PhD Graduation

Location, date and time:

Location

 

Who's bad? Molecular identification reveals seasonal dynamics of toxic and non-toxic freshwater cyanobacteria

W.E.A. Kardinaal

 

The development of molecular tools allowed identification of cyanobacteria to the strain level and differentiation of toxic versus non-toxic strains. In addition, the ITS-DGGE technique proved useful in the early detection of harmful cyanobacteria of the genera Planktothrix and Microcystis. More specifically, we demonstrated that the rRNA ITS sequence of the genus Microcystis is sufficiently heterogeneous for the differentiation of microcystin and non-microcystin producers. In other words, by analyzing rRNA ITS diversity, toxic and non-toxic genotypes could be identified and their ecology could be studied. Our field studies revealed coexistence of several toxic and non-toxic genotypes within field populations of the cyanobacterium Microcystis. Moreover, successional patterns could be observed in some cases, explaining the sudden changes in microcystin content of the Microcystis population. In competition experiments with different Microcystis strains, it was shown that competition for light resulted in competitive exclusion of the toxic strains. This suggests that light availability might be an important factor driving the succession of Microcystis genotypes in eutrophic lakes.

Date

September 21, 2007

Duration

2:00 PM to 3:30 PM