Gut microbiota of the pine weevil degrades conifer diterpenes and increases insect fitness

Abstract

The pine weevil (Hylobius abietis), a major pest of conifer forests throughout Europe, feeds on the bark and cambium, tissues rich in terpenoid resins that are toxic to many insect herbivores. Here, we report the ability of the pine weevil gut microbiota to degrade the diterpene acids of Norway spruce. The diterpene acid levels present in ingested bark were substantially reduced on passage through the pine weevil gut. This reduction was significantly less upon antibiotic treatment, and supplementing the diet with gut suspensions from untreated insects restored the ability to degrade diterpenes. In addition, cultured bacteria isolated from pine weevil guts were shown to degrade a Norway spruce diterpene acid. In a metagenomic survey of the insect's bacterial community, we were able to annotate several genes of a previously described diterpene degradation (dit) gene cluster. Antibiotic treatment disrupted the core bacterial community of H. abietis guts and eliminated nearly all dit genes concordant with its reduction in diterpene degradation. Pine weevils reared on an artificial diet spiked with diterpenes, but without antibiotics, were found to lay more eggs with a higher hatching rate than weevils raised on diets with antibiotics or without diterpenes. These results suggest that gut symbionts contribute towards host fitness, but not by detoxification of diterpenes, as these compounds do not show toxic effects with or without antibiotics. Rather the ability to thrive in a terpene-rich environment appears to allow gut microbes to benefit the weevil in other ways, such as increasing the nutritional properties of their diet.

Abdominal microbial communities in ants depend on colony membership rather than caste and are linked to colony productivity

“…If we assume that the number of eggs in a nest upon collection reflects a queen's fecundity, then our results indicate that a queen's abdominal microbiome might affect her egg production and ultimately colony fitness. This is in line with other studies on insects, which found that bacterial gut residents can influence egg production (e.g., Ben-Yosef, Pasternak, Jurkevitch, & Yuval, 2014;Berasategui et al, 2017;Rosengaus et al, 2011). However, our observation could be confounded by factors such as diet, health, and genetics.…”

Established Cotton Stainer Gut Bacterial Mutualists Evade Regulation by Host Antimicrobial Peptides

“…Across the seven treatments, developmental time and insect weight upon adult emergence were not significantly different ( Fig. 4a and b) (Friedman test: developmental time, 2 [6] ϭ 5.282, P ϭ 0.508; weight at emergence, 2 [6]…”

“…Gordonibacter,2 [6] ϭ 4.041, P ϭ 0.671; Klebsiella, 2 [6] ϭ 12.143, P ϭ 0.059).Similarly, adults that emerged from the dsRNA-treated nymphs showed minor changes in the bacterial community, with only Hungatella sp. showing statistically…”

Peer Review #2 of "Current state of knowledge on Wolbachia infection among Coleoptera: a systematic review (v0.2)"

“…Single studies used groEL (Monochamus alternatus, Aikawa et al, 2009; Tribolium madens, Fialho & Stevens, 2000) or ITS genes (Tribolium madens, Fialho & Stevens, 2000). So far, only five studies have used next-generation sequencing technology (Illumina or 454) to detect Wolbachia; two used 16S rDNA for metabarcoding of microbiota (Sitona obsoletus, Steriphus variabilis, White et al, 2015; Aleochara bilineata and Aleochara bipustulata, Bili et al, 2016; Hylobius abietis, Berasategui et al, 2016;Brontispa longissimi, Takano et al, 2017; Harmonia axyridis, Dudek et al, 2017) and one used shotgun genomic sequencing (Amara alpine, Heintzman et al, 2014). For genotyping of hosts, 52.4% of studies utilized fragments of COI from mtDNA (usually a barcode fragment of this gene).…”