Abstract
Excessive Microcystis aeruginosa in aquaculture water can affect the quality and safety of aquatic products. An algicidal strain Penicillium chrysogenum (CHS) was isolated from a mix of sediment and water samples from an aquaculture pond. Subsequently, the inhibition mechanism of CHS on M. aeruginosa growth and physiological-biochemical index were investigated. The inhibition rate of M. aeruginosa growth was found to be 69.56% with CHS inoculum density of 3.85% after 6 days. The mycelium or spores of CHS did not inhibit the growth of M. aeruginosa. The CHS inhibited the growth of M. aeruginosa indirectly by secreting extracellular substances. The results showed that CHS secretions destroyed the cell wall and organelles of M. aeruginosa as well as the antioxidant system of M. aeruginosa. The super oxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione S-transferase (GST) activities of M. aeruginosa were significantly different from the control group (p < 0.05) with CHS inoculum density higher than 1.32%. CHS secretions also affected the expression of photosynthesis genes and microcystin synthesis genes of M. aeruginosa. The expression of genes psaB and rbcL involved in photosynthesis were inhibited, while the expression of gene psbD1 was promoted. The relative transcriptional abundance of genes mcyA, mcyB and mcyD involved in microcystins synthesis was significantly reduced. On the 6th day, the microcystin-LR (MC-LR) concentration was reduced by 75.4% and 32.0% in the groups with CHS inoculum density of 1.32% and 2.60%, respectively. The concentration of penicillin V and penicillin G, the main components believed to be inhibiting M. aeruginosa, was 15.23 mg ml−1 and 18.97 mg ml−1, respectively in the CHS solution.
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