Virus, Bacteria, BGA and Mycoplasma: Quick Study Material
Virus, Bacteria, BGA and Mycoplasma: Quick Study Material
Virus
⚫ Study of virus: Virology
⚫ Father of virology: Stanley
⚫ Term virus was coined by Louis Pasteur.
⚫ Link between living and non living.
⚫ Contain either DNA or RNA.
⚫ No metabolism.
⚫ Host specificity.
⚫ Obligate parasite.
⚫ Living character of virus is the presence of nucleic acid (DNA/RNA) and its non living property is that it can be crystallized. So virus is also called as Biological puzzle.
⚫ Virus is a living particle.
⚫ Virions: The fully assembled mature particle of virus capable of causing infection. It contains both protein and nucleic acid.
⚫ Viriods: Smallest infectious agent contains only nucleic acid(RNA) without protein coat.
⚫ Virusoids: Fragment of RNA. Normally non-infectious.
⚫ Prions: Infectious agents which contain only protein.
⚫ Plant virus: Usually RNA virus but Cauliflower Mosaic Virus posses DNA.
⚫ Animal virus: Usually DNA virus but Retrovirus, reo virus posses RNA.
⚫ Viral disease can be diagnosed by antigen-antibody reactions.
⚫ Apical meristem- Virus free plant part- Used in tissue culture to produce virus free plant.
⚫ Diseases caused by virus:
-Tobacco mosaic disease
-Leaf curl of papaya
-Grassy shoot of papaya
-Bunchy top of banana
-Tomato leaf culr
-Mosaic of sugarcane
-Tungro disease of rice
Bacteria
⚫ Study of bacteria - Bacteriology
⚫ Term bacteria was coined by Ehrwenberg.
⚫ Father of bacteriology is Robert Koch.
⚫ Father of microbiology is Louis Pasteur.
⚫ Single, circular DNA(ds) Molecule without histone protein is present, called Nucleoid or Incipient nucleus.
⚫ Ribosome: 70s type (50s+30s).
⚫ Smallest bacterium is Dialister pneumosintes and longest bacteria are spirillium.
⚫ Insulin is the first hormones which obtained from genetically engineered bacteria E. coli.
Types of Bacteria
On the basis of shape:
✒ Coccus : Spherical. eg.
✒ Vibrio : Comma shaped. eg. Vibrio cholera
✒ Spirillum : Spiral shaped eg.
✒ Pleomorphic : No fixed shape. eg.
On the basis of flagellation:
✒ Monotrichous: Only one flagellum attached at one pole of organism. Eg. Vibrio cholera.
✒ Amphitrichous: 2 flagella one on each end. Eg. Nitrosomonas.
✒ Cephalotrichous: Tuft of flagella attached only at one end. Eg. Helicobacter pylori, Spirochaeta, Treponema pallidum
✒ Lophotrichous: Tuft of flagella attached to both end. Eg. Azotobacter, Pseudomonas.
✒ Peritrichous: Flagella distributed all over the surface of the cell. Eg. Escherichia coli, Salmonella typhi, Clostridium.
On the basis of their functions
✒ Free living: Azotobacter, Clostridium, Rhodospirillium
✒ Symbiotic: Rhizobium
✒ Ammonifying bacteria: Bacillus vulgaris
✒ Nitrifying bacteria (oxidizes NH3 to NO3): Nitrosomonas, Nitrobacter, etc.
✒ Denitrifying bacteria: Convert nitrate to atmospheric N2 gas. Eg. Pseudomonas denitrificans.
On the basis of gram staining:
On the basis of gram staining, Bacteria are of two types. They are "Gram +ve" and "Gram -ve".
Gram +ve |
Gram -ve |
---|---|
1. They attain purple/violet color in Gram stain. | 1. They attain red/pink color in Gram stain. |
2. Thick peptidoglycan cell wall. | 2. Thin peptidoglycan cell wall but more complex. |
3. More easily treatable with antibiotics. | 3. Harder to treat with antibiotics. |
4. Mostly coccus and non-capsulated. | 4. Mostly bacillus and capsulated. |
5. Flagellation is less common. | 5. Flagellation is common |
6. Mesosome is present. | 6. Mesosome is absent. |
7. Exotoxin is present. | 7. Only endotoxin is present. |
Reproduction in bacteria:
Vegetative reproduction
a. Binary fission
b. Budding
c. Fragmentation
Asexual reproduction
a. Endospore formation
b. Conidia formation
c. Zoospores
Sexual reproduction
a. Transformation
b. Transduction
c. Conjugation
Bacteria as a source of Antibiotics
✒ Neomycin = Streptomyces fradiae
✒ Terramycin = Streptomyces ramosus
✒ Chloramphenicol = Streptomyces venezuelae
✒ Streptomyoin = Streptomyces griseus
Plant diseases
✒ Citrus canker = Xanthomonas citri
✒ Crown gall diseases = Agrobacterium tumefaciens
✒ Fire blight of apple and pear = Erwitia amylovora
✒ Potato wilt = Pseudomonas solanacearum
✒ Ear rot of wheat = Corneybacterium tritici
Mycoplasma
⚫ Simplest, non motile, free-living highly pleomorphic, lack cell wall.
⚫ Highly pleomorphic and can change their shape. Hence, called "Jokers of plant kingdom".
⚫ Sensitive to tetracycline and resistance to penicillin.
Cyanobacteria
⚫ Oxygen producing prokaryotic organism.
⚫ Connecting link between bacteria and algae.
⚫ They have photoautotrophic and symbiotic mode of nutrition.
⚫ Photosynthetic pigments are phycoerythrin, phycocyanin, chlorophyll-a, carotene, xanthophylls
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