Basic microbiology

1
Bacterial Taxonomy

• Dr. Jyotsna Agarwal
• Professor, Dept. of Microbiology,
• King Georges Medical University

2
What is taxonomy

• Classification Orderly arrangement and placement
  of bacteria based on certain characters ie.
  Address
• Nomenclature giving Names

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 gt 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

8
Bacterial Growth Metabolism
9
Prokaryotes

• Asexual reproduction - binary fission
• Generation time or doubling time
• Clinical implication?

10
Bacterial Growth Curve 4
phases
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 gt2 lt38 ATP
• Absence of oxygen

16
Factors affecting bacterial growth

• Oxygen Obligate /facultative aerobes /
  anaerobes microaerophilics
• Temperature
• Ph
• Osmotic pressure
• CO2

17
Summary

• Bacterial Taxonomy
• Bacterial growth curve
• Fastidious /non fastidious bacteria
• Obligate/facultative anaerobe
• Obligate aerobes