Characterization of phosphate solubilizing bacteria in the sediments of eutrophic lakes and their potential for cyanobacterial recruitment

Microbes may induce endogenous phosphorus (P) migration from lacustrine sediment. This study focused on the role of phosphate-solubilizing bacteria (PSB) disturbance in affecting the sediment P release and further contributing to cyanobacterial recruitment in Meiliang Bay, Lake Taihu. Gluconic acid was the main mechanism of phosphate solubilizing by PSB. The dominant PSB (Burkholderia) isolated from eutrophic lake sediments was used as a representative to investigate the effects of disturbance on endogenous P release using diffusive gradients in thin films (DGT) and high-resolution dialysis (HR-Peeper). The results show that soluble reactive phosphorus (SRP) and iron (Fe (II)) concentrations could reach 0.51 mg L-1 and 33.56 mg L-1 in pore water, respectively. And the sediment DGT-P and DGT-Fe were relatively reduced by PSB. Subsequent the chlorophyll a (Chl a) concentrations reached peaks of 344.8 μg L-1 in overlying water. The abundance of the dominant PSB (Burkholderia-Caballeronia-Paraburkholderia) were significantly associated with Chl a (P < 0.05) and algal effective state phosphorus (AAP) (P < 0.05), respectively. PSB mainly regulates AAP leaching to pore water and then diffusing across the sediment-water interface to the overlying water, producing the effect of cyanobacteria recruitment. The results provide new insights into early management of cyanobacterial resuscitation in a large eutrophic lake.

Recruitment of cyanobacteria by reverse transcription quantitative real-time PCR based on expression of Microcystis gene

In this study, a SYBR Green quantitative real-time PCR method was established and applied. Relative expression of the synthetic genes from Microcystis gas vesicles (gvpC), algal toxin genes (mcyA), and polysaccharides (espL) from water and sediments of Meiliang Bay and from the center of Lake Taihu were tested from January to June, 2017. Indoor Microcystis aeruginosa was used as the control group. The kit for total RNA extraction in Microcystis was optimized. Results showed that the optimized kit extracted high-concentrations and high-quality total RNA from Microcystis. The extraction purity and concentration were significantly higher than those extracted by the original kit. The transcription level of gvpC increased gradually until a peak was reached in March. However, expression of gvpC decreased continuously at the proliferating and floating stages of Cyanobacterial biomass. The maximum level of expression of gvpC in April in comparison to expression of mcyA in March occurred first. We found that the SYBR Green qRT-PCR method, which is characterized by high specificity, repeatability, is rapid, and can be used for quantitative detection of expression of gvpC, mcyA, and espL. The recruitment of cyanobacteria is the process in which cyanobacteria in the sediment began to regain their activity, started to grow and migrated to the water column.