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Nutritional requirement and genetics of bacteria
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Plant microbe association
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Introduction to plant pathogenic microorganism
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Learn Agricultural Microbiology with Rahul

Genetics of bacteria

  • The change in genome is usually brought about by mutation and by transfer of genes between organisms.
  • Bacteria are generally haploid and genes transferred in bacterial cells don’t form zygote but partially diploid are produced called merozygotes.
  • The original genome of the recipient is named as endogenote and a portion of DNA introduced from a donor cell in to the recipient cell is called exogenote.
  • Variation in sequence or grouping of genetic nucleotides is called recombination and this mechanism is known as recombination mechanisms.

 

Mechanism of Recombination

  1. Conjugation:
  • Most common process of reproduction and includes the direct transfer of genetic material from one bacterium to another.
  • In conjugation, two bacteria lie close together and a connection forms between them.
  • A plasmid or a part of the bacterial chromosome passes from one cell (the donor) to the other (the recipient).
  • Subsequent to conjugation, crossing over takes place between homologous sequences in the transferred DNA and the chromosome of the recipient cell.
  • In conjugation, DNA is transferred only from donor to recipient, with no reciprocal exchange of genetic material.

Bacterial Conjugation- Definition, Principle, Process, Examples

 

  1. Transformation:
  • DNA in the medium surrounding a bacterium is taken up.
  • After transformation; recombination may take place between the introduced genes and those of the bacterial chromosome.
  • Griffith (1928) initially conducted the experiment on transformation.
  • In transformation, the genetic material is transformed from one shape to another form.
  • In several bacteria like Bacillus, Salmonella, Streptococcus, Rhizobium etc., normally transformation of genes (incipient DNA and RNA) occurs but in E. coli doesn’t occur.
  • The main function in this type is; DNA from donor cell is incorporated in the chromosomes of receptor cell and transformed thereby in a cell with entirely new properties.

7.11B: Bacterial Transformation - Biology LibreTexts

 

  1. Transduction:
  • bacterial viruses (bacteriophages) carry DNA from one bacterium to another.
  • Once inside the bacterium, the newly introduced DNA may undergo recombination with the bacterial chromosome.

Bacterial Transduction

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