| Microcystis can produce microcystin what do damage to the liver of humanand animals, if the drinking of microcystin-polluted water for a long time may causeliver cancer. Microcystin poses huge threat to human health through a variety ofways by bioconcentration. In addition, algal blooms also cause a series of ecologicaland environmental problems, thus attracting enormous attention worldwide.The classification of Microcystis is still very controversial. The traditionaltaxonomy of Microcystis mainly rely on the morphological characteristics whichmay change with environmental conditions, and the same phenotypes may havedifferent morphological characteristics, some strains may have mixed and transitivemorphological characteristics, so morphological identification is not accurate andunbelievable. Besides, a lot of studies have shown that the genotypes is far morethan the morphospecies, so traditional classification greatly underestimate thediversity and potential features of Microcystis.60rDNA ITS sequences in Guang zhou landscape lakes and18sequences ineight large and medium-sized reservoirs in Guangdong province were determined bywhole-cell PCR and DNA extraction after cell culture respectively, combined with37homologous sequences downloaded from the GenBank, totally115sequenceswere analyzed in the present study. The determined length of rDNA ITS sequencewas477bp, the resultant length was368bp by removal of the conserved sequence in5’ and3’ terminals, of which65sites were variable, i.e. there were17.66%variablesites in the compared sequences, and48sites were parsimony-informative, i.e.there were13.04%in the analyzed sequences, indicating that73.85%variable siteswere parsimony-informative. The average content of the four bases T, C, A and Gwere18.1%,20.3%,35.1%,26.5%, of which the A is significantly higher than theother three bases. The ratio of A+T/G+C of the sequence was52.9/47.1, and A+Twas slightly higher than G+C. Genetic distance among all the algae strains were0.000-0.0650, genetic distances among different phenotypes were0.0255-0.0450,genetic distance among different geographical origin were0.0322-0.0644. In the molecular phylogenetic tree, the same or similar morphotypes strainswere placed in the same or distant branches of the molecular phylogenetic tree, thesame or similar morphotypes were not distinguished clearly; Different morphotypesof algae strains with the same or different genotype were placed in the same ordistant clades, the different morphotypes could not distinguished clearly; Some ofthe same geographical strains were placed in the adjacent or distant position, and thedifferent geographical strains was placed in distant or adjacent branches; the sameor different geographical strains were unable distinguished clearly.The genetic differentiation of Microcystis in Guangzhou lakes suggested thatthe genetic diversity was low. Morphological characters were not correlated withhaplotypes, the strains in different lakes was not correlated with haplotypes, too. Inaddition, the composition of morphotypes and abundance in each lakes ofGuangzhou was different, the genetic diversity and genetic differentiation amongdifferent lakes were also inconsistent. Combined with the results of previous studies,the present study suggested that the genetic background was different in each lakes,indicating that it should be adapted to local conditions in monitoring and controllingof microcystis bloom.Although a series of achievements in classification and identification andgenetic diversity of Microcystis by molecular biology methods were made, there arestill many problems, such as the conflicts and contradictions between the results ofmolecular marker and traditional classification. In order to understand the origin, themechanism of distribution, genetic background and diversity of Microcystis,comprehensive analysis in aspects of morphology, biogeography, ecology,physiological and biochemical remains to be studied, at last a complete system willbe established. |
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