B6 - Bacteria

• cell wall keeps shape + stops bursting
• strand of DNA in cytoplasm
• ^ controls cell's activities + replication
• sometimes several loops of DNA = plasmids
• sometimes have a flagellum to help them move
• come in 4 shapes: rods, curved rods, spheres + spirals
• dif can survive in dif habitats as some comsume range of organic nutrients from their surroundings others produce their own

• asexual reproduction
• each is a clone
• binary fission = process in which they reproduce
• they reproduce very quickly
• ^ how sometimes you get ill as body can't respond quick enough
• reproduce quicker when warm + good source of nutrients
• ^ = need to store food carefully

You can culture (grow) bacteria on an agar plate - a Petri dish containing agar jelly. Bacteria can be transferred to the plate from a sample using a wire inoculation loop.

It's important to use aseptic techniqye to protect yourself from infection and stop the agar from being contaminated by other microbes.

• Wear gloves + keep long hair tied back
• Sterilising equipment before + after use ( pass through bunsen burner)
• Sealing the dish once you've transferred the bacteria onto it
• Disposing of cultures safely after use - usually done by pressure sterilising in an autoclave

How to make yoghurt:

• sterilise equipment to kill off any unwanted microorganisms
• pasterurise the milk (heat up to 72oC for 15 secs) - to kill "
• let the milk cool
• add a starter culture of Lactobacillus bacteria
• incubate the mixture (heat to about 40oC) in a fermenter

• The bacteria break down the lactose sugar in the milk into lactic acid
• lactic acid causes the milk to clot + solidify into yoghurt

• a sample is taken to see if it's the right consistency
• flavours + colours are then sometimes added
• then the yoghurt is packaged