Photorhabdus Boemare et al. 1993
General information
Description and emendation
Gram-negative, as porogenous rods. Cell size is highly variable within and between cultures, ranging from 2 by 0.5 to 10 by 2 µm, with occasional filaments up to 30 µm long; spheroplasts occur in the last stage of exponential growth. Motile and peritrichous. Most strains produced red, pink, or yellow-pigmented colonies, especially on rich media (tryptic soya agar, yolk nutritive agar). Facultatively anaerobic; metabolism respiratory and fermentative. Bioluminescent, usually detectable by a dark-adapted eye; bioluminescence intensity varies within and between isolates and may be detectable only with a photometer or scintillation counter in some isolates. One nonluminescent isolate is known. Catalase positive. Does not reduce nitrate. Negative for oxidase, o-nitrophenyl-β-D-galactopyranoside, Voges-Proskauer, arginine dihydrolase, and lysine and ornithine decarboxylase tests. Proteolytic for gelatin. Lipolytic activity on Tween 20; many strains are lipolytic for Tween 40, Tween 60, Tween 80 and/or Tween 85. Acid is produced from glucose without gas; acid is produced from very few other carbohydrates. Acid is produced from fructose, mannose, and N-acetylglucosamine; acid production from glycerol, ribose, and maltose is variable. Succinate, fumarate, L-tyrosine, L-glutamate, and glucosamine are utilized as sole carbon and energy sources. The optimum temperature is usually ca. 25°C; some strains do not grow at 37°C. Pathogenic for insects; the 50% lethal dose is less than 100 cells when the organisms are injected into Galleria mellonella hemocoel. The G+C content of the DNA is 43 to 44 mol%. The natural habitat for most strains is the intestinal lumen of entomopathogenic nematodes belonging to the family Heterorhabditidae and insects infected by these nematodes; one DNA relatedness group is associated with human clinical specimens. Within an isolate colony morphology may be highly variable. Two extreme types are characterized as phases one and two. Phase one is found in the infective stage of the nematode host; phase two is known only from in vitro culture and clinical specimens. Phase one cultures produce highly mucoid colonies and absorb dye, forming red colonies from MacConkey agar; they also adsorb other dyes, such as bromothymol blue and Congo red. A large proportion of cells contain proteinic inclusion bodies. Phase one cultures produce agar-diffusible antimicrobial compounds and lecithinase. Phase one is very much more bioluminescent and more lipolytic than phase two. In pigmented strains, phase one is differently pigmented than phase two. Phase two colonies are not mucoid and do not absorb dye; very weak antimicrobial and lecithinase activities may be detected. The change from phase one to phase two usually occurs during the stationary period of in vitro cultures; change from phase two to phase one has not been demonstrated. Several intermediate colony forms, possessing at least some phase one properties, have been described.
Subdivision(s)
MID | Name | Rank | Taxon ID |
---|---|---|---|
M022506080505002 | Photorhabdus akhurstii | Species | 171438 |
M022506080505003 | Photorhabdus asymbiotica | Species | 291112 |
M022506080505004 | Photorhabdus australis | Species | 286156 |
M022506080505005 | Photorhabdus bodei | Species | 2029681 |
M022506080505006 | Photorhabdus caribbeanensis | Species | 1004165 |
M022506080505007 | Photorhabdus cinerea | Species | 471575 |
M022506080505008 | Photorhabdus hainanensis | Species | 1004166 |
M022506080505009 | Photorhabdus heterorhabditis | Species | 880156 |
M022506080505010 | Photorhabdus kayaii | Species | 230088 |
M022506080505011 | Photorhabdus khanii | Species | 1004150 |
M022506080505012 | Photorhabdus kleinii | Species | 768034 |
M022506080505013 | Photorhabdus laumondii | Species | 2218628 |
M022506080505001 | Photorhabdus luminescens | Species | 29488 |
M022506080505014 | Photorhabdus namnaonensis | Species | 1851568 |
M022506080505015 | Photorhabdus noenieputensis | Species | 1208607 |
M022506080505016 | Photorhabdus stackebrandtii | Species | 1123042 |
M022506080505017 | Photorhabdus tasmaniensis | Species | 1004159 |
M022506080505018 | Photorhabdus temperata | Species | 574560 |
M022506080505019 | Photorhabdus thracensis | Species | 230089 |