Abstract
The ecological interactions between phytoplankton and marine bacteria have important implications for the productivity and biogeochemistry of ocean ecosystems. In this study we characterized the microbial assemblages associated with multiple isolates of the ecologically important diatom Leptocylindrus using amplicon sequencing of the 16S rRNA gene, to examine levels of conservation of the microbiome across closely related species or strains. We also assessed if the microbiome structure of a given diatom strain was dependent on the location from which it was isolated and if the microbiome of cultured isolates significantly changed overtime from the seawater in which they were isolated. The bacterial assemblages from 36 strains belonging to three species (Leptocylindrus danicus, Leptocylindrus convexus, and Leptocylindrus aporus) isolated from six locations spanning > 1000 km of south east Australian coastline over 1 year, were dominated by the Rhodobacteraceae (∼60%) and the Flavobacteriaceae (∼10%). Across all strains, only one ‘core OTU’ (Roseovarius sp.) was identified across all samples. We observed no significant differences in bacterial community composition between diatom species. Significant differences in microbiome structure were, however, observed between diatom strains collected at different sampling times and from differing locations, albeit these two factors were coupled. Moreover, while bacterial communities under domestication varied from the seawater in which they were isolated, they remained specific to the location/month of origin, i.e., different regions and time points harbored distinct bacterial communities. Our study delivers new knowledge in relation to diatom-bacterial associations, revealing that the location/time from which a diatom is isolated plays an important role in shaping its microbiome.
Highlights
The interactions between phytoplankton and bacteria are among the most significant ecological associations in the global ocean (Amin et al, 2012)
To investigate the co-existence of natural communities of bacteria and Leptocylindrus, we addressed three questions: Do bacterial communities associated with closely related Leptocylindrus species differ between and within species? Does the bacterial community associated with Leptocylindrus significantly change over time from the original seawater from which it was isolated? Is the microbiome of each diatom strain predetermined by its collection time or location? By characterizing the bacteria that live in association with marine phytoplankton, we may begin to understand the function of a host organism’s microbiome, and its interaction within this microenvironment
While previous algal-bacterial studies have examined a limited number of model organisms from long term laboratory culture collections, our study examines 16S rRNA sequences obtained from 36 clonal isolates spanning 3 species of the diatom Leptocylindrus, collected over a 1-year period and from six locations spanning 1000 km of the coastline
Summary
The interactions between phytoplankton and bacteria are among the most significant ecological associations in the global ocean (Amin et al, 2012). Many species of marine phytoplankton exhibit strong ecological links with specific members of the Proteobacteria and Bacteriodetes, including species of Sulfitobacter, Roseobacter, Alteromonas, and Flavobacterium (Amin et al, 2012; Buchan et al, 2014) These bacterial associates have been demonstrated to modify the growth, behavior and physiology of the microalgal host (Sison-Mangus et al, 2014; Segev et al, 2016; Bolch et al, 2017; van Tol et al, 2017), and to become abundant during phytoplankton blooms, for which they may play a role in governing bloom dynamics (Buchan et al, 2014; Bunse et al, 2016; Hattenrath-Lehmann and Gobler, 2017; Needham et al, 2017; Song, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
