Symbiotic Associations in the Phenotypically-Diverse Brown Alga Saccharina japonica

Abstract

The brown alga Saccharina japonica (Areschoug) Lane, Mayes, Druehl et Saunders is a highly polymorphic representative of the family Laminariaceae, inhabiting the northwest Pacific region. We have obtained 16S rRNA sequence data in symbiont microorganisms of the typical form (TYP) of S. japonica and its common morphological varieties, known as “longipes” (LON) and “shallow-water” (SHA), which show contrasting bathymetric distribution and sharp morphological, life history traits, and ecological differences. Phylogenetic analysis of the 16S rRNA sequences shows that the microbial communities are significantly different in the three forms studied and consist of mosaic sets of common and form-specific bacterial lineages. The divergence in bacterial composition is substantial between the TYP and LON forms in spite of their high genetic similarity. The symbiont distribution in the S. japonica forms and in three other laminarialean species is not related to the depth or locality of the algae settlements. Combined with our previous results on symbiont associations in sea urchins and taking into account the highly specific character of bacteria-algae associations, we propose that the TYP and LON forms may represent incipient species passing through initial steps of reproductive isolation. We suggest that phenotype differences between genetically similar forms may be caused by host-symbiont interactions that may be a general feature of evolution in algae and other eukaryote organisms. Bacterial symbionts could serve as sensitive markers to distinguish genetically similar algae forms and also as possible growth-promoting inductors to increase algae productivity.

A Functional Perspective Analysis of Macroalgae and Epiphytic Bacterial Community Interaction

“…In this review, the number of bacterial taxa found with molecular methods, was greater than those identified using cultures, which allowed more precise characterization of the EBCs associated with the macroalgae. Different studies have used these methodologies to generate information, at the phylum level, about some of the factors that can affect the abundance, composition and structure of these microbial communities, such as the macroalgae section (Staufenberger et al, 2008 ), its phenotype (Balakirev et al, 2012 ), and the site and conditions inhabited (Hengst et al, 2010 ; Bengtsson et al, 2012 ).…”

Community composition of thePlanctomycetesassociated with different macroalgae

“…(Hengst et al, 2010), Macrocystis pyrifera (Michelou et al, 2013), U. australis (Longford et al, 2007;Burke et al, 2011), D. pulchra (Longford et al, 2007), L. hyperborea (Bengtsson & Ovreas, 2010), and Porphyra umbilicalis (Miranda et al, 2013). Interestingly, they were absent in other algae, for example, Saccharina japonica (Balakirev et al, 2012), Laminaria saccharina (Staufenberger et al, 2008). This can be due to the primers used, as some are known to contain mismatches to the phylum Planctomycetes or PCR conditions.…”

Arenicella chitinivorans sp. nov., a gammaproteobacterium isolated from the sea urchin Strongylocentrotus intermedius

“…The results of the phylogenetic analysis indicated that its closest relative was Arenicella xantha KMM 3895 T with 98.2 % 16S rRNA gene sequence similarity. Other close relatives of the novel isolate were uncultivated bacteria associated with the brown alga Saccharina japonica collected from the Sea of Japan with 98.0-98.4 % 16S rRNA gene sequence identity (Balakirev et al, 2012). It is interesting that the adult sea urchins of the genus Strongylocentrotus often feed on macrophytes, among these the kelps are prevalent (Lawrence, 2007).…”