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.BACTERIA.

.BACTERIA. BACTERIA. Bacteria are microscopic, unicellular, prokaryotic µ organisms. The study of bacteria is called bacteriology. Bacteria were omnipresent. range in size from 0.5µ m to 600µ m. Plague Bacteria. BACTERIA.

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.BACTERIA.

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  1. .BACTERIA.

  2. BACTERIA • Bacteria are microscopic, unicellular, prokaryotic µ organisms. • The study of bacteria is called bacteriology. • Bacteria were omnipresent. • range in size from 0.5µ m to 600µ m.

  3. Plague Bacteria

  4. BACTERIA • The bacteria are either spherical or rod shaped o or spiral or curved. • The arrangement of bacteria in pairs, clusters, chains, trichomas and filamentous. • The appendages which are visible by special staining techniques or by electron microscope

  5. Bacteria: Structure

  6. BACTERIAL CULTURE • All bacteria need nutrients for their growth. • They need a nutrient medium for their growth and culture. • The culture medium is composed of carbohydrates, proteins, nucleotides, lipids, vitamins and other organic substances. • Certain complex materials include peptones, meat extract and yeast extract etc. • Agar is also added to this medium as solidifying agent. • This culture medium is suitable for growth of heterotrophic bacteria.

  7. Preparation of Bacteriological media: the steps involved. • The above said complex substances dissolved in the appropriate volume of distilled water. • pH of medium is determined. • Agar is added and the medium is boiled to dissolve agar. • medium is dispersed in flasks or tubes. • medium is sterilised by auto claving. • growth of bacteria also require the physical conditions like temperature, gaseous conditions and pH.

  8. Bacterial Genetics - Recombination • Recombination is the rearrangement and reshuffling of genes resulting in new genotypes. • Bacterial recombination is brought about by the transfer of genetic materials from one bacterium to other. • The bacterium which donates the genetic material is called donor and the bacterium which receives it is called recipient. • Recombination occurs in three methods. They are conjugation, transformation and transduction.

  9. Bacterial Genetics - Recombination

  10. CONJUGATION • The transfer of genetic material from one bacteria to the other by the union of two cells is called conjugation. • This was reported by Laderberg and Tatum in E.coli.The two bacteria join together are called conjugants. • One bacteria donate the genetic material to the other bacteria and is called donor or male cell ( F +). • The other bacteria is called female cell or recipient ( F - ). • The male cell bears sex pilli, but the female cell has no pilli.

  11. CONJUGATION…. • A conjugation tube is established between F+ and F_ cells. A nick develops in the F plasmid of F+ cell and 5’ end of one strand enters the F - cell through the conjugation tube. • As a result one strand of the F plasmid completely enters the F – cell and becomes circular. • The single strand of F plasmid in both F + and F – cell than synthesis its complementary strand. • After that the two conjugantes separate from each other. Here F – cell receives genetic material of the donor cell and becomes F+ cell.

  12. Click here for Bacterial conjugation illustration

  13. Transformation • Bacterial transformation is a process in which cell free or naked DNA containing the genetic information is transferred from one bacterial cell to another. • This was first observed by an English health officer, Griffith in 1928 in the culture of Diplococcus pneumoniae. • The transforming principle was identified as DNA by Avery method and Mc Carthy in 1944.

  14. Transduction • The transfer of genetic material from one bacteria to another through bacteriophage is called transduction. • Here the bacteriophage infect a bacterium and multiplies with in it. • During this process the new phages pick up certain genes from the bacterial genome. • After that, the new phages infect another bacterium. • During this period, the gene picked up by the phage is injected to the bacterium. • Therefore the new bacterium shows some characters of the old host of the phage virus.

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