Influence of physiological factors on the lysis effect of Cytophaga on the red microalga Rhodella reticulata

The influence of different factors on the lysis of the red microalga, Rhodella reticulata, by Cytophaga sp. LR2 was studied. The pathogenic bacterial strain was more resistant than the alga to the physiological parameters studied, which assured long-term survival of bacteria in algal cultures. Cytophaga sp. LR2 infected R. reticulata at temperatures between 15 and 30 degrees C, in the illuminated as well as the non-illuminated cultures, at pH values between 5.0 and 9.0, and in the presence of NaCl and CaCl2 in the culture medium. SEM showed a different morphology of the bacteria in algal cultures from those of axenic cultures of Cytophaga. Observations of specific associations between algal and bacterial cells revealed that the role of the slime extrusions on the bacterial surface was attachment of Cytophaga to algal cells, and that their clumping leads to rapid lysis.