AsianScientist (May 3, 2016) – A group of researchers in Japan have revealed that Vibrio cholerae, the bacterium which causes cholera, is attracted by bile. This group has also successfully observed the ligand binding to the bacterial chemoreceptor in vivo for the first time. These results, published in Scientific Reports, may significantly advance research on mechanism and control of V. cholerae.
Cholera, an acute diarrheal disease caused by the infection of the Gram-negative bacterium V. cholerae, remains a global threat to public health.
V. cholerae does not produce toxins in nutrient-poor aquatic environments. However, in a nutrient-rich environment, such as inside of the human small intestine, it begins to form colonies and expresses pathogenic proteins that cause the serious diarrheal disease. Thus, sensing environmental chemicals is crucial for V. cholerae to thrive and infect the host.
Professor Katsumi Imada and graduate student Mr. Yohei Takahashi at Osaka Univeresity and colleagues found that V. cholerae is actually attracted by taurine, a bile component, and that taurine is recognized by a chemotaxis receptor protein, Mlp37.
The structural study of the Mlp37 sensor domain in complex with taurine and serine revealed that the ligands bind to the same pocket and that taurine is recognized essentially in the same way as serine. The sensor domain of the ligand complex has a small opening, which would accommodate a larger side chain group, accounting for the broad ligand specificity of Mlp37.
This group has also successfully visualized the ligand binding to the bacterial chemoreceptor as fluorescent spots. This is the first example of the direct detection of the ligand binding to the bacteria chemoreceptor in vivo.
The finding of taurine taxis sheds new light on the survival of V. cholerae in the host intestine as well as its pathogenicity, or ability to cause disease. Inhibition of taurine taxis might lead to prevention of infection and pathogenesis of V. cholerae.
The structural basis of taurine recognition by the chemoreceptor Mlp37 provides a significant contribution to the development of new drugs for cholera. Moreover, this group’s fluorescent labeling technique provides a powerful cell biological tool to study bacterial chemotactic behavior, which is essential for bacterial survival and infection.
The article can be found at: Nishiyama et al. (2016) Identification of a Vibrio cholerae Chemoreceptor that Senses Taurine and Amino Acids as Attractants.
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Source: Osaka University; Photo: CDC Global/Flickr/CC.
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