The Microbiome of the Reef Macroalga Sargassum ilicifolium in Singapore

Abstract

The large canopy-forming macroalga, Sargassum ilicifolium, provides shelter and food for numerous coral reef species, but it can also be detrimental at high abundances where it outcompetes other benthic organisms for light and space. Here, we investigate the microbial communities associated with S. ilicifolium in Singapore, where it is an abundant and important member of coral reef communities. We collected eight complete S. ilicifolium thalli from eight island locations along an approximate 14 km east-to-west transect. Each thallus was dissected into three separate parts: holdfast, vesicles, and leaves. We then characterized the bacterial communities associated with each part via polymerase chain reaction (PCR) amplification of the 16S rRNA gene V4 region. We then inferred predicted metagenome functions using METAGENassist. Despite the comparatively short distances between sample sites, we show significant differences in microbial community composition, with communities further differentiated by part sampled. Holdfast, vesicles and leaves all harbor distinct microbial communities. Functional predictions reveal some separation between holdfast and leaf communities, with higher representation of sulphur cycling taxa in the holdfast and higher representation of nitrogen cycling taxa in the leaves. This study provides valuable baseline data that can be used to monitor microbial change, and helps lay the foundation upon which we can begin to understand the complexities of reef-associated microbial communities and the roles they play in the functioning and diversity of marine ecosystems.

The Mangrove Microbiome of the Malay Peninsula

“…Consistent with other work examining microbial community structure in a variety of host taxa, we show that microbial community structure does exist around the Malay Peninsula [39, 40, 54, 55, 78, 79], and this structure is driven primarily by plant part sampled, location sampled, and host identity. It is likely that these differences are driven by local environmental conditions, with locations closer together tending to have more similar environmental conditions in comparison to those that are more geographical distant.…”

Diversity of the holopelagic Sargassum microbiome from the Great Atlantic Sargassum Belt to coastal stranding locations

“…This matches well with previous studies on the 2017) that showed that the phylum Proteobacteria or specifically Alphaproteobacteria and Gammaproteobacteria were among the most abundant classes of bacteria. These observations were also reported for the benthic Sargassum muticum (Serebryakova et al, 2018) and Sargassum ilicifolium (Oh et al, 2021). The high abundances of Rhodobacteraceae, Pseudomonadaceae and Vibrionaceae were likely related to the high release of dissolved organic matter (DOM) by holopelagic Sargassum in open waters (Powers et al, 2019;Shank et al, 2010a;Shank et al, 2010b), which stimulates the proliferation of DOM-degrading bacteria in these families of Proteobacteria (Buchan et al, 2014;Hervé et al, 2021).…”

Quorum Sensing Regulates Bacterial Processes That Play a Major Role in Marine Biogeochemical Cycles

“…Macroalgal biomass recycling is mainly mediated by colonizing epiphytic bacteria that form dense biofilms comprising 10 3 -10 9 cells cm −2 (Martin et al, 2014;Lage and Graça, 2016). Alphaproteobacteria (e.g., Rhodobacterales and Sphingomonadales), Gammaproteobacteria (e.g., Alteromonadales, Pseudomonadales, Vibrionales), Bacteroidetes (e.g., Cytophagales and Flavobacteriales), Firmicutes (e.g., Bacillales), Actinobacteria (e.g., Actinomycetales) or Planctomycetes (e.g., Planctomycetales) are the major components of these communities (Hollants et al, 2013;Martin et al, 2014;Lage and Graça, 2016;Oh et al, 2021).…”

“…Actinobacteria (Gram-positive) are ubiquitous in the ocean realm (Giovannoni and Stingl, 2005) and can reach high abundance in deep-sea sediments (Zinger et al, 2011;Chen et al, 2016), marine aggregates (Grossart et al, 2004) and macroalgae (Oh et al, 2021). Although their metabolism and roles are largely unknown, these bacteria possess various extracellular hydrolytic enzymes that are able to degrade recalcitrant OM (Lam, 2006;Chen et al, 2016).…”

“…Firmicutes members are mostly Gram-positive bacteria. Their role and prevalence in the oceans are poorly characterized, but they can constitute an important fraction of the epiphytic macroalgal community (Hollants et al, 2013;Oh et al, 2021), microbial mats (Bolhuis and Stal, 2011) and sediments (Zinger et al, 2011). A few studies have reported Firmicutes-affiliated strains isolated from marine environments with AHL-based QS or QQ capacities (Supplementary Table 2).…”