The xnp1 P2-Like Tail Synthesis Gene Cluster Encodes Xenorhabdicin and Is Required for Interspecies Competition

Abstract

Xenorhabdus nematophila, the mutualistic bacterium of the nematode Steinernema carpocapsae, produces the R-type bacteriocin called xenorhabdicin, which is thought to confer a competitive advantage for growth in the insect host. We have identified a P2-like tail synthesis gene cluster (xnp1) that is required for xenorhabdicin production. The xnp1 genes were expressed constitutively during growth and were induced by mitomycin C. Deletion of either the sheath (xnpS1) or fiber (xnpH1) genes eliminated xenorhabdicin production. Production of R-type bacteriocins in a host organism had not been shown previously. We show that xenorhabdicin is produced in the hemocoel of insects infected with the wild type but not with the ⌬xnpS1 deletion strain. Xenorhabdicin prepared from the wild-type strain killed the potential competitor Photorhabdus luminescens TT01. P. luminescens was eliminated during coculture with wild-type X. nematophila but not with the ⌬xnpS1 strain. Furthermore, P. luminescens inhibited reproduction of S. carpocapsae in insect larvae, while coinjection with wild-type X. nematophila, but not the ⌬xnpS1, strain restored normal reproduction, demonstrating that xenorhabdicin was required for killing P. luminescens and protecting the nematode partner. Xenorhabdicin killed X. nematophila from Steinernema anatoliense, demonstrating for the first time that it possesses intraspecies activity. In addition, activity was variable against diverse strains of Xenorhabdus and Photorhabdus and was not correlated with phylogenetic distance. These findings are discussed in the context of the role of xenorhabdicin in the life cycle of the mutualistic bacterium X. nematophila.

Death Becomes Them: Bacterial Community Dynamics and Stilbene Antibiotic Production in Cadavers of Galleria mellonella Killed by Heterorhabditis and Photorhabdus spp

“…S5A in the supplemental material, and reference 57). Many of their identities are currently unknown, but they may mediate additional competitive interactions, even between different symbionts, as has been suggested (84)(85)(86)(87)(88)(89)(90)(91). Additional work should also explore the archaeal, viral, protist, and invertebrate inhabitants of this community.…”

How the insect pathogen bacteria Bacillus thuringiensis and Xenorhabdus/Photorhabdus occupy their hosts

“…This was actually demonstrated for the phage-tail like bacteriocin of X. nematophila that is required for protecting the nematode partner, Steinernema carpocapsae, against bacterial competitors in G. mellonella [54 ]. Interestingly, among those antimicrobial molecules, the hydroxy-stilbene, produced by P. luminescens, and the benzylideneacetone, produced by X. nematophila, have a dual function both as inhibitors of the phenoloxidase activity and as antimicrobials against microbial competitors in the insect cadaver [55,56].…”

A New Member of the Growing Family of Contact-Dependent Growth Inhibition Systems in Xenorhabdus doucetiae

“…Antagonism with other Xenorhabdus or closely related bacterial genera may also be mediated by ribosomal-encoded bacteriocins [13, 14]. Xenorhabdus produces phage-derived bacteriocins [15, 16] and colicin E3-type killer proteins [17]. …”