Protozoal ciliate promotes bacterial autoinducer-2 accumulation in mixed culture with Escherichia coli

The Journal of General and Applied Microbiology

Satoshi Oguri⁴  Junji Matsuo¹  Kouzi Akizawa⁴  Chikara Shimizu⁴  Kasumi Ishida¹  Shigeru Kamiya²  Tatsuya Fukumoto⁴  Tomohiro Yamazaki¹  Hiroyuki Yamaguchi¹  Torahiko Okubo¹  Tomoko Hanawa²  Shinji Nakamura³ 

[1] Department of Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University;Department of Infectious Diseases, Kyorin University School of Medicine;Division of Biomedical Imaging Research, Juntendo University Graduate School of Medicine;Hokkaido University Hospital

关键词: autoinducer-2;    ciliates;    Escherichia coli;    luxS;    quorum sensing;    Tetrahymena thermophila;    vacuole;    ydgG;   

DOI  :  10.2323/jgam.61.203

学科分类：微生物学和免疫学

来源: Applied Microbiology, Molecular and Cellulrar Biosciences Research Foundation

【 摘 要 】

We have previously demonstrated conjugation of Escherichia coli into vacuoles of the protozoal ciliate (Tetrahymena thermophila). This indicated a possible role of ciliates in evoking bacterial quorum sensing, directly connecting bacterial survival via accumulation in the ciliate vacuoles. We therefore assessed if ciliates promoted bacterial autoinducer (AI)-2 accumulation with vacuole formation, which controls quorum sensing. E. coli AI-2 accumulation was significantly enhanced in the supernatants of a mixed culture of ciliates and bacteria, likely depending on ciliate density rather than bacterial concentration. As expected, AI-2 production was significantly correlated with vacuole formation. The experiment with E. coli luxS mutants showed that ciliates failed to enhance bacterial AI-2 accumulation, denying a nonspecific phenomenon. Fluorescence microscopy revealed accumulation of fragmented bacteria in ciliate vacuoles, and, more importantly, expulsion of the vacuoles containing disrupted bacteria into the culture supernatant. There was no increase in the expression of luxS (encoding AI-2) or ydgG (a transporter for controlling bacterial export of AI-2). We conclude that ciliates promote bacterial AI-2 accumulation in a mixed culture, via accumulation of disrupted bacteria in ciliate vacuoles followed by expulsion of the vacuoles, independently of luxS or ydgG gene induction. This is believed to be the first demonstration of a relationship between E. coli AI-2 dynamics and ciliates. In the natural environment, ciliate biotopes may provide a survival advantage to bacteria inhabiting such biotopes, via evoking quorum sensing.

【 授权许可】

Unknown