2. • Classification: Orderly arrangement and
placement of bacteria based on certain characters
ie. Address
• Nomenclature: giving Names
What is taxonomy
3. • Families - related bacteria eg. Enterobacteriaceae
• Within a family - numerous genus eg. Escherichia,
Klebsiella, Salmonella
• A genus contains many species eg. E. coli, E. tarda
4. Species
• Taxonomical unit
• Based on morpholopgy, biochemical properties &
antigenic characters
• Nucleotide base ratio constant for a given species
(AT : GC)
• Genetic homology demonstrated by DNA
hybridization > 98%
5. Interspecies Classification
They are identical, may show some differences
due to mutation
• Biotype - based on biochemical reactions
• Serotype - based on antigens on bacteria
• Phage type - susceptibility to particular phage
• Colicin type - substance secreted by some bacteria
• Molecular typing: Plasmid profile, DNA sequence
6. • A bacterial population derived from a single
bacteria by binary fission is called CLONE
• A bacterial population obtained from a particular
source is called STRAIN
7. Nomenclature
• Casual name / Scientific name:
eg. Gonococcus / Neisseriae gonorrhoeae
Pneumococcus / Streptococcus pneumoniae
• Name could be a character: Staphylococcus aureus
• Place of discovery: Salmonella london
• Scientist: Clostridium welchii
• Disease: Clostridium tetani
11. What is a Bacterial colony?
• Colony - visible growth on a
culture plate.
• Colony Forming Unit- CFU ?
12. Bacterial Nutrition
• Autotrophs - photo /chemo
• Heterotrophs
– Need preformed organic compounds
– Includes most pathogenic bacteria
• Fastidious heterotrophs
13. Bacterial Metabolism
• Help us in identifying bacteria by their end
products
• Help us in knowing how to inhibit bacteria
14. Energy Generating Process
• Sugars formed or obtained - broken down to
release energy
– Aerobic respiration
– Anaerobic respiration
– Fermentation
• Microbes that use aerobic respiration, detoxify
generated waste:
Catalase: H2O2 ------- H20 and 02
Superoxide dismutase : oxygen radical ----- H20 and O2
15. Energy Generating Process
• Aerobic respiration:
– COMPLETE breakdown of glucose to CO2 & H2O
– Final electron receptor O2
– Yield = 38 ATP
• Fermentation:
– Yield = 2 ATP
– Endproducts: Lactic acid/Alcohol
– Final electron receptor is organic molecule
• Anaerobic respiration:
– Yield >2 <38 ATP
– Absence of oxygen
Shorter incubation period eg… e. coli can produce 1 billion copies in 10 hrs
Adapt to new environment, not multiplying, grow in size
Exponential growth 1-2-4-8-16
Death rate equalizes multiplication rate
Accumulation of waste product run out on nutrition/ immune rersponse, antibiotics etc.
Microbes that don’t make these enzymes cannot exist in presence of oxygen
