Taxonomy of Australian clinical isolates of the genus Photorhabdus and proposal of Photorhabdus asymbiotica subsp. asymbiotica subsp. nov. and P. asymbiotica subsp. australis subsp. nov.
The relationship of Photorhabdus isolates that were cultured from human clinical specimens in Australia to Photorhabdus asymbiotica isolates from human clinical specimens in the USA and to species of the genus Photorhabdus that are associated symbiotically with entomopathogenic nematodes was evaluated. A polyphasic approach that involved DNA-DNA hybridization, phylogenetic analyses of 16S rRNA and gyrB gene sequences and phenotypic characterization was adopted. These investigations showed that gyrB gene sequence data correlated well with DNA-DNA hybridization and phenotypic data, but that 16S rRNA gene sequence data were not suitable for defining species within the genus Photorhabdus. Australian clinical isolates proved to be related most closely to clinical isolates from the USA, but the two groups were distinct. A novel subspecies, Photorhabdus asymbiotica subsp. australis subsp. nov. (type strain, 9802892T=CIP 108025T=ACM 5210T), is proposed, with the concomitant creation of Photorhabdus asymbiotica subsp. asymbiotica subsp. nov. Analysis of gyrB sequences, coupled with previously published data on DNA-DNA hybridization and PCR-RFLP analysis of the 16S rRNA gene, indicated that there are more than the three subspecies of Photorhabdus luminescens that have been described and confirmed the validity of the previously proposed subdivision of Photorhabdus temperata. Although a non-luminescent, symbiotic isolate clustered consistently with P. asymbiotica in gyrB phylogenetic analyses, DNA-DNA hybridization indicated that this isolate does not belong to the species P. asymbiotica and that there is a clear distinction between symbiotic and clinical species of Photorhabdus.
Division of Entomology, Commonwealth Scientific and Industrial Research Organization, Canberra ACT 2601, Australia.
R J
RJ
Akhurst
Ecologie microbienne des Insectes et Interaction Hôte-pathogène Unité EMIP INRA 1133, Université Montpellier II, 34095 Montpellier CEDEX 5, France.
N E
NE
Boemare
Department of Microbiology and Immunology, University of Melbourne, Vic. 3010, Australia.
P H
PH
Janssen
Department of Microbiology and Immunology, University of Melbourne, Vic. 3010, Australia.
M M
MM
Peel
Gold Coast Hospital, Southport Qld 4215, Australia.
D A
DA
Alfredson
Division of Entomology, Commonwealth Scientific and Industrial Research Organization, Canberra ACT 2601, Australia.
C E
CE
Beard
D000328:Adult; D000368:Aged; D000818:Animals; D001315:Australia; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D027081:DNA Gyrase / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry; D004756:Enterobacteriaceae Infections / Q000382:microbiology*; D005260:Female; D020459:Genes, rRNA; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009348:Nematoda / Q000382:microbiology*; D009693:Nucleic Acid Hybridization; D020637:Photorhabdus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014481:United States
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D027081:DNA Gyrase