The planktonic protist interactome: where do we stand after a century of research?

Abstract

Microbial interactions are crucial for Earth ecosystem function, but our knowledge about them is limited and has so far mainly existed as scattered records. Here, we have surveyed the literature involving planktonic protist interactions and gathered the information in a manually curated Protist Interaction DAtabase (PIDA). In total, we have registered~2500 ecological interactions from~500 publications, spanning the last 150 years. All major protistan lineages were involved in interactions as hosts, symbionts (mutualists and commensalists), parasites, predators, and/or prey. Predation was the most common interaction (39% of all records), followed by symbiosis (29%), parasitism (18%), and 'unresolved interactions' (14%, where it is uncertain whether the interaction is beneficial or antagonistic). Using bipartite networks, we found that protist predators seem to be 'multivorous' while parasite-host and symbiont-host interactions appear to have moderate degrees of specialization. The SAR supergroup (i.e., Stramenopiles, Alveolata, and Rhizaria) heavily dominated PIDA, and comparisons against a global-ocean molecular survey (TARA Oceans) indicated that several SAR lineages, which are abundant and diverse in the marine realm, were underrepresented among the recorded interactions. Despite historical biases, our work not only unveils large-scale eco-evolutionary trends in the protist interactome, but it also constitutes an expandable resource to investigate protist interactions and to test hypotheses deriving from omics tools.

Contrasting responses of protistan plant parasites and phagotrophs to ecosystems, land management and soil properties

“…Therefore, it is essential, not only to conduct large-scale molecular environmental sampling studies in soil, but also to attribute ecologically meaningful traits to the identified sequences. This is now facilitated by publicly available databases of protistan functional traits, including trophic guilds (Bjorbaekmo et al, 2019;Dumack et al, 2019), and by community efforts to improve the reference databases for taxonomic annotation (del Campo et al, 2018).…”

“…Recent large-scale environmental sampling investigations of soil protists in natural and seminatural environments gave insights into their multiple feeding modes, and how each trophic guild reacts to environmental filters and human-induced disturbances. Nonetheless, it must be noted that although the relative proportion of the main trophic guilds is known for planktonic protists (43 % symbionts, 43 % predators) (Bjorbaekmo et al, 2019), such a comprehensive catalogue has not yet been realized for soil. Only inventories limited -in space, by their specific aims and by methodological biases -gave partially overlapping results: a worldwide soil survey indicated that protistan communities were largely composed of "consumers" with a minority of parasites and phototrophs (Oliverio et al, 2020).…”

Making sense of environmental sequencing data: Ecologically important functional traits of the protistan groups Cercozoa and Endomyxa (Rhizaria)

“…Using the functional traits of ciliates, complex predator-prey interactions models could be assessed (Tirok & Gaedke, 2010). Recently, the planktonic Protist Interaction DAtabase (PIDA) has been compiled using the available literature and it revealed that all major planktonic protistan lineages were involved in interactions as hosts, symbionts, parasites, predators and/or prey, with symbiotic association as the main interaction (Bjorbaekmo, Evenstad, Røsaeg, Krabberød, & Logares, 2019).…”

Disentangling environmental effects in microbial association networks

“…Although microbial communities are highly interconnected Layeghifard et al (2017), our knowledge about ecological interactions in the microbial world is still limited Bjorbaekmo et al (2019); Krabberød et al (2017).…”