Metabolic relationships of uncultured bacteria associated with the microalgae Gambierdiscus

Abstract

Microbial communities inhabit algae cell surfaces and produce a variety of compounds that can impact the fitness of the host. These interactions have been studied via culturing, single-gene diversity and metagenomic read survey methods that are limited by culturing biases and fragmented genetic characterizations. Higher-resolution frameworks are needed to resolve the physiological interactions within these algalbacterial communities. Here, we infer the encoded metabolic capabilities of four uncultured bacterial genomes (reconstructed using metagenomic assembly and binning) associated with the marine dinoflagellates Gambierdiscus carolinianus and G. caribaeus. Phylogenetic analyses revealed that two of the genomes belong to the commonly algae-associated families Rhodobacteraceae and Flavobacteriaceae. The other two genomes belong to the Phycisphaeraceae and include the first algae-associated representative within the uncultured SM1A02 group. Analyses of all four genomes suggest these bacteria are facultative aerobes, with some capable of metabolizing phytoplanktonic organosulfur compounds including dimethylsulfoniopropionate and sulfated polysaccharides. These communities may biosynthesize compounds beneficial to both the algal host and other bacteria, including iron chelators, B vitamins, methionine, lycopene, squalene and polyketides. These findings have implications for marine carbon and nutrient cycling and provide a greater depth of understanding regarding the genetic potential for complex physiological interactions between microalgae and their associated bacteria.

Genomic and proteomic profiles of biofilms on microplastics are decoupled from artificial surface properties

“…Further, Alphaproteobacteria-protist associations appeared to be an integral component of the PE and PS biofilms in our study, with both groups frequently detected on these samples. A range of Alphaproteobacteria are known symbionts or pathogens of eukaryotes (Le et al, 2014;Gong et al, 2016) or play important roles in the microbiomes of microalgae (Amin et al, 2012;Kimbrel et al, 2019;Rambo et al, 2019). These typical lifestyle characteristics of Alphaproteobacteria, namely, adaptation to life on the sea surface and associations with protists, point to an opportunistic colonization of microplastics, which is decoupled from an active use of this substratum.…”

Microbiomes associated with cultures of Gambierdiscus australes and Ostreopsis cf. ovata, two epibenthic dinoflagellates from the NE Atlantic Ocean (Las Palmas, Gran Canaria)

“…However, SM1A02 were also described as facultative aerobic organisms able to metabolize dimethylsulfoniopropionate, an osmolyte produced by several microalgae including O. cf. ovata (Vanucci et al, 2016), as well as sulfated polysaccharides (Deschaseaux et al, 2018;Rambo et al, 2020). Another example is provided by the Alphaproteobacteria consortium, which was already reported as dominant over all the growth phases of O. cf.…”

Metagenomic analysis of Raphidiopsis raciborskii microbiome: beyond the individual

“…It has been proposed as a novel anammox (anaerobic ammonia oxidiser) bacterium ( Tian et al 2017 ) found in many activated sludges with good nitrifying performance ( Chen et al 2019 ). It has been also found in the phycosphere of the marine microaglae Gambierdiscus from different locations (Pacific Ocean, Atlantic Ocean, Caribbean Sea), suggesting that it may be broadly associated with this dinoflagellate ( Rambo et al 2019 ). The anaerobic oxidation of ammonium to nitrogen gas appears to be a metabolic pathway present in virtually any anoxic environment where fixed nitrogen (ammonium, nitrate, nitrite) is found.…”