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Updated: Aug 16, 2026
High-Resolution Comparison of Bacterial Conjugation Frequencies
Published on: January 10, 2019
Plasmid donor affects host range of promiscuous IncP-1beta plasmid pB10 in an activated-sludge microbial community
Leen De Gelder1, Frederik P J Vandecasteele, Celeste J Brown
1Department of Biological Sciences, 252 Life Sciences South, University of Idaho, Moscow, ID 83844-3051, USA.
Abstract:
Horizontal transfer of multiresistance plasmids in the environment contributes to the growing problem of drug-resistant pathogens. Even though the plasmid host cell is the primary environment in which the plasmid functions, possible effects of the plasmid donor on the range of bacteria to which plasmids spread in microbial communities have not been investigated. In this study we show that the host range of a broad-host-range plasmid within an activated-sludge microbial community was influenced by the donor strain and that various mating conditions and isolation strategies increased the diversity of transconjugants detected. To detect transconjugants, the plasmid pB10 was marked with lacp-rfp, while rfp expression was repressed in the donors by chromosomal lacI(q). The phylogeny of 306 transconjugants obtained was determined by analysis of partial 16S rRNA gene sequences. The transconjugants belonged to 15 genera of the alpha- and gamma-Proteobacteria. The phylogenetic diversity of transconjugants obtained in separate matings with donors Pseudomonas putida SM1443, Ralstonia eutropha JMP228, and Sinorhizobium meliloti RM1021 was significantly different. For example, the transconjugants obtained after matings in sludge with S. meliloti RM1021 included eight genera that were not represented among the transconjugants obtained with the other two donors. Our results indicate that the spectrum of hosts to which a promiscuous plasmid transfers in a microbial community can be strongly influenced by the donor from which it transfers.
Insights
The bacterial strain donating a plasmid significantly impacts which bacteria receive it in environmental communities. Understanding donor effects is crucial for tracking antimicrobial resistance spread.
Area of Science:
- Environmental microbiology
- Molecular biology
- Antimicrobial resistance
Background:
- Horizontal gene transfer of multiresistance plasmids fuels the rise of drug-resistant pathogens.
- The influence of plasmid donor strains on plasmid transfer range in microbial communities remains largely unexplored.
Purpose of the Study:
- To investigate how the plasmid donor strain affects the host range of a broad-host-range plasmid in activated sludge.
- To determine if different mating conditions and isolation methods impact the diversity of detected transconjugants.
Main Methods:
- A plasmid (pB10) was marked for detection (lacp-rfp), with expression repressed in donors (lacI(q)).
- Phylogenetic analysis of 306 transconjugants using partial 16S rRNA gene sequences.
- Conjugation experiments were performed using different donor strains (Pseudomonas putida, Ralstonia eutropha, Sinorhizobium meliloti) in activated sludge.
Main Results:
- The host range of the plasmid was significantly influenced by the donor strain used.
- Transconjugants spanned 15 genera within alpha- and gamma-Proteobacteria.
- Specific donor strains, like S. meliloti RM1021, facilitated transfer to a broader and distinct range of bacterial genera compared to other donors.
Conclusions:
- The bacterial donor strain plays a critical role in determining the spectrum of recipients for plasmid transfer in complex microbial communities.
- Optimizing detection methods and considering donor-specific effects are essential for accurately assessing plasmid mobility and antimicrobial resistance dissemination.
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