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KMID : 0613820190290010097
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Journal of Life Science
2019 Volume.29 No. 1 p.97 ~ p.104
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Studies on a Toxin/Antitoxin System in Streptococcus iniae
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Yoon Seong-Yong
Kim Yeon-Ha
Jeong Ye-Seul
Seong Min-Ji
Yoo Ah-Young
Lee Dong-Hee
Moon Ki-Hwan
Kang Ho-Young
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Abstract
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Streptococcus iniae is a typical fish pathogen causing streptococcosis and it can also cause zoonotic infectious diseases. We studied S. iniae FP5228 isolated from infected olive flounder in Wando, Korea. In a study to find virulence factors in FP5228, we found that the number of live bacteria decreased dramatically in culture medium containing S. iniae FP5228 for more than 24 hr. This phenomenon was hypothesized to be related to Toxin ζ and Antitoxin ε genes, components of the Toxin/ Antitoxin (TA) system on the 14 kb plasmid of FP5228. We used a protein overexpression system to identify it. The pBP1140 vector system was constructed to regulate the expression of Toxin ζ and Antitoxin ε by IPTG and Arabinose. E. coli/pBP1140 strain grew slowly in early growth under toxin expression condition, and it was confirmed by microscopic observation that the strain became longer. S. iniae CK287, lacking a 14 kb plasmid of S. iniae FP5228 strain, was constructed. CK287 bacterial cells did not show rapid killing during culture, and the ability to produce biofilm was also decreased, and toxicity was weakened in cytotoxicity test and fish test. These results suggest that the TA system is involved in physiological regulation and expression of virulence factors in S. iniae FP5228.
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KEYWORD
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Curing, Streptococcus iniae, toxin/antitoxin system, viability decrease
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