Disentangling the Influence of Environment, Host Specificity and Thallus Differentiation on Bacterial Communities in Siphonous Green Seaweeds

Abstract

Siphonous green seaweeds, such as Caulerpa , are among the most morphologically complex algae with differentiated algal structures (morphological niches). Caulerpa is also host to a rich diversity of bacterial endo- and epibionts. The degree to which these bacterial communities are species-, or even niche-specific remains largely unknown. To address this, we investigated the diversity of bacteria associated to different morphological niches of both native and invasive species of Caulerpa from different geographic locations along the Turkish coastline of the Aegean sea. Associated bacteria were identified using the 16S rDNA marker gene for three morphological niches, such as the endobiome, epibiome, and rhizobiome. Bacterial community structure was explored and deterministic factors behind bacterial variation were investigated. Of the total variation, only 21.5% could be explained. Pronounced differences in bacterial community composition were observed and variation was partly explained by a combination of host species, biogeography and nutrient levels. The majority of the explained bacterial variation within the algal holobiont was attributed to the micro-environments established by distinct morphological niches. This study further supports the hypothesis that the bacterial assembly is largely stochastic in nature and bacterial community structure is most likely linked to functional genes rather than taxonomy.

Promising prospects of nanopore sequencing for algal hologenomics and structural variation discovery

“…using 16S metabarcoding have identified some of these families, but in much lower abundance (e.g. see [17, 39]). In these studies, authors made an effort to sterilize and DNA decontaminate the sample surface to reduce epiphytic DNA, and future whole genome sequencing of Caulerpa with long or short reads could follow such methodology.…”

“…Caulerpa spp. are popular in the aquarium trade [14] and infamous alien species [15, 16], emerging as model species to study algal hologenomes [17].

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A Multi-Omics Analysis Suggests Links Between the Differentiated Surface Metabolome and Epiphytic Microbiota Along the Thallus of a Mediterranean Seaweed Holobiont

“…With the increasing number of studies and models showing such interactions, it has been shown that the chemical production at the surface of algae may represent one of the main parameter driving the dynamic of epiphytic microbial communities (Nylund et al, 2010;Lachnit et al, 2013;Saha et al, 2014). In addition, environmental parameters also seem to be involved in the shaping of surface microbiota of seaweed holobionts such as Fucus vesiculosus, Ecklonia radiata, Caulerpa prolifera, Caulerpa cylindracea, Macrocystis pyrifera, Delisea pulchra, and Sargassum muticum (Stratil et al, 2013(Stratil et al, , 2014Marzinelli et al, 2015Marzinelli et al, , 2018Zozaya-Valdés et al, 2016;Aires et al, 2018;Minich et al, 2018;Morrissey et al, 2019;Qiu et al, 2019). Nevertheless, while the microbial communities associated with the surface of algae are increasingly studied, the chemical composition of the surface of the algal hosts and the variations of the metabolic production at the thallus scale have been only rarely investigated to date.…”

Diversity of bacteria populations associated with different thallus regions of the brown alga Laminaria digitata

“…The structure of macroalgae-associated bacterial populations may be influenced by geographical location, host algal species composition, as well as functional differences between morphologically distinct parts of the alga [23]. Host species, tissue age, biogeography together with nutrient levels have been shown to contribute to the bacterial communities in Caulerpa prolifera, Caulerpa cylindraecea, Nereocystis luetkeana and Macrocystis pyrifera [23,24].…”