Metagenomic analysis of the complex microbial consortium associated with cultures of the oil‐rich alga Botryococcus braunii

<jats:title>Abstract</jats:title><jats:p>Microalgae are widely viewed as a promising and sustainable source of renewable chemicals and biofuels. <jats:italic>Botryococcus braunii</jats:italic> synthesizes and secretes significant amounts of long‐chain (C<jats:sub>30</jats:sub>‐C<jats:sub>40</jats:sub>) hydrocarbons that can be subsequently converted into gasoline, diesel, and aviation fuel. <jats:italic>B. braunii</jats:italic> cultures are not axenic and the effects of co‐cultured microorganisms on <jats:italic>B. braunii</jats:italic> growth and hydrocarbon yield are important, but sometimes contradictory. To understand the composition of the <jats:italic>B. braunii</jats:italic> microbial consortium, we used high throughput Illumina sequencing of metagenomic <jats:styled-content style="fixed-case">DNA</jats:styled-content> to profile the microbiota within a well established, stable B<jats:italic>. braunii</jats:italic> culture and characterized the demographic changes in the microcosm following modification to the culture conditions. <jats:styled-content style="fixed-case">DNA</jats:styled-content> sequences attributed to <jats:italic>B. braunii</jats:italic> were present in equal quantities in all treatments, whereas sequences assigned to the associated microbial community were dramatically altered. Bacterial species least affected by treatments, and more robustly associated with the algal cells, included members of Rhizobiales, comprising <jats:italic>Bradyrhizobium</jats:italic> and <jats:italic>Methylobacterium</jats:italic>, and representatives of <jats:italic>Dyadobacter</jats:italic>,<jats:italic> Achromobacter</jats:italic> and <jats:italic>Asticcacaulis</jats:italic>. The presence of bacterial species identified by metagenomics was confirmed by additional 16S r<jats:styled-content style="fixed-case">DNA</jats:styled-content> analysis of bacterial isolates. Our study demonstrates the advantages of high throughput sequencing and robust metagenomic analyses to define microcosms and further our understanding of microbial ecology.</jats:p>