COMAMONAS TESTOSTERONI COLONY PHENOTYPE INFLUENCES EXOPOLYSACCHARIDE PRODUCTION AND COAGGREGATION WITH YEAST-CELLS

A Comamonas testosteroni strain was isolated from activated sludge on the basis of its ability to coaggregate with yeast cells, On agar plat es the following two types of colonies were formed: colonies with a mu coid appearance and colonies with a nonmucoid appearance, On plates th is strain alternated between the two forms, making sectored colonies, In liquid medium with constant agitation no such change was observed, In the absence of agitation and in contact with a glass surface a cult ure,vith predominantly nonmucoid-colony-forming cells very rapidly shi fted to a culture dominated by mucoid-colony-forming cells. In liquid medium the reverse was observed under stress conditions imposed by hyd rogen peroxide, sodium dodecyl sulfate, or starvation, Nonmucoid cells formed very rapidly settling flocs with yeast cells, while coaggregat ion of mucoid cells with yeast cells did not occur. These findings may be relevant to the behavior of activated sludge microbial communities .