Competition, Not Cooperation, Dominates Interactions among Culturable Microbial Species

Abstract

Microbial cells secrete numerous enzymes, scavenging molecules, and signals that can promote the growth and survival of other cells around them [1-4]. This observation is consistent with the evolution of cooperation within species [5], and there is now an increasing emphasis on the importance of cooperation between different microbial species [4, 6]. We lack, however, a systematic test of the importance of mutually positive interactions between different species, which is vital for assessing the commonness and importance of cooperative evolution in natural communities. Here, we study the extent of mutually positive interaction among bacterial strains isolated from a common aquatic environment. Using data collected from two independent experiments evaluating community productivity across diversity gradients, we show that (1) in pairwise species combinations, the great majority of interactions are net negative and (2) there is no evidence that strong higher-order positive effects arise when more than two species are mixed together. Our data do not exclude the possibility of positive effects in one direction where one species gains at the expense of another, i.e., predator-prey-like interactions. However, these do not constitute cooperation and our analysis suggests that the typical result of adaptation to other microbial species will be competitive, rather than cooperative, phenotypes.

Next‐generation studies of microbial biofilm communities

“…Further, we and others have observed that such mixed communities have heightened tolerance to antimicrobials, chemical stress and predation (Burmolle et al ., 2006; Lee et al ., 2014; Kumar and Ting, 2015). Additional models allow for studies of autotroph–heterotroph interactions (Elenter et al ., 2007; Cole et al ., 2014), metabolic cooperation to degrade xenobiotics (Christensen et al ., 2002) and cooperation and competition between different species (Foster and Bell, 2012; Fiegna et al ., 2015), as examples of biofilm community interactions recently explored.…”

“…However, the results indicated that the communities within the anaerobic digestors were consistent at a species level, and thus the authors concluded that there must be other, strong selection forces at work within the reactors responsible for the community dynamic observed. Similarly, community composition and function have been described in terms of competition (Foster and Bell, 2012), cooperation (Ren et al ., 2015), resource partitioning and the role of interspecific and intraspecific variation in population‐ and community‐level resilience (Lee et al ., 2016). While microbiologists are increasingly embracing this approach, studies of molecular microbial ecology will greatly benefit not only from such an interdisciplinary uptake but ideally from the perspective of an experimental and theoretical platform where microbiologists and ecologists begin to unify macro‐ and micro‐ecology.…”

Biodiversity acts as insurance of productivity of bacterial communities under abiotic perturbations

“…Complementarity among different species (Bell et al, 2005;Venail and Vives, 2013), species identity (Hodgson et al, 2002) or both the mechanisms (Eisenhauer et al, 2013) may be responsible for positive effects of diversity on ecosystem functioning. On the other hand, the prevalence of antagonistic interactions is the main cause behind negative relationships (Becker et al, 2012;Foster and Bell, 2012). The impacts of abiotic stress on biodiversity-ecosystem functioning relationship of microbial systems are generally found negative (Steudel et al, 2012) or positive in some cases (Li et al, 2010).…”

Intensive aquaculture selects for increased virulence and interference competition in bacteria

“…The within-host competitive interactions have been traditionally linked to virulence via faster growth of more virulent parasite strains, which is expected to influence dynamics of disease epidemics [1,2,[9][10][11][12][13][14]. However, bacterial interactions towards each other are mainly negative [15]. Competition over limited resources can promote selective interference competition mechanisms targeted to exclude competitors through the release of toxins [16,17], and lead to decreased virulence during bacterial infection [18,19].…”