THE IMPORTANCE OF USING OUTGROUP REFERENCE ORGANISMS IN PHYLOGENETIC STUDIES - THE ATOPOBIUM CASE

Comparative 16S rDNA studies of lactic acid bacteria and some of their phylogenetic relatives of the Clostridium/Bacillus subphylum of Gram-positive bacteria indicated that three misclassified Lactobacillus and Streptococcus species, described as members of the novel genus Atopobium, formed separate subline of descent within this subphylum. Inclusion of outside reference organisms such as members of the order Actinomycetales and a cyanobacterial species, serving as the root of Gram-positive bacteria, clearly showed Atopobium species to branch off within the actinomycetes line of descent. The importance of the use of an appropriate selection of reference organisms in phylogenetic studies is discussed.