Continental‐scale variation in seaweed host‐associated bacterial communities is a function of host condition, not geography

Abstract

Interactions between hosts and associated microbial communities can fundamentally shape the development and ecology of 'holobionts', from humans to marine habitat-forming organisms such as seaweeds. In marine systems, planktonic microbial community structure is mainly driven by geography and related environmental factors, but the large-scale drivers of host-associated microbial communities are largely unknown. Using 16S-rRNA gene sequencing, we characterized 260 seaweed-associated bacterial and archaeal communities on the kelp Ecklonia radiata from three biogeographical provinces spanning 10° of latitude and 35° of longitude across the Australian continent. These phylogenetically and taxonomically diverse communities were more strongly and consistently associated with host condition than geographical location or environmental variables, and a 'core' microbial community characteristic of healthy kelps appears to be lost when hosts become stressed. Microbial communities on stressed individuals were more similar to each other among locations than those on healthy hosts. In contrast to biogeographical patterns of planktonic marine microbial communities, host traits emerge as critical determinants of associated microbial community structure of these holobionts, even at a continental scale.

Functional biogeography and host specificity of bacterial communities associated with the Marine Green Alga Ulva spp.

“…However, in other cases, biogeography seems to play less of a role, such as for the sponge Ircinia spp . (Pita, López‐Legentil, & Erwin, ; Pita, Turon, López‐Legentil, & Erwin, ), as well as the macroalgae Delesseria sanguinea , Phycodrys rubens (Lachnit et al., ) and Ecklonia radiata (Marzinelli et al., ).…”

Ecophysiological Plasticity and Bacteriome Shift in the Seagrass Halophila stipulacea along a Depth Gradient in the Northern Red Sea

“…Microbial communities, due to their capability to rapidly shift in structure and function as a response to environmental change, may influence the health of their hosts (Zilber-Rosenberg and Rosenberg, 2008) by several means such as providing protection against pathogens (Rosenberg et al, 2007; Taylor et al, 2007), nitrogen fixation (Singh et al, 2004), and securing nutrient availability (Rout et al, 2013; Coats and Rumpho, 2014). In the same way, host condition (Marzinelli et al, 2015), rather than just environmental variables (Campbell et al, 2015a,b), may determine the structure of the closely associated microbial communities. Simultaneous assessments of seagrass ecophysiology and microbial community structure are therefore important to understand the capacity of the holobiont to persist under changing environmental conditions.…”

Novel ssDNA Viruses Detected in the Virome of Bleached, Habitat-Forming Kelp Ecklonia radiata

“…These phentoypes are described in Marzinelli et al (2015). Viral particles were isolated from kelp tissue as described in Lachnit et al (2015).…”

“…The bacterial components of the microbiome of bleached vs. nonbleached E. radiata were distinct, suggesting that the microbiome of the algae undergoes a shift associated with the disruption of normal function (e.g., photosynthesis; Marzinelli et al, 2015). However, specific bacterial pathogens, which induce bleaching, have not yet been extensively characterized.…”