Bacterial community profile after the lethal infection of Steinernema–Xenorhabdus pairs into soil-reared Tenebrio molitor larvae

Abstract

The host microbiota may have an impact on pathogens. This is often studied in laboratory-reared hosts but rarely in individuals whose microbiota looks like that of wild animals. In this study, we modified the gut microbiota of the insect Tenebrio molitor by rearing larvae in soil sampled from the field. We showed by high throughput sequencing methods that this treatment modifies the gut microbiota so that it is more diversified than that of laboratory-reared insects, and closely resembled the one of soil-dwelling insects. To describe what the entomopathogenic bacterial symbiont Xenorhabdus (Enterobacteriaceae), vectored by the soil-dwelling nematode Steinernema, might experience in natural conditions, we studied the infestation of the soil-reared T. molitor larvae with three Steinernema–Xenorhabdus pairs. We performed the infestation at 18°C, which delays the emergence of new infective juveniles (IJs), the soil-dwelling nematode forms, but which is a temperature compatible with natural infestation. We analyzed by high throughput sequencing methods the composition of the bacterial community within the insect cadavers before the first emergences of IJs. These bacterial communities were generally characterized by one or two non-symbiont taxa. Even for highly lethal Steinernema–Xenorhabdus pairs, the symbiont does not dominate the bacterial community within the insect cadaver.

Chemical ecology of an apex predator life cycle

“…The Photorhabdus phb genes encode proteins that sequester iron from the cadaver to fend off soil-dwelling bacterial colonizers that exploit the cadaver, and X. nematophila does not have any homologs to these genes. X. nematophila does not completely dominate the bacterial community of the insect host, suggesting that other taxa such as Alcaligenes are possibly responsible for this concentration shift {Cambon, 2020}.…”

Comparative Nanopore Sequencing-Based Evaluation of the Midgut Microbiota of the Summer Chafer (Amphimallon solstitiale L.) Associated with Possible Resistance to Entomopathogenic Nematodes

“…A study on coleopteran T. molitor larvae confirmed their susceptibility to Steinernema spp. [ 43 ]. On the other hand, coleopteran larvae such as A. solstitiale or M. melolontha are relatively resistant to both Heterorhabditis and Steinernema nematodes [ 13 , 16 , 44 ].…”

“…This is consistent with the findings reported by Cambon et al, who showed that the identity of three Steinernema spp. used for the infestation of insect larvae had no effect on the composition of the gut bacterial community in the early stage of infection [ 43 ]. However, it is also possible that we were not able to detect the discrete changes due to the high intra-individual variability of microbiota compositions.…”

First record of entomopathogenic nematodes from Yucatán State, México and their infectivity capacity against Aedes aegypti

“…Some of these bacteria have been reported to have low pathogenicity to mosquito larvae, especially those of the genera Lysinibacillus and Paenibacillus (Rojas-Pinzón & Dussán, 2017). Cambon et al (2020) mentioned that the host's 'normal' microbiota may be present in the host without causing damage, but under specific stress conditions such as infection with EPN, these opportunistic bacteria could manifest if the host immune system is suppressed. In the current study, the role these bacteria play during the infection process of the mosquito larvae or their interaction with the immune capacity of these larvae is unknown.…”