Fischer-Le Saux M, Viallard V, Brunel B, Normand P, Boemare N E
Laboratoire de Pathologie comparée, CNRS-INRA URA 2209, Université Montpellier II, France.
Int J Syst Bacteriol. 1999 Oct;49 Pt 4:1645-56. doi: 10.1099/00207713-49-4-1645.
The taxonomic position of Photorhabdus strains was examined through the results of DNA relatedness (S1 nuclease method) studies associated with the determination of delta Tm, 16S rRNA phylogenetic inferences and phenotypic characterization, including morphological, auxanographic, biochemical and physiological properties. Three genomic species were delineated on a consensus assessment. One of these species corresponded to Photorhabdus luminescens, since strains were at least 50% related to the type strain of this species with delta Tm less than 7 degrees C. The two other species were novel genomic species II and III, which were less than 40% related to each other with delta Tm higher than 9 degrees C. A comparison of the complete 16S rDNA sequences of several representatives of genomic species II and genomic species III revealed that each of them formed a stable lineage independent of the cluster generated by P. luminescens strains. The genomic species differed in their maximum temperatures for growth. A correlation with the ecological 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. Group II (maximum growth temperature 33-35 degrees C) encompassed symbionts from Heterorhabditis megidis, Heterorhabditis zealandica and group NC1 of H. bacteriophora, nematodes isolated in temperate climates. Group III were bacteria isolated from human specimens. Two new species, Photorhabdus temperata sp. nov. (type strain CIP 105563T) and Photorhabdus asymbiotica sp. nov. (type strain ATCC 43950T), are proposed for genomic species II and III, respectively. Species I and II can be separated into sub-groups on the basis of high DNA-DNA relatedness (more than 80% DNA binding with delta Tm < 1.5 degrees C), 16S rDNA branching and phenotypic characters. Therefore, we propose that the two species P. luminescens and P. temperata should be subdivided into subspecies as follows: P. luminescens subsp. luminescens subsp. nov. (type strain ATCC 29999T), P. luminescens subsp. akhurstii subsp. nov. (type strain CIP 105564T), P. luminescens subsp. laumondii subsp. nov. (type strain CIP 105565T) and P. temperata subsp. temperata subsp. nov.
通过与ΔTm测定相关的DNA相关性（S1核酸酶法）研究结果、16S rRNA系统发育推断以及包括形态、营养谱、生化和生理特性在内的表型特征分析，对发光杆菌属菌株的分类地位进行了研究。基于共识评估确定了三个基因组种。其中一个种对应于发光杆菌，因为这些菌株与该种的模式菌株至少有50%的相关性，且ΔTm小于7℃。另外两个种是新的基因组种II和III，它们彼此之间的相关性小于40%，ΔTm高于9℃。对基因组种II和基因组种III的几个代表菌株的完整16S rDNA序列进行比较后发现，它们各自形成了一个独立于发光杆菌菌株产生的簇的稳定谱系。这些基因组种在其最高生长温度上存在差异。注意到与细菌样本的生态起源存在相关性。耐热的I组（最高生长温度35 - 39℃）对应于分别生活在温暖和热带国家的嗜线虫致病杆菌Brecon和HP88组以及印度嗜线虫致病杆菌的共生菌。II组（最高生长温度33 - 35℃）包括来自大异小杆线虫、新西兰异小杆线虫和嗜线虫致病杆菌NC1组的共生菌，这些线虫是在温带气候中分离得到的。III组是从人类标本中分离得到的细菌。分别为基因组种II和III提出了两个新种，即温和发光杆菌新种（模式菌株CIP 105563T）和非共生发光杆菌新种（模式菌株ATCC 43950T）。种I和种II可以根据高DNA - DNA相关性（DNA结合率超过80%，ΔTm < 1.5℃）、16S rDNA分支和表型特征分为亚组。因此，我们建议将发光杆菌和温和发光杆菌这两个种细分为以下亚种：发光杆菌发光亚种新亚种（模式菌株ATCC 29999T）、发光杆菌阿克赫斯特亚种新亚种（模式菌株CIP 105564T）、发光杆菌拉蒙迪亚种新亚种（模式菌株CIP 105565T）和温和发光杆菌温和亚种新亚种。
