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BACTERIA • The oldest form of life on earth, evolving 5 billion years ago. • The most numerous form of life on earth (there are more bacteria in a tub of natural yoghurt than there are humans on the entire planet!!) • The most ubiquitous form of life on earth. They are EVERYWHERE!! • They are possibly the most successful form of life on earth. • If mammals disappeared bacteria wouldn’t even blink. If bacteria disappeared all other life would be dead inside a month STRUCTURE • • • Unicellular Prokaryotic (no nucleus or other organelles) 3 basic shapes: – Round (cocci) – Rod Shaped (bacilli) • (Lacto-bacillus caseii immunitas) – Spiral (spirillum) NUTRITION • • Autotrophic (make their own food!) – Photosynthetic (use light as a source of energy). – Chemosynthetic (use chemicals as a source of energy Heterotrophic (get their food elsewhere!) – Parasites- feed on live hosts – pathogenic? – Saprophytes- feed on dead organisms - decomposers – Symbionts- live inside a host with mutual benefit. (They may be Aerobic or Anaerobic) REPRODUCTION • • Sexual Reproduction – very complex! – involves the exchange of plasmids Asexual Reproduction: – By Binary Fission – In optimum conditions (H2O, Warmth, Nutrients, pH, Oxygen?) can reproduce every 20 minutes. Growth Curve for Population of Bacteria (or other micro-organisms) 5 Stages on the graph 1. Lag 2. Log 3. Plateau (stationary) 4. Decline (death) 5. Survival and Endospore formation ENDOSPORES: If conditions become intolerable the DNA replicates and the contents of the bacterial cell shrink. A thick wall then forms around it. This is called an ENDOSPORE. The endospore can survive dormant for many years until favourable conditions return. ECONOMIC IMPORTANCE • • Beneficial: – Production of yoghurt and cheese – Some produce antibiotics – Can be genetically engineered to produce commercial products Harmful: – Disease: TB, Cholera, Pneumonia, Syphilis, Salmonella (‘Pathogens’) – Food Spoilage Food Preservation: Need to know how each method works! • Drying • Salting • Chilling/Freezing • Canning • Pickling • Vacuum packing