In synthetic ecology, researchers aim to construct consortia with specific properties. Towards this end, rational design -- the strategy of creating new communities with a certain functionality based upon the ability to predict how the community structure will affect its function -- can be employed. Such an approach typically involves sourcing organisms with considerable diversity, both genetic and functional. Here, we focus on intrageneric algal consortia of Nannochloropsis as well as algal-bacteria consortia to maintain consistent biomass composition for downstream processing within commercial applications. We couple rational design (of intrageneric algal consortia) with a high-throughput microfluidics tool (to isolate growth-promoting bacteria) to generate complex consortia for use in microalgal cultivation systems. For the rational design pipeline, we used temperature, salinity, and pest tolerance datasets to construct Nannochloropsis consortia with the potential for withstanding perturbations in the field. For the microfluidics pipeline, we encapsulated individual Nannochloropsis cells with up to five environmentally-sourced bacterial cells in agarose microdroplets to capture growth-promoting bacteria. After iterations of this process, the bacteria associated with the best performing algae were isolated, identified, and amended to algal cultures. Consortia performance was tested against that of a baseline strain via bioassays and photobioreactor trials.
Results/Conclusions
We present results comparing the productivity and stability of intrageneric Nannochloropsis consortia and algal-bacteria consortia to that of our monoculture baseline – a microalgal field strain previously used in industrial applications. For the intrageneric algal consortia, we demonstrate the coexistence of multiple Nannochloropsis strains for up to two weeks via a molecular tracking tool. In a series of assays, ranging from a deep-well plate-format to the flask-scale with environmentally-relevant field conditions, we show that certain consortia outperform the monoculture baseline in terms of productivity and stability. Increases in productivity and stability range from marginal (i.e., 10%) to dramatic (i.e., crash of monoculture and survival of consortia), depending on culture conditions. For the algal-bacteria consortia, we identified the abundance and diversity of bacteria using the 16S rRNA gene for each iteration of the screen. We also describe the results of plate-scale assays, in which improvements in algal productivity were found when co-cultured with growth-promoting bacterial isolates. This work underscores the importance of community structure and function in building and managing consortia within the realm of applied ecology.