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Miguel Trabajo T, Guex I, Dubey M, Sarton-Lohéac E, Todorov H, Richard X, Mazza C, van der Meer JR. Inferring bacterial interspecific interactions from microcolony growth expansion. MICROLIFE 2024; 5:uqae020. [PMID: 39524022 PMCID: PMC11549556 DOI: 10.1093/femsml/uqae020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2024] [Revised: 08/19/2024] [Accepted: 10/03/2024] [Indexed: 11/16/2024]
Abstract
Bacterial species interactions significantly shape growth and behavior in communities, determining the emergence of community functions. Typically, these interactions are studied through bulk population measurements, overlooking the role of cell-to-cell variability and spatial context. This study uses real-time surface growth measurements of thousands of sparsely positioned microcolonies to investigate interactions and kinetic variations in monocultures and cocultures of Pseudomonas putida and P. veronii under substrate competition (succinate) or substrate independence (d-mannitol and putrescine). In monoculture, microcolonies exhibited expected substrate-dependent expansion rates, but individual colony sizes were affected by founder cell density, spatial positioning, growth rates, and lag times. In coculture, substrate competition favored P. putida, but unexpectedly, reduced the maximum growth rates of both species. In contrast, 10% of P. veronii microcolonies under competition grew larger than expected, likely due to founder cell phenotypic variation and stochastic spatial positioning. These effects were alleviated under substrate independence. A linear relationship between founder cell ratios and final colony area ratios in local neighborhoods (6.5-65 µm radius) was observed in coculture, with its slope reflecting interaction type and strength. Measured slopes in the P. putida to P. veronii biomass ratio under competition were one-third reduced compared to kinetic predictions using a cell-agent growth model, which exometabolite analysis and simulations suggested may be due to metabolite cross-feeding or inhibitory compound production. This indicates additional factors beyond inherent monoculture growth kinetics driving spatial interactions. Overall, the study demonstrates how microcolony growth experiments offer valuable insights into bacterial interactions, from local to community-level dynamics.
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Affiliation(s)
- Tania Miguel Trabajo
- Department of Fundamental Microbiology, University of Lausanne, Batiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland
| | - Isaline Guex
- Department of Fundamental Microbiology, University of Lausanne, Batiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland
- Department of Mathematics, University of Fribourg, 1700 Fribourg, Switzerland
| | - Manupriyam Dubey
- Department of Fundamental Microbiology, University of Lausanne, Batiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland
| | - Elvire Sarton-Lohéac
- Department of Fundamental Microbiology, University of Lausanne, Batiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland
| | - Helena Todorov
- Department of Fundamental Microbiology, University of Lausanne, Batiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland
| | - Xavier Richard
- Department of Mathematics, University of Fribourg, 1700 Fribourg, Switzerland
| | - Christian Mazza
- Department of Mathematics, University of Fribourg, 1700 Fribourg, Switzerland
| | - Jan Roelof van der Meer
- Department of Fundamental Microbiology, University of Lausanne, Batiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland
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Batsch M, Guex I, Todorov H, Heiman CM, Vacheron J, Vorholt JA, Keel C, van der Meer JR. Fragmented micro-growth habitats present opportunities for alternative competitive outcomes. Nat Commun 2024; 15:7591. [PMID: 39217178 PMCID: PMC11365936 DOI: 10.1038/s41467-024-51944-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 08/20/2024] [Indexed: 09/04/2024] Open
Abstract
Bacteria in nature often thrive in fragmented environments, like soil pores, plant roots or plant leaves, leading to smaller isolated habitats, shared with fewer species. This spatial fragmentation can significantly influence bacterial interactions, affecting overall community diversity. To investigate this, we contrast paired bacterial growth in tiny picoliter droplets (1-3 cells per 35 pL up to 3-8 cells per species in 268 pL) with larger, uniform liquid cultures (about 2 million cells per 140 µl). We test four interaction scenarios using different bacterial strains: substrate competition, substrate independence, growth inhibition, and cell killing. In fragmented environments, interaction outcomes are more variable and sometimes even reverse compared to larger uniform cultures. Both experiments and simulations show that these differences stem mostly from variation in initial cell population growth phenotypes and their sizes. These effects are most significant with the smallest starting cell populations and lessen as population size increases. Simulations suggest that slower-growing species might survive competition by increasing growth variability. Our findings reveal how microhabitat fragmentation promotes diverse bacterial interaction outcomes, contributing to greater species diversity under competitive conditions.
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Affiliation(s)
- Maxime Batsch
- Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Isaline Guex
- Department of Mathematics, University of Fribourg, CH-1700, Fribourg, Switzerland
| | - Helena Todorov
- Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Clara M Heiman
- Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Jordan Vacheron
- Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Julia A Vorholt
- Institute for Microbiology, Swiss Federal Institute of Technology (ETH Zürich), CH-8049, Zürich, Switzerland
| | - Christoph Keel
- Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Jan Roelof van der Meer
- Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland.
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Čaušević S, Dubey M, Morales M, Salazar G, Sentchilo V, Carraro N, Ruscheweyh HJ, Sunagawa S, van der Meer JR. Niche availability and competitive loss by facilitation control proliferation of bacterial strains intended for soil microbiome interventions. Nat Commun 2024; 15:2557. [PMID: 38519488 PMCID: PMC10959995 DOI: 10.1038/s41467-024-46933-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 03/13/2024] [Indexed: 03/25/2024] Open
Abstract
Microbiome engineering - the targeted manipulation of microbial communities - is considered a promising strategy to restore ecosystems, but experimental support and mechanistic understanding are required. Here, we show that bacterial inoculants for soil microbiome engineering may fail to establish because they inadvertently facilitate growth of native resident microbiomes. By generating soil microcosms in presence or absence of standardized soil resident communities, we show how different nutrient availabilities limit outgrowth of focal bacterial inoculants (three Pseudomonads), and how this might be improved by adding an artificial, inoculant-selective nutrient niche. Through random paired interaction assays in agarose micro-beads, we demonstrate that, in addition to direct competition, inoculants lose competitiveness by facilitating growth of resident soil bacteria. Metatranscriptomics experiments with toluene as selective nutrient niche for the inoculant Pseudomonas veronii indicate that this facilitation is due to loss and uptake of excreted metabolites by resident taxa. Generation of selective nutrient niches for inoculants may help to favor their proliferation for the duration of their intended action while limiting their competitive loss.
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Affiliation(s)
- Senka Čaušević
- Department of Fundamental Microbiology, University of Lausanne, 1015, Lausanne, Switzerland
| | - Manupriyam Dubey
- Department of Fundamental Microbiology, University of Lausanne, 1015, Lausanne, Switzerland
| | - Marian Morales
- Department of Fundamental Microbiology, University of Lausanne, 1015, Lausanne, Switzerland
| | - Guillem Salazar
- Department of Biology Institute of Microbiology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland
| | - Vladimir Sentchilo
- Department of Fundamental Microbiology, University of Lausanne, 1015, Lausanne, Switzerland
| | - Nicolas Carraro
- Department of Fundamental Microbiology, University of Lausanne, 1015, Lausanne, Switzerland
| | - Hans-Joachim Ruscheweyh
- Department of Biology Institute of Microbiology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland
| | - Shinichi Sunagawa
- Department of Biology Institute of Microbiology, ETH Zurich, Vladimir-Prelog-Weg 4, 8093, Zurich, Switzerland
| | - Jan Roelof van der Meer
- Department of Fundamental Microbiology, University of Lausanne, 1015, Lausanne, Switzerland.
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