Algae−bacteria interactions that balance the planktonic microbiome

Abstract

Summary Phytoplankton communities within the photic zones of the oceans and lakes are characterised by highly complex assemblages of unicellular microalgae and associated bacteria. The interconnected evolutionary history of algae and bacteria allowed the formation of a wide spectrum of associations defined by orchestrated nutrient exchange, mutual support with growth factors, quorum sensing mediation, and episodic killing of the partners to obtain more resources. In this review, we discuss how these cross‐kingdom interactions shape plankton communities that undergo annual, seasonal switching between alternative states with balanced multispecies consortia. We illustrate how these microscopic interactions can have consequences that scale up to influence global element cycling.

A community perspective on the concept of marine holobionts: current status, challenges, and future directions

“…For instance, seaweeds can chemically garden beneficial microbes, facilitating normal morphogenesis and increasing disease resistance (Kessler et al 2018;Saha and Weinberger 2019), and seaweeds and corals structure their surface-associated microbiome by producing chemo-attractants and anti-bacterial compounds (Harder et al 2012;Ochsenkühn et al 2018). There are fewer examples of chemical gardening in unicellular hosts, but it seems highly likely that similar processes are in place (Gribben et al 2017;Cirri and Pohnert 2019).…”

Diatom modulation of select bacteria through use of two unique secondary metabolites

“…Several biotic and abiotic factors have been shown to drive microbiome assembly and modulation in special compartments and organelles of multicellular eukaryotes such as squid light organs (2), coral skeletons (3), mammalian guts (4), and roots and leaves of terrestrial plants (5). In contrast, unicellular eukaryotes such as diatoms lack developmental features that can harbor microbes, yet rely heavily on essential bacterial growth factors (6)(7)(8) to proliferate and thrive in their environment. Diatoms are ubiquitous primary producers in aquatic environments that account for ∼40% of marine carbon export (9).…”

Microbial and chemical dynamics of a toxic dinoflagellate bloom

“…Combined with the results from the binomial regression model, these networks provide a baseline for assessing HAB microbial communities at various stages of bloom intensity. The network results also identify specific microbes (those with the strongest connections to K. brevis) for study as HAB-associated taxa that may play important roles in the intensity and duration of K. brevis blooms, potentially via chemical interdependencies similar to those common in other phytoplankton-bacteria interactions (Seyedsayamdost et al, 2011;Amin et al, 2015;Seymour et al, 2017;Cirri & Pohnert, 2019).…”

“…The latter play major roles in marine carbon and nitrogen cycles and act as agents of ecological disturbance, including through harmful algal blooms (HABs) (Field et al, 1998;Mills & Arrigo, 2010). Phytoplankton-bacterial associations include a range of mutualistic, antagonistic, and commensal interactions (Seymour et al, 2017;Cirri & Pohnert, 2019) and bacterioplankton communities change in taxonomic of algal blooms. Both molecular and metabolomic data are highly complex and traditional ecological statistics are often unsuited to analyzing diversity patterns (Thorsen et al, 2016;Tsilimigras & Fodor, 2016;Gloor et al, 2017;Weiss et al, 2017).…”