A new understanding of Acanthamoeba castellanii: dispelling the role of bacterial pore-forming toxins in cyst formation and amoebicidal actions.

Pore-forming toxins (PFTs) are recognized as major virulence factors produced by both Gram-positive and Gram-negative bacteria. While the effects of PFTs have been extensively investigated using mammalian cells as a model system, their interactions with the environmental host, Acanthamoeba castellanii remains less understood. This study employed high-throughput image screening (HTI), advanced microscopy, western blot analysis, and cytotoxicity assays to evaluate the impact of PFT-producing bacterial species on their virulence against A.

MakC and MakD are two proteins associated with a tripartite toxin of .

Pathogenic serotypes of , transmitted through contaminated water and food, are responsible for outbreaks of cholera, an acute diarrheal disease. While the cholera toxin is the primary virulence factor, also expresses other virulence factors, such as the tripartite toxin MakABE that is secreted via the bacterial flagellum. These three proteins are co-expressed with two accessory proteins, MakC and MakD, whose functions remain unknown.

Bacterial protein MakA causes suppression of tumour cell proliferation via inhibition of PIP5K1α/Akt signalling.

Recently, we demonstrated that a novel bacterial cytotoxin, the protein MakA which is released by Vibrio cholerae, is a virulence factor, causing killing of Caenorhabditis elegans when the worms are grazing on the bacteria. Studies with mammalian cell cultures in vitro indicated that MakA could affect eukaryotic cell signalling pathways involved in lipid biosynthesis. MakA treatment of colon cancer cells in vitro caused inhibition of growth and loss of cell viability.

Protein-lipid interaction at low pH induces oligomerization of the MakA cytotoxin from .

The α-pore-forming toxins (α-PFTs) from pathogenic bacteria damage host cell membranes by pore formation. We demonstrate a remarkable, hitherto unknown mechanism by an α-PFT protein from . As part of the MakA/B/E tripartite toxin, MakA is involved in membrane pore formation similar to other α-PFTs.

A tripartite cytolytic toxin formed by proteins with flagellum-facilitated secretion.

The protein MakA was discovered as a motility-associated secreted toxin from Here, we show that MakA is part of a gene cluster encoding four additional proteins: MakB, MakC, MakD, and MakE. MakA, MakB, and MakE were readily detected in culture supernatants of wild-type , whereas secretion was very much reduced from a flagellum-deficient mutant. Crystal structures of MakA, MakB, and MakE revealed a structural relationship to a superfamily of bacterial pore-forming toxins.

Ecotin and LamB in Escherichia coli influence the susceptibility to Type VI secretion-mediated interbacterial competition and killing by Vibrio cholerae.

Background: A prevailing action of the Type VI secretion system (T6SS) in several Gram-negative bacterial species is inter-bacterial competition. In the past several years, many effectors of T6SS were identified in different bacterial species and their involvement in inter-bacterial interactions were described. However, possible defence mechanisms against T6SS attack among prey bacteria were not well clarified yet.

Phosphatidic acid-mediated binding and mammalian cell internalization of the Vibrio cholerae cytotoxin MakA.

Vibrio cholerae is a noninvasive intestinal pathogen extensively studied as the causative agent of the human disease cholera. Our recent work identified MakA as a potent virulence factor of V. cholerae in both Caenorhabditis elegans and zebrafish, prompting us to investigate the potential contribution of MakA to pathogenesis also in mammalian hosts.