An ABC guide to the bacterial toxin complexes.
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Animals↗
Biomedical subjects
Nicholas Waterfield
Publications and source records attributed to Nicholas Waterfield.
The Photorhabdus Pir toxins are similar to a developmentally regulated insect protein but show no juvenile hormone esterase activity.
The genome of the insect pathogen Photorhabdus luminescens strain TT01 contains numerous genes predicting toxins and proteases. Within the P. luminescens TT01 genome, the products of two loci, plu 4093-plu 4092 and plu 4437-plu 4436, show oral insecticidal activity against both moth and mosquito larvae. The proteins encoded by these loci, here termed 'Photorhabdus insect related' (Pir) proteins A and B, show similarity both to delta-endotoxins from Bacillus thuringiensis (Bts) and a developmentally regulated protein from a beetle, Leptinotarsa decemlineata. The beetle protein has been inferred to possess juvenile hormone esterase (JHE) activity due to its developmentally regulated pattern of expression and the Photorhabdus proteins PirA and PirB have been proposed to be mimics of insect JHEs that can disrupt insect metamorphosis by metabolizing the insect growth regulator juvenile hormone (JH) [Nat. Biotechnol. 21 (2003) 1307-1313]. Here we confirm that, when injected together, PirA and PirB from two different Photorhabdus strains have insecticidal activity against caterpillars of the moth Galleria mellonella but show no oral activity against a second moth species Manduca sexta. Direct measurement of JHE activity, however, shows that the Pir proteins are not able to metabolise JH. These data show that the Pir proteins have no JHE activity, as suggested, but leave the mode of action of these interesting proteins uncertain.
Amino Acid Sequence↗
An ABC Guide to the Bacterial Toxin Complexes.
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Journal Article↗
Human infection with Photorhabdus asymbiotica: an emerging bacterial pathogen.
The three currently recognised Photorhabdus species are bioluminescent bacteria that are pathogenic to insects. P. luminescens and P. temperata form a symbiotic relationship with nematodes that infect insects. P. asymbiotica, on the other hand, has only been isolated from human clinical specimens from the USA and Australia. The bacterium has been associated with locally invasive soft tissue and disseminated bacteraemic infections. An invertebrate vector for P. asymbiotica has not yet been identified.
Communicable Diseases, Emerging↗
Photorhabdus: towards a functional genomic analysis of a symbiont and pathogen.
Pathogenicity and symbiosis are central to bacteria-host interactions. Although several human pathogens have been subjected to functional genomic analysis, we still understand little about bacteria-invertebrate interactions despite their ecological prevalence. Advances in our knowledge of this area are often hindered by the difficulty of isolating and working with invertebrate pathogenic bacteria and their hosts. Here we review studies on pathogenicity and symbiosis in an insect pathogenic bacterium Photorhabdus and its entomopathogenic nematode vector and model insect hosts. Whilst switching between these hosts, Photorhabdus changes from a state of symbiosis with its nematode vector to one of pathogenicity towards its new insect host and both the bacteria and the nematode then cooperatively exploit the dying insect. We examine candidate genes involved in symbiosis and pathogenicity, their secretion and expression patterns in culture and in the host, and begin to dissect the extent of their genetic coregulation. We describe the presence of several large genomic islands, putatively involved in pathogenicity or symbiosis, within the otherwise Yersinia-like backbone of the Photorhabdus genome. Finally, we examine the emerging comparative genomics of the Photorhabdus group and begin to describe the interrelationship between anti-invertebrate virulence factors and those used against vertebrates.
Animals↗
Using a DNA microarray to investigate the distribution of insect virulence factors in strains of photorhabdus bacteria.
Photorhabdus is an insect-pathogenic bacterium in which oral toxicity to insects is found in two distinct taxonomic groups. Using a DNA microarray and comparative genomics, we show that oral toxicity is associated with toxin complex genes tcaABC and that this locus can be mobilized or deleted within different strains.
Administration, Oral↗
The lumicins: novel bacteriocins from Photorhabdus luminescens with similarity to the uropathogenic-specific protein (USP) from uropathogenic Escherichia coli.
Bacteriocins are proteins produced by bacteria to destroy other bacteria occupying their ecological niche. Photorhabdus luminescens is an insect pathogenic bacterium carried by an entomopathogenic nematode and occupies several different niches in its life cycle. The nematode enters the insect and releases a single strain of P. luminescens. The bacteria then kill the host and the bacteria and nematodes replicate within the cadaver. Strikingly, at the end of the infection the cadaver is still occupied by a single strain of bacterium, suggesting that P. luminescens can destroy other bacteria entering, or present within, the insect. Here we describe four loci encoding 'lumicins' in P. luminescens subsp. akhurstii strain W14. The lumicins are novel bacteriocins capable of killing other strains of Photorhabdus and Escherichia coli. These loci predict killer proteins and multiple dual type immunity proteins with domains similar to pyocins and colicins. The killer proteins are chimeric in nature with multiple domains, one of which is similar to the uropathogenic-specific protein (USP) described from uropathogenic E. coli. The implications of these novel bacteriocins for the lifestyle of Photorhabdus and the potential role of USP as a bacteriocin in E. coli are discussed.
Amino Acid Sequence↗