MICROBIAL ECOLOGY OF PLANKTONIC FILAMENTOUS PHOTOTROPHIC BACTERIA IN HOLOMICTIC FRESH-WATER LAKES

The microbial ecology of the filamentous phototrophic bacterium, Chloronema giganteum has been studied in the water column of three central European lakes (Schlein, Buchen and Vechten). In these lakes an anoxic layer, termed the transition zone, was located between the oxycline and the redoxcline. The migration capacity of Chloronema through this zone appears to be responsible for the natural preponderance of either straight or spiral forms. When the transition zone is less than 1 m thick the straight form is dominant, but when this transition zone is wider than 2 m the spiral form is enriched. The intermediate situations favour both filamentous forms.