An Ecological Understanding of Quorum Sensing-Controlled Bacteriocin Synthesis

Bacteriocins are common antimicrobial agents that bacteria secrete to suppress the growth of competitors. Their production is often conditional, governed by underlying quorum sensing regulatory circuitry. Although the molecular underpinnings of controlled bacteriocin synthesis have been increasingly revealed, its quantitative ecological role has not been well characterized. Here, we present an integrated model of bacteriocin synthesis in the context of two-species contests where one species opposes the other for resource utilization. In a well-mixed environment, we find that bacteriocin production can contribute positively or negatively to the outcome of species competition, determined by the tradeoff between the benefit of bacteriocins in mediating competition and the fitness cost due to metabolic load. The tradeoff also determines the relative advantage between constitutive bacteriocin production and quorum sensing (QS) controlled production. Interestingly, under the naturally occurring scenario where bacteriocin production has a high cost, QS controlled synthesis outperforms constitutive, which offers a quantitative interpretation for the wide prevalence of density-related bacteriocin production in nature. Furthermore, by extending our study to include spatial dynamics of competing communities, we show that our finding, the superiority of QS controlled synthesis in the high cost regime, remains valid for complex settings. This work provides ecological insights into bacteriocin synthesis by revealing its cost and benefit during population growth, advancing our fundamental understanding of bacteriocin-mediated community organization as well as microbial ecology in general.