Journal of Microbiology

Research Support, Non-U.S. Gov't

NOTE] Comparative Assessment of the Intracellular Survival of the Burkholderia pseudomallei bopC Mutant: Varintip Srinon , Sunsiree Muangman , Nithima Imyaem , Veerachat Muangsombut , Natalie R. Lazar Adler , Edouard E. Galyov , Sunee Korbsrisate; J. Microbiol. 2013;51(4):522-526. Published online August 30, 2013; DOI: https://doi.org/10.1007/s12275-013-2557-3

Abstract: Burkholderia pseudomallei, the causative agent of melioidosis, is a Gram-negative saprophytic bacterium capable of surviving within phagocytic cells. To assess the role of BopC (a type III secreted effector protein) in the pathogenesis of B. pseudomallei, a B. pseudomallei bopC mutant was used to infect J774A.1 macrophage-like cells. The bopC mutant showed significantly reduced intracellular survival in infected macrophages compared to wild-type B. pseudomallei. In addition, the bopC mutant displayed delayed escape from endocytic vesicles compared with the wild-type strain. This indicates that BopC is important, and at least in part, needed for intracellular survival of B. pseudomallei.

Review

REVIEW] The Role of Type III Secretion System 2 in Vibrio parahaemolyticus Pathogenicity: Hyeilin Ham , Kim Orth; J. Microbiol. 2012;50(5):719-725. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2550-2

Abstract: Vibrio parahaemolyticus, a Gram-negative marine bacterial pathogen, is emerging as a major cause of food-borne illnesses worldwide due to the consumption of raw seafood leading to diseases including gastroenteritis, wound infection, and septicemia. The bacteria utilize toxins and type III secretion system (T3SS) to trigger virulence. T3SS is a multi-subunit needle-like apparatus used to deliver bacterial proteins, termed effectors, into the host cytoplasm which then target various eukaryotic signaling pathways. V. parahaemolyticus carries two T3SSs in each of its two chromosomes, named T3SS1 and T3SS2, both of which play crucial yet distinct roles during infection: T3SS1 causes cytotoxicity whereas T3SS2 is mainly associated with enterotoxicity. Each T3SS secretes a unique set of effectors that contribute to virulence by acting on different host targets and serving different functions. Emerging studies on T3SS2 of V. parahaemolyticus, reveal its regulation, translocation, discovery, characterization of its effectors, and development of animal models to understand the enterotoxicity. This review on recent findings for T3SS2 of V. parahaemolyticus highlights a novel mechanism of invasion that appears to be conserved by other marine bacteria.

Research Support, Non-U.S. Gov't

Effect of Acidic pH on the Invasion Efficiency and the Type III Secretion System of Burkholderia thailandensis: Siroj Jitprasutwit , Wisansanee Thaewpia , Veerachat Muangsombut , Aroonlug Lulitanond , Chanvit Leelayuwat , Ganjana Lertmemongkolchai , Sunee Korbsrisate; J. Microbiol. 2010;48(4):526-532. Published online August 20, 2010; DOI: https://doi.org/10.1007/s12275-010-0078-x

Abstract: Burkholderia thailandensis is a close relative of Burkholderia pseudomallei. These organisms are very similar, but B. thailandensis is far less virulent than B. pseudomallei. Nucleotide sequencing and analysis of 14 B. thailandensis isolates revealed variation in the regions coding for the type III secreted BipD protein. The degree of B. thailandensis BipD sequence variation was greater than that found in B. pseudomallei. Western blot analysis indicated that, unlike B. pseudomallei, B. thailandensis type III secreted proteins including BipD and BopE could not be detected in the supernatant of culture medium unless induced by acidic conditions. In addition, culturing B. thailandensis under acidic growth conditions (pH 4.5) can induce the ability of this bacterium to invade human respiratory epithelial cells A549. The identification of an environmental stimulus that increases the invasion capability of B. thailandensis invasion is of value for those who would like to use this bacterium as a model to study B. pseudomallei virulence.

Genetic and Environmental Control of Salmonella Invasion: Craig Altier; J. Microbiol. 2005;43(1):85-92.

Abstract: An early step in the pathogenesis of non-typhoidal Salmonella species is the ability to penetrate the intestinal epithelial monolayer. This process of cell invasion requires the production and transport of secreted effector proteins by a type III secretion apparatus encoded in Salmonella pathogenicity island I (SPI-1). The control of invasion involves a number of genetic regulators and environmental stimuli in complex relationships. SPI-1 itself encodes several transcriptional regulators (HilA, HilD, HilC, and InvF) with overlapping sets of target genes. These regulators are, in turn, controlled by both positive and regulators outside SPI-1, including the two-component regulators BarA/SirA and PhoP/Q, and the csr post-transcriptional control system. Additionally, several environmental conditions are known to regulate invasion, including pH, osmolarity, oxygen tension, bile, Mg^2+ concentration, and short chain fatty acids. This review will discuss the current understanding of invasion control, with emphasis on the interaction of environmental factors with genetic regulators that leads to productive infection.

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