TY - JOUR
T1 - A robust phylogenetic framework for the bacterial genus Photorhabdus and its use in studying the evolution and maintenance of bioluminescence: A case for 16S, gyrB, and glnA
AU - Peat, S M
AU - Ffrench-Constant, R H
AU - Waterfield, Nicholas R
AU - Marokhazi, J
AU - Fodor, A
AU - Adams, B J
PY - 2010/11
Y1 - 2010/11
N2 - Photorhabdus spp., the only known bioluminescent terrestrial bacteria are well known for their symbiotic association with heterorhabditid nematodes. This association, along with their ability to kill insects, has aroused interest in the evolutionary relationships within this bacterial group. Currently, three species are recognized within the genus Photorhabdus; P. temperata and P. luminescens, which are endosymbionts of Heterorhabditis spp., and P. asymbiotica, which has been isolated from human wounds and has recently been shown to also have a heterorhabditid nematode vector. To examine phylogenetic relationships among these taxa, we utilize total evidence Bayesian, likelihood, and parsimony based analyses of three genetic loci (16S rRNA gene, gyrB, and glnA) to construct a robust evolutionary hypothesis for the genus Photorhabdus. Here we use this phylogeny to evaluate existing specific and sub-specific taxonomic statements within the genus, identify previously undescribed Photorhabdus strains, test the utility of 16S rRNA gene, gyrB, and glnA in resolving various levels of relationships within the genus, and, finally, to investigate the evolution of bioluminescence. The genes examined produced the most robust phylogenetic hypothesis to date for the genus Photorhabdus, as indicated by strong bootstrap and posterior probability values at previously unresolved or poorly resolved nodes. We show that glnA is particularly useful in resolving specific and intra-specific relationships poorly resolved in other studies. We conclude that P. asymbiotica is the sister group to P. luminescens and that the new strains HIT and JUN should be given a new group designation within P. asymbiotica. Furthermore, we reveal a pattern of decline in bioluminescent intensity through the evolution of Photorhabdus, suggesting that this may be a trait acquired and maintained under previous ecological (aquatic) selection pressures that is now gradually being lost in (C) its terrestrial environment.
AB - Photorhabdus spp., the only known bioluminescent terrestrial bacteria are well known for their symbiotic association with heterorhabditid nematodes. This association, along with their ability to kill insects, has aroused interest in the evolutionary relationships within this bacterial group. Currently, three species are recognized within the genus Photorhabdus; P. temperata and P. luminescens, which are endosymbionts of Heterorhabditis spp., and P. asymbiotica, which has been isolated from human wounds and has recently been shown to also have a heterorhabditid nematode vector. To examine phylogenetic relationships among these taxa, we utilize total evidence Bayesian, likelihood, and parsimony based analyses of three genetic loci (16S rRNA gene, gyrB, and glnA) to construct a robust evolutionary hypothesis for the genus Photorhabdus. Here we use this phylogeny to evaluate existing specific and sub-specific taxonomic statements within the genus, identify previously undescribed Photorhabdus strains, test the utility of 16S rRNA gene, gyrB, and glnA in resolving various levels of relationships within the genus, and, finally, to investigate the evolution of bioluminescence. The genes examined produced the most robust phylogenetic hypothesis to date for the genus Photorhabdus, as indicated by strong bootstrap and posterior probability values at previously unresolved or poorly resolved nodes. We show that glnA is particularly useful in resolving specific and intra-specific relationships poorly resolved in other studies. We conclude that P. asymbiotica is the sister group to P. luminescens and that the new strains HIT and JUN should be given a new group designation within P. asymbiotica. Furthermore, we reveal a pattern of decline in bioluminescent intensity through the evolution of Photorhabdus, suggesting that this may be a trait acquired and maintained under previous ecological (aquatic) selection pressures that is now gradually being lost in (C) its terrestrial environment.
KW - heterorhabditis
KW - glnA
KW - phylogenetic systematics
KW - gyrB
KW - 16S rRNA gene
KW - photorhabdus
KW - bioluminescence
UR - http://www.scopus.com/inward/record.url?scp=78049359995&partnerID=8YFLogxK
UR - http://dx.doi.org/10.1016/j.ympev.2010.08.012
U2 - 10.1016/j.ympev.2010.08.012
DO - 10.1016/j.ympev.2010.08.012
M3 - Article
SN - 1055-7903
VL - 57
SP - 728
EP - 740
JO - Molecular Phylogenetics and Evolution
JF - Molecular Phylogenetics and Evolution
IS - 2
ER -