BACTERIA

1. BACTERIA Bacteria are found nearly EVERYWHERE on Earth. Have been found at the bottom of ocean trenches. Are on every surface. Have changed into hundreds of thousands of species. Numbers are estimated to be over 5 billion trillion trillion. The earliest forms are believed to be around 3.5 billion year old.

2. Bacteria • Bacteria are sometimes known as germswhich is really an incorrect word to use as most bacteria are beneficialand not harmful. • Bacteria that are classed as harmful are known as pathogens.

3. Different types of bacteria • Bacteria come in all shapes from spheres & spirals to rod shaped.

4. Structure of Bacteria • Bacterium cells differ from those of other living things: • No clearly defined nucleus • Has a single closed loop chromosome • Cells are very small (0.5 to 2 μm)

5. Structure of Bacteria • The structure of different bacteria varies, but all have: • A cell wall – gives rigidity and protects the cell from swelling and bursting. • A cell or plasma membrane – regulates the movement of substances into and out of the cell. • A single chromosome that is a closed loop – this contains genetic material of the bacterium and controls the cell. There is no nuclear membrane but found in a specific area called the nucleoid. • Ribosomes – where proteins are made.

6. Structure of Bacteria • Other structures are not always present and depend on the individual types of bacteria: • Slime capsule – gives it protection for example against white blood cells or stomach acid. • Pilli– structures that help the bacterium to stick to surfaces. • Flagella – these propel bacteria and make them able to move about.

7. Useful or beneficial bacteria • Bacteria used to make some foods eg yoghurt & cheese. • Useful bacteria in the digestive system • Decompose dead material • Provide drugs and hormones

8. Harmful or pathogenic bacteria • Many bacteria cause disease and infections in both humans, other animals and plants.