Bacterial Reproduction Lecture # Dr. Sobia Manzoor

Introduction: Bacteria (singular: bacterium) prokaryotic micro organisms. Few micrometers in length, Have a number of shapes, ranging from spheres to rods and spirals. Were among the first life forms to appear on Earth, Inhabits soil, water, acidic hot springs, radioactive waste and the deep portions of Earth’s crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Acidic hot springs

Reproduction /procreation: A Biological process by which new "offspring" individual organisms are produced from their "Parents". A fundamental feature of all known Life Each individual organism exists as the result of reproduction Biologically dead or biologically alive Mule (offspring of a male donkey and a female horse)

Methods of reproduction Broadly grouped into two main types Sexual and Asexual Asexual reproduction: an individual can reproduce without involvement with another individual of that species. Not limited to single celled organisms. Most plants have the ability to reproduce asexually. Sexual reproduction: typically requires the involvement of two individuals or gamestes , one each from opposite type of sex.

I. Asexual Reproduction: Mostly by asexual reproduction which is a mode of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only Under ideal conditions, lots of food, proper temperature and lots of space, bacteria divide every 20 minutes and in 24 hours a single bacterial cell could produce 2 million kg of bacterial cells. Binary Fission Spore formation

1.Binary Fission When a cell has almost doubled in size it will replicate its DNA and divide in half This produces 2 genetically identical daughter cells – clones cell divides exactly in half single cell division reproduction of the entire organism form of asexual reproduction Asexual reproduction does not involve the exchange of genetic material Binary fission is the evolutionary precursor to mitosis E. coli undergoing cell division

2.Spore Formation Bacteria form spores during unfavorable conditions One type is called an endospore Cell forms a thick internal wall that encloses its DNA Spores can remain dormant for months until conditions improve

Endospore Germination The transformation of dormant spores into active vegetative cells seems almost as complex a process as sporogenesis. It occurs in three stages: activation, germination, and outgrowth Activation is a process that prepares spores for germination and usually results from treatments like heating. It is followed by germination process is characterized by spore swelling, rupture or absorption of the spore coat, loss of resistance to heat and other stresses, release of spore components, and increase in metabolic activity. Outgrowth; cell prepare for division

II. Sexual reproduction: Sexual reproduction is a process that creates a new organism by combining the genetic material of two organisms. Genetic recombination is responsible for generating diversity within bacterial populations There present 3 types of sexual reproduction in bacteria Conjugation Transduction Transformation

1.Conjugation: "Conjugation is the direct transfer of genetic material between two bacterial cells that are temporarily joined. It resembles sexual reproduction, Two bacteria join (mate) and exchange genes. Conjugation is a ‘one way’ transfer of DNA. DNA is transferred from one cell (donor) to another (recipient) The DNA donor uses appendages called sex pili to attach to the recipient. This is followed by the formation of a cytoplasmic bridge for which DNA can be transferred through, and promote recombination.

2. Transduction Phages (viruses that infect bacteria) carry bacterial genes from one host cell to another as a result of mistakes in the phage reproductive cycle Bacterial DNA found in the phage is transferred to the new host and is incorporated into the host genome In the process called generalized transduction, this transfer is random

3.Transformation: Living cells take up DNA from their environment. A foreign gene is incorporated into a bacterial chromosome by replacing the native allele. The transformed cell now has a chromosome/plasmid containing DNA from two different cells. Many bacteria possess cell surface proteins that facilitate transformation in natural populations E. coli is used in biotechnology applications of genetic recombination