Contribution of bacterial-fungal balance to plant and animal health

Surfaces of plants and animals are colonized by complex multi-kingdom microbial communities that comprise prokaryotic (i.e. archaea, bacteria) and eukaryotic (i.e. fungi, protists) microbes. Composition and variation in these multi-kingdom microbial communities are influenced by host and environmental cues that drive microbial community differentiation between host niches. Recent evidence indicates that, beyond these major forces, interactions between microbiota members also contribute to the establishment, the stability, and the resilience of host-associated microbial communities. Particularly, the interplay between bacteria and fungi in host niches appears critical for community functionality and alteration of the balance between these microbes emerges as a potential cause of disease. Here, we discuss the extent to which interactions between these microbes drive variation in community composition across plant and animal niches and we provide examples illustrating that altering bacterial-fungal balance in the microbiome can lead to disease.