Growth and types of reproduction in Bacteria
Growth refer to change in population of bacteria. Bacteria have ability to reproduce very readily due to large surface area and get their food from environment by active transport and diffusion method. There are two type of reproduction in bacteria sexual and asexual.
- Growth of bacteria is affected by temperature, PH, nutrient and ion concentration.
- The optimum condition speed up of production of bacteria. in optimum condition cell division take place every 20 minutes.
- After division number of cells become double. This condition is called exponential growth. The time interval known as Generation time.
Bacteria Pass through different phases of growth.
- Lag Phase
- Log phase
- Stationary phase
- Death Phase
it is first stage of bacterial growth in which growth not start. In which bacteria only adopt themselves to new environment.
Log Phase (Exponential phase):
In this phase Bactria start their growth and become double if optimum condition available.
In this phase resource are limited and competition b/w bacteria increase. Bacteria growth slow down or stop. The number of cells remain constant this condition known as stationary phase.
In this phase resource become exhausted and toxic waste product are produce and bacteria become start die.
Reproduction in Bacteria:
Both types of reproduction in bacteria present but mostly bacteria produce through Sexual reproduction method. In bacteria primitive type of reproduction.
- Asexual Reproduction
- Sexual reproduction
Binary fission and endospore are most common asexual reproduction method in bacteria.
Fission occur when situation is good for growth. A cell grows into twice in size and then divide into to identical cell. Every daughter cell grows and then become a like parent cell. This process knows as a life cycle.
Mechanism of Binary division:
- When bacteria start division, they take nutrients from the environment, Synthesis cell part such as DNA, RNA, enzyme, protein and other important substance.
- The cell mass and cell size also increase.
- The DNA replicate and plasmic membrane start to grow inward at the center of bacteria cell.
- DNA attach with mesosoma and hold it position in replication and then inward growth was start that result development of septum start.
- Septum separated the into new daughter cell.
Endospore Formation Method:
Endospore are oval, spherical, ellipsoidal and cylindrical mass of protoplast surrounded by with a multiple layer.
- Outermost wall layer is called exospore.
- Beneath the outer wall a spore coat composes by several layer of proteins.
- The spore coat followed by thick cortex made that made up of peptidoglycan.
- Protoplast compose by calcium and (DPA) Dipicolinic Acid which protect from heat resistance.
Genetic recombination does the sexual reproduction in bacteria. New genotype is formed by recombination of gene and exchange of genetic material between homologous gene.
Sexual reproduction differs from the eukaryotic sexual reproduction. Gamete and fertilization process are absent in bacteria.
Bacteria Recombination Method:
- Bacterial combination the cell does not fuse, usually a part of DNA from the donor cell to transfer to acceptor cell.
- After receiving the DNA part is positioned alongside the recipient DNA in that way homologous gene are adjacent.
- Enzyme act as recipient DNA.
- That cause nicks & and removal of fragment.
- The donor DNA is integrated into recipient DNA.
- Then recipient cell become recombinant DNA.
- Both donor and recipient DNA present in a same place.
Key Steps to remember Bacteria Recombination Method
Donor cell DNA > Recipient cell > position Both DNA Donor And Recipient > Homologous Gene > Recipient Enzyme act > cut and remove> integrated Donor DNA with recipient DNA > Recombinant DNA