Characterization of Monospecies Biofilm Formation by Helicobacter pylori

Abstract

As all bacteria studied to date, the gastric pathogen Helicobacter pylori has an alternate lifestyle as a biofilm. H. pylori forms biofilms on glass surfaces at the air-liquid interface in stationary or shaking batch cultures. By light microscopy, we have observed attachment of individual, spiral H. pylori to glass surfaces, followed by division to form microcolonies, merging of individual microcolonies, and growth in the third dimension. Scanning electron micrographs showed H. pylori arranged in a matrix on the glass with channels for nutrient flow, typical of other bacterial biofilms. To understand the importance of biofilms to the H. pylori life cycle, we tested the effect of mucin on biofilm formation. Our results showed that 10% mucin greatly increased the number of planktonic H. pylori while not affecting biofilm bacteria, resulting in a decline in percent adherence to the glass. This suggests that in the mucus-rich stomach, H. pylori planktonic growth is favored over biofilm formation. We also investigated the effect of specific mutations in several genes, including the quorum-sensing gene, luxS, and the cagE type IV secretion gene. Both of these mutants were found to form biofilms approximately twofold more efficiently than the wild type in both assays. These results indicate the relative importance of these genes to the production of biofilms by H. pylori and the selective enhancement of planktonic growth in the presence of gastric mucin.Helicobacter pylori, the primary etiological agent of gastritis, colonizes both the surface of gastric epithelial cells and the mucus gel layer. However, several recent studies have also identified H. pylori in water distribution systems (18,29,34,38), surface wells or groundwater (16), rivers (11), and wastewater systems (17,25,29,30) in several countries. In addition, H. pylori has been found existing on the inner surface of water storage earthenware in Gambia (3). While the mechanism of transmission of H. pylori is thought to be primarily by the fecal-oral route, the possibility that it may exist as a biofilm (most likely mixed species) on surfaces exposed to water may provide another route of infection.Biofilms have been intensively studied as communities of bacteria able to survive in environments unfavorable to planktonic (free-living) bacteria (7,24). In response to quorumsensing signals, bacteria migrate and adhere to a surface, divide to form microcolonies, and expand laterally and vertically (8,40,48). Channels are formed in the biofilm to allow nutrients to reach bottom layers of bacteria. The mature biofilm is more resistant to killing by biocides and antibiotics, presumably due to the differentiation and survival of persister cells or slow growth rate (42). To further expand, sections of the biofilm shear off for colonization elsewhere (6).Two studies have alluded to the ability of H. pylori to form a biofilm. A polysaccharide-containing biofilm has been observed at the air-liquid interface when H. pylori is grown in a glass fermenter (43). H. pylori is als...

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…In E. coli O157:H7, indole has the opposite effect of reducing attachment to both abiotic surfaces and epithelial cells (8). While mucin is thought to enhance P. aeruginosa attachment and biofilm formation in the lungs (88), it serves to promote planktonic growth of Helicobacter pylori within the stomach environment (25). Observations such as these underscore the importance of extracellular cues in driving attachment but also caution against making generalizing conclusions regarding the universal impact of particular environmental conditions on adherence capabilities of various bacterial species.…”

Quorum sensing dependent phenotypes and their molecular mechanisms inCampylobacterales

“…It seems that H. pylori favours planktonic growth over biofilm formation in the mucous-rich stomach. The luxS mutant strains of H. pylori SD14 and SD3 showed two-to threefold increased biofilm formation as compared to their wild type strains [50]. These data show that a luxS mutant alters biofilm formation in both C. jejuni and H. pylori strains but with opposite outcome.…”

A proposed role for diffusible signal factors in the biofilm formation and morphological transformation of Helicobacter pylori

“…These authors have thus suggested the ability of H. pylori to produce self-inhibiting substances with bacteriostatic activity. It appears, however, that the effect of the apparent inhibition of the bacteria was due to the transition of the microorganisms into the VBNC state, which in the case of H. pylori is connected with spiral-to-coccoid transformation (9,10,14,22,33). Cis-2-tetradecenic acid (C 14 :Δ 2 ), which is produced by X. fastidiosa, is responsible for biofilm formation and autoaggregative behavior associated with the increased synthesis of hemagglutinin-like HxfA/B proteins.…”

“…The altered phenotype and transcription of these genes was restored by the exogenous addition of AI-2 or 4,5-dihydroxy-2,3-pentandione (DPD, an AI-2 precursor) to the culture medium or by complementing the luxS gene. The experiment conducted by Cole et al (33) showed that H. pylori luxS mutants have the ability to grow in a similar manner as wild-type strains, i.e. there were no defects in adhesion, formation of microcolonies or spatial biofilm structure, or in physiological transition of bacteria from the spiral to the coccoid form.…”