Molecular causes of an evolutionary shift along the parasitism-mutualism continuum in a bacterial symbiont
| Autor: | Lena König, Matthias Horn, Thomas Kempinger, Thomas Rattei, Paul Herrera, Cecilia Wentrup, Hyunsoo Na, Stephan Köstlbacher, Markus Zojer, Lisa N. Schuster, Florian Wascher, Jasmin Schwarz |
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| Rok vydání: | 2020 |
| Předmět: |
0106 biological sciences
Virulence chlamydia Biology 010603 evolutionary biology 01 natural sciences Microbiology host–microbe interaction 03 medical and health sciences Symbiosis Animals Parasites transmission mode Amoeba Gene 030304 developmental biology Mutualism (biology) 0303 health sciences Experimental evolution Multidisciplinary Genome Obligate Bacteria Host Microbial Interactions intracellular bacteria Intracellular parasite Bacterial biochemical phenomena metabolism and nutrition Biological Sciences virulence evolution Biological Evolution Evolutionary biology Horizontal transmission Genome Bacterial |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America Proceedings of the National Academy of Sciences of the United States of America, vol 117, iss 35 |
| ISSN: | 1091-6490 |
| Popis: | Significance Symbiotic relationships with microbes are ubiquitous among living beings and can be parasitic, such as in bacterial pathogens, or mutualistic, as in beneficial microbiomes. Among other factors, the outcome of microbe–host relationships is determined by the mode of symbiont transmission from host to host. Here we describe how bacterial symbionts increased in infectivity and virulence toward their amoeba host when transmission to a new host was essential for survival. The enhanced parasitism is a result of genomic changes and a pronounced switch of gene expression altering the symbionts’ mechanisms for host interaction. Our study provides both a molecular explanation as well as a blueprint for how changes in gene expression are sufficient to confer enhanced parasitism in microbes. Symbiosis with microbes is a ubiquitous phenomenon with a massive impact on all living organisms, shaping the world around us today. Theoretical and experimental studies show that vertical transmission of symbionts leads to the evolution of mutualistic traits, whereas horizontal transmission facilitates the emergence of parasitic features. However, these studies focused on phenotypic data, and we know little about underlying molecular changes at the genomic level. Here, we combined an experimental evolution approach with infection assays, genome resequencing, and global gene expression analysis to study the effect of transmission mode on an obligate intracellular bacterial symbiont. We show that a dramatic shift in the frequency of genetic variants, coupled with major changes in gene expression, allow the symbiont to alter its position in the parasitism–mutualism continuum depending on the mode of between-host transmission. We found that increased parasitism in horizontally transmitted chlamydiae residing in amoebae was a result of processes occurring at the infectious stage of the symbiont’s developmental cycle. Specifically, genes involved in energy production required for extracellular survival and the type III secretion system—the symbiont’s primary virulence mechanism—were significantly up-regulated. Our results identify the genomic and transcriptional dynamics sufficient to favor parasitic or mutualistic strategies. |
| Databáze: | OpenAIRE |
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