This is part of Stoned Science — science that makes you go "whoa." Or is it woah?

If lighting up makes you want to snuggle up, then it's good thing you're not bacteria — otherwise those innocent post-brownie cuddle puddles might end up leaving you with some extra DNA you didn't ask for. When they get close enough, certain bacteria share packets of DNA with each other in what essentially looks like a super intimate handshake or hug. 

This process is called bacterial conjugation, and it's about as close as bacteria get to sex. But unlike sex, conjugation isn't a reproductive process. Instead of leading to new bacteria, it transfers genes from one existing bacterium to another. 

One partner, called the donor, builds a little appendage called a pilus out of protein and uses it to connect with the recipient cell, reeling it in for a close embrace. The two temporarily fuse a small section of their cell membranes, allowing the donor to transfer a bit of DNA to the recipient. Usually, the two bacteria simply exchange DNA and then go on their merry ways. But certain bacteria can end up scrambling their genomes so thoroughly that they emerge from their liaison as hybrid mixtures of each other. 

But conjugation isn't all innocent hugs and good vibes. It has a dark side. Gene transfer via conjugation is so important for spreading antibiotic resistance that some scientists have even proposed developing drugs that target conjugation systems as a way to gain the upper hand in the antibiotics arms race. 

Talk about a mood killer.