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Transfer of conjugative plasmid pAM beta 1 from Lactococcus lactis to mouse intestinal bacteria
1Department of Biomedical Food Research, National Institute of Health, Tokyo, Japan. igimi@nih.go.jp
Abstract:
Conjugal transfer of plasmid pAM beta 1 from Lactococcus lactis to intestinal bacteria of BALB/c mice was studied. Plasmid transfer was observed to Enterococcus faecalis in vitro by a filter mating method with transfer frequencies of 2.3 x 10-3 and with lower frequencies to other species. In vivo, using gastric intubation with the pAM beta 1-bearing Lactococcus lactis as donor and Ent. faecalis as recipient, a few transconjugants were detected from faecal Ent. faecalis. However, when these mice were given erythromycin through drinking water, a large number of conjugated Ent. faecalis were detected in faeces. Plasmid transfer to Ent. faecalis occurred at high frequency, 1.2 x 10-3, in mice whose anus was artificially closed after gastric intubation with pAM beta 1-bearing Lactococcus lactis. These results demonstrate clearly that pAM beta 1 transfer occurs between Gram-positive bacteria in the gut of mice harbouring many species of bacteria.
Insights
Plasmid pAM beta 1 can transfer from Lactococcus lactis to intestinal bacteria like Enterococcus faecalis in mice. Antibiotic pressure significantly increases this plasmid transfer within the gut environment.
Area of Science:
- Microbiology
- Genetics
- Gastroenterology
Background:
- Conjugal plasmid transfer is a key mechanism for bacterial adaptation and spread of antibiotic resistance.
- Lactococcus lactis is a common bacterium found in fermented foods and the gut microbiome.
- Enterococcus faecalis is a significant opportunistic pathogen often associated with hospital-acquired infections.
Purpose of the Study:
- To investigate the in vitro and in vivo conjugal transfer of plasmid pAM beta 1 from Lactococcus lactis to intestinal bacteria in BALB/c mice.
- To determine the frequency and conditions influencing plasmid transfer within the murine gut environment.
Main Methods:
- Filter mating experiments were conducted for in vitro plasmid transfer analysis.
- In vivo studies involved gastric intubation of donor Lactococcus lactis into mice, followed by analysis of fecal samples.
- Antibiotic pressure (erythromycin) and artificial anus closure were used to modulate and assess plasmid transfer efficiency in vivo.
Main Results:
- Plasmid pAM beta 1 transferred efficiently to Enterococcus faecalis in vitro (2.3 x 10^-3 frequency).
- In vivo transfer was detected at low frequencies but significantly increased under erythromycin pressure.
- Artificial anus closure in mice led to high-frequency plasmid transfer to Enterococcus faecalis (1.2 x 10^-3).
Conclusions:
- Conjugal transfer of plasmid pAM beta 1 between Gram-positive bacteria, specifically to Enterococcus faecalis, occurs within the complex microbial environment of the mouse gut.
- Environmental factors, such as antibiotic presence, can dramatically enhance plasmid dissemination in the gut microbiome.