PHYLOGENY OF THE FAMILY MORAXELLACEAE BY 16S RDNA SEQUENCE-ANALYSIS, WITH SPECIAL EMPHASIS ON DIFFERENTIATION OF MORAXELLA SPECIES

Thirty-three strains previously classified into 11 species in the bact erial family Moraxellaceae were subjected to phylogenetic analysis bas ed on 16S rRNA sequences, The family Moraxellaceae formed a distinct c lade consisting of four phylogenetic groups as judged from branch leng ths, bootstrap values and signature nucleotides. Group I contained the classical moraxellae and strains of the coccal moraxellae, previously known as Branhamella, with 16S rRNA similarity of greater than or equ al to 95 %. A further division of group I into five tentative clusters is discussed. Group II consisted of two strains representing Moraxell a atlantae and Moraxella osloensis. These strains were only distantly related to each other (93.4 %) and also to the other members of the Mo raxellaceae (less than or equal to 93 %), Therefore, reasons for recla ssification of these species into separate and new genera are discusse d. Group III harboured strains of the genus Psychrobacter and strain 7 52/52 of [Moraxella] phenylpyruvica. This strain of [M.] phenylpyruvic a formed an early branch from the group III line of descent, Interesti ngly, a distant relationship was found between Psychrobacter phenylpyr uvicus strain ATCC 23333(T) (formerly classified as [M.] phenylpyruvic a) and [M.] phenylpyruvica strain 752/52, exhibiting less than 96% nuc leotide similarity between their 165 rRNA sequences, The establishment of a new genus for [M.] phenylpyruvica strain 752/52 is therefore sug gested. Group IV contained only two strains of the genus Acinetobacter , Strategies for the development of diagnostic probes and distinctive sequences for 165 rRNA-based species-specific assays within group I ar e suggested. Although these findings add to the classificatory placeme nts within the Moraxellaceae, analysis of a more comprehensive selecti on of strains is still needed to obtain a complete classification syst em within this family.