Helicobacter pylori Adaptation In Vivo in Response to a High-Salt Diet

Abstract

e Helicobacter pylori exhibits a high level of intraspecies genetic diversity. In this study, we investigated whether the diversification of H. pylori is influenced by the composition of the diet. Specifically, we investigated the effect of a high-salt diet (a known risk factor for gastric adenocarcinoma) on H. pylori diversification within a host. We analyzed H. pylori strains isolated from Mongolian gerbils fed either a high-salt diet or a regular diet for 4 months by proteomic and whole-genome sequencing methods. Compared to the input strain and output strains from animals fed a regular diet, the output strains from animals fed a highsalt diet produced higher levels of proteins involved in iron acquisition and oxidative-stress resistance. Several of these changes were attributable to a nonsynonymous mutation in fur (fur-R88H). Further experiments indicated that this mutation conferred increased resistance to high-salt conditions and oxidative stress. We propose a model in which a high-salt diet leads to high levels of gastric inflammation and associated oxidative stress in H. pylori-infected animals and that these conditions, along with the high intraluminal concentrations of sodium chloride, lead to selection of H. pylori strains that are most fit for growth in this environment. Helicobacter pylori is a Gram-negative bacterium that persistently colonizes the human stomach in half of the world's population (1, 2). H. pylori exhibits a high level of intraspecies genetic diversity, characterized by marked variation among strains in gene content, as well as a high level of variation in the nucleotide sequences of individual genes (3, 4). A high rate of allelic diversity is attributable to both a high mutation rate and intraspecies recombination (5, 6).Most H. pylori-infected persons remain asymptomatic, but the presence of this bacterium increases the risk of peptic ulcer disease and gastric cancer (1, 2, 7, 8). The clinical outcome of H. pylori infection is determined by a combination of bacterial, host, and environmental factors. For example, H. pylori strains containing the cag pathogenicity island (PAI) are associated with a higher risk of symptomatic disease than are strains that lack the cag PAI (9). One of the proteins encoded by the cag PAI, CagA, enters host cells and causes numerous cellular alterations linked to malignant transformation (10). The cag PAI also encodes multiple protein components of a type IV secretion system required for entry of CagA into host cells (11). H. pylori strains that secrete specific types of the VacA toxin are also linked to adverse disease outcome, in comparison to strains that secrete relatively nontoxic forms of the VacA protein (12, 13).One of the environmental factors associated with increased gastric cancer risk is a high-salt diet (14). Epidemiologic studies have demonstrated a link between high dietary salt consumption and increased gastric cancer risk in many parts of the world (15-17), and a high-salt diet also increases the gastric cancer risk in animal models (...

High-Salt Conditions Alter Transcription of Helicobacter pylori Genes Encoding Outer Membrane Proteins

“…The transcriptional changes described in this study presumably enhance the ability of the bacteria to tolerate these changes. In addition to short-term transcriptional alterations in response to changes in salt concentration, a recent study revealed proteomic and genomic changes in H. pylori strains isolated from Mongolian gerbils fed a high-salt diet for 4 months (56). Thus, high-salt stress can lead to the adaptation and selection of H. pylori strains with enhanced fitness for growth in a high-salt environment.…”

In VitroandIn VivoAntibacterial Activities of Patchouli Alcohol, a Naturally Occurring Tricyclic Sesquiterpene, against Helicobacter pylori Infection

“…Moreover, 3% salt was added to the drinking water to enhance H. pylori colonization (44,45). After 2 weeks, PCR, RUT, and bacterial culture experiments were carried out to examine the infection status of H. pylori.…”

Role of a Stem-Loop Structure in Helicobacter pylori cagA Transcript Stability

“…Mutagenesis of the ؉59 DNA motif in H. pylori strain PZ5056. To evaluate the effect of the ϩ59 DNA sequences on cagA expression, unmarked mutations were introduced upstream of the cagA open reading frame (ORF) using a previously described counterselection protocol involving a cat-rpsL cassette (41)(42)(43)(44). Briefly, streptomycin-resistant mutants were generated by transforming H. pylori strain PZ5056 with a nonreplicating plasmid containing a cloned H. pylori rpsL gene harboring a lysine-to-arginine mutation at codon 43 of rpsL (42,44).…”

“…To evaluate the effect of the ϩ59 DNA sequences on cagA expression, unmarked mutations were introduced upstream of the cagA open reading frame (ORF) using a previously described counterselection protocol involving a cat-rpsL cassette (41)(42)(43)(44). Briefly, streptomycin-resistant mutants were generated by transforming H. pylori strain PZ5056 with a nonreplicating plasmid containing a cloned H. pylori rpsL gene harboring a lysine-to-arginine mutation at codon 43 of rpsL (42,44). As a next step, the plasmid pcagA::cat-rpsL was generated by PCR amplification of a region extending from approximately 500 bp upstream of the cagA translational start site to 500 bp downstream of the cagA translational start site from H. pylori PZ5056 with primers 5=-GAAGCTGTCTTTGAAAATCTGTCC-3= and 5=-AATATCCAACCAATCCCCACCAG-3=.…”