Diversity and metabolic potential of the microbiota associated with a soil arthropod

Abstract

Springtails are important members of the soil fauna and play a key role in plant litter decomposition, for example through stimulation of the microbial activity. However, their interaction with soil microorganisms remains poorly understood and it is unclear which microorganisms are associated to the springtail (endo) microbiota. Therefore, we assessed the structure of the microbiota of the springtail Orchesella cincta (L.) using 16S rRNA gene amplicon sequencing. Individuals were sampled across sites in the field and the microbiota and in particular the endomicrobiota were investigated. The microbiota was dominated by the families of Rickettsiaceae, Enterobacteriaceae and Comamonadaceae and at the genus level the most abundant genera included Rickettsia, Chryseobacterium, Pseudomonas, and Stenotrophomonas. Microbial communities were distinct for the interior of the springtails for measures of community diversity and exhibited structure according to collection sites. Functional analysis of the springtail bacterial community suggests that abundant members of the microbiota may be associated with metabolism including decomposition processes. Together these results add to the understanding of the microbiota of springtails and interaction with soil microorganisms including their putative functional roles.

Figure 1

Alpha diversity measurements of the microbiota and endomicrobiota of Orchesella cincta sampled across locations. Boxplot displaying the observed number of OTUs (a), the estimated richness (b); ChaoI index) and evenness (c); Shannon’s index) (n = 3). The boxplot bounds the interquartile range (IQR) divided by the median, the whiskers extend to 1.5 × IQR beyond the box.

Figure 2

Composition and abundance of the springtail microbiota. Heatmap representing the 25 most abundant OTUs detected across sites, with the genus level or highest possible taxonomic classification displayed. Samples are sorted by microbiota and endomicrobiota and site.

Figure 3

Beta diversity analysis of the microbiota of Orchesella cincta. Principal coordinate analysis (PCoA) on unweighted UniFrac distances between samples. Samples are colored by microbiota and endomicrobiota.

Figure 4

Predicted metabolic profiles. Heatmap of the association of the 15 most abundant OTUs of the gut flora of the springtail Orchesella cincta with Level 2 KEGG pathways. MEP = methylerythritol phosphate pathway, Rib-P = Ribosome P. Heatmap is sorted using a dendrogram based on unweighted UniFrac distances between samples. Samples are colored by microbiota (red) and endomicrobiota (blue).