The reproducibility of the bacterial community present in the cultures of the marine diatom Haslea ostrearia

Abstract Background: The pigment produced by Haslea ostrearia , the marennine, is of an important medical and economic interest. Unfortunately this microalgae is complex to grow under axenic conditions, and H. ostrearia probably needs its own bacterial procession to survive. Consequently, this important bacterial presence greatly complicates any study of its ecological, physiological and genomic content. We have therefore tested a first approach of a protocol to control the bacterial concentration without killing the microalgae, by growing four H. ostrearia NCC 532 cultures under two culture conditions: two with and two without antibiotic treatment. We also sought a first bacterial identification method by 16S sequencing adapted to the bacterial community of H. ostrearia. Results: The V3V4 16S region allowed precise identification of bacteria present in H. ostrearia culture. Also, an antibiotic treatment was found necessary to stabilize the bacterial population of the cultures before the DNA extraction. Conclusions: These first results will allow the testing of other antibiotic treatments specific to these bacteria, as well as a wider study of other H. ostrearia isolates to determine the essential bacterial community of this microalga.