Dynamics of microcystin-degrading bacteria in mucilage of Microcystis

• Published in: Microbial ecology 2003-08, Vol.46 (2), p.279-288
• Main Authors: Maruyama, T, Kato, K, Yokoyama, A, Tanaka, T, Hiraishi, A, Park, H. -D
• Format: Article
• Language: English
• Subjects: Adhesives; Animal, plant and microbial ecology; Bacteria; bacterial communities; Biodegradation; Biodegradation of pollutants; Biological and medical sciences; Biotechnology; Blooms; Carcinogens - metabolism; Cells; Chlorophylls; Colonies; Community structure; Cytophaga; Degradation; Detoxification; Dynamic tests; Ecology; Environment and pollution; Fish populations; Flavobacteria; Flavobacterium; Fluorescence; Fluorescence in situ hybridization; Freshwater; Fundamental and applied biological sciences. Psychology; hepatotoxicity; Hybridization; In Situ Hybridization, Fluorescence; Industrial applications and implications. Economical aspects; Inland waters; Lake water; Lakes; Macromolecules; Microbial ecology; Microbiology; Microcystins; Microcystis; Microcystis - genetics; Microcystis - physiology; Mucilage; nucleotide sequences; Oligonucleotide probes; Oligonucleotides; Peptides, Cyclic - metabolism; Population Dynamics; Probes; Proteobacteria; ribosomal RNA; rRNA 16S; Sensors; Sequencing; summer; Surface water; Toxicity; Toxins; Various environments (extraatmospheric space, air, water); Water Microbiology; Water Supply
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-002-3007-7

To reveal the process of degradation of hepatotoxic microcystin produced in Microcystis cells during the Microcystis bloom period, we used fluorescence in situ hybridization (FISH) to analyze the population dynamics of microcystin-degrading bacteria in Microcystis mucilage. We designed and applied an oligonucleotide probe targeted to the 16S rRNA sequence of strain Y2 of a microcystin-degrading bacterium (MCD-bacterium), which was isolated from Lake Suwa, Japan. In both the 1998 and 1999 tests, FISH clearly showed that MCD-bacteria existed in the mucilage and that, when a high concentration of cell-bound microcystin was detected, MCD-bacteria exceeded 10% of the sum of bacteria hybridized with group-specific probes. The concentration of MCD-bacteria was highest in summer 1998, when a toxic species, M. viridis, was dominant. There was a high correlation between the number of MCD-bacteria in the mucilage and the concentration of cell-bound microcystin in the lake. Our results suggest that MCD-bacteria responded to changes in the concentration of microcystin and degraded the microcystin when it was released from Microcystis cells. We also analyzed changes in the bacterial community structure associated with the Microcystis colonies by using domain- and group-specific oligonucleotide probes. Changes in the concentrations of the Cytophaga/Flavobacterium group and 8-Proteobacteria, which can degrade macromolecules derived from Microcystis cells, were synchronized with changes in the concentration of Microcystis. The results not only suggest the significant role of MCD-bacteria in detoxification, but also demonstrate a possible sequence of degradation from Microcystis cells to microcystin maintained in the cell, which is then carried out by bacterial consortia in the mucilage.