Characterization of Two Toxin-Antitoxin Systems in Deep-Sea <i>Streptomyces</i> sp. SCSIO 02999
2019
Waner Zhan | Jianyun Yao | Kaihao Tang | Yangmei Li | Yunxue Guo | Xiaoxue Wang
Toxin-antitoxin (TA) systems are ubiquitous and abundant genetic elements in bacteria and archaea. Most previous TA studies have focused on commensal and pathogenic bacteria, but have rarely focused on marine bacteria, especially those isolated from the deep sea. Here, we identified and characterized three putative TA pairs in the deep-sea-derived <i>Streptomyces</i> sp. strain SCSIO 02999. Our results showed that Orf5461/Orf5462 and Orf2769/Orf2770 are <i>bona fide</i> TA pairs. We provide several lines of evidence to demonstrate that Orf5461 and Orf5462 constitute a type-II TA pair that are homologous to the YoeB/YefM TA pair from <i>Escherichia coli</i>. Although YoeB from SCSIO 02999 was toxic to an <i>E. coli</i> host, the homologous YefM antitoxin from SCSIO 02999 did not neutralize the toxic effect of YoeB from <i>E. coli</i>. For the Orf2769/Orf2770 TA pair, Orf2769 overexpression caused significant cell elongation and could lead to cell death in <i>E. coli,</i> and the neighboring Orf2770 could neutralize the toxic effect of Orf2769. However, no homologous toxin or antitoxin was found for this pair, and no direct interaction was found between Orf2769 and Orf2770. These results suggest that Orf2769 and Orf2770 may constitute a novel TA pair. Thus, deep-sea bacteria harbor typical and novel TA pairs. The biochemical and physiological functions of different TAs in deep-sea bacteria warrant further investigation.
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