Fertility factor (bacteria)

The fertility factor (first named F by one of its discoverers Esther Lederberg; also called the sex factor in E. coli or the F sex factor; also called F-plasmid) allows genes to be transferred from one bacterium carrying the factor to another bacterium lacking the factor by conjugation. The F factor was the first plasmid to be discovered. Unlike other plasmids, F factor is constitutive for transfer proteins due to a mutation in the gene finO. The F plasmid belongs to a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system. Esther M. Lederberg and Luigi L. Cavalli-Sforza discovered "F," subsequently publishing with Joshua Lederberg. Once her results were announced, two other labs joined the studies. "This was not a simultaneous independent discovery of F (I names as Fertility Factor until it was understood.) We wrote to Hayes, Jacob, & Wollman who then proceeded with their studies." The discovery of "F" has sometimes been confused with William Hayes' discovery of "sex factor", though he never claimed priority. Indeed, "he [Hayes] thought F was really lambda, and when we convinced him [that it was not], he then began his work." The most common functional segments constituting F factors are: OriT (Origin of Transfer): The sequence which marks the starting point of conjugative transfer. OriV (Origin of Vegetative Replication): The sequence starting with which the plasmid-DNA will be replicated in the recipient cell. tra-region (transfer genes): Genes coding the F-Pilus and DNA transfer process. IS (Insertion Elements) composed of one copy of IS2, two copies of IS3, and one copy of IS1000: so-called "selfish genes" (sequence fragments which can integrate copies of themselves at different locations). Some F plasmid genes and their Function: traA: F-pilin, Major subunit of the F-pilus. The episome that harbors the F factor can exist as an independent plasmid or integrate into the bacterial cell's genome.