Gan Nanqin

Quantitative assessment of toxic and nontoxic Microcystis colonies in natural environments using fluorescence in situ hybridization and flow cytometry

Toxic cyanobacterial blooms constitute a threat to human safety because Microcystis sp. releases microcystins during growth, and particularly during cell death. Therefore, analysis of toxic and nontoxic Microcystis in natural communities is required in order to assess and predict bloom dynamics and toxin production by these organisms. In this study, an analysis combining fluorescence in situ hybridization (FISH) with flow cytometry (FCM) was used to discriminate between toxic and nontoxic Microcystis and also to quantify the percentage of toxic Microcystis present in blooms. The results demonstrate that the combination of FISH and flow cytometry is a useful approach for studying the ecology of Microcystis toxin production and for providing an early warning for toxic Microcystis blooms.

Recent progress in research of the biological function of microcystins

Cyanobacterial bloom has become a frequent and problematic feature of many freshwater bodies over a wide geographical area, especially in China. Microcystis species are widely known for their production of the potent hepatotoxins called microcystins (MCs) . While the toxicity of MCs on animals, including humans, has been well studied, the biological role of MCs on the organ⁃ ism from which they originate has not been clearly elucidated. In this paper, we summarized MCs production, especially MCs bio⁃ logical function with the development of technology in recent years. We reviewed and discussed the biological role of MCs in four as⁃ pects: Serving as allelochemical, involving in photosynthesis, taking part in the wintering and recovery of Microcystis and in the sustaining and formation of Microcystis colonies. In addition, MCs may act as signal molecule inside and outside Microcystis cells, relevant research has also been reviewed. Global climatic change which favour cyanobacterial blooms in eutrophic waters, may also influence the competition between MC⁃producing and non⁃MC⁃producing strains and their dominance. The study on the competition between MC⁃producing and non⁃MC⁃producing strains and the biological role of protein⁃bound MCs should be focused on for further investigation, fast development of variable ⁃omics would favor the investigation.

Effects of environmental factors on the growth and ingestion characteristics of chrysophycean Poterioochromonas sp.

A chrysophycean Poterioochromonas sp.with two different flagella,isolated from Microcystis cultures in 2002,can not only photosynthesize with chloroplast,but also efficiently ingest and digest preys,such as Microcystis.In order to investigate the potential role of Poterioochromonas sp.in cyanobacteria bloom control,experiments were carried out to study its growth and ingestion characteristics under different environmental factors in both autotrophic and mixotrophic conditions.The results showed that the growth rate of autotrophic Poterioochromonas sp.was significantly affected by light intensity and temperature except pH.When providing preys,the growth of Poterioochromonas sp.was accelerated significantly.The growth and ingestion rate of Poterioochromonas sp.increased hyperbolically with prey concentration,and their relationships could be estimated respectively by the Michaelis-Menten equation and Monod equation.The correlation between the growth of mixotrophic Poterioochromonas sp.and light intensity was significant,while there were no relationships between the growth rate and temperature and pH.PH had negative effects on the ingestion rate,while the correlations between the ingestion rate and temperature and light intensity were not significant.In a word,this Poterioochromonas has the ability to grow and graze Microcystis in many culture conditions.The present study had also shed light on the possibility of utilizing this organism,together with other agents,for the control of Microcystis bloom.