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Understanding Bacterial Taxonomy and Growth: Key Concepts Explained

Explore bacterial taxonomy, growth curves, and metabolic processes in this comprehensive guide by Dr. Jyotsna Agarwal, a Microbiology Professor. Learn about classification, nomenclature, colony formation, metabolism, and factors influencing bacterial growth. Text in English.

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Understanding Bacterial Taxonomy and Growth: Key Concepts Explained

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  1. Bacterial Taxonomy Dr. Jyotsna Agarwal Professor, Dept. of Microbiology, King George’s 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 > 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 >2 <38 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

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