Bacteria prokaryotes means they are very simple, single-celled organisms. The majority of their reproduction is done asexually via binary fission. This means that they simply double their genetic material and divide in half, much like cell division. The advantage to bacteria to reproduce in this manner is that they can do so extraordinarily quickly. Their reproduction rate in a favorable environment is exponential. They can grow so quickly in a petri dish that they soon must be transferred to a new home or they will die as a result of consuming all the food available to them. Some bacteria are harmless while others can be pathogenic.
Asexual reproduction also gives bacteria an advantage in numbers. A bacterial infection can often come on very quickly because the bacteria reproduce faster than the host’s immune system can keep up with. Eventually, the host’s immune system will catch up and fight off the onslaught of bacterial growth. However, the sheer numbers of bacteria that can grow in a short period of time is staggering.
A disadvantage of asexual reproduction is that there is no exchange of genetic material. This means that there is no genetic variety in the bacteria. Any traits that could help the bacteria in its environment are not able to be shared between cells. This makes it difficult to pass on desirable traits like antibiotic resistance or to prevent genetic defects from being passed on to offspring. There is however an exception to this rule: conjugation.
Some bacteria can exchange genetic material through bacterial conjugation. This is not true sexual reproduction, but it does allow for the exchange of genetic material. A sexus pilus forms and attaches one bacterial cell to another. The genes for the bacteria form into something called a plasmid. The plasmid is then transferred from one bacterium to another. In this way bacteria can pass valuable genes that can assist them in survival. The gene is then copied and transferred to the other cell. The new gene can then be copied and transferred when the bacterial cell goes through binary fission.
The most common gene that reproducing cells will pass is antibiotic resistance. Many bacteria acquire the antibiotic resistance gene through bacterial conjugation. It is to the evolutionary benefit of bacteria to acquire these genes as they will help them to survive and live longer. The more exposure to antibiotics the more likely it is that these bacteria will acquire these genes.