Microbiomes Reduce Their Host’s Sensitivity to Interspecific Interactions

Abstract

Bacteria associated with eukaryotic hosts can affect host fitness and trophic interactions between eukaryotes, but the extent to which bacteria influence the eukaryotic species interactions within trophic levels that modulate biodiversity and species coexistence is mostly unknown. Here, we used phytoplankton, which are a classic model for evaluating interactions between species, grown with and without associated bacteria to test whether the bacteria alter the strength and type of species interactions within a trophic level. We demonstrate that host-associated bacteria alter host growth rates and carrying capacity. This did not change the type but frequently changed the strength of host interspecific interactions by facilitating host growth in the presence of an established species. These findings indicate that microbiomes can regulate their host species’ interspecific interactions. As between-species interaction strength impacts their ability to coexist, our findings show that microbiomes have the potential to modulate eukaryotic species diversity and community composition. IMPORTANCE Description of the Earth’s microbiota has recently undergone a phenomenal expansion that has challenged basic assumptions in many areas of biology, including hominid evolution, human gastrointestinal and neurodevelopmental disorders, and plant adaptation to climate change. By using the classic model system of freshwater phytoplankton that has been drawn upon for numerous foundational theories in ecology, we show that microbiomes, by facilitating their host population, can also influence between-species interactions among their eukaryotic hosts. Between-species interactions, including competition for resources, has been a central tenet in the field of ecology because of its implications for the diversity and composition of communities and how this in turn shapes ecosystem functioning.

The study of host–microbiome (co)evolution across levels of selection

“…Moreover, separating interaction networks at the scale of microbial versus 'macrobial' organisms is likely to result in incomplete understanding of the system. Recent work from phytoplankton communities found that the hostassociated bacteria not only changed host growth rate, but also altered the carrying capacity of host populations [58]. Given the importance of carrying capacity and growth rate in shaping competition and community diversity, this finding emphasizes the great need for better integration of host and microbial networks in understanding species' ecologies, and highlights how host-microbiome interactions can drive eco-evolutionary dynamics.…”

New insight into the divergent responses of plants to warming in the context of root endophytic bacterial and fungal communities

“…Climate changes also affect plant ranges and allow some species to expand or narrow their ranges ( Morin, Viner & Chuine, 2008 ). The formation of new interspecific relationships between plant species under climate change may drive these ecological processes ( Little et al, 2016 ), and endophytes may modulate the interspecific interactions and vegetation composition ( Porras-Alfaro & Bayman, 2011 ; Jackrel et al, 2020 ).…”

Effects of lipid emulsions on the formation of Escherichia coli–Candida albicans mixed-species biofilms on PVC

“…The carbon chain lengths were C6-24. Moreover, the interactions between species are very complex, ranging from cooperation to competition and even predation 33,34 . E. coli can significantly influence candidal growth and induce hyphal death 35 .…”