Altered Microbiome Leads to Significant Phenotypic and Transcriptomic Differences in a Lipid Accumulating Chlorophyte

Given the challenges facing the economically
favorable production
of products from microalgae, understanding factors that might impact
productivity rates including growth rates and accumulation of desired
products, for example, triacylglycerols (TAG) for biodiesel feedstock,
remains critical. Although operational parameters such as media composition
and reactor design can clearly effect growth rates, the role of microbe–microbe
interactions is just beginning to be elucidated. In this study an
oleaginous marine algae Chlorella spp. C596 culture
is shown to be better described as a microbial community. Perturbations
to this microbial community showed a significant impact on phenotypes
including sustained differences in growth rate and TAG accumulation
of 2.4 and 2.5 fold, respectively. Characterization of the associated
community using Illumina 16S rRNA amplicon and random shotgun transcriptomic
analyses showed that the fast growth rate correlated with two specific
bacterial species (Ruegeria and Rhodobacter spp). The transcriptomic response of the Chlorella species revealed that the slower growing algal consortium C596-S1
upregulated genes associated with photosynthesis and resource scavenging
and decreased the expression of genes associated with transcription
and translation relative to the initial C596-R1. Our studies advance
the appreciation of the effects microbiomes can have on algal growth
in bioreactors and suggest that symbiotic interactions are involved
in a range of critical processes including nitrogen, carbon cycling,
and oxidative stress.