Biology subjects

Chakraborty, B.

Publications and source records attributed to Chakraborty, B..

3 recordsLinked to original sources

bioRxiv2018

Species Designations Belie Phenotypic and Genotypic Heterogeneity in Oral Streptococci

Health-associated oral Streptococcus species are promising probiotic candidates to protect against dental caries. Ammonia production through the arginine deiminase system (ADS), which can increase the pH of oral biofilms, and direct antagonism of caries-associated bacterial species are desirable properties for oral probiotic strains. ADS and antagonistic activities can vary dramatically among individuals, but the genetic basis for these differences is unknown. We sequenced whole genomes of a diverse set of clinical oral Streptococcus isolates and examined the genetic basis of variability in ADS and antagonistic activities. A total of 113 isolates were included and represented ten species: S. australis, A12-like, S. cristatus, S. gordonii, S. intermedius, S. mitis, S. oralis including S. oralis subsp. dentisani, S. parasanguinis, S. salivarius, and S. sanguinis. Mean ADS activity and antagonism on Streptococcus mutans UA159 were measured for each isolate, and each isolate was whole genome-shotgun sequenced on an Illumina MiSeq. Phylogenies were built of genes known to be involved in ADS activity and antagonism. Several approaches to correlate the pan-genome with phenotypes were performed. Phylogenies of genes previously identified in ADS activity and antagonism grouped isolates by species but not by phenotype. GWAS identified additional genes potentially involved in ADS activity or antagonism across all the isolates we sequenced as well as within several species. Phenotypic heterogeneity in oral streptococci is not necessarily reflected by genotype and is not species-specific. Probiotic strains must be carefully selected based on characterization of each strain, and not based on inclusion within a certain species.\n\nImportanceRepresentative type strains are commonly used to characterize bacterial species, yet species are phenotypically and genotypically heterogeneous. Conclusions about strain physiology and activity based on a single strain therefore may be inappropriate and misleading. When selecting strains for probiotic use, the assumption that all strains within a species share the same desired probiotic characteristics share those characteristics may result in selection of a strain that lacks the desired traits, and therefore makes a minimally effective or ineffective probiotic. Health-associated oral streptococci are promising candidates for anti-caries probiotics, but strains need to be carefully selected based on observed phenotypes. We characterized the genotype and anti-caries phenotypes of strains from ten species of oral Streptococci and demonstrate poor correlation between genotype and phenotype across all species.

microbiology↗

bioRxiv2017

Systemic Inflammation Mediates the Relationship between Obesity and Health Related Quality of Life

BackgroundAt the population level, obesity has been reported to be positively associated with low-level chronic inflammation, and negatively associated with several indices of health-related quality of life (HRQOL). It is however not clear if obesity-associated inflammation is partly responsible for the observed negative associations between obesity and HRQOL. The present study investigates this question by testing the hypothesis that systemic inflammation is a mediator of the observed association between obesity and a specific HRQOL index called \"healthy days\", as measured via a subset of the CDC HRQOL-4 questionnaire.\n\nMethodsDemographic, body mass index (BMI), C-reactive protein (CRP), inflammatory disease status, medication use, smoking, and HRQOL data were obtained from NHANES (2005-2008) and analyzed using sampling-weighted generalized linear models. Both main effects and interaction effects were analyzed to evaluate possible mediator-outcome confounding. Model robustness was tested via sensitivity analysis. Prior to model development, data was subjected to multiple imputation in order to mitigate information loss from survey non-response. Averaged results from the imputed datasets were reported in the form of odds ratios (OR) and confidence intervals (CI).\n\nResultsObesity (BMI >30kg/m2) was positively associated with poor physical healthy days (OR: 1.59, 95% CI: 1.15-2.21) in unadjusted models. Elevated and clinically raised levels of the inflammation marker CRP were also positively associated with poor physical healthy days (OR= 1.61, 95% CI: 1.23-2.12, and OR= 2.45, 95% CI: 1.84-3.26, respectively); additionally clinically raised CRP was positively associated with mental unhealthy days (OR= 1.66, 95% CI: 1.26-2.19). The association between obesity and physical HRQOL was rendered non-significant in models including CRP. Association between elevated and clinically raised CRP and physical unhealthy days remained significant even after adjustment for obesity or inflammation-modulating covariates (OR= 1.36, 95% CI :1.02-1.82, and OR= 1.75, 95% CI: 1.21-2.54, respectively).\n\nConclusionsSystemic inflammation is a significant mediator of the association between obesity and physical unhealthy days. and is also an independent determinant of physical and mental unhealthy days. Importantly, elevated inflammation below the clinical threshold is also negatively associated with physical healthy days and may warrant more attention from a population health perspective than currently appreciated.

epidemiology↗

bioRxiv2017

Electron microscopy reveals unique nano forms of bacterial spores

Endospore formation under environmental stress conditions is a well-established phenomenon for members of bacterial phylum Firmicutes, among which the most well studied ones belong to genus Bacillus and Clostridium. So far, known sizes of the spores are all larger than 500 nm. Nano-forms of bacteria have been reported but the notion still remains controversial. In this study, we provide visual evidences of living nano-entities (named here as nano-spores) formed by a bacterial species Bacillus cereus under prolonged stress, which are capable of escaping though standard sterile filtration procedure. The existence of nano-forms of bacteria was initially identified in a yeast ribosome preparation. We further demonstrate the transformation of the nano-spores into mature cells upon nutrient supply. Our study not only demonstrates the ability of bacteria to get transformed into yet-unknown form in order to survive under harsh environment, but also brings to light the existence of the smallest possible form of life.

microbiology↗