[Conjugal plasmid transfer in Bacillus subtilis in soil microcosms]

Area of Science:

• Microbiology
• Environmental Science
• Genetics

Background:

• Conjugal plasmid transfer is a key mechanism for horizontal gene exchange in bacteria.
• Understanding plasmid mobility in soil environments is crucial for microbial ecology and biotechnology.
• The small plasmid pUB110 is a well-characterized model system for studying plasmid transfer.

Purpose of the Study:

• To investigate the conjugal transfer efficiency of the small plasmid pUB110 between Bacillus subtilis strains.
• To determine the influence of soil conditions (sterile vs. nonsterile) on plasmid transfer.
• To assess the impact of different inoculation methods (vegetative cells vs. spores) and temperatures on transfer rates.

Main Methods:

• Utilizing soil microcosms to simulate environmental conditions for bacterial conjugation.
• Employing sterile and nonsterile soil setups to evaluate the role of the soil microbiome.
• Inoculating microcosms with either vegetative Bacillus subtilis cells or their spores containing the pUB110 plasmid.
• Incubating microcosms at different temperatures (30°C and 22-23°C) to monitor plasmid transfer.

Main Results:

• Conjugal transfer of the pUB110 plasmid was demonstrated in both sterile and nonsterile soil microcosms.
• Successful plasmid transfer was achieved using both vegetative partner cells and spores for inoculation.
• Plasmid transfer occurred across a range of temperatures, specifically at 30°C and 22-23°C, indicating environmental adaptability.

Conclusions:

• The small plasmid pUB110 can be conjugally transferred between Bacillus subtilis strains within soil environments.
• Both vegetative cells and spores of Bacillus subtilis can mediate plasmid transfer in soil.
• Environmental factors such as temperature and the presence of a soil microbiome do not completely inhibit, and may support, plasmid mobility.