Related Bacteria Research Articles

Comparison of oral microbiome profiles in 18-month-old infants and their parents

The onset and progress of dental caries and periodontal disease is associated with the oral microbiome. Therefore, it is important to understand the factors that influence oral microbiome formation. One of the factors that influence oral microbiome formation is the transmission of oral bacteria from parents. However, it remains unclear when the transmission begins, and the difference in contributions of father and mother. Here, we focused on the oral microbiome of 18-month-old infants, at which age deciduous dentition is formed and the oral microbiome is likely to become stable, with that of their parents. We collected saliva from forty 18-month-old infants and their parents and compared the diversity and composition of the microbiome using next-generation sequencing of 16S rRNA genes. The results showed that microbial diversity in infants was significantly lower than that in parents and composition of microbiome were significantly different between infants and parents. Meanwhile, the microbiome of the infants was more similar to that of their mothers than unrelated adults. The bacteria highly shared between infants and parents included not only commensal bacteria but also disease related bacteria. These results suggested that the oral microbiome of the parents influences that of their children aged < 18 months.

Comparative Genomics of Leuconostoc carnosum.

Leuconostoc carnosum is a known colonizer of meat-related food matrices. It reaches remarkably high loads during the shelf life in packaged meat products and plays a role in spoilage, although preservative effects have been proposed for some strains. In this study, the draft genomes of 17 strains of L. carnosum (i.e., all the strains that have been sequenced so far) were compared to decipher their metabolic and functional potential and to determine their role in food transformations. Genome comparison and pathway reconstruction indicated that L. carnosum is a compact group of closely related heterofermentative bacteria sharing most of the metabolic features. Adaptation to a nitrogen-rich environment, such as meat, is evidenced by 23 peptidase genes identified in the core genome and by the autotrophy for nitrogen compounds including several amino acids, vitamins, and cofactors. Genes encoding the decarboxylases yielding biogenic amines were not present. All the strains harbored 1–4 of 32 different plasmids, bearing functions associated to proteins hydrolysis, transport of amino acids and oligopeptides, exopolysaccharides, and various resistances (e.g., to environmental stresses, bacteriophages, and heavy metals). Functions associated to bacteriocin synthesis, secretion, and immunity were also found in plasmids. While genes for lactococcin were found in most plasmids, only three harbored the genes for leucocin B, a class IIa antilisterial bacteriocin. Determinants of antibiotic resistances were absent in both plasmids and chromosomes.

Direct detection of Corynebacterium striatum, Corynebacterium propinquum, and Corynebacterium simulans in sputum samples by high-resolution melt curve analysis

BackgroundPulmonary infections caused by non-diphtheriae corynebacteria are increasing. However, rapid identification of Corynebacterium species poses a challenge due to the low genetic variation within the genus.MethodsThree reference strains and 99 clinical isolates were used in this study. A qPCR followed by high-resolution melting (HRM) targeting ssrA was performed to simultaneously identify C. striatum, C. propinquum and C. simulans. To further evaluate this assay’s performance, 88 clinical sputum samples were tested by HRM and the detection results were compared with those of the traditional culture method and multiple cross-displacement amplification (MCDA) assay.ResultsThe melting curve produced by a pair of universal primers generated species-specific HRM curve profiles and could distinguish the three target species from other related bacteria. The limit of detection of HRM assay for DNA from the three purified Corynebacterium species was 100 fg. Compared with the culture method, HRM detected 22 additional positive specimens, representing a 23.9% relative increase in detection rate. The HRM assay had 98.4% (95% confidence interval [CI], 90.5–99.9%) sensitivity and 100% (95% CI, 82.8–100%) specificity. Additionally, 95.5% concordance between HRM and MCDA (κ = 0.89 [95% CI, 0.79–0.99]) was noted.ConclusionsThe HRM assay was a simple, rapid, sensitive, and specific diagnostic tool for detecting C. striatum, C. propinquum, and C. simulans, with the potential to contribute to early diagnosis, epidemiological surveillance, and rapid response to outbreak.

Vancomycin-lock therapy for prevention of catheter-related bloodstream infection in very low body weight infants

BackgroundThis study was to evaluate the effectiveness and safety of vancomycin- lock therapy for the prevention of catheter-related bloodstream infection (CRBSI) in very low body weight (VLBW) preterm infant patients.MethodsOne hundred and thirty-seven cases of VLBW preterm infants who retained peripherally inserted central catheters (PICCs) were retrospectively reviewed, including 68 treating with heparin plus vancomycin (vancomycin-lock group) and 69 with heparin only (control group). The incidence of CRBSI, related pathogenic bacteria, adverse events during the treatment, complications, antibiotic exposure, PICC usage time, hospital stay, etc. were compared between the above two groups.ResultsThe incidence rate of CRBSI in the vancomycin-lock group (4.4%, 3/68) was significantly less than in the control group (21.7%, 15/69, p = 0.004). Total antibiotic exposure time during the whole observation period was significantly shorter in the group than in the control group (11.2 ± 10.0 vs 23.6 ± 16.1 d; p < 0.001). No hypoglycemia occurred during the locking, and the blood concentrations of vancomycin were not detectable.ConclusionsVancomycin-lock may effectively prevent CRBSI in Chinese VLBW preterm infants and reduce the exposure time of antibiotics, without causing obvious side complications.

ВЛИЯНИЕ ЦИКЛОДЕКСТРИНА НА ДЕСТРУКЦИЮ ФЕНОЛА БАКТЕРИЯМИ PSEUDOMONAS STUTZERI И PAENIBACILLUS MACERANS В ВОДНОЙ СРЕДЕ

Cyclodextrins (CD) by their chemical nature are typical "host molecules" that can encapsulate a wide range of molecules, one or two benzene rings, including a phenolic ring. CDs can affect the bioavailability of contaminants during biodegradation, as well as the toxicity of the contaminant to microorganisms due to their ability to form inclusion complexes with organic compounds. In this work, the phenol destructor strains Pseudomonas stutzeri IB-I6C and Paenibacillus macerans IB-I4 were used, which have different growth characteristics in relation to the tested substrates: phenol (200 µg/ml) and CD (2 mg/ml). It was shown that when cultivating strains on a nutrient medium containing phenol+cyclodextrin, the degradation potential of bacteria in relation to phenol significantly increases. The amount of residual phenol in the presence of CD for P. stutzeri IB-I6C culture decreased by 8% by the end of cultivation, and for P. macerans IB-I4 this value was 10%. In the presence of CD in the medium, the time to achieve the maximum possible destruction of phenol was almost halved for both destructor strains. The rate of phenol consumption by pseudomonas IB-I6C in the presence of CD increased by 1,36 times, and utilization by the P. macerans strain IB-I4 was 1,31 times faster. The positive effect of CD in the destruction of phenol was found even in the case when CD is poorly utilized by the microorganism, as is observed in the strain P. stutzeri IB-I6C.

Depression and anxiety in patients with active ulcerative colitis: crosstalk of gut microbiota, metabolomics and proteomics

ABSTRACT Patients with ulcerative colitis (UC) have a high prevalence of mental disorders, such as depression and anxiety. Gut microbiota imbalance and disturbed metabolism have been suggested to play an important role in either UC or mental disorders. However, little is known about their detailed multi-omics characteristics in patients with UC and depression/anxiety. In this prospective observational study, 240 Chinese patients were enrolled, including 129 patients with active UC (69 in Phase 1 and 60 in Phase 2; divided into depression/non-depression or anxiety/non-anxiety groups), 49 patients with depression and anxiety (non-UC), and 62 healthy people. The gut microbiota of all subjects was analyzed using 16S rRNA sequencing. The serum metabolome and proteome of patients with UC in Phase 2 were analyzed using liquid chromatography/mass spectrometry. Associations between multi-omics were evaluated by correlation analysis. The prophylactic effect of candidate metabolites on the depressive-like behavior of mice with colitis was investigated. In total, 58% of patients with active UC had depression, while 50% had anxiety. Compared to patients with UC without depression/anxiety, patients with UC and depression/anxiety had lower fecal microbial community richness and diversity, with more Lactobacillales, Sellimonas, Streptococcus, and Enterococcus but less Prevotella_9 and Lachnospira. Most metabolites (e.g., glycochenodeoxycholate) were increased in the serum, while few metabolites, including 2ʹ-deoxy-D-ribose and L-pipecolic acid, were decreased, accompanied by a general reduction in immunoglobulin proteins. These related bacteria, metabolites, and proteins were highly connected. A prophylactic administration of 2ʹ-deoxy-D-ribose and L-pipecolic acid significantly reduced the depressive-like behaviors in mice with colitis and alleviated the inflammatory cytokine levels in their colon, blood and brain. This study has identified a comprehensive multi-omics network related to depression and anxiety in active UC. It is composed of a certain set of gut microbiota, metabolites, and proteins, which are potential targets for clinical intervention for patients with UC and depression/anxiety.

Metabolic Labeling of Live Mycobacteria with Trehalose-Based Probes.

The mycobacterial cell envelope includes a unique outer membrane, also known as the mycomembrane, which is the major defense barrier that confers intrinsic drug tolerance to Mycobacterium tuberculosis (Mtb) and related bacteria. The mycomembrane is typified by long-chain mycolic acids that are esterified to various acceptors, including: (1) trehalose, forming trehalose mono- and di-mycolate; (2) arabinogalactan, forming arabinogalactan-linked mycolates; and (3) in some species, protein serine residues, forming O-mycoloylated proteins. Synthetic trehalose and trehalose monomycolate analogs have been shown to specifically and metabolically incorporate into mycomembrane components, facilitating their analysis in native contexts and opening new avenues for the specific detection and therapeutic targeting of mycobacterial pathogens in complex settings. This chapter highlights trehalose-based probes that have been developed to date, briefly discusses their applications, and describes protocols for their use in mycobacteria research.

Gut lactate-producing bacteria promote CD4 T cell recovery on Anti-retroviral therapy in HIV-infected patients

Anti-retroviral therapy (ART) effectively suppresses viral replication in HIV-infected patients, however CD4 + cell restoration to normal value is not achieved by 15–20% of patients who are called immune non-responders. Gut microbiota composition has been shown to influence host immunity. Herein, to identify intestinal microbial agents that may influence the CD4 recovery in HIV-infected patients, we utilized a “Quasi-paired cohort” method to analyze intestinal metagenome data from immunological responders (IRs) and immunological non-responders (INRs). This method identified significant enrichment for Streptococcus sp. and related lactate-producing bacteria (LAB) in IRs. In a validation cohort, positive correlations between the abundance of these LAB and the post-ART CD4 + recovery was observed, and a prediction model based on these LAB performed well in predicting immune recovery. Finally, experiments using a germ-free mouse model of antibody-induced CD4 + cell depletion showed that supplementation with a lactate-producing commensal Streptococcus thermophilus strongly promoted CD4 recovery. In conclusion, our study identified a group of LAB that was associated with enhanced immune recovery in post-ART HIV-infected patients and promotes CD4 + cell restoration in a mouse model. These findings favour supplementation of LAB commensal as a therapeutic strategy for CD4 + cell count improvement in HIV-infected patients.

Haemophilin-Producing Strains of Haemophilus haemolyticus Protect Respiratory Epithelia from NTHi Colonisation and Internalisation.

Nontypeable Haemophilus influenzae (NTHi) is a significant respiratory tract pathogen responsible for infections that collectively pose a substantial health and socioeconomic burden. The clinical course of these infections is largely dictated by NTHi interactions with host respiratory epithelia, and thus, approaches that disrupt colonisation and invasion may have significant therapeutic potential. Survival, successful host–cell interactions, and pathogenesis are reliant on NTHi’s ability to sequester host-derived haem. Previously, we demonstrated the therapeutic potential of exploiting this haem-dependence using a closely related competitor bacterium, Haemophilus haemolyticus (Hh). Hh strains capable of producing the novel haem-binding protein haemophilin (Hpl) possessed potent inhibitory activity by restricting NTHi access to haem in a broth co-culture environment. Here, we extend this work to cell culture models that more closely represent the human respiratory epithelium and show that Hh strains with high levels of hpl expression protect epithelial cell line monolayers against adhesion and invasion by NTHi. Inhibitory activity was dependent on the level of Hpl production, which was stimulated by NTHi challenge and nasopharyngeal cell exposure. Provided these protective benefits translate to in vivo applications, Hpl-producing Hh may have probiotic utility against NTHi infections by inhibiting requisite nasopharyngeal colonisation.

Association between gallbladder diseases and Helicobacter pylori infection

Background: Helicobacter pylorus is one of the most harmful human pathogens &amp; carcinogen. Of the world's population, more than 50% has H. pylori in their upper gastrointestinal tracts. It has been linked to a variety of extra gastric disorders. In correlation to hepatobiliary diseases; recently, the bacterium has been implicated as a risk factor for various diseases ranging from chronic cholecystitis and primary biliary sclerosing cholangitis to gall bladder cancer and primary hepatic carcinomas. However, the association between Helicobacter pylori (H. pylori) and gallbladder diseases is still vague and is controversial.&#x0D; Aim of study: To elucidate the association of H pylori and gallbladder diseases (calculus, acalculous, polyp), the feasibility of using rapid urease test in post-operative diagnosis, and many factors related bacterium.&#x0D; Subjects &amp; methods: This case series study was conducted in Al-Kindy Teaching hospital - surgical unit during a period extended for 2 years from September 2016 to September 2018, where patients suffered from signs and symptoms of gallbladder disease were interviewed using a predesigned questionnaire including age, gender, occupation, residency and whether the drinking water was safe (purified) or not. Physical examination was done including weight status, BMI was calculated (BMI=wt. (kg)/ height (M) [2]. Provisional diagnosis of gallbladder disease was confirmed by examination, necessary laboratory investigations (Hematology, Biochemistry, and radiology).&#x0D; Cholecystectomy was done by using Laparoscopic cholecystectomy or open surgery.&#x0D; The presence of H.pylori in the mucosa of excised gallbladder was studied by using:&#x0D; 1) Rapid urease kit (HNAN C., LTD)&#x0D; 2) Histopathology &amp; chemical analysis of associated gallstone&#x0D; Results: Seventy-eight patients undergoing cholecystectomy for symptomatic gallbladder disease, the gallbladder mucosa of 30 patients were tested positive for H. pylori with any one of the tests used in this study. The rapid urease test was sensitive 57.1% and specific 58.3 % of the cholecystectomies performed in our study. The mean age of studied patients was (34 ± 4 years). Females constitute 73.1% (57 out of the total 78 of patients). Of the studied cases; 26 patients (33.3%) were obese. Employee patients constitute 43 (55.1%) of patients, and 53 patients (67.9%) lived in urban areas. Purified water consumed by 61 (78.2%) of the studied population.&#x0D; Gallstones were detected in 56 (71.8%) of studied cases, acalculus chronically inflamed gallbladder was found in 20 (25.64%), and 2 cases (2.56%). were found to have gallbladder polyp. pylori infection was diagnosed in 30 (38.5%) of total cases (of the 56 calculus confirmed cases 48.2% were H.pylori positive, and of the 22 acalculus cases 13.6% H.pylori positive).&#x0D; Conclusion:&#x0D; Significant association is found between chronic calculus cholecystitis and H.pylori infection. While no significant association was found in correlation with acalculus cholecystitis and other gallbladder pathology. In regard to feasibility of using urease kit test, it is found that this test is sensitive 57.1%, and specific 58.3%, as such it is less accurate than histopathology study. Significant correlation was found between age, gender, weight status, and non-purified water source with H.pylori infection..

Comparison of Microbiological Characteristics and Genetic Diversity between Burkholderia cepacia Complex Isolates from Vascular Access and Other Clinical Infections.

Burkholderia cepacia complex (BCC) is a group of closely related bacteria with widespread environmental distribution. BCC bacteria are opportunistic pathogens that cause nosocomial infections in patients, especially cystic fibrosis (CF). Multilocus sequence typing (MLST) is used nowadays to differentiate species within the BCC complex. This study collected 41 BCC isolates from vascular access infections (VAIs) and other clinical infections between 2014 and 2020. We preliminarily identified bacterial isolates using standard biochemical procedures and further conducted recA gene sequencing and MLST for species identification. We determined genetic diversity indices using bioinformatics software. We studied 14 isolates retrieved from patients with VAIs and observed that Burkholderia cepacia was the predominant bacterial species, and B. contaminans followed by B. cenocepacia were mainly retrieved from patients with other infections. According to MLST data, we identified that all B. contaminans isolates belonged to ST102, while a wide variety of sequence types (STs) were found in B. cenocepacia isolates. In summary, the high diversity and easy transmission of BCC increase BCC infections, which provides insights into their potential clinical effects in non-CF infections.

Comparative genomics with a multidrug-resistant Klebsiella pneumoniae isolate reveals the panorama of unexplored diversity in Northeast Brazil.

The emergence of community acquired infections increases the public health concern on K. pneumoniae and closely related bacteria among which antimicrobial resistance spreads. We report a multidrug-resistant K. pneumoniae isolate, B31, of a patient infected in the community and admitted to an intensive care unit in Northeast Brazil. Antimicrobial susceptibility and genome information were thoroughly investigated to characterize B31 in front of 172 sequenced strains of different countries. Assigned to the Sequence Type 15, which is globally spread, B31 presented extended spectrum beta-lactamase, tigecycline and ciprofloxacin resistance. Genome sequencing revealed most resistance genes being carried by plasmids with high dissemination potential. The absence of main virulence factors, like yersiniabactin and colibactin, apparently suggests a mild pathogenic strain which, on the contrary, persisted and caused severe infection in a previously healthy patient. The present study contributes to unveil the unclear genomic scenario of virulent and multidrug-resistant K. pneumoniae in Brazil.

A conserved arginine residue in a staphylococcal anti-sigma factor is required to preserve its kinase activity, structure, and stability

RsbW, σB, and RsbV, encoded by Staphylococcus aureus and related bacteria, act as an anti-sigma factor, an sigma factor, and an anti-anti-sigma factor, respectively. The interaction between RsbW and σB blocks the transcription initiation activity of the latter protein. RsbW also functions as a serine kinase and phosphorylates RsbV in the presence of ATP. Our modeling study indicates that the RsbW-RsbV complex is stabilized by twenty-four intermolecular non-covalent bonds. Of the bond-forming RsbW residues, Arg 23, and Glu 49 are conserved residues. To understand the roles of Arg 23 in RsbW, rRsbW[R23A], a recombinant S. aureus RsbW (rRsbW) harboring Arg to Ala change at position 23, was investigated using various probes. The results reveal that rRsbW[R23A], like rRsbW, exists as the dimers in the aqueous solution. However, rRsbW[R23A], unlike rRsbW, neither interacted with a chimeric RsbV (rRsbV) nor formed the phosphorylated rRsbV in the presence of ATP. Furthermore, the tertiary structure and hydrophobic surface area of rRsbW[R23A] matched little with those of rRsbW. Conversely, both rRsbW[R23A] and rRsbW showed interaction with a recombinant σB (rσB). rRsbW and rRsbW[R23A] were also unfolded via the formation of at least one intermediate in the presence of urea. However, the thermodynamic stability of rRsbW significantly differed from that of rRsbW[R23A]. Our molecular dynamics (MD) simulation study also reveals the substantial change of structure, dimension, and stability of RsbW due to the above mutation. The ways side chain of critical Arg 23 contributes to maintaining the tertiary structure, and stability of RsbW was elaborately discussed. Communicated by Ramaswamy H. Sarma

Microbiome-Mitochondria Communication in the Regulation of Host Longevity

Mitochondria are ancient relatives of bacteria in eukaryotic cells and dynamically interconnected through organelle fusion and fission. Given the close relationship between bacteria and eukaryotic mitochondria during evolution, my group is interested in understanding the critical role of their communication in regulating host’s longevity. We have conducted genome-scale screens to decipher how bacterial genetic composition impacts host longevity, leading to the discovery of specific bacteria-secreted metabolites that fine-tune the mitochondrial fusion-fission balance and consequently promotes longevity across different host species. We have further developed optogenetic approaches to manipulate bacterial gene expression and metabolite production inside the gut of live organisms, in order to investigate the microbiome-mitochondria communication in time and space. Our studies demonstrate a novel mode of signaling communication between bacteria and mitochondria, reveal its vital impacts on host healthy aging, and provide new methods to decipher the spatiotemporal relationship between the microbiome and the host.

Membrane insertion mechanism and molecular assembly of the bacteriophage lysis toxin ΦX174-E.

The bacteriophage ΦX174 causes large pore formation in Escherichiacoli and related bacteria. Lysis is mediated by the small membrane-bound toxin ΦX174-E, which is composed of a transmembrane domain and a soluble domain. The toxin requires activation by the bacterial chaperone SlyD and inhibits the cell wall precursor forming enzyme MraY. Bacterial cell wall biosynthesis is an important target for antibiotics; therefore, knowledge of molecular details in the ΦX174-E lysis pathway could help to identify new mechanisms and sites of action. In this study, cell-free expression and nanoparticle technology were combined to avoid toxic effects upon ΦX174-E synthesis, resulting in the efficient production of a functional full-length toxin and engineered derivatives. Pre-assembled nanodiscs were used to study ΦX174-E function in defined lipid environments and to analyze its membrane insertion mechanisms. The conformation of the soluble domain of ΦX174-E was identified as a central trigger for membrane insertion, as well as for the oligomeric assembly of the toxin. Stable complex formation of the soluble domain with SlyD is essential to keep nascent ΦX174-E in a conformation competent for membrane insertion. Once inserted into the membrane, ΦX174-E assembles into high-order complexes via its transmembrane domain and oligomerization depends on the presence of an essential proline residue at position 21. The data presented here support a model where an initial contact of the nascent ΦX174-E transmembrane domain with the peptidyl-prolyl isomerase domain of SlyD is essential to allow a subsequent stable interaction of SlyD with the ΦX174-E soluble domain for the generation of a membrane insertion competent toxin.

Metapangenomics of the oral microbiome provides insights into habitat adaptation and cultivar diversity

BackgroundThe increasing availability of microbial genomes and environmental shotgun metagenomes provides unprecedented access to the genomic differences within related bacteria. The human oral microbiome with its diverse habitats and abundant, relatively well-characterized microbial inhabitants presents an opportunity to investigate bacterial population structures at an ecosystem scale.ResultsHere, we employ a metapangenomic approach that combines public genomes with Human Microbiome Project (HMP) metagenomes to study the diversity of microbial residents of three oral habitats: tongue dorsum, buccal mucosa, and supragingival plaque. For two exemplar taxa, Haemophilus parainfluenzae and the genus Rothia, metapangenomes reveal distinct genomic groups based on shared genome content. H. parainfluenzae genomes separate into three distinct subgroups with differential abundance between oral habitats. Functional enrichment analyses identify an operon encoding oxaloacetate decarboxylase as diagnostic for the tongue-abundant subgroup. For the genus Rothia, grouping by shared genome content recapitulates species-level taxonomy and habitat preferences. However, while most R. mucilaginosa are restricted to the tongue as expected, two genomes represent a cryptic population of R. mucilaginosa in many buccal mucosa samples. For both H. parainfluenzae and the genus Rothia, we identify not only limitations in the ability of cultivated organisms to represent populations in their native environment, but also specifically which cultivar gene sequences are absent or ubiquitous.ConclusionsOur findings provide insights into population structure and biogeography in the mouth and form specific hypotheses about habitat adaptation. These results illustrate the power of combining metagenomes and pangenomes to investigate the ecology and evolution of bacteria across analytical scales.

Isolation and genomic characterization of the ibuprofen-degrading bacterium Sphingomonas strain MPO218.

The presence of pharmaceutical compounds in waters and soils is of particular concern because these compounds can be biologically active, even at environmental concentrations. Most pharmaceutical contaminants result from inefficient removal of these compounds during wastewater treatment. Although microorganisms able to biodegrade pharmaceuticals compounds have been described, the isolation and characterization of new bacterial strains capable of degrading drugs remain important to improve the removal of this pollutant. In this work, we describe the Sphingomonas wittichii strain MPO218 as able to use ibuprofen as the sole carbon and energy source. The genome of MPO218 consists of a circular chromosome and two circular plasmids. Our analysis shows that the largest plasmid, named pIBU218, is conjugative and can horizontally transfer the capability of growing on ibuprofen after conjugation with another related bacterium, Sphingopyxis granuli TFA. This plasmid appears to be unstable since it undergoes different deletions in absence of selection when growth on ibuprofen is not selected. This is the first described example of a natural and conjugative plasmid that enables growth on ibuprofen and is another example of how horizontal gene transfer plays a crucial role in the evolution of bacteria.

Genomic Characterization of a Novel Tenericutes Bacterium from Deep-Sea Holothurian Intestine.

Intestinal bacterial communities are highly relevant to the digestion, nutrition, growth, reproduction, and immunity of animals, but little is known about the composition and function of intestinal microbiota in deep-sea invertebrates. In this study, the intestinal microbiota of six holothurian Molpadia musculus were investigated, showing that their midguts were predominantly occupied by Izemoplasmatales bacteria. Using metagenomic sequencing, a draft genome of 1,822,181 bp was successfully recovered. After comparison with phylogenetically related bacteria, genes involved in saccharide usage and de novo nucleotide biosynthesis were reduced. However, a set of genes responsible for extracellular nucleoside utilization and 14 of 20 amino acid synthesis pathways were completely retained. Under oligotrophic condition, the gut-associated bacterium may make use of extracellular DNA for carbon and energy supplement, and may provide essential amino acids to the host. The clustered regularly interspaced short palindromic repeat (CRISPR) and restriction–modification (RM) systems presented in the genome may provide protection against invading viruses. A linear azol(in)e-containing peptide gene cluster for bacteriocin synthesize was also identified, which may inhibit the colonization and growth of harmful bacteria. Known virulence factors were not found by database searching. On the basis of its phylogenetic position and metabolic characteristics, we proposed that the bacterium represented a novel genus and a novel family within the Izemoplasmatales order and suggested it be named “Candidatus Bathyoplasma sp. NZ”. This was the first time describing host-associated Izemoplasmatales.

Structure and Function of N-Acetylmannosamine Kinases from Pathogenic Bacteria.

Several pathogenic bacteria import and catabolize sialic acids as a source of carbon and nitrogen. Within the sialic acid catabolic pathway, the enzyme N-acetylmannosamine kinase (NanK) catalyzes the phosphorylation of N-acetylmannosamine to N-acetylmannosamine-6-phosphate. This kinase belongs to the ROK superfamily of enzymes, which generally contain a conserved zinc-finger (ZnF) motif that is important for their structure and function. Previous structural studies have shown that the ZnF motif is absent in NanK of Fusobacterium nucleatum (Fn-NanK), a Gram-negative bacterium that causes the gum disease gingivitis. However, the effect in loss of the ZnF motif on the kinase activity is unknown. Using kinetic and thermodynamic studies, we have studied the functional properties of Fn-NanK to its substrates ManNAc and ATP, compared its activity with other ZnF motif-containing NanK enzymes from closely related Gram-negative pathogenic bacteria Haemophilus influenzae (Hi-NanK), Pasteurella multocida (Pm-NanK), and Vibrio cholerae (Vc-NanK). Our studies show a 10-fold decrease in substrate binding affinity between Fn-NanK (apparent KM ≈ 700 μM) and ZnF motif-containing NanKs (apparent KM ≈ 60 μM). To understand the structural features that combat the loss of the ZnF motif in Fn-NanK, we solved the crystal structures of functionally homologous ZnF motif-containing NanKs from P. multocida and H. influenzae. Here, we report Pm-NanK:unliganded, Pm-NanK:AMPPNP, Pm-NanK:ManNAc, Hi-NanK:ManNAc, and Hi-NanK:ManNAc-6P:ADP crystal structures. Structural comparisons of Fn-NanK with Hi-NanK, Pm-NanK, and hMNK (human N-acetylmannosamine kinase domain of UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase, GNE) show that even though there is less sequence identity, they have high degree of structural similarity. Furthermore, our structural analyses highlight that the ZnF motif of Fn-NanK is substituted by a set of hydrophobic residues, which forms a hydrophobic cluster that helps the proper orientation of ManNac in the active site. In summary, ZnF-containing and ZnF-lacking NanK enzymes from different Gram-negative pathogenic bacteria are functionally very similar but differ in their metal requirement. Our structural studies unveil the structural modifications in Fn-NanK that compensate the loss of the ZnF motif in comparison to other NanK enzymes.

The Effect of Ambient Temperature on Infectious Diarrhea and Diarrhea-like Illness in Wuxi, China.

The disease burden of infectious diarrhea cannot be underestimated. Its seasonal patterns indicate that weather patterns may play an important role and have an important effect on it. The objective of this study was to clarify the relationship between temperature and infectious diarrhea, and diarrhea-like illness. Distributed lag non-linear model, which was based on the definition of a cross-basis, was used to examine the effect. Viral diarrhea usually had high incidence in autumn-winter and spring with a peak at -6°C; Norovirus circulated throughout the year with an insignificant peak at 8°C, while related bacteria usually tested positive in summer and peaked at 22°C. The lag-response curve of the proportion of diarrhea-like cases in outpatient and emergency cases revealed that at -6°C, with the lag days increasing, the proportion increased. Similar phenomena were observed at the beginning of the curves of virus and bacterial positive rate, showing that the risk increased as the lag days increased, peaking on days 16 and 9, respectively. The shape of lag-response curve of norovirus positive rate was different from others, presenting m-type, with 2 peaks on day 3 and day 18. Weather patterns should be taken into account when developing surveillance programs and formulating relevant public health intervention strategies.