微生物膜对厚壳贻贝稚贝附着的影响

Effects of biofilms on settlement of plantigrades of the mussel Mytilus coruscus

为研究微生物膜在厚壳贻贝稚贝附着过程中的作用,通过海洋化学生态学和分子微生物学方法分析了微生物膜形成过程中其干重、附着细菌密度、底栖硅藻密度、叶绿素a含量等随日龄变化情况及其对厚壳贻贝稚贝附着的影响。同时,利用DGGE指纹图谱技术对不同日龄微生物膜中的细菌群落结构多样性进行了分析。结果发现,微生物膜的干重、附着细菌密度及底栖硅藻密度明显随着日龄的增加而增加,在28 d达到最高值,其干重、细菌和硅藻密度分别为0.87 mg/cm2、1.5×107/cm2、1.0×106/cm2,均与日龄显著相关。叶绿素a含量在14 d时达到最大,为2.2μg/cm2,随日龄的增加呈持续下降的趋势,相关性分析表明叶绿素a含量与日龄无直接关系。随着日龄的增加,微生物膜诱导的稚贝附着率逐渐增加,28 d时达到最高值,为76%。相关性分析显示,微生物膜的活性与干重、附着细菌密度及底栖硅藻密度显著相关,其相关性系数分别为0.717、0.711和0.754。然而,微生物膜的附着诱导活性与叶绿素a无直接相关性。细菌群落结构在厚壳贻贝稚贝附着过程中发挥了重要作用。

The effect of biofilms developed in the aquariums on settlement of plantigrades of the mussel Mytilus coruscus was examined in the laboratory.Various aspects of biofilm biology were investigated including age,dry weight,chlorophyll a（Chl.a）content,bacterial and diatom densities.Bacterial community in biofilms was analyzed by the DGGE fingerprint technique.The correlation between the inducing activity of the biofilms and dry weight,bacterial and diatom densities,Chl.a content was also investigated.With the increase of biofilm age,dry weight,bacterial and diatom densities increased significantly and the maximum values were,respectively,0.87 mg/cm2,1.5×107/cm2 and 1.0×106/cm2 after 28 d.Furthermore,above three parameters were correlated with biofilm age.Chl.a content reached the maximum of 2.22 μg/cm2 after 14 d and no correlation between Chl.a content and biofilm age was observed.Plantigrades of M.coruscus preferred to settle on the biofilmed surfaces rather than the surfaces unfilmed.Overall the settlement of plantigrades on biofilms that formed in the aquariums increased with biofilm age,and the maximum of 76% settlement was obtained after 28 d.The enhanced settlement correlated to dry weight,bacterial density and diatom density,and their corresponding correlation coefficients were 0.717,0.711 and 0.754.In contrast,there was no correlation between inducing activity of biofilms and Chl.a content.Moreover,Shannon diversity index of bacteria community in DGGE profiles increased up to 28 d following immersion.The shift in bacterial community composition over time may be responsible for the higher settlement of plantigrades of M.coruscus on the older biofilms,indicating that bacterial community play an important role in the settlement of plantigrades in this species.