Effects of microcystin on protein profile in hepatopancreas of Litopenaeus vannamei.

For intensive aquaculture in freshwater ponds, microcystin (MC-LR) generated from cyanobacterial blooms is one of the bottlenecks for the healthy and sustainable development of shrimp aquaculture industry. In this study, we measured the MC-LR content in the hepatopancreas and muscles of Litopenaeus vannamei stressed by MC-LR, and analyzed protein expression in the hepatopancreas using DIA high-throughput proteomics technology. The results showed that MC-LR content in the hepatopancreas and muscles reached the highest at 1 h after MC-LR injection, which was (6.12±0.45) µg·kg-1 and (5.00±0.19) µg·kg-1, respectively. Then, it decreased gra-dually, with that in the hepatopancreas being significantly higher than in muscles. We identified 820 differential expressed proteins, including 586 up-regulated and 234 down-regulated ones. Results of bioinformatics analysis showed that MC-LR stress significantly affected immune-related pathways such as lysosome, RIG-Ⅰ receptor signals and interleukin-2. It also altered energy metabolisms including citrate cycle, metabolism of starch and sucrose, and interconversion of pentose and glucoronate, which in turn led to the disorder of carbohydrate metabolism. In addition, MC-LR significantly upregulated 19 cytoskeleton-related blood shadow proteins and damaged the hepatopancreas cytoskeleton. It was concluded that MC-LR mainly affected the physiological processes associated with immunity, energy metabolism, and cytoskeleton in the hepatopancreas of L. vannamei.

Effects of lead(II) on the extracellular polysaccharide (EPS) production and colony formation of cultured Microcystis aeruginosa.

To investigate the effects of lead(II) on the production of extracellular polysaccharides (EPS), including bound extracellular polysaccharides (bEPS) and soluble extracellular polysaccharides (sEPS), and the colony formation of Microcystis aeruginosa, cultures of M. aeruginosa were exposed to four concentrations (5.0, 10.0, 20.0 and 40.0 mg/L) of lead(II) for 10 d under controlled laboratory conditions. The results showed that 5.0 and 10.0 mg/L lead(II) stimulated M. aeruginosa growth throughout the experiment while 20.0 and 40.0 mg/L lead(II) inhibited M. aeruginosa growth in the first 2 d exposure and then stimulated it. As compared to the control group, significant increases in the bEPS and sEPS production were observed in 20.0 and 40.0 mg/L lead(II) treatments (P < 0.05). Large colony formations were not observed throughout the experiment. However, four tested concentrations of lead(II) could significantly promote the formation of small and middle colonies after 10 d exposure (P < 0.05), and 40.0 mg/L lead(II) had the best stimulatory effect. Lead(II) could stimulate bEPS production, which conversely promoted colony formation, suggesting that heavy metals might be contributing to the bloom-forming of M. aeruginosa in natural conditions.