of gene transfer the donor cell gets attached to the recipient cell with the help of pili. The pilus grows in size and forms the conjugation tube. The plasmid of donor cell which has the F + (fertility factor) undergoes replication. Only one strand of DNA is transferred to the recipient cell through conjugation tube.
The recipient completes the structure of double stranded DNA by synthesizing the strand that complements the strand acquired from the donor (Figure . ). F plasmid Conjugation pilus Chromosome F + cell F + cell F + cell F - cell Figure . : Conjugation .
Transformation Transfer of DNA from one bacterium to another is called transformation (Figure . ). In the bacteriologist Frederick Griffith . Chemoorganotrophs This type of bacteria oxidize organic compounds to release energy.
Examples: . Methane bacteria – Methanococcus . Acetic acid bacteria – Acetobacter . Lactic acid bacteria – Lactobacillus II.
Heterotrophic Bacteria They are Parasites ( Mycobacterium ) Saprophytes ( Bacillus mycoides ) or Symbiotic (Rhizobium in root nodules of leguminous crops). . . Reproduction in Bacteria Bacteria reproduces asexually by binary fission, conidia and endospore formation (Figure .
). Among these, binary fission is the most common one. Binary fission Under favourable conditions the cell divides into two daughter cells. The nuclear material divides first and it is followed by the formation of a simple median constriction which finally results in the separation of two cells.
( a) ( b) Daughter cells Cell wall Nucleoid Endospore Thick wall Figure . : Asexual Reproduction in Bacteria (a) Binary fission, (b) Endospore Endospores During unfavourable condition bacteria produce endospores. Endospores are produced in Bacillus megaterium , Bacillus sphaericus DNA of another strain into the former is called Transformation. .
Transduction Zinder and Lederberg ( ) discovered Transduction in Salmonella typhimurum . Phage mediated DNA transfer is called Transduction (Figure . ). Transduction is of two types (i) Generalized transduction (ii) Special- ized or Restricted transduction (i) Generalized Transduction The ability of a bacteriophage to carry genetic material of any region of bacterial DNA is called generalised transduction.
(ii) Specialized