Method of Sexual Reproduction in Bacteria
In bacteria sexual reproduction are common method to increase population. In sexual reproduction both male and female take part and different method use to exchange (DNA) genetic information. Method of Sexual Reproduction in Bacteria are given below.
Method of Bacterial Recombination:
In bacteria three way to transfer gene for genetic recombination.
First time exchange of hereditary material in bacteria was founded in 1928 by Griffith.
Experiment of Transforming Hereditary material:
In 1928 Griffith working on a bacterium (Streptococcus Pneumonia) that cause fever. They found that two type of strains were found.
- One was capsulated and because infection make colonies when grow on ager. It’s called S type of colony.
- The second was non-capsulated and not cause diseases, that make a rough colony when grow on colonies. Its called R type of bacteria.
- Griffith inject R-cells in a mouse to test the affect and Killed S cell with Heat.
- The mouse death occurred after few days.
- When he studies the dead mouse blood, they found that S cell was living in blood.
- After study he said that S cell release a factor that develop capsules for R cell and become virulent.
- This type of transformation was creating to be heritable.
- This transformation is also called transforming principle.
Identification of transformation Principal:
McCarty and Macleod identified the transformation principal of DNA in 1994. According to him genetic material is transformed through agent.
During transformation a small piece of DNA is given by donor and taken by recipient. Same mechanism of transformation also observed in Azotobacterial and Bacillus.
Conjugation mean transfer of DNA form one organism to other through direct content method.
First time this process was explain by Joshua Lederberg and Edward Tatum in 1946 in E. coli bacteria.
- According to him E. coli can synthesis all kind of amino acid if glucose and slat are present in optimum
- For experiment purpose they induce mutation in bacteria.
- They obtain two type of mutation bacteria, in one type of bacteria they are not able to synthesis a vitamin (biotin) and methionine amino acid.
- In other type of mutation, they cannot synthesis an amino acid threonine and leucine.
- Both type of bacteria was mixed and grow in a culture.
- Theoretically none of cell should be grow in medium but few colonies grow in medium from a bacterium.
- The transformation was ruled out as no chemical was founded
- Electron microscope show that direct cells contact was occur in coli bacteria.
A scientist Francois Jacob and Wolman demonstrate the mechanism of conjugation in E. coli. According to him some bacteria have an extra chromosome of DNA that called Fertility factor or F factor.
- The cell having these factors are called Male donor cell.
- Those cells have not these factors called Female or recipient cell.
- E. coli have one pili from outside, but F factor have 3 additional pilli which are responsible for physical contact with cell.
- They make a tube-like structure that called conjugation tube.
- A single stand F factor cross to recipient cell through the sex pilus.
- It refers as transmission of double stranded DNA from donor cell to recipient cell through a agent or third party. Mostly bacteriophage use for this purpose.
- First time in history of bacteria Zinder and Lederberg demonstrate the transduction mechanism in 1952 when they are study on typhoid causing virus (salmonella typhimurium).
- They mix two mutant bacteria that was unable to synthesis certain nutrient in a culture medium.
- They separated the Recombinant that was able to synthesis all essential nutrients.
- They said genetic material exchange through conjugation method.
- Later they carry an experiment are called U-tube experiment.
- They place the nutritional mutants in each arm of tube and keep separated with the help of filter that not allow the bacteria to passing in it.
- They fine out recombination was found even them.
- They say that some filterable agents are present in the bacteria that cross the non-filterable tube and recombine them to create next generation.
- Later told that bacteriophage or virus are these agents.
There are two patterns of transduction.
- Specialized Transduction
- If all bacterial DNA part have chance to enter in transduction phage this process known as generalization transduction.
- Virus enzyme hydrolysis host chromosome in many small parts and any part of bacterial chromosome incorporated into the phage head in the process of phage assembly.
- It’s not attached on any viral DNA.
- A very large population transduction virus carries different part of bacteria chromosome.
- A small portion of bacteria DNA is carried through phages.
- They infect the bacterial DNA of recipient and become a part bacterium.
- In which temperate phages transfer the restricted gene of bacterial chromosome to pro phage bacterial.
- This process is called restricted transduction.
- So this process occurs when a bacteriophage genome integrated as pro phage in host DNA.
- Then again become free upon induction and carry into the phage head.
- When they infect the bacteria and become the part of these bacteria DNA genome.
- This type of specialized transduction study in E. coli.