Bacteria are prokaryotes because they have single cell and cannot be seen by the naked eyes. They are neither plants nor animals hence kept separately in the kingdom of classification. Beside these important points, one thing must be noted down is that bacteria are not always harmful. In fact most of the bacteria that are present around us are useful in one or the other respect. There are even bacteria present in human gut that helps to digest the food materials and protect the alimentary canal. Moreover, many bacteria are used in the field of science for different experiments so as to get the possible outputs.
When bacteria are used in scientific researches, it is important to have detailed information about them so that their characters, advantages, disadvantages and most importantly their life forms are known. Hence, two scientists named Lederberg and Tatum, investigated on bacteria and located different information about them. Firstly they studied two strain of E.coli with different set of auxotrophic mutation. Here the word auxotroph denotes the mutant form of bacteria that requires additional nutrients for its growth. Hence, when they studied two auxotrophic bacteria, they found that Strain A can grow in presence of methionine and biotin and strain B can grow in presence of threonine, leucine and thiamine. Now these two strains of bacteria were mixed together and incubated for a period of time. They were plated in a medium of minimal growth. In this case no bacteria were supposed to be seen but surprisingly they noticed some bacteria in the plate and hence called them heterotrophs. Heterotrophs refer to the bacteria that can grow in the minimal medium without the need of additional supplement. When two autotrophs where mixed and plated in minimal media, heterotrophs were seen and this was the thing that scientist mainly focused on. So, in order to find the reason behind this, they plated some dishes with Strain A, and rest with strain B and didn’t noticed any heterotrophs. Thus, they concluded that some changes have taken place when both strains were mixed and hence resulted in heterotrophs. To investigate about it further, Bernard Davis conducted an experiment using a tube which is named as U-tube. The tube was designed in such a way that it has filter for the separation of two arms. This filter has small holes for the passage of essential nutrients. But bacteria could not cross this hole because of the smaller pores. When he poured Strain A in one arm and Strain B in the other, and incubated the tube. No heterotrophs were found. Hence, he concluded that, for the exchange of genetic material, physical contact between bacteria is important.
Definition conjugation: It is the direct transfer of genetic material from one bacterium to the other where one serve as the donor and the other as recipient.
Then one more scientist, named W. Hyes, found out that, when two bacteria comes in contact, one that have F factor also called fertility factor act as donor( F+) and other that lack this factor act as recipient and is named(F-). It is only one side process and no reversible transfer of genetic material takes place. Hence when two bacteria come in contact; pilus present in the surface of bacteria initiates fusion of membrane. Then a nick is created in F plasmid by the enzyme relaxase. One strand of F plasmid is slowly transferred to F- bacteria by the involved of enzyme relaxasome and transferasome. At the same time DNA polymerase starts the synthesis of other strand in F+ plasmid. When the F plasmid is transferred to recipient bacteria, it now acts as the new donor bacteria.
This way the process of conjugation takes place in bacteria that helps in the exchange of genetic material.
Importance of conjugation: Generally, bacteria reproduce by binary fission; so this process will help in bringing variation in the genetic material of the newly formed bacteria. The other importance of conjugation is that newly formed bacteria develop resistance against different types of antibiotics.
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