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摘要
An algicidal bacterium EA-1was isolated from Liuhua Lake in Guangzhou. The 16S rDNA analysis showed that the strain EA-1belongs to the genus Enterobacter sp. The algicidal efficiency and mechanism of Enterobacter sp. EA-1on Microcystis aeruginosa was studied. The logarithmic phase EA-1exhibited the best algicidal effect. A 10% inoculation of EA-1could achieve a complete lysis against Microcystis aeruginosa within 3days with the initial Chl-a content of 1.43mg/L. An inhibition rate of 84.1%±1.3% (t=6d) was attained when the initial Chl-a content reached 2.39mg/L. EA-1lysed algae by secreting extracellular algicidal substances. The physiological and biochemical responses indicated that algae suffered serious lipid peroxidation, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities increased dramatically first and decreased subsequently under the oxidative stress of EA-1sterile filtrate. Three-dimensional fluorescence spectroscopy (EEM) analysis showed that the algae lysates were humic acid-like, fulvic acid-like and protein-like substances. Scanning electron microscopy (SEM) showed that the surface of algae cells appeared wrinkled, invaded and atrophied. Transmission electron microscopy (TEM) showed that the destruction process of algae was as followed: first, the colloidal layer was separated from the cell wall, the photosynthetic lamellae became loose and irregular, the contents were partially degraded. Subsequently, the photosynthetic lamellae were completely destroyed, the DNA nuclear material and nutrient particles such as polyphosphate were degraded, the internal structure of algae cells was completely destroyed and the algae cells died.
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