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Martinson JNV, Chacón JM, Smith BA, Villarreal AR, Hunter RC, Harcombe WR. Mutualism reduces the severity of gene disruptions in predictable ways across microbial communities. THE ISME JOURNAL 2023; 17:2270-2278. [PMID: 37865718 PMCID: PMC10689784 DOI: 10.1038/s41396-023-01534-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 10/03/2023] [Accepted: 10/06/2023] [Indexed: 10/23/2023]
Abstract
Predicting evolution in microbial communities is critical for problems from human health to global nutrient cycling. Understanding how species interactions impact the distribution of fitness effects for a focal population would enhance our ability to predict evolution. Specifically, does the type of ecological interaction, such as mutualism or competition, change the average effect of a mutation (i.e., the mean of the distribution of fitness effects)? Furthermore, how often does increasing community complexity alter the impact of species interactions on mutant fitness? To address these questions, we created a transposon mutant library in Salmonella enterica and measured the fitness of loss of function mutations in 3,550 genes when grown alone versus competitive co-culture or mutualistic co-culture with Escherichia coli and Methylorubrum extorquens. We found that mutualism reduces the average impact of mutations, while competition had no effect. Additionally, mutant fitness in the 3-species communities can be predicted by averaging the fitness in each 2-species community. Finally, we discovered that in the mutualism S. enterica obtained vitamins and more amino acids than previously known. Our results suggest that species interactions can predictably impact fitness effect distributions, in turn suggesting that evolution may ultimately be predictable in multi-species communities.
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Affiliation(s)
- Jonathan N V Martinson
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
| | - Jeremy M Chacón
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
- Minnesota Super Computing Institute, University of Minnesota, Minneapolis, MN, USA
| | - Brian A Smith
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
| | - Alex R Villarreal
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN, USA
| | - Ryan C Hunter
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN, USA
| | - William R Harcombe
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA.
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA.
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Martinson JNV, Chacón JM, Smith BA, Villarreal AR, Hunter RC, Harcombe WR. Mutualism reduces the severity of gene disruptions in predictable ways across microbial communities. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.08.539835. [PMID: 37214994 PMCID: PMC10197568 DOI: 10.1101/2023.05.08.539835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Predicting evolution in microbial communities is critical for problems from human health to global nutrient cycling. Understanding how species interactions impact the distribution of fitness effects for a focal population would enhance our ability to predict evolution. Specifically, it would be useful to know if the type of ecological interaction, such as mutualism or competition, changes the average effect of a mutation (i.e., the mean of the distribution of fitness effects). Furthermore, how often does increasing community complexity alter the impact of species interactions on mutant fitness? To address these questions, we created a transposon mutant library in Salmonella enterica and measured the fitness of loss of function mutations in 3,550 genes when grown alone versus competitive co-culture or mutualistic co-culture with Escherichia coli and Methylorubrum extorquens. We found that mutualism reduces the average impact of mutations, while competition had no effect. Additionally, mutant fitness in the 3-species communities can be predicted by averaging the fitness in each 2-species community. Finally, the fitness effects of several knockouts in the mutualistic communities were surprising. We discovered that S. enterica is obtaining a different source of carbon and more vitamins and amino acids than we had expected. Our results suggest that species interactions can predictably impact fitness effect distributions, in turn suggesting that evolution may ultimately be predictable in multi-species communities.
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Affiliation(s)
- Jonathan N V Martinson
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
| | - Jeremy M Chacón
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
- Current address: Minnesota Super Computing Institute, University of Minnesota, Minneapolis, MN, USA
| | - Brian A Smith
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
| | - Alex R Villarreal
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN, USA
| | - Ryan C Hunter
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN, USA
| | - William R Harcombe
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
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Environment Constrains Fitness Advantages of Division of Labor in Microbial Consortia Engineered for Metabolite Push or Pull Interactions. mSystems 2022; 7:e0005122. [PMID: 35762764 PMCID: PMC9426560 DOI: 10.1128/msystems.00051-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fitness benefits from division of labor are well documented in microbial consortia, but the dependency of the benefits on environmental context is poorly understood. Two synthetic Escherichia coli consortia were built to test the relationships between exchanged organic acid, local environment, and opportunity costs of different metabolic strategies. Opportunity costs quantify benefits not realized due to selecting one phenotype over another. The consortia catabolized glucose and exchanged either acetic or lactic acid to create producer-consumer food webs. The organic acids had different inhibitory properties and different opportunity costs associated with their positions in central metabolism. The exchanged metabolites modulated different consortial dynamics. The acetic acid-exchanging (AAE) consortium had a “push” interaction motif where acetic acid was secreted faster by the producer than the consumer imported it, while the lactic acid-exchanging (LAE) consortium had a “pull” interaction motif where the consumer imported lactic acid at a comparable rate to its production. The LAE consortium outperformed wild-type (WT) batch cultures under the environmental context of weakly buffered conditions, achieving a 55% increase in biomass titer, a 51% increase in biomass per proton yield, an 86% increase in substrate conversion, and the complete elimination of by-product accumulation all relative to the WT. However, the LAE consortium had the trade-off of a 42% lower specific growth rate. The AAE consortium did not outperform the WT in any considered performance metric. Performance advantages of the LAE consortium were sensitive to environment; increasing the medium buffering capacity negated the performance advantages compared to WT. IMPORTANCE Most naturally occurring microorganisms persist in consortia where metabolic interactions are common and often essential to ecosystem function. This study uses synthetic ecology to test how different cellular interaction motifs influence performance properties of consortia. Environmental context ultimately controlled the division of labor performance as shifts from weakly buffered to highly buffered conditions negated the benefits of the strategy. Understanding the limits of division of labor advances our understanding of natural community functioning, which is central to nutrient cycling and provides design rules for assembling consortia used in applied bioprocessing.
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Hammarlund SP, Gedeon T, Carlson RP, Harcombe WR. Limitation by a shared mutualist promotes coexistence of multiple competing partners. Nat Commun 2021; 12:619. [PMID: 33504808 PMCID: PMC7840915 DOI: 10.1038/s41467-021-20922-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Accepted: 01/04/2021] [Indexed: 12/14/2022] Open
Abstract
Although mutualisms are often studied as simple pairwise interactions, they typically involve complex networks of interacting species. How multiple mutualistic partners that provide the same service and compete for resources are maintained in mutualistic networks is an open question. We use a model bacterial community in which multiple 'partner strains' of Escherichia coli compete for a carbon source and exchange resources with a 'shared mutualist' strain of Salmonella enterica. In laboratory experiments, competing E. coli strains readily coexist in the presence of S. enterica, despite differences in their competitive abilities. We use ecological modeling to demonstrate that a shared mutualist can create temporary resource niche partitioning by limiting growth rates, even if yield is set by a resource external to a mutualism. This mechanism can extend to maintain multiple competing partner species. Our results improve our understanding of complex mutualistic communities and aid efforts to design stable microbial communities.
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Affiliation(s)
- Sarah P Hammarlund
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA
| | - Tomáš Gedeon
- Department of Mathematical Sciences, Montana State University, Bozeman, MT, USA
| | - Ross P Carlson
- Department of Chemical and Biological Engineering, Center for Biofilm Engineering, Montana State University, Bozeman, MT, USA
| | - William R Harcombe
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA.
- BioTechnology Institute, University of Minnesota, St. Paul, MN, USA.
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Venters M, Carlson RP, Gedeon T, Heys JJ. Effects of Spatial Localization on Microbial Consortia Growth. PLoS One 2017; 12:e0168592. [PMID: 28045924 PMCID: PMC5207726 DOI: 10.1371/journal.pone.0168592] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 12/02/2016] [Indexed: 11/19/2022] Open
Abstract
Microbial consortia are commonly observed in natural and synthetic systems, and these consortia frequently result in higher biomass production relative to monocultures. The focus here is on the impact of initial spatial localization and substrate diffusivity on the growth of a model microbial consortium consisting of a producer strain that consumes glucose and produces acetate and a scavenger strain that consumes the acetate. The mathematical model is based on an individual cell model where growth is described by Monod kinetics, and substrate transport is described by a continuum-based, non-equilibrium reaction-diffusion model where convective transport is negligible (e.g., in a biofilm). The first set of results focus on a single producer cell at the center of the domain and surrounded by an initial population of scavenger cells. The impact of the initial population density and substrate diffusivity is examined. A transition is observed from the highest initial density resulting in the greatest cell growth to cell growth being independent of initial density. A high initial density minimizes diffusive transport time and is typically expected to result in the highest growth, but this expected behavior is not predicted in environments with lower diffusivity or larger length scales. When the producer cells are placed on the bottom of the domain with the scavenger cells above in a layered biofilm arrangement, a similar critical transition is observed. For the highest diffusivity values examined, a thin, dense initial scavenger layer is optimal for cell growth. However, for smaller diffusivity values, a thicker, less dense initial scavenger layer provides maximal growth. The overall conclusion is that high density clustering of members of a food chain is optimal under most common transport conditions, but under some slow transport conditions, high density clustering may not be optimal for microbial growth.
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Affiliation(s)
- Michael Venters
- Chemical and Biological Engineering Department, Montana State University, Bozeman, Montana, United States of America
| | - Ross P. Carlson
- Chemical and Biological Engineering Department, Montana State University, Bozeman, Montana, United States of America
| | - Tomas Gedeon
- Department of Mathematical Sciences, Montana State University, Bozeman, Montana, United States of America
| | - Jeffrey J. Heys
- Chemical and Biological Engineering Department, Montana State University, Bozeman, Montana, United States of America
- * E-mail:
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Alkema W, Boekhorst J, Wels M, van Hijum SAFT. Microbial bioinformatics for food safety and production. Brief Bioinform 2015; 17:283-92. [PMID: 26082168 PMCID: PMC4793891 DOI: 10.1093/bib/bbv034] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Indexed: 12/14/2022] Open
Abstract
In the production of fermented foods, microbes play an important role. Optimization of fermentation processes or starter culture production traditionally was a trial-and-error approach inspired by expert knowledge of the fermentation process. Current developments in high-throughput 'omics' technologies allow developing more rational approaches to improve fermentation processes both from the food functionality as well as from the food safety perspective. Here, the authors thematically review typical bioinformatics techniques and approaches to improve various aspects of the microbial production of fermented food products and food safety.
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