HIGH-DEGREE OF GENETIC-VARIATION IN PROCHLOROCOCCUS (PROCHLOROPHYTA) REVEALED BY RFLP ANALYSIS

A genetic characterization of nine strains of Prochlorococcus originat ing from various depths of the Mediterranean Sea, the Sargasso Sea, th e North and the tropical Atlantic Ocean and the Pacific Ocean was perf ormed by restriction fragment length polymorphism (RFLP) mapping using probes for rbcL, rbcS, psbA and woxA. This study revealed extensive g enetic variation among strains, which were grouped into two distinct c lusters. Unexpectedly, with one exception (TATL1 strain), the strains clustered by isolation depth (i.e. near surface versus deep isolates) rather than by geographic origin. These relationships were confirmed b y secondary RFLP analysis of psbA amplification products using Prochlo rococcus-specific polymerase chain reaction (PCR) primers.