Nematophilic bacteria associated with entomopathogenic nematodes and drug development of their biomolecules

Abstract

The importance of Xenorhabdus and Photorhabdus symbionts to their respective Steinernema and Heterorhabditis nematode hosts is that they not only contribute to their entomopathogenicity but also to their fecundity through the production of small molecules. Thus, this mini-review gives a brief introductory overview of these nematophilic bacteria. Specifically, their type species, nematode hosts, and geographic region of isolations are tabulated. The use of nucleotide sequence-based techniques for their species delineation and how pangenomes can improve this are highlighted. Using the Steinernema–Xenorhabdus association as an example, the bacterium-nematode lifecycle is visualized with an emphasis on the role of bacterial biomolecules. Those currently in drug development are discussed, and two potential antimalarial lead compounds are highlighted. Thus, this mini-review tabulates forty-eight significant nematophilic bacteria and visualizes the ecological importance of their biomolecules. It further discusses three of these biomolecules that are currently in drug development. Through it, one is introduced to Xenorhabdus and Photorhabdus bacteria, their natural production of biomolecules in the nematode-bacterium lifecycle, and how these molecules are useful in developing novel therapies.

Analyses ofXenorhabdus griffiniaegenomes reveal two distinct sub-species that display intra-species variation due to prophages

“…This indicates that effector proteins possibly contribute to traits that vary within a species. One of these traits is nematode host specificity, which varies within both X. griffiniae and X. bovienii species [7]. In X. bovienii, the inactivation of vgrG in XG2-T6SS loci in strain SS-2004 resulted in the near loss (200-fold decrease) of the bacterium's capacity to colonise its nematode host [129].…”

“…These insect-killing roundworms have been found in 51 countries to date [1][2][3][4][5][6] and are profitable commercial products for the control of insect crop pests. In addition, they are colonized by microbes, including obligate symbiotic bacteria from the genus Xenorhabdus, that produce a battery of useful biomolecules [7].…”

“…Each Steinernema nematode is colonized in the receptacle by a specific Xenorhabdus species. However, some Xenorhabdus species associate with multiple Steinernema nematode hosts [7] suggesting a relatively fluid partnership landscape in which the molecular determinants of host-symbiont specificity across the two genera are still being defined. Key to this understanding is a robust comparative analysis of the phylogenetic relatedness and genomic content of Xenorhabdus isolates.…”

“…These insect-killing roundworms have been found in 51 countries to date [1–6] and are profitable commercial products for the control of insect crop pests. In addition, they are colonized by microbes, including obligate symbiotic bacteria from the genus Xenorhabdus , that produce a battery of useful biomolecules [7]. To date, 31 Xenorhabdus species have been described [7–9] found in association with Steinernema nematodes, and the two species work in tandem to infect and kill insects and exploit the nutrient rich cadaver for the reproductive stage of their shared lifecycle.…”

Draft genomes, phylogenomic reconstruction and comparative genome analysis of three Xenorhabdus strains isolated from soil-dwelling nematodes in Kenya

“…( 16) L. 466 and L. 470: replace "nascent" with "draft" (17) L. 474: replace "failed to pass conspecific thresholds" with more specific language that describes the actual result, i.e., that the dDDH, ANI, and GGD values were not consistent with these strains belonging to the same species. (18) L. 474: the "sp. nov." designation should only be used when describing a new binomial name, and thus is inappropriate here.…”