Functional divergence of flagellar type III secretion system: A case study in a non-flagellated, predatory bacterium.
Functional divergence of flagellar type III secretion system: A case study in a non-flagellated, predatory bacterium.
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鞭毛 III 型分泌系统的功能分歧：非鞭毛捕食性细菌的案例研究
DOI：
10.1016/j.csbj.2020.10.029
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发表时间：
2020
影响因子：
6
通讯作者：
Qian G
中科院分区：
文献类型：
--
作者：
Fulano AM;Shen D;Zhang EH;Shen X;Chou SH;Minamino T;Puopolo G;Qian G
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Flagellar type III secretion system (FT3SS) is widely employed by flagellated bacteria to transport flagellar subunit proteins for flagellum assembly in vivo and for motility (upper). We found that in a soil, non-flagellated bacterium known as Lysobacter enzymogenes OH11, the remaining FT3SS genes appear to assemble a functional FT3SS-like system, which most likely undergoes a functional divergence to mediate the export of antifungal toxins to inhibit the growth of co-habited fungi (bottom), thereby strengthening its predatory capacity. The lack of functional flagella and the ability to prey upon other microorganisms are well-known traits of Lysobacter enzymogenes, a plant beneficial bacterial species. Here, we report a possible link between these two traits in the model strain L. enzymogenes OH11 (OH11). The genome of OH11 encompasses several homologous genes involved in the flagellum formation but it lacks a functional fliC, encoding the flagellin. Despite the lack of the main component of the flagellum, OH11 genome includes genes involved in the flagellar type III secretion system (FT3SS), which is commonly deployed by flagellated bacteria to transport flagellar subunit proteins. To understand the role played by FT3SS in OH11, we showed that the remaining FT3SS genes were expressed under laboratory conditions. Subsequently, we showed that the identified FT3SS genes involved in the secretion of the hook-capping protein FlgD, suggesting OH11 likely possessed a functional FT3SS system. Blocking FT3SS in OH11 via inactivation of the ATPase FliI impaired the secretion of the proteins Le3970 (protease), Le4493 (ß-1,3-glucanase A) and Le1659 (halo acid dehalogenase family), that showed a toxic activity against the yeast Saccharomyces cerevisiae. The possible link between FT3SS and OH11 antagonism towards S. cerevisiae was also confirmed by loss of toxicity in both mutants of ΔfliI and ΔflhB that lacks the FT3SS structural gene flhB when co-cultured with the yeast strain. The design of synthetic proteins toxic against the Gram-negative bacterium Ralstonia solanacearum further supported the involvement of FT3SS in the ability of OH11 to parasitize other microorganisms. Overall, these results revealed a possible cooption of components of FT3SS system in the competition with other microorganisms in the plant beneficial bacterium OH11 and highlighted a functional divergence of FT3SS between flagellated and non-flagellated bacteria.
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细菌鞭毛III型蛋白质输出中使用的能量转导机制。
影响因子：
16.6
作者：
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影响因子：
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作者：
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