Profiling of bacterial community associated with monocultures of potential live feed haptophyte Isochrysis galbana: a culture dependent and metagenomic exploration

Bacterial diversity coexisting in the monocultures of the marine haptophyte Isochrysis galbana was examined by employing both culture-based techniques and culture-independent Illumina Next-Gen Sequencing (NGS) platform. Thirty-one isolates obtained from the different growth stages of I. galbana using the culture-based approach were assigned to four unique bacterial strains belonging to the classes Alphaproteobacteria, Gammaproteobacteria and Flavobacterium-Cytophaga-Bacteroides (FCB) Group. The culture-independent approach amplified the V3-V4 region of the 16S rDNA gene from which the 51 unique entities were assigned to 33 genera using the Greengenes2 database. 90% of all bacteria belonged to Phylum Proteobacteria, with Marinobacter accounting for 28% of all bacterial genera. Metabolism of cofactors and vitamins like folate, nicotinamide, thiamine, and riboflavin, as well as membrane transport, was one of the most abundantly predicted functions using PICRUSt. This study provides a holistic view of the bacteria inhabiting the phycosphere of I. galbana and highlights the need for more studies into their potential influence on growth.