Friends With Benefits: Exploring the Phycosphere of the Marine Diatom Skeletonema marinoi

• Published in: Frontiers in microbiology Vol. 10; p. 1828
• Main Authors: Johansson, Oskar N, Pinder, Matthew I M, Ohlsson, Fredrik, Egardt, Jenny, Töpel, Mats, Clarke, Adrian K
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 06.08.2019
• Subjects: algicidal bacteria; bacteria; benthic diatoms; blooms; diatoms; Environmental Sciences; genome; growth; marine; marinobacter-adhaerens hp15; Microbiology; microbiome; Miljövetenskap; organic-compounds; phytoplankton; siderophore; symbiosis; thalassiosira-weissflogii; bacteria; diatoms; microbiome; symbiosis; marine
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2019.01828

Marine diatoms are the dominant phytoplankton in the temperate oceans and coastal regions, contributing to global photosynthesis, biogeochemical cycling of key nutrients and minerals and aquatic food chains. Integral to the success of marine diatoms is a diverse array of bacterial species that closely interact within the diffusive boundary layer, or phycosphere, surrounding the diatom partner. Recently, we isolated seven distinct bacterial species from cultures of , a chain-forming, centric diatom that dominates the coastal regions of the temperate oceans. Genomes of all seven bacteria were sequenced revealing many unusual characteristics such as the existence of numerous plasmids of widely varying sizes. Here we have investigated the characteristics of the bacterial interactions with , demonstrating that several strains ( strain SMS7, strain SMR5, strain SMR4y, strain SMR1, strain SMR4r and strain SMR3) stimulate growth of the diatom partner. Testing of many different environmental factors including low iron concentration, high and low temperatures, and chemical signals showed variable effects on this growth enhancement by each bacterial species, with the most significant being light quality in which green and blue but not red light enhanced the stimulatory effect on growth by all bacteria. Several of the bacteria also inhibited growth of one or more of the other bacterial strains to different extents when mixed together. This study highlights the complex interactions between diatoms and their associated bacteria within the phycosphere, and that further studies are needed to resolve the underlying mechanisms for these relationships and how they might influence the global success of marine diatoms.