BIOL112

• Bacterias have a way of exchanging DNA, we can see that through oxytrophic phenotypes. You can find bacteria that you have to supplement their media with methionine or biotin in order to grow. There are other strains that you have to supplement with leucine and threonine (act kind of like vitamins). If you mix these two strains of bacteria they will exchange genes and a small fraction can grow without adding those supplements. 
• One of the ways that bacteria can exchange genetic material is by forming conjugation tubes. Bacteria have plasmids that have a gene that allows them to form these little tubes. The tube allows DNA to go from one bacteria to the other. It’s called a sex pilus. Plasmids are double stranded. One strand of a plasmid gets transferred through the tube to the other bacteria and they replicate a reverse complementary strand for each of the two single stranded pieces of DNA in each of the bacteria. 
• Sometimes the plasmids get inserted into the bacterial chromosome and you end up with something called high frequency of recombination. Once they are inserted they become hyperactive and form the conjugation tubes more frequently than they normally would. This allows more DNA to be transferred. If the plasmid is inserted to the bacterial chromosome, one strand of the bacterial chromosome gets transferred through the sex pilus to the other bacteria. 
• The bacterial chromosome breaks off so that a piece of it is transferred with the plasmid. The piece can recombine with the endogenous chromosome, the native chromosome and introduce new alleles with new genes into that bacteria.