两株浅层底泥菌对铜绿微囊藻休眠体复苏的调控作用

Regulation of two benthic bacteria on the recruitment of dormant Microcystis aeruginosa in upper sediment

将起始浓度不同的单菌和混合菌(Ba.sp06+Str.v13)分别与铜绿微囊藻休眠体及底泥共包埋,在梯度温度下进行24 d休眠体复苏实验.结果表明,温度低于10℃时,菌株Str.v13的生长增殖能力显著强于菌株Ba.sp06,各菌组休眠体复苏率最高为0.02%;在温度为15和20℃条件下,Ba.sp06与Str.v13两菌株浓度比例(以下简称"菌比")为1∶1时混合菌组休眠体复苏率(15℃时为15.5%,20℃时为23.5%)与对照组无显著差异(15℃时为15%,20℃时为22.6%),但显著低于Ba.sp06单菌组(34.5%);菌比2∶1时Ba.sp06菌对Str.v13菌具抑制效应,混合菌组复苏率(15℃时为31%,20℃时为35%)显著高于对照组,而与Ba.sp06单菌组无显著差异;菌比为1∶2时Str.v13菌对Ba.sp06菌具抑制效应,混合菌组休眠体复苏率(15℃时为6%,20℃时为6.5%)均显著低于菌比为1∶1、2∶1时及Ba.sp06单菌组,但高于Str.v13单菌组(3%).同时,各复苏阶段对复苏率的贡献主要集中在启动复苏的第12~18 d.实验表明,底泥表层铜绿微囊藻休眠体复苏不仅受温度影响(>10℃),且复苏率受底栖菌Ba.sp06与Str.v13的起始浓度影响,Ba.sp06菌的起始浓度高于Str.v13菌时促进休眠体复苏,低于Str.v13菌时复苏受到抑制.因此,可以在铜绿微囊藻休眠体复苏前期通过调节Ba.sp06与Str.v13菌比来调控休眠体复苏率,为从源头防控微囊藻水华暴发提供理论依据.

Benthic bacteria play an important role in nutrient cycling and stability of aquatic ecosystem. Understanding the role of benthic bacteria in recruitment of M. aeruginosa from sediment is essential for effective control of toxic blooming. In this study,we investigated the effect of different ratio of two benthic bacteria on recruitment of dormant M. aeruginosa cells from sediment under different temperature conditions. When benthic bacterial strains Ba.sp〈06 and Str.v13 were inoculated at the initial ratio of 1∶1 into the sediment embedded with dormant M. aeruginosa cells under different temperature conditions for 24 days,the growth and proliferation ability of strain Str.v13 was significantly stronger than that of strain Ba.sp〈06 at 10 ℃,but it had no significant impact on the recruitment rate of M. aeruginosa cells since the recruitment rates were limited to 0.02% among all groups. Ba.sp〈06 and Str.v13 mixture groups（ 15.5% at 15 ℃ and 23.5% at 20 ℃） had no significant influenceon the recruitment of M. aeruginosa,compared with the control（ 15% at15 ℃ and 22.6% at 20 ℃）,although was significantly lower than the single Ba.sp〈06 group. When the initial ratio of Ba.sp〈06 and Str.v13 was at 2∶1,Ba.sp〈06 significantly inhibited Str.v13 growth,leading to a significant increase in the recruitment rate of M. aeruginosa cells（ 31% at 15 ℃ and 35% at 20℃） from the sediment,compared to the control,and had no significant difference compared with the single Ba. sp〈06 group. However,when the initial ratio of strain Ba.sp〈06： Str.v13 was at 1∶2,Str.v13 significantly inhibited Ba.sp〈06 growth,resulting in significant inhibition of the recruitment rate of M.aeruginosa cells（ only 6% at 15 ℃ and 6.5% at 20 ℃）,which were significantly lower than 1∶1,2∶1 mixtures and single Ba.sp〈06 groups. In addition,there were differences in the specific recruitment rates of M. aeruginosa cells during different culture stages,the specific recruitment rates from day 12 to day 18 were significantly higher than that in early stage（ from day 6 to 12） and late stage（ from day 18 to 24） at both 15 ℃ and 20 ℃. There were no differences in the specific recruitment rates of M. aeruginosa cells among all groups within the same culture stages. These results indicate that the synergistic effect of benthic bacteria on the recruitment of M. aeruginosa cells occurs when the initial ratio of Ba.sp〈06 and Str.v13 was at above 2∶ 1,and retarding effect at below 1∶1 under the temperature of 15 ℃ and 20 ℃. Therefore,the recruitment rate of M. aeruginosa cells can be inhibited before the recruitment of microcystis dormancy by regulating ratio of Ba.sp〈06 and Str.v13 at above 10 ℃.