Biology subjects

Zlitni, S.

Publications and source records attributed to Zlitni, S..

5 recordsLinked to original sources

bioRxiv2025

A conserved sRNA regulates mucin adhesion and gut colonization across the Enterococcaceae

Enterococci, particularly E. faecalis, can survive in diverse settings within and outside human hosts. The capacity of E. faecalis to colonize these locations relies on its ability to adapt by altering gene expression in response to environmental exposures. One mechanism for quickly altering gene expression is through regulation by small noncoding RNAs (sRNAs); sRNAs can regulate one or many target genes and either up- or down-regulate transcript stability and protein expression. While many sRNAs have been predicted in E. faecalis, few have experimentally established target mRNAs or physiological functions. Here, we investigate the targets, function, and mechanism of Enterococcus sRNA 84. We found that sRNA 84 is conserved within the family Enterococcaceae, suggesting that it plays a role in the regulation of core genes and functions. RNA sequencing and proteomic analysis revealed that the absence of sRNA 84 led to downregulation of many cell surface proteins, including mucin-binding proteins. Consistent with these findings, an sRNA 84 knockout strain had reduced binding to mucin in vitro and impaired intestinal colonization of specific-pathogen-free mice. Taken together, these data support a model whereby sRNA 84 upregulates cell surface adhesins, which subsequently facilitate host colonization through binding to mucin. sRNA 84 is one of the first sRNAs in enterococci with demonstrated targets and function. This finding establishes the conserved sRNA 84 as a potential key regulator of enterococcal host adaptation, providing insight into how these organisms adapt their gene expression to survive both within and outside animal hosts.

microbiology↗

bioRxiv2024

Dual quorum-sensing control of purine biosynthesis drives pathogenic fitness of Enterococcus faecalis

Enterococcus faecalis is a resident of the human gut, though upon translocation to the blood or body tissues, it can be pathogenic. Here we discover and characterize two peptide-based quorum-sensing systems that transcriptionally modulate de novo purine biosynthesis in E. faecalis. Using a comparative genomic analysis, we find that most enterococcal species do not encode this system; E. moraviensis, E. haemoperoxidus and E. caccae, three species that are closely related to E. faecalis, encode one of the two systems, and only E. faecalis encodes both systems. We show that these systems are important for the intracellular survival of E. faecalis within macrophages and for the fitness of E. faecalis in a murine wound infection model. Taken together, we combine comparative genomics, microbiological, bacterial genetics, transcriptomics, targeted proteomics and animal model experiments to describe a paired quorum sensing mechanism that directly influences central metabolism and impacts the pathogenicity of E. faecalis.

microbiology↗

bioRxiv2023

Tomato brown rugose fruit virus Mo gene is a novel microbial source tracking marker

Microbial source tracking (MST) identifies sources of fecal contamination in the environment using fecal host-associated markers. While there are numerous bacterial MST markers, there are few viral markers. Here we design and test novel viral MST markers based on tomato brown rugose fruit virus (ToBRFV) genomes. We assembled eight nearly complete genomes of ToBRFV from wastewater and stool samples from the San Francisco Bay Area in the United States of America. Next, we developed two novel probe-based RT-PCR assays based on conserved regions of the ToBRFV genome, and tested the markers sensitivities and specificities using human and non-human animal stool as well as wastewater. TheToBRFV markers are sensitive and specific; in human stool and wastewater, they are more prevalent and abundant than a currently used marker, the pepper mild mottle virus (PMMoV) coat protein (CP) gene. We applied the assays to detect fecal contamination in urban stormwater samples and found that the ToBRFV markers matched cross-assembly phage (crAssphage), an established viral MST marker, in prevalence across samples. Taken together, ToBRFV is a promising viral human-associated MST marker. ImportanceHuman exposure to fecal contamination in the environment can cause transmission of infectious diseases. Microbial source tracking (MST) can identify sources of fecal contamination so that contamination can be remediated and human exposures can be reduced. MST requires the use of fecal host-associated MST markers. Here we design and test novel MST markers from genomes of tomato brown rugose fruit virus (ToBRFV). The markers are sensitive and specific to human stool, and highly abundant in human stool and wastewater samples.

microbiology↗

bioRxiv2022

Metabolic diversity in commensal protists regulates intestinal immunity and trans-kingdom competition

The microbiota influences intestinal health and physiology, yet the contributions of commensal protists to the gut environment have been largely overlooked. Here, we identified several new rodent- and human-associated parabasalid protists. Genomic and metabolomic analyses of murine parabasalids from the genus Tritrichomonas revealed species-level differences in the excretion of the metabolite succinate. This metabolic dissimilarity results in distinct small intestinal immune responses during protist colonization. Metabolic differences between Tritrichomonas species also determine their ecological niche within the microbiota. By manipulating dietary fibers and developing in vitro protist culture, we show that different parabasalid species preferentially rely on dietary polysaccharides or mucus glycans. These polysaccharide preferences create trans-kingdom competition with specific commensal bacteria, which affects intestinal immunity in a diet-dependent manner. Our findings reveal unappreciated diversity in commensal parabasalids, elucidate differences in commensal protist metabolism, and suggest how dietary interventions could regulate their impact on gut health.

microbiology↗

bioRxiv2020

Gut microbiota impairs insulin clearance during obesity

Hyperinsulinemia can be a cause and consequence of obesity and insulin resistance. Increased insulin secretion and reduced insulin clearance can contribute to hyperinsulinemia. The triggers for changes in insulin clearance during obesity are ill-defined. We found that oral antibiotics mitigated impaired insulin clearance in mice fed a high fat diet (HFD) for 12 weeks or longer. Short-term HFD feeding and aging did not alter insulin clearance in mice. Germ-free mice colonized with microbes from HFD-fed mice had impaired insulin clearance, but not C-peptide clearance, and only after mice were colonized for 6 weeks and then HFD-fed. Five bacterial taxa predicted >90% of the variance in insulin clearance. Our data indicate that gut microbes are an independent and transmissible factor that regulates obesity-induced changes in insulin clearance. A small cluster of microbes may be a target for mitigating defects in insulin clearance and the progression of obesity and Type 2 Diabetes. We propose that a small community in the gut microbiota can impair insulin clearance and increase insulin load and the risk of complications from hyperinsulinemia.

physiology↗