The core gut microbiome changes throughout life cycle and season of bark
beetle Ips typographus
Abstract
Ips typographus, the most serious pest of spruce forests in Europe, is
associated with microorganisms facilitating its invasion and development
inside spruce tissues. Despite the importance of I. typographus, little
is known about its core gut microbiome. Hereby, we describe the
composition of bacterial and fungal microbiomes throughout I.
typographus life cycle in spring and summer generations. We used
cultivation technique and molecular identification in combination with
DNA and RNA metabarcoding to achieve deep inside into the beetle’s
microbiome composition and structure. As it is not known whether
microbiome forms stable communities inside the beetle’s gut, we observed
gut epithelium for biofilm formation with Transmission Electron
Microscopy. Cultivation technique together with DNA and RNA
metabarcoding indicated similar dominant taxa. The bacterial community
belongs almost exclusively to the phylum Proteobacteria (newly
Pseudomonadota) and the most common orders and genera are
Enterobacteriales (Erwinia and Serratia), Pseudomonadales (Pseudomonas)
and Xanthomonadales (Pseudoxanthomonas, Stenotrophomonas). Yeasts
(Saccharomycetes) highly dominated the fungal microbiome, followed by
Sordariomycetes represented mainly by Ophiostoma bicolor and
Endoconidiophora polonica. The most common yeasts were Wickerhamomyces
bisporus, Kuraishia molischiana, Nakazawaea ambrosiae, Yamadazyma spp.
and Cyberlindnera sp. The proportions of the dominant taxa belonging to
the core microbiome of I. typographus change throughout its life cycle
and generations. We did not observe any biofilm formation on gut
epithelium, which suggests that microbial cells pass through the
beetle’s gut with chyme. We propose that species belonging to the core
microbiome has similar functions and alternate in the I. typographus
ecosystem depending on environmental conditions.