Polyphasic classification of the genus Photorhabdus and proposal of new taxa: P-luminescens subsp luminescens subsp nov., P-luminescens subsp akhurstii subsp nov., P-luminescens subsp laumondii subsp nov., P.temperata sp nov., P-temperata subsp temperata subsp nov and P-asymbiotica sp nov.

Citation
M. Fischer-le Saux et al., Polyphasic classification of the genus Photorhabdus and proposal of new taxa: P-luminescens subsp luminescens subsp nov., P-luminescens subsp akhurstii subsp nov., P-luminescens subsp laumondii subsp nov., P.temperata sp nov., P-temperata subsp temperata subsp nov and P-asymbiotica sp nov., INT J SY B, 49, 1999, pp. 1645-1656
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
INTERNATIONAL JOURNAL OF SYSTEMATIC BACTERIOLOGY
ISSN journal
0020-7713 → ACNP
Volume
49
Year of publication
1999
Part
4
Pages
1645 - 1656
Database
ISI
SICI code
0020-7713(199910)49:<1645:PCOTGP>2.0.ZU;2-M
Abstract
The taxonomic position of Photorhabdus strains was examined through the res ults of DNA relatedness (S1 nuclease method) studies associated with the de termination of Delta T-m, 16S rRNA phylogenetic inferences and phenotypic c haracterization, including morphological, auxanographic, biochemical and ph ysiological properties. Three genomic species were delineated on a consensu s assessment. One of these species corresponded to Photorhabdus luminescens , since strains were at least 50% related to the type strain of this specie s with Delta T-m less than 7 degrees C. The two other species were novel ge nomic species II and III, which were less than 40% related to each other wi th Delta T-m higher than 9 degrees C. A comparison of the complete 16S rDNA sequences of several representatives of genomic species II and genomic spe cies III revealed that each of them formed a stable lineage independent of the cluster generated by P. luminescens strains. The genomic species differ ed in their maximum temperatures for growth. A correlation with the ecologi cal origin of the bacterial samples was noticed. The heat-tolerant group I (maximum growth temperature 35-39 degrees C) corresponded to the symbionts of Heterorhabditis bacteriophora groups Brecon and HP88 and Heterorhabditis indica, nematodes living in warm and tropical countries, respectively. Gro up II (maximum growth temperature 33-35 degrees C) encompassed symbionts fr om Heterorhabditis megidis, Heterorhabditis zealandica and group NC1 of H. bacteriophora, nematodes isolated in temperate climates. Group III were bac teria isolated from human specimens. Two new species, Photorhabdus temperat e sp. nov. (type strain CIP 105563(T)) and Photorhabdus asymbiotica sp. nov . (type strain ATCC 43950(T)), are proposed for genomic species II and ill, respectively. Species I and II can be separated into sub-groups on the bas is of high DNA-DNA relatedness (more than 80% DNA binding with Delta T-m < 1.5 degrees C), 16S rDNA branching and phenotypic characters. Therefore, we propose that the two species P. luminescens and P. temperata should be sub divided into subspecies as follows: P. luminescens subsp. luminescens subsp . nov. (type strain ATCC 29999(T)), P. luminescens akhurstii subsp. nov. (t ype strain CIP 105564(T)), P. luminescens subsp. laumondii subsp, nov. (typ e strain CIP 105565(T)) and P. temperata subsp, temperata subsp. nov.