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- Title
Formation of large colonies: a defense mechanism of Microcystis aeruginosa under continuous grazing pressure by flagellate Ochromonas sp.
- Authors
Zhen Yang; Fanxiang Kong
- Abstract
Induced colony formation under grazing pressure has been reported in our previous results. However, the colonies induced in these studies comprised only tens of cells which are far smaller than the naturally occurring colonies. In this work, unicellular Microcystis aeruginosa Kützing were co-cultivated with flagellate Ochromonas sp. for 50 d to investigate colony formation in M. aeruginosa under continuous grazing pressure. Results revealed that colonial M. aeruginosa formed on the 10th d under the grazing pressure of flagellate. These algal colonies resulted from the daughter cells of freshly dividing cells that failed to separate during the reproductive process. The diameters and cell numbers of the colonies increased slowly with time. Under continuous grazing pressure by Ochromonas sp. for 50 d, the diameter of some colonies reached over 180 µm. Analysis showed that the extra cellular polysaccharide (EPS) content and relative gas vesicle (RGV) of each cell increased significantly after colony formation. However, there was no significant difference on the monosaccharide composition between unicellular and colonial M. aeruginosa. The loose aggregation of cells in the floating colonies suggests that a correlation probably exists between cell compactness and colony buoyancy.
- Subjects
MICROCYSTIS aeruginosa; MICROCYSTIS; CHROOCOCCACEAE; FLAGELLATA; OCHROMONAS
- Publication
Journal of Limnology, 2012, Vol 71, Issue 1, p61
- ISSN
1129-5767
- Publication type
Article
- DOI
10.4081/jlimnol.2012.e5