Phylogenetic diversity of intra-amoebal legionellae as revealed by 16S rRNA gene sequence comparison

1 Unité des Rickettsies, CNRS EP J 0054, Faculté de Médecine, 27 Boulevard Jean Moulin, 13385 Marseille, France 2 Leeds Public Health Laboratory, Bridle Path, York Road, Leeds LS15 7TR, UK 3 Atypical Pneumonia Unit, Respiratory and Systemic Infection Laboratory, Central Public Health Laboratory, 61 Colindale Avenue, London NW9 5HT, UK ABSTRACT Summary: Following a recent phylogenetic analysis of all 39 species of the genus Legionella and related organisms, the name Legionella lytica has been proposed for bacteria previously considered either as Sarcobium lyticum or as ‘Legionella -like amoebal pathogens’ (LLAPs). To investigate the phylogenetic integrity of this newly proposed species, we determined the 16S rRNA gene sequences of 10 LLAPs isolated from various environmental sources. All 10 isolates clustered within a monophyletic group containing all other members of the genus Legionella. Eight of the 10 isolates formed a monophyletic subgroup within the genus which also included the two previously characterized L. lytica strains. Four of these 10 isolates shared a specific and very close relationship with the L. lytica type strain (> 99% sequence similarity). However, although clearly legionellae, the remaining two LLAP strains bore no specific evolutionary relationship to either L. lytica or any other Legionella species (