Long-term manure exposure increases soil bacterial community potential for plasmid uptake

Area of Science:

• Environmental microbiology
• Soil science
• Bacteriology

Background:

• Agronomic practices significantly impact soil microbial community structure and function.
• Understanding horizontal gene transfer (HGT) in soil is crucial for assessing microbial adaptation and the spread of genetic traits.

Purpose of the Study:

• To evaluate the permissiveness of soil microbial communities, originating from diverse agronomic treatments, to broad host range plasmid acquisition.
• To investigate the influence of different plasmids and soil management practices on plasmid transfer efficiency and the resulting transconjugant community composition.

Main Methods:

• Solid surface filter matings were employed to challenge soil bacterial communities with three distinct broad host range plasmids (RP4, pIPO2tet, pRO101).
• Plasmid acquisition and maintenance by soil bacteria were quantified to determine community permissiveness.
• The diversity of transconjugant bacterial populations was analyzed.

Main Results:

• Approximately 1 in 10,000 soil bacterial cells could receive and maintain the tested plasmids.
• Community permissiveness varied significantly, reaching up to 100% in communities derived from manured soil.
• Plasmid transfer frequency was influenced by both the plasmid type and the soil's agronomic treatment.
• The diversity of the transconjugant pools was primarily dependent on the plasmid, with β- and γ-Proteobacteria dominating the recipients.

Conclusions:

• Soil management, particularly manuring, can enhance the capacity of microbial communities to accept foreign genetic material.
• Horizontal gene transfer in soil is a complex process influenced by both environmental conditions and genetic elements involved.
• The composition of recipient communities in soil is shaped by plasmid characteristics, favoring specific bacterial groups like Proteobacteria.