Bacteria

• bacteria belongs to the Kingdom Monera
• All members of Kingdom Monera are prokaryotes
• a prokaryote does not have a membrane bounded nucleus or membrane bounded organelles
• bacteria are single celled organisms that are found in all parts of the biosphere
• Types of bacteria - rod-shaped, round and spiral
• reproduction in bacteria is asexual - method called binary fission
• if conditions suitable - bacteria reproduce every 20 minutes
• an endospore is a thick tough-walled, dormant, dehydrated bacterial cell formed during unsuitable conditions
• autotrophs - photosynthetic and chemosynthetic
• photosynthetic - some bacteria have chlorophyll on their membrane (no chloroplasts). they use light to produce food eg. purple sulphur bacteria
• chemosynthetic - they make food using chemicals eg. nitrifying bacteria
• heterotrophs - saprophytes and parasites
• saprophytes - take in their food from dead organisms eg. bacteria of decay in the soil
• parasites - live in or on another organism causing harm eg. strep throat
• factors affecting growth - temperature, oxygen concentration, pH, external solute concentration, pressure
• a pathogen is a disease causing orgaisms
• Pathogenic bacteria is disease causing bacteria
• beneficial bacteria - used to make yoghurts and cheese, bacteria in our intestines
• harmful bacteria - cause food spoilage and can cause dieases like tb or strep throat
• antibiotics are substance produced by micro-organisms that kill or prevent the growth of bacteria and fungi - they have no effect on viruses
• lag phase - bacteria are adjusted to their environment - growth is slow to begin with as bacteria start to produce the enzyme they need to break down the substrate present
• log phase - bacteria have adjusted to their environment and start to digest the substrate very quickly and the rate of cell division is at its maximum
• stationary phase - nutrients start to run out and waste products start to build up - rate of growth slows down - the graph shows a horizontal line at this stage because the rate at which new cells are being produced is equal to the rate at which other cells are dying
• decline phase(death phase) - nutrients have almost run out and the toxins are at high levels - death of bacteria is much higher than the rate of reproduction
• survival phase - when conditions are unfavourable some bacteria form endospores - they are very resistant to heat and can remain dormant for years
• two main types of food processing - batch and continous flow