Isolation and characterization of an algicidal bacterium indigenous to lake Taihu with a red pigment able to lyse microcystis aeruginosa / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To isolate and characterize indigenous algicidal bacteria and their algae-lysing compounds active against Microcystis aeruginosa, strains TH1, TH2, and FACHB 905.</p><p><b>METHODS</b>The bacteria were identified using the Biolog automated microbial identification system and 16S rDNA sequence analysis. The algae-lysing compounds were isolated and purified by silica gel column chromatography and reverse-phase high performance liquid chromatography. Their structures were confirmed by Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FT-IR) spectroscopy. Algae-lysing activity was observed using microscopy.</p><p><b>RESULTS</b>The algae-lysing bacterium LTH-2 isolated from Lake Taihu was identified as Serratia marcescens. Strain LTH-2 secreted a red pigment identified as prodigiosin (C20H25N3O), which showed strong lytic activity with algal strains M. aeruginosa TH1, TH2, and FACHB 905 in a concentration-dependent manner. The 50% inhibitory concentration (IC50) of prodigiosin with the algal strains was 4.8 (± 0.4)× 10⁻² μg/mL, 8.9 (± 1.1)× 10⁻² μg/mL, and 1.7 (± 0.1)× 10⁻¹ μg/mL in 24 h, respectively.</p><p><b>CONCLUSION</b>The bacterium LTH-2 and its pigment had strong Microcystis-lysing activity probably related to damage of cell membranes. The bacterium LTH-2 and its red pigment are potentially useful for regulating blooms of harmful M. aeruginosa.</p>

The Toxic Effects of the Extracellular Active Components from One Algae-lysing Bacteria on Chlorella Pyrenoidosa / 微生物学通报

Toxic effects of L7 lyophilized powder of extracellular active components (L7-LPEAC), extracted from the Algae-lysing bacteria L7, on Chlorella pyrenoidosa were studied according to the changes of effective photosynthesis rate (EPR), the protein content, the chlorophyll a content and the MDA content of algae. The results showed that the growth of alga was promoted at low concentrations of L7-LPEAC (0.80 g/L, 1.25 g/L). The 96 h-EC50 and 120 h-EC50 upon Chlorella pyrenoidosa are 5.75 g/L and 2.55 g/L, respec tively. The chlorophyll a content increased firstly and then decreased at high concentrations of L7-LPEAC (≥2 g/L), so did the protein content. Compared with the control group, there is a significant statistics diff erence (P

Research on Separation Characteristics of the Extracellular Algae-lysing Components from Three Algae-lysing Bacteria / 微生物学通报

Three algae-lysing bacteria (L7、L8、L18) have been isolated. We used starch medium,which has no passive effect on growth of the Anabaena flos-aquae as cutivate medium. After being cultivated for 4d on a reciprocal shaker at 30℃ and a speed of 100 r/min,the cultivate broth were centrifugated at a speed of 4000 r/min for 20min、filtrated with 0.22 ?m membrane,and condensed by vacuum rotary evaporator at 65℃. The sterile condensed bacteria-free filtrate obtained are dialysed,sedimentated by ethanol,extracted by organic solvents,absorbed by activated carbon. The molecular weight of the extracellular algae-lysing components of L7 are less than 3.5 kD,while the molecular weight of extracellular algae-lysing components of L8 and L18 are between 3.5 kD～7 kD; ethanol can not separate extracellular algae-lysing components from other componets efficiently; carbon tetrachloride can separate the extracellular algae-lysing components of L7 into water-layer efficiently,while petroleum ether can separate the extracellular algae-lysing components of L8 and L18 into water-layer efficiently,the ex-tracellular algae-lysing