A New Species: Microcyclus marinus

For a number of years, only a single species of the genus Microcyclus Ørskov 1928, namely M. aquaticus Ørskov, was reported in the literature. Eventually, two more species, M. major Gromov 1963 and M. flavus Raj 1970, were named and described. Brief mention was also made in the literature of a marine Microcyclus strain (Raj 1970) originally isolated in 1966 from the Pacific Ocean and tentatively, hence not validly, named M. marinus. To establish its taxo-nomic status, the marine isolate was studied extensively and compared with M. aquaticus ATCC 25396 and M. flavus ATCC 23276, both from freshwater habitats. On the basis of its similarity index, as determined by numerical taxonomy with these previously named species, the marine microcyclus is believed to belong to a new species, for which the name Microcyclus marinus is proposed. The type strain of M. marinus has been deposited in the American Type Culture Collection under the number 25205 and in the Deutsche Sammlung von Mikro-organismen Collection under the number 745.