Biochemical,morphological, and genetic variations in Microcystis aeruginosa due to colony disaggregation |
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Authors: | Min Zhang Fanxiang Kong Xiao Tan Zhou Yang Huansheng Cao Peng Xing |
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Affiliation: | (1) Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, People’s Republic of China;(2) Graduate School of Chinese Academy of Sciences, Beijing, 100039, People’s Republic of China;(3) School of Biological Sciences, Nanjing Normal University, Nanjing, 210097, People’s Republic of China |
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Abstract: | Microcystis aeruginosa commonly occurs as large colonial morph under natural conditions, but disaggregates and exists as single cells in laboratory cultures. To demonstrate the adaptive changes, differentiation of carbohydrates, pigments, and protein between colonial and disaggregated M. aeruginosa were examined. Their morphological and ultrastructural characteristics were subsequently observed by scanning electron microscopy and transmission electron microscopy. Results showed that chlorophyll a and phycocyanin in cells, soluble carbohydrate produced in the culture medium, and total carbohydrate in cells and sheath of colonial M. aeruginosa are significantly higher (p < 0.05) compared with those in disaggregated cells. No significant change was found in protein concentration per cell (p > 0.05) between them. Their morphological and ultrastructural characteristics were evidently different, and by morphological criteria they could be separated into two morphotypes. In addition, the genetic diversity of 16S–23S internal transcribed spacer of them were examined and compared with reference strains of M. aeruginosa. The alignment of two sequences revealed that genetic identity level was extremely high (96.94%) and no significant difference was found in the nucleotide diversity (0.014 ± 0.008). This suggested that similar genotypes could present distinct morphotypes in M. aeruginosa. The tree topologies and analysis of molecular variance of the two sequences and reference sequences from GenBank database indicated that the genotypes of M. aeruginosa strains were not always related to their localities and exhibit heterogeneity within a species. |
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Keywords: | Carbohydrate Chlorophyll a Microcystis aeruginosa Morphology Phycocyanin Phylogenetics Ultrastructure |
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