二酮哌嗪类化合物诱导海洋共栖细菌NJ6-3-1产生抗菌活性的研究

Study on antibacterial activity of sponge associated marine bacterium Pseudoalteromonas sp. NJ6-3-1 induced by diketopiperazines

目的选择一株具有抗菌活性的海绵共栖细菌NJ6-3-1为实验菌株,研究其抗菌物质的代谢是否受到群体感应诱导信号分子的调控。方法研究在不同生长条件细菌NJ6-3-1代谢物的抗菌活性与细胞密度的关系,利用细菌NJ6-3-1自身代谢产物的3种二酮哌嗪类化合物(diketopiperazines,DKPs)作为自诱导物质(AI),研究了低密度条件下的细菌NJ6-3-1与3种不同DKPs共培养时的抗菌活性情况。结果实验发现细菌NJ6-3-1代谢抗菌物质的行为与细胞密度密切相关,且发现该菌具有群体感应机制的现象(quorumsens-ing),在高密度条件(OD630>0.4)下细菌才能产生抗菌活性,NJ6-3-1不产生抗菌物质的低密度生长条件:1/5 MB培养基、25℃;同时发现cyclo-(L-Phe-L-Val)能诱导NJ6-3-1在不产生抗菌物质的生长条件下代谢抗菌物质。结论以上结果初步说明细菌NJ6-3-1具有种内群体感应系统,其抗菌活性受到自诱导物cyclo-(L-Phe-L-Val)的调控。

Objective In this study, a sponge associated marine bacterium Pseudoalteromonas piscicida NJ6-3-1 with remarkable biological activities was chosen in a case study to investigate whether its antibacterial metabolites were regulated and induced by quorum sensing autoinducer molecules. Methods We studied the relationship between the antibacterial activity and bacterial density through changing the growth condition of bacterium NJ6-3-1. Results demonstrated it has the quorum sensing mechanism in NJ6-3-1. To use three kinds of dike- topiperazines of the metabolites of NJ6-3-1 as autoinducer molecules, we monitored the anti- bacterial activity of marine bacterium NJ6-3-1 with low cell density when the species were cocultured with these three kinds of diketopiperazines. Results The results demonstrated the existence of a close correlation between antibacterial activity and cell density, and the existence of quorum sensing mechanism in NJ6-3-1. Thus, the marine bacterium NJ6-3-1 could start producing antibacterial compounds but only on the high cell density （ OD630D0.4）, and the lower cell density conditions were as follow： 1/5MB,25℃. The results also demonstrated that cyclo（L-Phe-L Val） existing in the metabolites of NJ6-3-1 could induce the production of antibacterial substance from marine bacteria NJ6-3-1 even under low cell density conditions below the required threshold value. Concision The results as described above provide preliminary evidence to support the hypothesis that the antibacterial activity of NJ6-3-1 was controlled by the quorum sensing system of interspecies fashions,and its antibacterial activity was controlled by autoinducer molecule of cyclo（L-Phe-L-Val）