Fertility factor

The F plasmid (abbreviation for Fertilitätsplasmid also fertility factor ) is an plasmid, which confers the ability to conjugate bacteria ( horizontal gene transfer). The F plasmid allows a directed gene transfer from the donor ( this has the F- factor is also known as F denotes ) to the receiver ( F ). We also find the F plasmid is transferred even with very high probability at the receiver. This is the receiver (recipient ) is also a donor ( donor). Therefore, all of the bacterial cells, which have an F plasmid, potential donor cells.

Structural features

• Origin of Transfer ( OriT ): DNA sequence, where the conjugative transfer begins at the recipient.
• Origin of Replication ( OriV ): DNA sequence of the DNA replication begins.
• Tra region (transfer genes): Genes to form the so-called F- pilus and a DNA Transferpore.
• Insertion elements (IS): selfish known genes ( DNA sequence segments can integrate copies of sequence elsewhere)

From OriT from the plasmid by means of the rolling circle replication is transferred to the recipient during conjugation. At the end of both donor and recipient have an F plasmid. The transfer genes are required to enable the conjugation and the rolling circle replication.

From OriV from the F plasmid is propagated within the bacterium ( also referred to as vegetative replication of the plasmid, although this term in this context is somewhat misleading ). In this way, the copy number of the F- plasmid increases (bacteria usually have a multiple copies of the same plasmid ).

The F- plasmid still also has insertion elements (IS elements). Elements of similar sequence are also located on the bacterial chromosome. This allows the integration of the F- plasmid into the bacterial chromosome. An integrated F plasmid is similar to a non- integrated and also allows conjugation. Since, however, the F- plasmid is also made ​​part of the bacterial chromosome, the DNA sequences or genes of the donor can now be transmitted to the receiver where it may lead to recombination. Bacterial strains with integrated F plasmid are also HfR strains called ( engl. high frequency of recombination ).

Use

The discovery that the F plasmid can integrate into the bacterial chromosome, genetics has opened up new possibilities. Among other things, it has enabled gene mapping by interrupted chromosome transfer. Next it was now possible to carry certain genes from one bacterium to another. Today, there are for this special vectors, however, are still elements of the F- plasmid vector systems use, for example, two ( a plasmid with oriT without tra region and MCS selection markers for the gene to be cloned, and the other substantially greater, derived from F without plasmid oriT with tra genes ).

A ( similar ) conjugative transfer is also between bacteria and yeast cells, for example, or bacteria and plant cells possible ( cf. Agrobacterium tumefaciens ).

Another reason is to discuss in greater detail the F plasmid that F- plasmid or other conjugatively transferable plasmids play a role in the rapid spread of antibiotic resistance ( also between non more closely related bacterial species ) ( the F plasmid has more than one oriV, which function in different bacterial species or oriV functions in different bacterial species ). This means that a transposon antibiotic resistance genes, for example, from the bacterial chromosome or another plasmid of species A jump on a conjugal plasmid ( transpose ) can, from there it can be transferred by conjugation to species B. Now, if the gene in species B a survival benefit related ( eg in hospitals, etc.), it will remain - so -called R- plasmids can occur with many resistance genes on the same plasmid, which may be transferable to pathogenic bacteria!

By acridine dyes, the F plasmid can be removed during cell division of a bacterial cell.