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Colonization of gut microbiota by plasmid-carrying bacteria - Easy Microbial Genomics

Home > Paper Highlights >  Colonization of gut microbiota by plasmid-carrying bacteria

Colonization of gut microbiota by plasmid-carrying bacteria is facilitated by evolutionary adaptation to antibiotic treatment

Posted May 2, 2022

Antimicrobial resistance (AMR) has been recognized as a serious global health crisis and is expected to kill 10 million people by 2050 if no action is taken now. Antibiotic-resistant bacteria can spread among humans, animals and the environment. In particular, plasmid-bearing bacteria represent a very common multidrug-resistant (MDR) pathogen; they are prevalent in both clinical and environmental settings.

We already know that bacteria harboring multidrug resistance plasmids can transfer antibiotic resistance genes to other bacterial species. However, little is known about whether the evolutionary adaptations of plasmid-bearing bacteria after prolonged exposure to antibiotics affect their subsequent colonization in the human gut.

The research group of Dr Luo Yi et al. from Nankai University, China, combined the E. coli-based long-term evolutionary model K-12 MG1655 and the multidrug resistance plasmid RP4 to perform colonization experiments in mice. They found that evolutionary adaptations of plasmid-bearing bacteria to antibiotic exposure promote colonization of the mouse gut and subsequent transfer of plasmids to gut bacteria. Evolved plasmid-bearing bacteria exhibit phenotypic alterations, including multidrug resistance, enhanced bacterial growth and biofilm formation, and reduced plasmid fitness costs, likely caused by chromosomal mutations (SNPs in rpoC, proQ, and hcaT) and transcriptional modifications. Up-regulated transcriptional genes such as type I pilin protein fimbriae (fimA and fimH) and surface adhesin genes (flu) may be responsible for the enhanced biofilm formation ability. The gene tnaA, which encodes tryptophanase-catalyzed indole formation, was transcriptionally up-regulated, and increased indole production promoting the maximal population density of the evolved strain. In addition, several chromosomal genes encoding efflux pumps (acriflavine resistance proteins A and B (acrA, acrB), outer membrane protein (tolC), multidrug resistance protein (mdtM) and macrolide export protein A and B ( macA , macB) were transcriptionally up-regulated, while most plasmid-carrying genes (binding transfer proteins (traF) and ( trbB ), replicatin genes ( trfA ), β-lactamase TEM precursors ( bla TEM ), aminoglycoside 3'-phosphotransferase (aphA), and tetracycline-resistant protein A (tetA)) were down-regulated.

Collectively, these findings suggest that evolutionary adaptations of plasmid-bearing bacteria promote bacterial and plasmid colonization in the mouse gut in antibiotic-influenced environments.


Evolved plasmid-carrying bacteria colonize the gut and transfer plasmids to gut-resident bacteria

image source: ISME J

Reference

Zhang, P., Mao, D., Gao, H. et al. Colonization of gut microbiota by plasmid-carrying bacteria is facilitated by evolutionary adaptation to antibiotic treatment. ISME J 16, 1284–1293 (2022). https://doi.org/10.1038/s41396-021-01171-x