Determination of phylogenetic relationships of Flavobacterium psychrophilum (Flexibacter psychrophilus), Flavobacterium columnare (Flexibacter columnaris), and Flexibacter maritimus by sequence analysis of 16S ribosomal RNA genes amplified by polymerase chain reaction

The nearly complete small subunit 16S ribosomal RNA (rRNA) gene sequence am plified by polymerase chain reaction was determined for Flavobacterium psyc hrophilum (formerly Flexibacter psychrophilus) by using automated nucleotid e sequencing. The sequence was found to be 1,465 base pairs (bp) in length, a size consistent with previously determined sequences for 14 other bacter ial species from various taxa, including the yellow-pigmented bacteria. Seq uence signatures confirmed that this organism was a member of the bacterial division Bacteroides-Flavobacterium. Parsimonious and additive phylogeneti c trees were constructed with homology, and pairwise evolutionary distances , were used to estimate phylogenetic relationships. Data show that F. psych rophilum, F. columnare, and Flexibacter maritimus are closely related, have a common descent, and represent a distinct group within the division Bacte roides-Flavobacterium. This group also included other organisms from the ge nera Flavobacterium and Cytophaga. Further, Flavobacterium aquatile, the ty pe species For the genus Flavobacterium, was also determined to be a member of this "Flavobacterium-Cytophaga-Flexibacter subcomplex." This supports p revious assertions that the type strain of Flavobacterium should be changed to a more representative species such as Flavobacterium breve.