Microbes and Disease

Microbes and Disease

Growing microbes

Microbes (bacteria and fungi) can be grown in a liquid or on a solid material (e.g. agar) called a ‘growth medium’.

A growth medium will contain specific nutrients required for microbial growth:

• Carbohydrates (as an energy source)
• Proteins
• Vitamins
• Mineral ions

Viruses will only grow and reproduce inside other living cells

Bacteria reproduce rapidly by binary fission (to produce exact copies of themselves - clones).

They form visible colonies when grown on solid medium (contain millions of microbes)

Aseptic techniques

Special procedures called aseptic techniques are used to prevent contamination (from unwanted microbes) when trying to grow microbes safely in the laboratory. These include:

• Growing microbes at 25oC (rather than 37°C), to discourage the growth of potentially harmful bacteria (pathogens).
• Use sterilized growth medium to (so that it does not contain microbes) by heating to at 121°C in an autoclave
• Microbes are transferred from one medium to another, using sterilized equipment. e.g. flamed inoculating loop (flaming kills microbes on the loop).
• Petri dishes that contain microbes growing on nutrient agar are secured with a piece of sellotape to prevent the entry of unwanted microbes
• A lit bunsen burner in the working area causes air to rise. This prevents microbes from falling onto and contaminating the working area.

./ You may be asked to describe methods to prevent contamination when growing microbes. ,/ You may be asked how you should grow microbes safely in the laboratory

Fungi feed by secreting (releasing) digestive…