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Role of amoebae for survival and recovery of 'non-culturable' Helicobacter pylori cells in aquatic environments.

ABSTRACT: Helicobacter pylori is a fastidious Gram-negative bacterium that infects over half of the world's population, causing chronic gastritis and is a risk factor for stomach cancer. In developing and rural regions where prevalence rate exceeds 60%, persistence and waterborne transmission are often linked to poor sanitation conditions. Here we demonstrate that H. pylori not only survives but also replicates within acidified free-living amoebal phagosomes. Bacterial counts of the clinical isolate H. pylori G27 increased over 50-fold after three days in co-culture with amoebae. In contrast, a H. pylori mutant deficient in a cagPAI gene (cagE) showed little growth within amoebae, demonstrating the likely importance of a type IV secretion system in H. pylori for amoebal infection. We also demonstrate that H. pylori can be packaged by amoebae and released in extracellular vesicles. Furthermore, and for the first time, we successfully demonstrate the ability of two free-living amoebae to revert and recover viable but non-cultivable coccoid (VBNC)-H. pylori to a culturable state. Our studies provide evidence to support the hypothesis that amoebae and perhaps other free-living protozoa contribute to the replication and persistence of human-pathogenic H. pylori by providing a protected intracellular microenvironment for this pathogen to persist in natural aquatic environments and engineered water systems, thereby H. pylori potentially uses amoeba as a carrier and a vector of transmission.

SUBMITTER: Dey R

PROVIDER: S-EPMC7494403 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Role of amoebae for survival and recovery of 'non-culturable' Helicobacter pylori cells in aquatic environments.

Dey Rafik R Rieger Aja A Banting Graham G Ashbolt Nicholas J NJ

FEMS microbiology ecology 20201001 10

Helicobacter pylori is a fastidious Gram-negative bacterium that infects over half of the world's population, causing chronic gastritis and is a risk factor for stomach cancer. In developing and rural regions where prevalence rate exceeds 60%, persistence and waterborne transmission are often linked to poor sanitation conditions. Here we demonstrate that H. pylori not only survives but also replicates within acidified free-living amoebal phagosomes. Bacterial counts of the clinical isolate H. py ...[more]

PMID: 32897313

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Project description:The well-studied catalytic role of urease, the Ni-dependent conversion of urea into carbon dioxide and ammonia, has been shown to protect Helicobacter pylori against the low pH environment of the stomach lumen. We hypothesized that the abundantly expressed urease protein can play another noncatalytic role in combating oxidative stress via Met residue-mediated quenching of harmful oxidants. Three catalytically inactive urease mutant strains were constructed by single substitutions of Ni binding residues. The mutant versions synthesize normal levels of urease, and the altered versions retained all methionine residues. The three site-directed urease mutants were able to better withstand a hypochlorous acid (HOCl) challenge than a ?ureAB deletion strain. The capacity of purified urease to protect whole cells via oxidant quenching was assessed by adding urease enzyme to nongrowing HOCl-exposed cells. No wild-type cells were recovered with oxidant alone, whereas urease addition significantly aided viability. These results suggest that urease can protect H. pylori against oxidative damage and that the protective ability is distinct from the well-characterized catalytic role. To determine the capability of methionine sulfoxide reductase (Msr) to reduce oxidized Met residues in urease, purified H. pylori urease was exposed to HOCl and a previously described Msr peptide repair mixture was added. Of the 25 methionine residues in urease, 11 were subject to both oxidation and to Msr-mediated repair, as identified by mass spectrometry (MS) analysis; therefore, the oxidant-quenchable Met pool comprising urease can be recycled by the Msr repair system. Noncatalytic urease appears to play an important role in oxidant protection.IMPORTANCE Chronic Helicobacter pylori infection can lead to gastric ulcers and gastric cancers. The enzyme urease contributes to the survival of the bacterium in the harsh environment of the stomach by increasing the local pH. In addition to combating acid, H. pylori must survive host-produced reactive oxygen species to persist in the gastric mucosa. We describe a cyclic amino acid-based antioxidant role of urease, whereby oxidized methionine residues can be recycled by methionine sulfoxide reductase to again quench oxidants. This work expands our understanding of the role of an already acknowledged pathogen virulence factor and specifically expands our knowledge of H. pylori survival mechanisms.

Dataset Information

Role of amoebae for survival and recovery of 'non-culturable' Helicobacter pylori cells in aquatic environments.

Publications

Role of amoebae for survival and recovery of 'non-culturable' Helicobacter pylori cells in aquatic environments.

Similar Datasets

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