Fungal-bacterial interactions in the human gut of healthy individuals

Most studies concerning the microbiota in the human gut focus on the bacterial part, but in-creasing information shows that also intestinal fungi are important for maintaining health. This can either be by directly influencing the host, or by indirectly influencing the gut bacteria that link to host-health. Studies about fungal communities in large cohorts are scarce, therefore this study aims to get more insight in the mycobiome of healthy individuals and how this mycobiome in-teracts with the bacterial component of the microbiome. For this, on fecal samples of 163 indi-viduals that were available from two separate studies, ITS2 and 16S rRNA gene amplicon se-quencing was performed to analyze the fungal and bacterial microbiome, respectively, as well as their cross-kingdom interactions. The results showed a much lower fungal as compared to bacterial diversity. Ascomycota and Basidiomycota were dominant fungal phyla across all samples, but levels varied enormously between individuals. The ten most abundant fungal genera were Saccharomyces, Candida, Dipodascus, Aureobasidium, Penicillium, Hanseniaspora, Agaricus, Debary-omyces, Aspergillus and Pichia, and here also extensive inter-individual variation was observed. Correlations were made between bacteria and fungi, and only positive correlations were ob-served. One of the correlations was between Malassezia restricta and the genus Bacteroides, which both are described before to be alleviated in IBD. Most other correlations found were with fungi that are not known as gut colonizers, but originate from food and environment. To further in-vestigate the importance of the observed correlations found, more research is needed to dis-criminate between gut colonizers and transient species.