Biology subjects

Hathroubi, S.

Publications and source records attributed to Hathroubi, S..

3 recordsLinked to original sources

bioRxiv2026

The Helicobacter pylori ribosomal silencing factor RsfS is required for low-growth states and chronic infection

Helicobacter pylori is a prevalent bacterial pathogen that chronically colonizes the human gastric epithelium, but the bacteriums physiological mechanisms that promote this are understudied. Dormancy and low growth are known to facilitate other microbial chronic infections. A critical feature of low growth states is the down regulation of ribosome translational activity via regulation factors. The H. pylori genome is predicted to encode only one ribosome regulation factor, called RsfS (Ribosomal Silencing Factor S). In other bacterial species, RsfS prevents ribosome assembly by binding to a protein called L14 on the 50S large ribosomal subunit. Although H. pylori RsfS has not been experimentally investigated prior to this work, it conserves key residues, suggesting it is a bona fide RsfS homolog. To investigate phenotypes associated with rsfS, the gene was deleted and mutant phenotypes characterized. H. pylori rsfS null mutants had no defects during exponential phase but had viability defects in stationary phase and low growth factor conditions. Additionally, rsfS null mutants could not form biofilms, and instead were only able to form monolayers of multicellular aggregates. These defects were corrected by the re-introduction of rsfS in a second site on the chromosome. To explore whether rsfS is required in vivo, a mouse model was employed. rsfS mutants initially colonized in low numbers in both the glands and total stomach but were unable to develop robust long-term colonization. This work supports that H. pylori requires RsfS for survival in low growth states and to maintain chronic infections in the host. ImportanceH. pylori chronic infections are difficult to cure in part because H. pylori is proposed to adopt low-growth states known to render bacteria tolerant to antibiotics. One key signature of a low growth state includes low translation via ribosome regulation factors. Unlike other bacterial species, H. pylori contain only one known ribosome regulation factor called Ribosomal Silencing Factor S (RsfS). This gene was previously found to be transcriptionally upregulated in at least one low growth state, biofilms. In this work, we found that H. pylori rsfS is required for this microbe to thrive in low growth states and during infection. This study is one of only two studies that investigates the phenotypes of rsfS knockout mutants in any bacterial species and the first to address knowledge gaps in ribosomal regulation by H. pylori in vivo.

microbiology↗

bioRxiv2019

Helicobacter pylori biofilm cells are metabolically distinct, express flagella, and antibiotic tolerant

Biofilm growth protects bacteria against harsh environments, antimicrobials, and immune responses. Helicobacter pylori is a bacterium that has a robust ability to maintain colonization in a challenging environment. Over the last decade, H. pylori biofilm formation has begun to be characterized, however, there are still gaps in our understanding about how this growth mode is defined and its impact on H. pylori physiology. To provide insights into H. pylori biofilm growth properties, we characterized the antibiotic susceptibility, gene expression, and genes required for biofilm formation of a strong biofilm-producing H. pylori. H. pylori biofilms developed complex 3D structures and were recalcitrant to multiple antibiotics. Disruption of the protein-based matrix decreased this antibiotic tolerance. Using both transcriptomic and genomic approaches, we discovered that biofilm cells demonstrated lower transcripts for TCA cycle enzymes but higher ones for hydrogenase and acetone metabolism. Interestingly, several genes encoding for the natural competence Type IV secretion system 4 (tfs4) were up-regulated during biofilm formation along with several genes encoding for restriction-modification (R-M) systems, suggesting DNA exchange activities in this mode of growth. Flagella genes were also discovered through both approaches, consistent with previous reports about the importance of these filaments in H. pylori biofilm. Together, these data suggest that H. pylori is capable of adjusting its phenotype when grown as biofilm, changing its metabolism and elevating specific surface proteins including those encoding tfs4 and flagella.

microbiology↗

bioRxiv2018

The Helicobacter pylori biofilm involves a multi-gene stress-biased response including a structural role for flagella

Helicobacter pylori has an impressive ability to persist chronically in the human stomach. Similar characteristics are associated with biofilm formation in other bacteria. The H. pylori biofilm process, however, is poorly understood. To gain insight into this mode of growth, we carried out comparative transcriptomic analysis between H. pylori biofilm and planktonic cells, using the mouse colonizing strain SS1. Optimal biofilm formation was obtained with low serum and three-day growth, conditions which caused both biofilm and planktonic cells to be [~]80% coccoid. RNA-seq analysis found that 8.18% of genes were differentially expressed between biofilm and planktonic cell transcriptomes. Biofilm-downregulated genes included those involved in metabolism and translation, suggesting these cells have low metabolic activity. Biofilm-upregulated genes included those whose products were predicted to be at the cell envelope, involved in regulating a stress response, and surprisingly, genes related to formation of the flagellar apparatus. Scanning electron microscopy visualized flagella that appeared to be a component of the biofilm matrix, supported by the observation that an aflagellated mutant displayed a less robust biofilm with no apparent filaments. We observed flagella in the biofilm matrix of additional H. pylori strains, supporting that flagellar use is widespread. Our data thus supports a model in which H. pylori biofilm involves a multi-gene stress-biased response, and that flagella play an important role in H. pylori biofilm formation.\n\nIMPORTANCEBiofilms, communities of bacteria that are embedded in a hydrated matrix of extracellular polymeric substances, pose a substantial health risk and are key contributors to many chronic and recurrent infections. Chronicity and recalcitrant infections are also common features associated with the ulcer-causing human pathogen H. pylori. However, relatively little is known about the role of biofilms in H. pylori pathogenesis as well as the biofilm structure itself and the genes associated with this mode of growth. In the present study, we found that H. pylori biofilm cells highly expressed genes related to cell envelope, stress response and those encoding the flagellar apparatus. Flagellar filaments were seen in high abundance in the biofilm. Flagella are known to play a role in initial biofilm formation, but typically are downregulated after that state. H. pylori instead appears to have co-opted these structures for non-motility roles, including a role building a robust biofilm.

microbiology↗