海洋细菌生物被膜可拉酸含量影响厚壳贻贝稚贝附着

可拉酸是生物被膜上重要的胞外多糖之一，但细菌可拉酸对海洋无脊椎动物附着过程的影响还鲜少研究。本研究从自然生物被膜中分离出8株海洋细菌，对其种属进行鉴定及聚类分析，并测定其生物被膜的可拉酸含量及对稚贝附着的诱导能力。筛选所得海洋细菌形成生物被膜并测定其成膜能力及胞外产物含量，发现β-多糖的生物量与厚壳贻贝稚贝附着率呈显著正相关趋势（p < 0.05）。8株海洋细菌生物被膜中可拉酸含量的定量结果显示，3株革兰氏阳性菌无法产生可拉酸，5株革兰氏阴性菌均可检测到不同含量的可拉酸，其中革兰氏阴性菌Shewanella marisflavi的可拉酸含量最高，为1 076.43 μg/mL。不同可拉酸含量的海洋细菌单一生物被膜与厚壳贻贝稚贝附着率之间关系的研究结果显示，海洋细菌生物被膜对厚壳贻贝稚贝附着率的诱导效果与其可拉酸含量呈显著正相关（p < 0.05）。以上结果表明，细菌生物被膜中的可拉酸能够参与诱导厚壳贻贝稚贝的附着。本研究为探究海洋细菌生物被膜的化学物质与海洋贝类附着之间的相互作用及其对贝类附着机制提出了新的见解。

Effect of the content of colanic acid in marine bacterial biofilms on the settlement of Mytilus coruscus plantigrades

Colanic acid is one of the vital exopolysaccharides in biofilms, yet the effect of marine bacterial colanic acid on the settlement of invertebrates is still rarely covered. In this study, eight strains of marine bacteria isolated from natural biofilms were identified and the phylogenetic analysis was carried out, the colanic acid content and inducing ability of biofilms were also determined. Before that, the biofilm formation capacity and the extracellular products of the screened bacteria were detected. It was found that β-polysaccharide had a significant positive correlation with the settlement rate of Mytilus coruscus plantigrades (p < 0.05). The quantitative results of colanic acid content showed that among the five Gram-negative bacteria which could produce colanic acid, Shewanella marisflavi had the highest colanic acid yield of 1076.43 μg/mL, and three Gram-positive bacteria could not generate it. The results of plantigrade settlement induced by different biofilms showed that the inducing activity of marine bacterial biofilms on the settlement rate of M. coruscus was positively correlated with the content of colanic acid (p < 0.05). These findings prove that the Gram-negative bacteria with colanic acid can positively regulate the settlement of M. coruscus plantigrades, while the Gram-positive bacteria without colanic acid have no inducing activity. This study provides further insights to figure out the interaction between the chemical cues of biofilms and marine molluscs.