Diauxic lags explain unexpected coexistence in multi‐resource environments

Abstract

How the coexistence of species is affected by the presence of multiple resources is a major question in microbial ecology. We experimentally demonstrate that differences in diauxic lags, which occur as species deplete their own environments and adapt their metabolisms, allow slow‐growing microbes to stably coexist with faster‐growing species in multi‐resource environments despite being excluded in single‐resource environments. In our focal example, an Acinetobacter species (Aci2) competitively excludes Pseudomonas aurantiaca (Pa) on alanine and on glutamate. However, they coexist on the combination of both resources. Experiments reveal that Aci2 grows faster but Pa has shorter diauxic lags. We establish a tradeoff between Aci2’s fast growth and Pa’s short lags as their mechanism for coexistence. We model this tradeoff to accurately predict how environmental changes affect community composition. We extend our work by surveying a large set of competitions and observe coexistence nearly four times as frequently when the slow‐grower is the fast‐switcher. Our work illustrates a simple mechanism, based entirely on supplied‐resource growth dynamics, for the emergence of multi‐resource coexistence.

Controlling microbial co-culture based on substrate pulsing can lead to stability through differential fitness advantages

“…More precisely, upon GLU exhaustion, the yeast was able to increase its metabolic fitness based on the reassimilation of the overflow metabolites ETH and ACE. Such diauxic effect has been previously reported as a key driver leading to the stabilization of microbial communities [20,60,61].…”

“…This trend can be explained by the fact that S. cerevisiae is known to favor respiro-fermentative metabolism when growing at near maximum growth rate or under dissolved oxygen-limited conditions [39]. Interestingly, the diauxic shift has been recently recognized as an efficient driver for promoting community stability [20]. The data obtained was then further used for parameter estimation (Table 1).…”

Controlling microbial co-culture based on substrate pulsing can lead to stability through differential fitness advantages

“…More precisely, upon GLU exhaustion, the yeast was able to increase its metabolic fitness based on the reassimilation of the overflow metabolites ETH and ACE. Such diauxic effect has been previously reported as a key driver leading to the stabilization of microbial communities [ 20 , 61 , 62 ].…”

“…This trend can be explained by the fact that S. cerevisiae is known to favour respiro-fermentative metabolism when growing at near maximum growth rate or under dissolved oxygen-limited conditions [39]. Interestingly, the diauxic shift has been recently recognized as an efficient driver for promoting community stability [20]. The data obtained was then further used for parameter estimation (Table 1).…”

“…However, these microbes are also able to release side metabolites based on overflow metabolism, i.e., mainly acetate (ACE) and ethanol (ETH), leading to a diauxic shift when the primary carbon source (glucose, GLU) is depleted. This diauxic shift can, in turn, promote the growth of the slow grower yeast, potentially leading to co-culture stability [ 20 ]. However, in this case, an essential requirement for stability is that successive diauxic shifts must occur with a given periodicity during the continuous culture through, for example, GLU pulsing.…”