TAome analysis of type-II toxin-antitoxin system from Xenorhabdus nematophila

Abstract

Here we report the first essentially complete TAome analysis for type II toxin-antitoxin (TA) system, a major class of TA modules found in bacterial system, from entomopathogenic bacterium Xenorhabdus nematophila ATCC 19061 (NCBI RefSeq NC_014228). We summarize this analysis in terms of TA locus, accession identifier, hits in conserved domain database, toxin superfamily, antitoxin superfamily and chromosomal/mobile genome/plasmid occurrences. Moreover, for TA context analyses we use six different specifications namely virulence factors, mobile genetic elements (MGE), antibiotic resistance genes, secretion systems, prophage and a classification of mobile genetic elements (ACLAME); among these hits are found for only MGE, ACLAME and prophage. A total 39 sets of TA have been discovered in which numbers of TA encoded for MGE, ACLAME and prophage are 15, 15 and 5 respectively while the remaining four have no context hit. In addition, a comparative analysis of TAome was also done with closely related bacterium Photorhabdus luminescens subsp. laumondii TTO1 (NCBI RefSeq NC_005126) and results shows that a total 8 sets of TA are conserved. Further, a bootstrap Neighbor-Joining phylogenetic tree was also constructed for major toxin protein superfamily found namely RelE, HigB, GNAT, CcdB and MazF explored in the TAome of X. nematophila. We also characterized, the most abundantly found TA module (relBE) in this TAome, functionally and transcriptionally. This first TAome analysis of type II TA modules provides new insights in multi-drug tolerance in bacterial populations.

Keywords: Mobile genetic elements; Photorhabdus luminescens; Phylogenetic analysis; Xenorhabdus nematophila; relBE toxin-antitoxin system; β-galactosidase assay.