Photorhabdus luminescens

About: Photorhabdus luminescens is a research topic. Over the lifetime, 535 publications have been published within this topic receiving 19587 citations.

The genome sequence of the entomopathogenic bacterium Photorhabdus luminescens

Abstract: Photorhabdus luminescens is a symbiont of nematodes and a broad-spectrum insect pathogen. The complete genome sequence of strain TT01 is 5,688,987 base pairs (bp) long and contains 4,839 predicted protein-coding genes. Strikingly, it encodes a large number of adhesins, toxins, hemolysins, proteases and lipases, and contains a wide array of antibiotic synthesizing genes. These proteins are likely to play a role in the elimination of competitors, host colonization, invasion and bioconversion of the insect cadaver, making P. luminescens a promising model for the study of symbiosis and host-pathogen interactions. Comparison with the genomes of related bacteria reveals the acquisition of virulence factors by extensive horizontal transfer and provides clues about the evolution of an insect pathogen. Moreover, newly identified insecticidal proteins may be effective alternatives for the control of insect pests.

XENORHABDUS AND PHOTORHABDUS SPP.: Bugs That Kill Bugs

Abstract: ▪ Abstract Xenorhabdus and Photorhabdus spp. are gram negative gamma proteobacteria that form entomopathogenic symbioses with soil nematodes. They undergo a complex life cycle that involves a symbiotic stage, in which the bacteria are carried in the gut of the nematodes, and a pathogenic stage, in which susceptible insect prey are killed by the combined action of the nematode and the bacteria. Both bacteria produce antibiotics, intracellular protein crystals, and numerous other products. These traits change in phase variants, which arise when the bacteria are maintained under stationary phase conditions in the laboratory. Molecular biological studies suggest that Xenorhabdus and Photorhabdus spp. may serve as valuable model systems for studying signal transduction and transcriptional and posttranscriptional regulation of gene expression. Such studies also indicate that these bacterial groups, which had been previously considered to be very similar, may actually be quite different at the molecular level.

Insecticidal Toxins from the Bacterium Photorhabdus luminescens

Abstract: Transgenic plants expressing Bacillus thuringiensis (Bt) toxins are currently being deployed for insect control. In response to concerns about Bt resistance, we investigated a toxin secreted by a different bacterium Photorhabdus luminescens, which lives in the gut of entomophagous nematodes. In insects infected by the nematode, the bacteria are released into the insect hemocoel; the insect dies and the nematodes and bacteria replicate in the cadaver. The toxin consists of a series of four native complexes encoded by toxin complex loci tca, tcb, tcc, and tcd. Both tca and tcd encode complexes with high oral toxicity to Manduca sexta and therefore they represent potential alternatives to Bt for transgenic deployment.

Imaging of light emission from the expression of luciferases in living cells and organisms: a review.

Abstract: Luciferases are enzymes that emit light in the presence of oxygen and a substrate (luciferin) and which have been used for real-time, low-light imaging of gene expression in cell cultures, individual cells, whole organisms, and transgenic organisms. Such luciferin-luciferase systems include, among others, the bacterial lux genes of terrestrial Photorhabdus luminescens and marine Vibrio harveyi bacteria, as well as eukaryotic luciferase luc and ruc genes from firefly species (Photinus) and the sea pansy (Renilla reniformis), respectively. In various vectors and in fusion constructs with other gene products such as green fluorescence protein (GFP; from the jellyfish Aequorea), luciferases have served as reporters in a number of promoter search and targeted gene expression experiments over the last two decades. Luciferase imaging has also been used to trace bacterial and viral infection in vivo and to visualize the proliferation of tumour cells in animal models.

DNA relatedness between Xenorhabdus spp. (Enterobacteriaceae), symbiotic bacteria of entomopathogenic nematodes, and a proposal to transfer Xenorhabdus luminescens to a new genus, Photorhabdus gen. nov.

Abstract: The levels of DNA relatedness for a broad sample of Xenorhabdus strains isolated from different species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) and from different geographical sources were estimated by the hydroxyapatite method. The level of DNA-DNA relatedness for the two phases of each isolate tested was not significantly different from 100%, demonstrating unequivocally that the phase variation demonstrated by all Xenorhabdus spp. is not due to contamination. The isolates of the described Xenorhabdus species coalesced into different DNA relatedness groups, confirming that Xenorhabdus nematophilus, Xenorhabdus bovienii, Xenorhabdus poinarii, and Xenorhabdus beddingii, defined on the basis of phenotypic differences, are valid species. The symbiont of Steinernema intermedia also coalesced with the X. bovienii isolates. This was the only symbiont of seven recently described and unamed Steinernema spp. (including Steinernema ritteri, Steinernema rara, and Steinernema anomali) that formed a group with any of the previously described Xenorhabdus species; new species descriptions are required to accommodate the other taxa, but too few isolates were available to allow satisfactory descriptions of them. The DNA relatedness data also showed that the bacteria currently classified as Xenorhabdus luminescens are significantly different from all other Xenorhabdus strains. These data strongly support indications from previous studies of phenotypic characteristics, cellular fatty acids, and DNA relatedness that X. luminescens should be classified as a separate genus. A new genus, Photorhabdus, with an amended description of the type species, Photorhabdus luminescens, is proposed.