Phase Variation in the Helicobacter pylori Phospholipase A Gene and Its Role in Acid Adaptation

Abstract

Previously, we have shown that Helicobacter pylori can spontaneously and reversibly change its membrane lipid composition, producing variants with low or high content of lysophospholipids. The "lyso" variant contains a high percentage of lysophospholipids, adheres better to epithelial cells, and releases more proteins such as urease and VacA, compared to the "normal" variant, which has a low content of lysophospholipids. Prolonged growth of the normal variant at pH 3.5, but not under neutral conditions, leads to enrichment of lyso variant colonies, suggesting that the colony switch is relevant to acid adaptation. In this study we show that the change in membrane lipid composition is due to phase variation in the pldA gene. A change in the (C) tract length of this gene results in reversible frameshifts, translation of a full-length or truncated pldA, and the production of active or inactive outer membrane phospholipase A (OMPLA). The role of OMPLA in determining the colony morphology was confirmed by the construction of an OMPLA-negative mutant. Furthermore, variants with an active OMPLA were able to survive acidic conditions better than variants with the inactive form. This explains why the lyso variant is selected at low pH. Our studies demonstrate that phase variation in the pldA gene, resulting in an active form of OMPLA, is important for survival under acidic conditions. We also demonstrated the active OMPLA genotype in fresh isolates of H. pylori from patients referred to gastroscopy for dyspepsia.

Identification of Campylobacter jejuni Genes Contributing to Acid Adaptation by Transcriptional Profiling and Genome-Wide Mutagenesis

“…The pldA gene encodes phospholipase A, an enzyme that can cleave membrane phospholipids to yield lysophospholipids (22). In H. pylori, the expression of active phospholipase A leads to the increased production of lysophospholipids and the improved acid stress survival of the strain (15,79). It therefore appears that pldA plays a role in the acid stress response of both H. pylori and C. jejuni.…”

The impact of parietal cells onHelicobacter pyloritropism and host pathology: An analysis using gnotobiotic normal and transgenic mice

“…The present study raises the question of what effects parietal cells and acid have on bacterial gene expression, and what bacterial genes are critical for entry into and persistence within host niches that are relatively devoid of acid. For example, the impact of acid on phase variation of genes involved in production of outer membrane proteins (43) and surface carbohydrate epitopes (44) could influence attachment (persistence), nutrient acquisition (growth), and the degree to which synthesized bacterial surface immunodeterminants are recognized as foreign by the host. In vitro studies have shown that acid regulates expression of both acid-resistance and virulence genes, including members of the organism's 31 gene cag pathogenicity island (cagA and cagE), vacuolating cytotoxin (vacA), wbcJ (homologous to bacterial O-antigen biosynthetic proteins; links lipopolysaccharide expression and acid survival), and urease (buffers the organism from acid) (5).…”

Characterization of a haemolytic phospholipase A2 activity in clinical isolates of Campylobacter concisus

“…Such enzymes include PLA in pathogens such as H. pylori (Dorrell et al, 1999;Tannaes et al, 2001;Xerry & Owen, 2001), Legionella species (Flieger et al, 2000), C. coli (Grant et al, 1997), Yersinia enterocolitica (Schmiel et al, 1998) and PLA 1 in Aeromonas species (Merino et al, 1999).…”