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bioRxiv · 10.1101/083386

Growth-independent cross-feeding modifies boundaries for coexistence in a bacterial mutualism

McCully, A. L.·LaSarre, B.·McKinlay, J. B.
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Abstract

Nutrient cross-feeding can stabilize microbial mutualisms, including those important for carbon cycling in nutrient-limited anaerobic environments. It remains poorly understood how nutrient limitation within natural environments impacts mutualist growth, cross-feeding levels, and ultimately mutualism dynamics. We examined the effects of nutrient limitation within a mutualism using theoretical and experimental approaches with a synthetic anaerobic coculture pairing fermentative Escherichia coli and phototrophic Rhodopseudomonas palustris. In this coculture, E. coli and R. palustris resemble an anaerobic food web by cross-feeding essential carbon (organic acids) and nitrogen (ammonium), respectively. Organic acid cross-feeding stemming from E. coli fermentation can continue in a growth-independent manner during nutrient limitation, while ammonium cross-feeding by R. palustris is growth-dependent. When ammonium cross-feeding was limited, coculture trends changed yet coexistence persisted under both homogenous and heterogenous conditions. Theoretical modeling indicated that growth-independent fermentation was crucial to sustain cooperative growth under conditions of low nutrient exchange. We also show that growth-independent fermentation sets the upper E. coli cell density at which this mutualism is supported. Thus, growth-independent fermentation can conditionally stabilize or destabilize a mutualism, indicating the potential importance of growth-independent metabolism for nutrient-limited mutualistic communities.\n\nConflict of interestThe authors declare no conflict of interest.

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McCully, A. L., LaSarre, B., McKinlay, J. B.. 2016-10-25. Growth-independent cross-feeding modifies boundaries for coexistence in a bacterial mutualism. https://doi.org/10.1101/083386

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