F+ cell

An F+ cell is a bacterium that carries the F plasmid and can donate DNA during conjugation. In Microbiology, it is the starting point for horizontal gene transfer to an F- cell.

What is F+ cell?

An F+ cell is a bacterial cell that contains the F plasmid, also called the fertility factor. In Microbiology, that means the cell can act as a DNA donor during conjugation, the process where one bacterium passes genetic material directly to another.

The F plasmid carries genes that build the sex pilus, often called the conjugation pilus or F pilus. The pilus lets the F+ cell attach to an F- cell and form a bridge for DNA transfer. Once contact is made, a copy of the plasmid moves into the recipient, so the donor keeps its plasmid and the recipient can become F+ too.

That transfer is a form of horizontal gene transfer, which is different from ordinary cell division. Instead of passing genes only to daughter cells, bacteria move DNA between unrelated cells. This is one reason bacterial populations can change so quickly, especially when useful traits like antibiotic resistance are carried on plasmids.

You may also see F+ cells described as donor cells. That label is about function, not size or shape. The important feature is whether the cell has the F plasmid and can start conjugation, not whether it is a particular species.

One detail that often shows up in class is that the F plasmid does not have to stay separate forever. If it integrates into the bacterial chromosome, the cell becomes an Hfr cell instead of a simple F+ cell. That changes what DNA may be transferred, because conjugation can then carry chromosomal genes along with the plasmid sequence. So when you see F+ cell on a quiz or diagram, think: plasmid present, pilus formed, DNA donated, recipient can gain the plasmid.

Why F+ cell matters in MICROBIO

F+ cells show how asexual prokaryotes still create genetic diversity. Bacteria do not need sexual reproduction to share traits, because plasmids can move between cells and spread new genes through a population.

That matters most when the DNA on the plasmid gives an advantage. A common example in Microbiology is the spread of antibiotic resistance genes, including genes that encode enzymes such as beta-lactamases. If a plasmid moves from one bacterium to another, a useful trait can spread much faster than mutation alone would allow.

The F+ cell also gives you a clean way to trace conjugation step by step. You can identify the donor, the pilus, the DNA transfer, and the change in the recipient. That sequence shows up in diagrams, lab questions, and short-answer prompts about horizontal gene transfer.

It also connects to bigger bacterial genetics ideas. If the F plasmid is separate, the cell behaves as a standard donor. If it integrates into the chromosome, you start comparing F+ cells with Hfr cells, and the transfer pattern changes. That comparison is a common place where students get tripped up, so knowing what F+ means keeps the whole topic straight.

How F+ cell connects across the course

F- Cell

An F- cell lacks the F plasmid, so it cannot initiate conjugation on its own. It is the usual recipient in the transfer process, and after receiving the F plasmid it can become F+. This donor versus recipient distinction is the core comparison in conjugation problems.

Hfr Cell

An Hfr cell starts as a bacterium with the F factor integrated into its chromosome. That changes the transfer pattern because chromosomal genes can move along with F-related DNA. If you confuse Hfr with F+, check whether the F factor is separate plasmid DNA or part of the chromosome.

Sex Pilus

The sex pilus is the physical structure an F+ cell uses to attach to an F- cell. It is the first visible step in conjugation diagrams, and it explains how bacteria make direct cell-to-cell contact before DNA transfer begins.

F Plasmid

The F plasmid is the DNA molecule that makes a cell F+. It carries the genes for pilus formation and transfer machinery, so the plasmid itself is what gives the cell donor ability. Without the plasmid, the cell cannot perform the same conjugation process.

Is F+ cell on the MICROBIO exam?

A quiz or lab question may show a conjugation diagram and ask you to label the F+ cell, predict which cell donates DNA, or explain why the recipient becomes F+ after transfer. You may also need to compare F+ and Hfr cells, especially if the question asks whether only the plasmid or some chromosomal DNA is moving.

When you see a case about antibiotic resistance spreading through a bacterial population, look for conjugation as the mechanism and identify the F+ cell as the donor that starts the transfer. In a microscopy or diagram question, the sex pilus is a strong clue that the bacterium is F+.

F+ cell vs Hfr Cell

F+ cells carry the F plasmid as a separate plasmid and usually transfer that plasmid to an F- cell. Hfr cells have the F factor integrated into the chromosome, so conjugation can move chromosomal genes too. If the question mentions chromosomal gene transfer, it is probably Hfr, not a basic F+ donor.

Key things to remember about F+ cell

• An F+ cell is a bacterium that carries the F plasmid and can donate DNA during conjugation.

• The F plasmid includes genes that make the sex pilus, which lets the donor attach to an F- cell.

• After conjugation, the recipient can become F+ because it receives the F plasmid.

• F+ cells are a major example of horizontal gene transfer in bacteria, which increases genetic diversity without sexual reproduction.

• If the F factor integrates into the chromosome, the cell is treated as an Hfr cell instead of a simple F+ cell.

Frequently asked questions about F+ cell

What is an F+ cell in Microbiology?

An F+ cell is a bacterium that contains the F plasmid. That plasmid gives it the ability to form a sex pilus and transfer DNA to an F- cell during conjugation. In class, it usually shows up as the donor cell in horizontal gene transfer.

How is an F+ cell different from an F- cell?

An F+ cell has the F plasmid and can start conjugation. An F- cell does not have that plasmid, so it cannot donate DNA in the same way. If an F- cell receives the F plasmid, it can become F+.

Does an F+ cell transfer only the F plasmid?

Usually, yes, the main transfer is the F plasmid itself. If the F factor is integrated into the chromosome, the cell is no longer just a simple F+ cell and can transfer nearby chromosomal genes too. That is where Hfr cells come in.

Why do bacteria use F+ cells and conjugation?

Conjugation lets bacteria spread useful genes quickly, including plasmids that may carry antibiotic resistance. This is one way bacterial populations gain genetic diversity even though they reproduce asexually.