Sex, bugs, and videotape

Written byElie Dolgin

| 1 min read

Though linkurl:bacteria;http://www.the-scientist.com/article/display/14283/ usually reproduce asexually, they do occasionally yield to baser desires and have sex; or at least they linkurl:exchange DNA;http://www.the-scientist.com/article/display/14361/ through a sex-like process known as conjugation, or linkurl:horizontal transfer.;http://www.the-scientist.com/article/display/22780/ For the first time, scientists have filmed Escherichia coli in the act. The videos — linkurl:published;http://www.sciencemag.org/cgi/content/abstract/319/5869/1533 today in Science — offer insight into how bacteria acquire new genes for increased virulence or antibiotic resistance. "No one has ever seen the transfer of DNA in real time," said linkurl:Miroslav Radman;http://www.necker.fr/tamara/pages/miro.html of the University of Paris, who led the study. And for the scientific voyeur, the videos also reveal just how captivating conjugation (highlighted by the appearance of bright green dots in the videos) can be.

Sex cells: Recipient (green) bacteria contain a yellow fluorescent protein (YFP) that binds methylated DNA. YFP is originally diffused throughout the cell, but forms bright green dots after binding to methylated donor DNA following conjugation with donor (red) bacteria.

Bacterial blushing: Donor (red) bacteria have a repressor that blocks red fluorescent protein (RFP). Following conjugation, a bacterium (indicated by the arrow) that lacks the repressor receives the RFP gene and integrates it into its genome, leading to overexpression of RFP and a scarlet red color.

Doing it at a distance: The bright green dots trace DNA shuttling between bacteria without direct cell-to-cell contact, which was observed at distances up to 12 μm.