genes on conjugative plasmids highlights the potential for widespread transmission via horizontal gene transfer. Understanding the mechanisms of antibiotic resistance in hospital wastewater is crucial for developing targeted interventions aimed at reducing transmission, thereby safeguarding public health and preserving the efficacy of antimicrobial therapies.

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.

Analysis of gut microbiota of ladybug beetle (Harmonia axyridis) after feeding on different artificial diets.

BACKGROUND: Harmonia axyridis is an effective natural enemy insect to a variety of phloem-sucking pests and Lepidopteran larvae, such as aphids, scabies, and phylloxera, while its industrial production is limited due to unmature artificial diet. Insect intestinal microbiota affect host development and reproduction. The aim of this study is to understand intestinal microbiota composition of H. axyridis and screen effective probiotics on artificial diet. Considering the role of the components and composition of the diet on the structure and composition of the intestinal microbiome, four kinds of diets were set up: (1) aphid; (2) basic diet; (3) basic diet + glucose; (4) basic diet + trehalose. The gut microbiota of H. axyridis was detected after feeding on different diets. RESULTS: Results showed that the gut microbiota between artificial diet group and aphid groups were far apart, while the basic and glucose groups were clearly clustered. Besides, the glucose group and trehalose group had one unique phylum, Cryptophyta and Candidatus Saccharibacteria, respectively. The highest abundance of Proteobacteria was found in the aphid diet. The highest abundance of Firmicutes was found in the basic diet. However, the addition of glucose or trehalose alleviated the change. In addition, the relative abundance of Enterobacter, Klebsiella, Enterobacteriaceae_unclassified, Enterobacteriales_unclassified and Serratia in the aphid group was higher than other groups. Moreover, the function of gut genes in each group also showed clear differences. CONCLUSION: These results have offered a strong link between artificial diets and gut microbes, and also have provided a theoretical basis for the screening of synergistic probiotics in artificial diet.

Rapid growth rate of Enterobacter sp. SM3 determined using several methods.

BACKGROUND: Bacterial growth rate, commonly reported in terms of doubling time, is frequently determined by one of two techniques: either by measuring optical absorption of a growing culture or by taking samples at different times during their growth phase, diluting them, spreading them on agar plates, incubating them, and counting the colonies that form. Both techniques require measurements of multiple repeats, as well careful assessment of reproducibility and consistency. Existing literature using either technique gives a wide range of growth rate values for even the most extensively studied species of bacteria, such as Escherichia coli, Pseudomonas aeruginosa, and  Staphylococcus aureus. This work aims to apply several methods to reliably determine the growth rate of a recently identified species of Enterobacteriaceae, called Enterobacter sp. SM3, and to compare that rate with that of a well-known wildtype E. coli strain KP437. RESULTS: We extend conventional optical density (OD) measurements to determine the growth rate of Enterobacter sp. SM3. To assess the reliability of this technique, we compare growth rates obtained by fitting the OD data to exponential growth, applying a relative density method, and measuring shifts in OD curves following set factors of dilution. The main source of error in applying the OD technique is due to the reliance on an exponential growth phase with a short span. With proper choice of parameter range, however, we show that these three methods yield consistent results. We also measured the SM3 division rate by counting colony-forming units (CFU) versus time, yielding results consistent with the OD measurements. In lysogeny broth at 37oC, SM3 divides every 21 ± 3 min, notably faster than the RP437 strain of E. coli, which divides every 29 ± 2 min. CONCLUSION: The main conclusion of this report is that conventional optical density (OD) measurements and the colony-forming units (CFU) method can yield consistent values of bacterial growth rate. However, to ensure the reproducibility and reliability of the measured growth rate of each bacterial strain, different methods ought to be applied in close comparison. The effort of checking for consistency among multiple techniques, as we have done in this study, is necessary to avoid reporting variable values of doubling time for particular species or strains of bacteria, as seen in the literature.

High genetic diversity and different type VI secretion systems in Enterobacter species revealed by comparative genomics analysis.

The human-pathogenic Enterobacter species are widely distributed in diverse environmental conditions, however, the understanding of the virulence factors and genetic variations within the genus is very limited. In this study, we performed comparative genomics analysis of 49 strains originated from diverse niches and belonged to eight Enterobacter species, in order to further understand the mechanism of adaption to the environment in Enterobacter. The results showed that they had an open pan-genome and high genomic diversity which allowed adaptation to distinctive ecological niches. We found the number of secretion systems was the highest among various virulence factors in these Enterobacter strains. Three types of T6SS gene clusters including T6SS-A, T6SS-B and T6SS-C were detected in most Enterobacter strains. T6SS-A and T6SS-B shared 13 specific core genes, but they had different gene structures, suggesting they probably have different biological functions. Notably, T6SS-C was restricted to E. cancerogenus. We detected a T6SS gene cluster, highly similar to T6SS-C (91.2%), in the remote related Citrobacter rodenitum, suggesting that this unique gene cluster was probably acquired by horizontal gene transfer. The genomes of Enterobacter strains possess high genetic diversity, limited number of conserved core genes, and multiple copies of T6SS gene clusters with differentiated structures, suggesting that the origins of T6SS were not by duplication instead by independent acquisition. These findings provide valuable information for better understanding of the functional features of Enterobacter species and their evolutionary relationships.

High prevalence of multidrug-resistant Enterobacterales carrying extended-spectrum beta-lactamase and AmpC genes isolated from neonatal sepsis in Ahvaz, Iran.

OBJECTIVES: In the recent years, multidrug resistant (MDR) neonatal septicemia-causing Enterobacterales has been dramatically increased due to the extended-spectrum beta-lactamases (ESBLs) and AmpC enzymes. This study aimed to assess the antibiotic resistance pattern, prevalence of ESBLs/AmpC beta-lactamase genes, and Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR) fingerprints in Enterobacterales isolated from neonatal sepsis. RESULTS: In total, 59 Enterobacterales isolates including 41 (69.5%) Enterobacter species, 15 (25.4%) Klebsiella pneumoniae and 3 (5.1%) Escherichia coli were isolated respectively. Resistance to ceftazidime and cefotaxime was seen in all of isolates. Furthermore, all of them were multidrug-resistant (resistant to three different antibiotic categories). The phenotypic tests showed that 100% of isolates were ESBL-positive. Moreover, AmpC production was observed in 84.7% (n = 50/59) of isolates. Among 59 ESBL-positive isolates, the highest percentage belonged to blaCTX-M-15 gene (66.1%) followed by blaCTX-M (45.8%), blaCTX-M-14 (30.5%), blaSHV (28.8%), and blaTEM (13.6%). The frequency of blaDHA, blaEBC, blaMOX and blaCIT genes were 24%, 24%, 4%, and 2% respectively. ERIC-PCR analysis revealed that Enterobacterales isolates were genetically diverse. The remarkable prevalence of MDR Enterobacterales isolates carrying ESBL and AmpC beta-lactamase genes emphasizes that efficient surveillance measures are essential to avoid the more expansion of drug resistance amongst isolates.

Unravelling the transcriptome response of Enterobacter sp. S-33 under varying temperature.

Enterobacter genus includes the bacteria occupying every aspect of environment, however, their adaptability at varying temperature is not clear. In the present study, we analyzed the transcriptome response of Enterobacter sp. S-33 and their functional genes under various temperatures (30-45 ℃) that were expressed and accumulated in cells under temperature-stress. During a temperature shift from 37 to 45 ℃, 165 genes showed differential expression including 112 up-regulated and 53 down-regulated. In particular, heat-shock genes such as CspA, 16 kDa heat shock protein A/B and transcriptional regulators such as LysR, TetR, and LuxR were differentially expressed, indicating the role of complex molecular mechanism of Enterobacter adapting to temperature stress. Similarly, genes associated to signal transduction, ABC transporters, iron homeostasis, and quorum sensing were also induced. The Gene ontology enrichment analysis of differentially expressed genes (DEGs) were categorized into "transmembrane transport", "tRNA binding", "hydrogen sulfide biosynthetic process" and "sulfate assimilation" terms. In addition, Kyoto Encyclopedia of Genes and Genomes pathways showed that ABC transporter as well as quorum sensing pathways were significantly enriched. Overall, current study has contributed to explore the adaptive molecular mechanisms of Enterobacter spp. upon temperature change, which further opens new avenues for future in-depth functional studies.

Emergence of a novel FRI-type carbapenemase; blaFRI-12 in Enterobacter asburiae located on an IncR plasmid.

Carbapenem-resistance in Enterobacter spp due to acquisition of mobile carbapenemases is of concern. An Enterobacter spp grew on ChromID CARBA medium and was positive for the mCIM carbapenemase detection assay. Susceptibility testing showed resistance to aztreonam and reduced susceptibility to imipenem. Conventional PCR using FRI primers detected a blaFRI gene. Whole genome sequencing reveled a new variant; blaFRI-12 was closest in sequence to blaFRI-5 differing by 13 amino acids and was found on a unique 110Kb IncR plasmid. Given the intrinsic nature of Enterobacter spp. to be carbapenem non-susceptible, blaFRI-types may be under reported globally.

Next-Generation Sequencing-Based Identification of Enterobacter hormaechei as Causative Agent of High Mortality Disease in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) Mice.

NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice, lacking many components of a mature immune system, are at increased risk of disease. General understanding of potential pathogens of these mice is limited. We describe a high mortality disease outbreak caused by an opportunistic bacterial infection in NSG mice. Affected animals exhibited perianal fecal staining, dehydration, and wasting. Histopathologic lesions included a primary necrotizing enterocolitis, with inflammatory and necrotizing lesions also occurring in the liver, kidneys, heart, and brain of some mice. All affected individuals tested negative for known opportunistic pathogens of immunodeficient mice. We initially identified a member of Enterobacter cloacae complex (ECC) in association with the outbreak by traditional diagnostics. ECC was cultured from extraintestinal organs, both with and without histopathologic lesions, suggesting bacteremia. Infrared spectroscopy and MALDI-TOF mass spectrometry demonstrated that isolates from the outbreak shared molecular features and likely a common origin. We subsequently hypothesized that advanced sequencing methods would identify a single species of ECC associated with clinical disease. Using a novel targeted amplicon-based next-generation sequencing assay, we identified Enterobacter hormaechei in association with this outbreak. Knowledge of this organism as a potential opportunistic pathogen in NSG mice is critical for preclinical studies to prevent loss of animals and confounding of research.

Some virulence genes are associated with antibiotic susceptibility in Enterobacter cloacae complex.

BACKGROUND: Enterobacter cloacae complex (ECC) including different species are isolated from different human clinical samples. ECC is armed by many different virulence genes (VGs) and they were also classified among ESKAPE group by WHO recently. The present study was designed to find probable association between VGs and antibiotic susceptibility in different ECC species. METHODS: Forty-five Enterobacter isolates that were harvested from different clinical samples were classified in four different species. Seven VGs were screened by PCR technique and antibiotic susceptibility assessment was performed by disk-diffusion assay. RESULT: Four Enterobacter species; Enterobacter cloacae (33.3%), Enterobacter hormaechei (55.6%), Enterobacter kobei (6.7%) and Enterobacter roggenkampii (4.4%) were detected. Minimum antibiotic resistance was against carbapenem agents and amikacin even in MDR isolates. 33.3% and 13.3% of isolates were MDR and XDR respectively. The rpoS (97.8%) and csgD (11.1%) showed maximum and minimum frequency respectively. Blood sample isolated were highly virulent but less resistant in comparison to the other sample isolates. The csgA, csgD and iutA genes were associated with cefepime sensitivity. CONCLUSION: The fepA showed a predictory role for differentiating of E. hormaechei from other species. More evolved iron acquisition system in E. hormaechei was hypothesized. The fepA gene introduced as a suitable target for designing novel anti-virulence/antibiotic agents against E. hormaechei. Complementary studies on other VGs and ARGs and with bigger study population is recommended.

Arsenite Mediates Selenite Resistance and Reduction in Enterobacter sp. Z1, Thereby Enhancing Bacterial Survival in Selenium Environments.

Arsenic (As) is widely present in the environment, and virtually all bacteria possess a conserved ars operon to resist As toxicity. High selenium (Se) concentrations tend to be cytotoxic. Se has an uneven regional distribution and is added to mitigate As contamination in Se-deficient areas. However, the bacterial response to exogenous Se remains poorly understood. Herein, we found that As(III) presence was crucial for Enterobacter sp. Z1 to develop resistance against Se(IV). Se(IV) reduction served as a detoxification mechanism in bacteria, and our results demonstrated an increase in the production of Se nanoparticles (SeNPs) in the presence of As(III). Tandem mass tag proteomics analysis revealed that the induction of As(III) activated the inositol phosphate, butanoyl-CoA/dodecanoyl-CoA, TCA cycle, and tyrosine metabolism pathways, thereby enhancing bacterial metabolism to resist Se(IV). Additionally, arsHRBC, sdr-mdr, purHD, and grxA were activated to participate in the reduction of Se(IV) into SeNPs. Our findings provide innovative perspectives for exploring As-induced Se biotransformation in prokaryotes.

Genomic insight of phosphate solubilization and plant growth promotion of two taxonomically distinct winter crops by Enterobacter sp. DRP3.

AIMS: Study of rhizospheric microbiome-mediated plant growth promotional attributes currently highlighted as a key tool for the development of suitable bio-inoculants for sustainable agriculture purposes. In this context, we have conducted a detailed study regarding the characterization of phosphate solubilizing potential by plant growth-promoting bacteria that have been isolated from the rhizosphere of a pteridophyte Dicranopteris sp., growing on the lateritic belt of West Bengal. METHODS AND RESULTS: We have isolated three potent bacterial strains, namely DRP1, DRP2, and DRP3 from the rhizoids-region of Dicranopteris sp. Among the isolated strains, DRP3 is found to have the highest phosphate solubilizing potentiality and is able to produce 655.89 and 627.58 µg ml-1 soluble phosphate by solubilizing tricalcium phosphate (TCP) and Jordan rock phosphate, respectively. This strain is also able to solubilize Purulia rock phosphate moderately (133.51 µg ml-1). Whole-genome sequencing and further analysis of the studied strain revealed the presence of pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase gdh gene along with several others that were well known for their role in phosphate solubilization. Further downstream, quantitative reverse transcriptase PCR-based expression study revealed 1.59-fold upregulation of PQQ-dependent gdh gene during the solubilization of TCP. Root colonization potential of the studied strain on two taxonomically distinct winter crops viz. Cicer arietinum and Triticum aestivum has been checked by using scanning electron microscopy. Other biochemical analyses for plant growth promotion traits including indole acetic acid production (132.02 µg ml-1), potassium solubilization (3 mg l-1), biofilm formation, and exopolymeric substances productions (1.88-2.03 µg ml-1) also has been performed. CONCLUSION: This study highlighted the active involvement of PQQ-dependent gdh gene during phosphate solubilization from any Enterobacter group. Moreover, our study explored different roadmaps for sustainable farming methods and the preservation of food security without endangering soil health in the future.

Enterobacter sp. HIT-SHJ4 isolated from wetland with carbon, nitrogen and sulfur co-metabolism and its implication for bioremediation.

Both autotrophic and heterotrophic denitrification are known as important bioprocesses of microbe-mediated nitrogen cycle in natural ecosystems. Actually, mixotrophic denitrification co-driven by organic matter and reduced sulfur substances are also common, especially in hypoxic environments such as estuarine sediments. However, carbon, nitrogen and sulfur co-metabolism during mixotrophic denitrification in natural water ecosystems has rarely been reported in detail. Therefore, this study investigated the co-metabolism of carbon, nitrogen and sulfur using samples collected from four distinct natural water ecosystems. Results demonstrated that samples from various sources all exhibited the ability for co-metabolism of carbon, nitrogen and sulfur. Microbial community analysis showed that Pseudomonas and Paracoccus were dominant bacteria ranging from 65.6% to 75.5% in mixotrophic environment. Enterobacter sp. HIT-SHJ4, a mixotrophic denitrifying strain which owned the capacity for co-metabolism of carbon, nitrogen and sulfur, was isolated and reported here for the first time. The strain preferred methanol as its carbon source and demonstrated remarkable efficiency for removing sulfide and nitrate with below 100 mg/L sulfide. Under weak acid conditions (pH 6.5-7.0), it exhibited enhanced capability in converting sulfide to elemental sulfur. Its bioactivity was evident within a temperature from 25 °C to 40 °C and C/N ratios from 0.75 to 3. This study confirmed the widespread presence of microbial-mediated synergistic carbon, nitrogen and sulfur metabolism in natural aquatic ecosystems. HIT-SHJ4 emerges as a novel strain, shedding light on carbon, nitrogen and sulfur co-metabolism in natural water bodies. Furthermore, it also serves as a promising candidate microorganism for in-situ ecological remediation, particularly in dealing with contamination posed by nitrate, sulfide, and organic matter.