阿拉伯海假交替单胞菌N1230-9两个甲基受体趋化蛋白的功能鉴定

【目的】作为海洋中的特有及优势种群，假交替单胞菌(Pseudoalteromonas)普遍拥有多个甲基受体趋化蛋白(methyl-accepting chemotaxis protein, MCP)，探究这些趋化受体的功能。【方法】以太平洋表层海水来源的一株阿拉伯海假交替单胞菌(Pseudoalteromonas arabiensis) N1230-9为研究对象，利用软琼脂平板法测试该菌株对23种碳源的趋化能力，继而利用同源重组策略构建2个含sCache结构域MCP编码基因(woc28264和woc27036)缺失突变体，并分析突变体对10种碳源的趋化能力。【结果】菌株N1230-9对海藻糖、麦芽糖、蔗糖、N-乙酰氨基葡萄糖、l-苹果酸、乙酸钠、丙酸钠、丙酮酸钠、柠檬酸和琥珀酸10种碳源具有趋化能力。WOC28264是l-苹果酸和蔗糖的特异性趋化受体，WOC27036则是柠檬酸和琥珀酸的特异性趋化受体。此外，WOC28264和WOC27036还均是N-乙酰氨基葡萄糖和海藻糖的趋化受体。【结论】WOC28264和WOC27036存在重叠的碳源效应物。

Functions of two methyl-accepting chemotaxis proteins of Pseudoalteromonas arabiensis N1230-9

Objective] Pseudoalteromonas, an endemic and dominant genus in the ocean, possesses multiple methyl-accepting chemotaxis proteins (MCPs), the functions of which remain unclear. Methods] The chemotaxis of Pseudoalteromonas arabiensis N1230-9 isolated from surface seawater of the Pacific Ocean towards 23 carbon sources was analyzed by a plate-based assay for swimming motility. Two sCache domain-containing genes (woc28264 and woc27036) encoding MCPs were deleted by homologous recombination. The chemotaxis of the two mutants to 10 carbon sources was then analyzed. Results] Strain N1230-9 showed obvious chemotaxis to 10 carbon sources: trehalose, maltose, sucrose, N-acetylglucosamine, l-malic acid, sodium acetate, sodium propionate, sodium pyruvate, citric acid, and succinic acid. WOC28264 was a specific chemotactic receptor for l-malic acid and sucrose, while WOC27036 was a specific chemotactic receptor for citric acid and succinic acid. Both WOC28264 and WOC27036 were chemotactic receptors for N-acetylglucosamine and trehalose. Conclusion] WOC28264 and WOC27036 have overlapping carbon source effectors.