Bacteria are genetic packrats. They scavenge genic snippets from the environment, including long-dead organisms. DNA fragments several hundreds of thousands of years old may provide valuable adaptive information.
Bacteria use their pili to snag DNA. The process of incorporating retrieved DNA is termed natural transformation.
Bacteria are DNA connoisseurs. They are choosy about the genic bits they acquire. This involves intelligent analysis for content quality.
Bacteria commonly swap genes among themselves. Many selectively shed and uptake plasmids, which are independent DNA molecules separate from genophoric DNA.
Like a genetic copying machine, plasmids divide independently. Plasmids provide extra survival information that is both useful to a bacterium and transferable.
These transfers enable bacteria to adapt to novel environmental conditions, access new food sources, or evade destruction by antibiotics and toxic compounds: sometimes by alchemic genes that can transform mercury or other heavy metals into less noxious forms.
When antibiotics hit the dirt, resident soil bacteria tweak themselves to resistance. Bacteria may at times refuse to share such defensive knowledge, but some transfer does take place to itinerant pathogens on their way to the next host.
With its dry patches and air pockets presenting insurmountable obstacles, the soil is difficult terrain for bacteria. To get around they need a liquid film in which to swim. Fungal filaments (hyphae) provide the perfect motorway. Even better, soil fungi create wide-ranging networks, termed mycelia – a wondrous cosmopolitan infrastructure for bacteria. In such comfortable environs, bacteria are especially generous with their genetic exchanges.
It’s possible that over the course of the Earth’s history, bacterial diversity increased massively with the development of mycelium-forming fungi. ~ Swiss environmental microbiologist Lukas Wick
Generally, horizontal gene transfer is common, and occurs between distantly related organisms: microbes, fungi, plants, and animals. Plants extensively employ genic exchange to foster their mutualistic relationships with bacteria and fungi.