Unravelling the gut bacteriome of Ips (Coleoptera: Curculionidae: Scolytinae): identifying core bacterial assemblage and their ecological relevance

Amrita Chakraborty,Amit Roy,Fredrik Schlyter,Muhammad Zubair Ashraf,Jiří Synek,Roman Modlinger

doi:10.1038/s41598-020-75203-5

Abstract

Bark beetles often serve as forest damaging agents, causing landscape-level mortality. Understanding the biology and ecology of beetles are important for both, gathering knowledge about important forest insects and forest protection. Knowledge about the bark beetle gut-associated bacteria is one of the crucial yet surprisingly neglected areas of research with European tree-killing bark beetles. Hence, in this study, we survey the gut bacteriome from five Ips and one non-Ips bark beetles from Scolytinae. Results reveal 69 core bacterial genera among five Ips beetles that may perform conserved functions within the bark beetle holobiont. The most abundant bacterial genera from different bark beetle gut include Erwinia, Sodalis, Serratia, Tyzzerella, Raoultella, Rahnella, Wolbachia, Spiroplasma, Vibrio, and Pseudoxanthomonas. Notable differences in gut-associated bacterial community richness and diversity among the beetle species are observed. Furthermore, the impact of sampling location on the overall bark beetle gut bacterial community assemblage is also documented, which warrants further investigations. Nevertheless, our data expanded the current knowledge about core gut bacterial communities in Ips bark beetles and their putative function such as cellulose degradation, nitrogen fixation, detoxification of defensive plant compounds, and inhibition of pathogens, which could serve as a basis for further metatranscriptomics and metaproteomics investigations.

Highlights

Bark beetles often serve as forest damaging agents, causing landscape-level mortality
A total of 5,194,234 paired-end reads were generated after the sequencing of six different species of bark beetles (Coleoptera: Curculionidae: Scolytinae): Ips typographus (IT), Ips duplicatus (ID), Ips cembrae (IC); Ips sexdentatus (SX), Ips acuminatus (IAC) and Polygraphus poligraphus (PP)
The study reveals the core bacterial communities in the gut of two spruce feeding, two pine feeding, and one larch feeding Ips bark beetles collected from two forest locations within Czech Republic and their putative functional relevance in bark beetle holobiont

Summary

Introduction

Bark beetles often serve as forest damaging agents, causing landscape-level mortality. Our data expanded the current knowledge about core gut bacterial communities in Ips bark beetles and their putative function such as cellulose degradation, nitrogen fixation, detoxification of defensive plant compounds, and inhibition of pathogens, which could serve as a basis for further metatranscriptomics and metaproteomics investigations. On top of impacting the tree defence physiology adversely, repeated years of drought trigger more recurrent and devastating bark beetle outbreaks leading to large scale forest decline[3,4] This is not true for healthy trees as conifers can produce entomotoxic defensive chemicals, such as monoterpenes, in addition to releasing anti-aggregation compound such as 4-allylanisole to defend themselves against bark beetle attacks[5,6,7,8,9,10]. It is worth mentioning here that the potential of terpene degradation is not limited to bark beetle associated bacteria, i.e., some environmental bacteria such as Burkholderia xenovorans[42] and Pseudomonas abietaniphila BKME-943 can do that as well

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Results

Conclusion