A freshwater bacterial strain, Shewanella sp. Lzh-2, isolated from Lake Taihu and its two algicidal active substances, hexahydropyrrolo[1,2-a]pyrazine-1,4-dione and 2, 3-indolinedione

Abstract

Cyanobacterial blooms have become a serious problem in Lake Taihu during the last 20 years, and Microcystis aeruginosa and Synechococcus sp. are the two dominant species in cyanobacterial blooms of Lake Taihu. A freshwater bacterial strain, Shewanella sp. Lzh-2, with strong algicidal properties against harmful cyanobacteria was isolated from Lake Taihu. Two substances with algicidal activity secreted extracellularly by Shewanella sp. Lzh-2, S-2A and S-2B, were purified from the bacterial culture of strain Lzh-2 using ethyl acetate extraction, column chromatography, and high performance liquid chromatography (HPLC) in turn. The substances S-2A and S-2B were identified as hexahydropyrrolo[1,2-a]pyrazine-1,4-dione and 2, 3-indolinedione (isatin), respectively, based on liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS), and hydrogen-nuclear magnetic resonance (H-NMR) analyses, making this the first report of their algicidal activity toward cyanobacteria. S-2A (hexahydropyrrolo[1,2-a]pyrazine-1,4-dione) had no algicidal effects against Synechococcus sp. BN60, but had a high level of algicidal activity against M. aeruginosa 9110. The LD50 value of S-2A against M. aeruginosa 9110 was 5.7 μg/ml. S-2B (2, 3-indolinedione) showed a potent algicidal effect against both M. aeruginosa 9110 and Synechococcus sp. BN60, and the LD50 value of S-2B against M. aeruginosa 9110 and Synechococcus sp. BN60 was 12.5 and 34.2 μg/ml, respectively. Obvious morphological changes in M. aeruginosa 9110 and Synechococcus sp. BN60 were observed after they were exposed to S-2A (or S-2B) for 24 h. Approximately, the algicidal activity, the concentration of S-2A and S-2B, and the cell density of Lzh-2 were positively related to each other during the cocultivation process. Overall, these findings increase our knowledge about algicidal substances secreted by algicidal bacteria and indicate that strain Lzh-2 and its two algicidal substances have the potential for use as a bio-agent in controlling cyanobacterial blooms in Lake Taihu.

Quorum sensing of microalgae associated marine Ponticoccus sp. PD-2 and its algicidal function regulation

“…It is interesting to find that some algicidal bacteria such as Cytophaga strains J18/M01 (Mirsutani et al 1992) and A5Y (Imai et al 1993), Flavobacterium strain 5N-3 (Imai et al 1992), and Flavobacteriaceae strain S03 (Roth et al 2007) must reach a cell density of at least 10 6 cells mL −1 before they show any algicidal activity. Li et al (2014) found that Shewanella sp. Lzh-2 must reach a bacterial cell density threshold of at least 10 8 cells mL −1 before any algicidal compound can be detected.…”

The algicidal activity of Aeromonas sp. strain GLY‐2107 against bloom‐forming Microcystis aeruginosa is regulated by N‐acyl homoserine lactone‐mediated quorum sensing

“…Lzh‐2, showed algicidal activity. Cyclo(Gly‐Phe) belongs to the diketopiperazine family, which contains a large group of small molecules produced by a wide range of microbes that exhibit many valuable biological properties (Ortiz‐Castro et al ., ), including antibacterial (Fdhila et al ., ), algicidal (Li et al ., ; Guo et al ., ; Li et al ., ; Lin et al ., ) and signal (sexual pheromone) (Gillard et al ., ) activities. During the sexual reproduction of the diatom Seminavis robusta , diproline (proline‐derived diketopiperazine) acting as the sexual pheromone of the attracting mating type (MT − cells) can induce the migratory behavior of the migrating mating type (MT + cells) (Gillard et al ., ).…”

“…Li et al . () found that another indole derivative, isatin, which is produced by Shewanella sp. Lzh‐2, showed algicidal activity.…”

“…Therefore, it is urgent to control harmful Microcystis blooms. To date, the high costs and secondary pollution of the available physical and chemical methods have prevented their widespread applications (Li et al ., ). Biocontrol technologies have drawn increasing attention and have been deemed an effective strategy for controlling harmful algal blooms due to their potential efficacy and eco‐friendliness (Anderson, ; Zheng et al ., ).…”

“…Li et al . () found that Shewanella sp. Lzh‐2 must reach a threshold bacterial cell density of at least 10 8 cells ml −1 before any algicidal compound was detectable.…”