1. 4.4 Microbiology

2. Classifying Bacteria - shape According to shape Coccus -plural Cocci Bacillus -plural Bacilli Spirillum – plural Spirilli

3. Classifying Bacteria – Gram Stain

4. Classifying Bacteria – Gram Positive or Gram Negative Cell wall gives a bacterium shape and prevents them from bursting osmotically. Gram Positive Bacteria Retain the Gram Stain Have a thick layer of peptidoglycan Are affected by antibiotics such as Penicillin and the enzyme lysozyme (in tears) which interfere with the cross linking of peptidoglycan Gram Negative Bacteria Do not retain the Gram Stain, only pick up the counter stain Have a thinner but more complex 2 layered cell wall Very little peptidoglycan but outer layer is another membrane.

5. Classifying Bacteria – Gram Stain

6. Culturing Bacteria - Growth Lag Phase – Cells adapting to new environment – synthesising new enzymes etc. Log Phase / Exponential Growth – No limiting factors Stationary Phase – Limiting factors affecting growth death rate equals birth rate Death / Decline Phase – All nutrients used, toxin accumulating. Oxygen concentration decreasing.

7. Culturing Bacteria – Conditions Needed for Growth Nutrients – Carbon / Nitrogen Sources as well vitamins and minerals Water -Solvent for biochemical reactions, cell expansion Temperature & pH -Particular to specific species Oxygen-Obligate aerobes (need O2 all the time) Obligate anaerobes find oxygen toxic Facultative anaerobes – grow better in the presence of oxygen

8. Aseptic Technique Compete with cultured microbe, may produce toxins and/or contaminate the product / Protect from pathogenic species

9. Measuring Bacterial Growth Turbidity – indirect method (total or viable?)

10. Measuring Bacterial Growth Haemocytometer (total or viable?) May need to dilute beforehand and then factor in the dilution factor. Total count.

11. Measuring Bacterial Growth Plating and Counting Colonies

12. Fermentation Culturing of microorganisms both aerobically and anaerobically in fermentation tanks. Metabolism – reactions of living organisms Metabolites – products from the reactions Two types of metabolite: Primary metabolite – produced by an organism as part of its normal growth Secondary metabolite – substances produced by an organism that are not part of its normal growth (usually begins after the log phase)

13. Industrial Scale Fermenters

14. Batch Versus Continuous Nutrients added Product removed Growth rates Product quality Repercussions if contaminated

15. Penicillin Production Secondary metabolite Batch culture Penicillium chrysogenum or Penicillium notatum Fungus – Aerobic / 24oC / pH6.5 Inhibits peptidoglycan cross links – Cell wall weakened – osmotic bursting