A Vibrio cholerae protease needed for killing of Caenorhabditis elegans has a role in protection from natural predator grazing

Abstract

Vibrio cholerae is the causal bacterium of the diarrheal disease cholera, and its growth and survival are thought to be curtailed by bacteriovorous predators, e.g., ciliates and flagellates. We explored Caenorhabditis elegans as a test organism after finding that V. cholerae can cause lethal infection of this nematode. By reverse genetics we identified an extracellular protease, the previously uncharacterized PrtV protein, as being necessary for killing. The killing effect is associated with the colonization of bacteria within the Caenorhabditis elegans intestine. We also show that PrtV is essential for V. cholerae in the bacterial survival from grazing by the flagellate Cafeteria roenbergensis and the ciliate Tetrahymena pyriformis. The PrtV protein appears to have an indirect role in the interaction of V. cholerae with mammalian host cells as judged from tests with tight monolayers of human intestinal epithelial cells. Our results demonstrate a key role for PrtV in V. cholerae interaction with grazing predators, and we establish Caenorhabditis elegans as a convenient organism for identification of V. cholerae factors involved in host interactions and environmental persistence.cholera ͉ host interactions ͉ environmental persistence C holera continues to be a major public and individual health problem, especially in those regions of the world where it is endemic. Colwell (1) first hypothesized that coastal waters were an important reservoir of Vibrio cholerae. Huq et al. (2) reported that V. cholerae O1 cells could be observed to be attached to a variety of phytoplankton and zooplankton species. The incidence and severity of epidemics have been linked to salinity, water temperature, turbidity, and plankton blooms (3, 4). Cholera epidemics occur in a regular seasonal pattern. It has been suggested that during interepidemic periods V. cholerae exists in an unexplained ecological association with aquatic organisms (5). During the environmental phase, V. cholerae resides in diverse aquatic environments, often in association with marine plankton (6). The association of V. cholerae with zooplankton has proven to be a key factor in deciphering the global nature of cholera epidemics (7). In such natural bacterioplankton communities V. cholerae and other bacteria are also at the base of the pelagic microbial food web (8). Bacterial growth and survival are subject to constraint by bacteriovorous predators, e.g., protozoa such as ciliates and flagellates (9, 10). Little has been known about mechanisms and adaptations of bacteria to reduce grazing mortality compared with adaptations toward abiotic factors (substrate, temperature, pH, etc.) (11).V. cholerae expresses well characterized factors to establish and cause disease in the mammalian host, including cholera toxin (CT) and toxin-coregulated pili (Tcp). It has been shown that quorum sensing (QS) plays a role in the regulation of virulence in V. cholerae (12). At least three autoinducer signaling circuits function through the action of LuxO, leading to the repression of...

Comparative genomics of clinical and environmental Vibrio mimicus

“…VMP of VM223 and MB451 also showed significant similarity at both the nucleotide (80%) and amino acid level (88%) to HA/ protease of V. cholerae. Both genomes also contained homologs (VII_000021; VMA_001265) of the prtV protease of V. cholerae on C-II, which recently has been shown to be a virulence factor in a Caenorhabditis elegans model (31). In addition, they possessed a number of other homologs of proteases, including a membranebound zinc metalloprotease (VII_001591; VMA_002784), protease IV (VII_001833; VMA_002551), and htpX protease (VII_002671; VMA_001839).…”

Salt in Surroundings Influences the Production of Serine Protease into Milieu by Aeromonas sobria

“…For example, it is known that some proteases of Vibrio cholerae (31) and Pseudomoans fluorescens (11) are deeply involved in resistance to protozoan grazing. This may also be applicable to Aeromonas; that is, Aeromonas may be easily preyed upon by protozoa when protease production is stopped.…”

Genomic and proteomic analyses of the coral pathogen Vibrio coralliilyticus reveal a diverse virulence repertoire

“…This protein cleaves host antibacterial proteins. Homologs of the immune inhibitor A, named PrtV, have been found in V. cholerae and V. anguillarum (Vaitkevicius et al, 2006(Vaitkevicius et al, , 2008. PrtV is required for killing C. elegans and has a cytotoxic effect, leading to cell death.…”