PHENOTYPIC AND GENETIC DIVERSITY WITHIN A COLONY MORPHOTYPE

Isolates showing different and similar colony morphologies were select ed from spread plates of bacteria from seawater samples taken in the n orthern Adriatic Sea. All isolates were characterised by restriction f ragment length polymorphism (RFLP) patterns of their PCR-amplified 16S rRNA gene and by 95 physiological tests (Biolog system). Cluster anal ysis of both genetic and phenotypic patterns showed that different col ony morphotypes were related to different species or biotypes. However . isolates belonging to the more well-defined, conspicuous colony type s had a high similarity, whereas those from the less conspicuous colon y morphotypes showed high genetic diversity. Although colony morphotyp es clearly underestimate taxonomic diversity, they can be used combine d with PCR-RFLP analysis and as a preliminary approach for ecological studies aimed at the isolation of different species. Furthermore, for some species forming very conspicuous pigmented colonies, such as some photosynthetic aerobic bacteria, colony morphology may be useful for a rapid and low-cost screening of their distribution in the natural en vironment, especially when combined with other molecular techniques. ( C) 1998 Federation of European Microbiological Societies, Published by Elsevier Science B.V.