Co-occurrence patterns between chaetoceros species and their associated bacteria

Oral presentation 12 th International Phycological Congress, 22–26 March 2021, Chile

Autotrophic phytoplankton and heterotrophic bacteria have been investigated in terms of taxonomy, physiology, metabolism and their role in biogeochemical cycles, however the relationship with one another is still little known. This relationship is often governed by microscale interactions played out within the region surrounding phytoplankton cells, called the phycosphere. Phytoplankton can interact with free bacteria but also maintain attached bacteria on their surface. We have analyzed phytoplankton samples from a fixed station in the Gulf of Naples (Italy) sampled weekly from October 2017 to September 2018 for qualitative analysis. Similarly, we have sampled marine bacterial communities with the aim of characterizing them by 16S rDNA sequencing and comparing bacterial communities free-living versus those attached to particles. We then explored interactions between the attached bacteria and the most abundant diatom species using a bipartite network. Chaetoceros spp. was the most abundant diatom species present and, of the 27 species present, only 10 formed statistically significant relationship with specific bacterial taxa. Bipartition network analysis highlighted the presence of 6 different networks, of which three were constituted by single species of Chaetoceros that interact with specific bacterial OTUs, namely, C. vixvisibilis, C. tenuissimus, C. simplex. Instead, the other three networks include multiple species of Chaetoceros with close relationships with specific OTUs but also with other bacterial OTUs common to the other species. Some bacterial phyla co-occurred with all Chaetoceros species while others were diatom-specific (e.g. Cyanobacteria co-occurred only with C. pseudocurvisetus, candidate-phylum-WPS with C. simplex and candidate-phylum-FBP with C. vixvisibilis)

ACT has been funded by a SZN-OU fellowship

Peer reviewed