Biology subjects

Letten, A.

Publications and source records attributed to Letten, A..

3 recordsLinked to original sources

bioRxiv2020

Human-associated microbiota suppress invadingbacteria even under disruption by antibiotics

In light of their adverse impacts on resident microbial communities, it is widely predicted that broad-spectrum antibiotics can promote the spread of resistance by releasing resistant strains from competition with other strains and species. We investigated the invasion success of a resistant strain of Escherichia coli inoculated into human-associated communities in the presence and absence of the broad and narrow spectrum antibiotics rifampicin and polymyxin B, respectively. We found strong evidence of community-level suppression of the resistant strain in the absence of antibiotics and, despite large changes in community composition and abundance following rifampicin exposure, suppression of the invading resistant strain was maintained in both antibiotic treatments. Instead, the strength of competitive suppression was more strongly associated with the individual donor from which the community was sampled. This suggests microbiome composition strongly influences susceptibility to invasion by antibiotic-resistant strains, but at least some antibiotic-associated disruption can be tolerated before invasion susceptibility increases. A deeper understanding of this association will aid the development of ecologically-aware strategies for managing antibiotic resistance.

ecology↗

bioRxiv2020

Rapid evolution promotes fluctuation-dependent species coexistence

AO_SCPLOWBSTRACTC_SCPLOWRecent studies have demonstrated that rapid contemporary evolution can play a significant role in regulating population dynamics on ecological timescales. Here we identify a previously unrecognized mode by which rapid evolution can promote species coexistence via temporal fluctuations and a trade-off between competitive ability and the speed of adaptive evolution. We show that this interaction between rapid evolution and temporal fluctuations not only increases the range of coexistence conditions under a gleaner-opportunist trade-off (i.e., low minimum resource requirement [R*] vs. high maximum growth rate), but also yields stable coexistence in the absence of a classical gleaner-opportunist trade-off. Given the propensity for both oscillatory dynamics and divergent rates of adaptation (including rapid evolution and phenotypic plasticity) in the real world, we argue that this expansion of fluctuation-dependent coexistence theory provides an important overlooked solution to the so-called paradox of the plankton.

ecology↗

bioRxiv2020

Antibiotics in microbial communities: an ecological frame of resistance

There is growing awareness that our ability to tackle antibiotic resistance is limited by a lack of mechanistic understanding of the communities in which resistant microbes are embedded. The widespread coexistence of resistant and sensitive bacteria in microbial systems presents an especially frustrating paradox. Recent advances in ecological coexistence theory offer a powerful framework to probe the mechanisms regulating intra- and inter-specific coexistence, but the significance of this body of theory to the problem of antimicrobial resistance has been largely overlooked. In this Perspectives article, we draw on emerging ecological theory to illustrate how changes in both competitive ability and niche overlap are critical for understanding costs of resistance and the persistence of pathogens in microbial systems. We then show how trade-offs in resource acquisition strategies can have counter-intuitive consequences for the coexistence of resistant and susceptible genotypes in variable environments. These insights highlight numerous opportunities for innovative experimental and theoretical research into antibiotic resistance in the microbiome.

ecology↗