Bacterial Promiscuity

Promiscuous behavior abounds in the microbial world! Unknown to the world at large, bacteria regularly "have sex" and transfer DNA. We can get them to do it in the lab too (they're not too picky about mood and music).

You can see photos and movies (G-rated) here.

Basically, the bacteria make an appendage on their surface called a "pilus." It's a long hollow tube, and it can attach to adjacent bacteria. When that happens, DNA can transfer from one cell to the other. This is called conjugation. In basic microbiology labs we do conjugation experiments. You basically grow up 2 different strains of E. coli (usually we use a non-infectious E. coli for these experiments), mix them together in a tube, and let it incubate for various times--usually up to 30 minutes.

You can determine that conjugation has occurred because the recipient strain will have acquired a new trait that is easily tested for--such as antibiotic resistance.

In nature, conjugation and other forms of DNA uptake occur all the time. This is one major reason for the great increase in antibiotic-resistant bacteria. If bacteria are exposed to a sub-lethal dose they can develop resistance. This happens quite often actually--we can demonstrate it in the laboratory. Sometimes this resistance can be transferred to other bacteria.

And after a long time of this happening, you get things like MRSA Staphylococcus aureus that is resistant to many commonly used antibiotics. MRSA is the bacterium getting a lot of press recently--wrestling teams coming down with skin infections, schools becoming infested with it. It's a S. aureus that has acquired some new tools to manage to resist medical onslaughts that attempt to kill it. You can treat it with the right stuff.

This phenomenon of resistance is a major health issue. The bacteria are just doing what comes naturally. They're wonderful at adaptation, and to them they are just adapting to chemical onslaughts and sharing the information. It's only a problem when the bacterium doing the adjusting also happens to be a human (or plant) pathogen.