BACTERIABacteria 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.

Bacteria

• Bacteria are sometimes known as germs which is really an incorrect word to use as most bacteria are beneficial and not harmful.

• Bacteria that are classed as harmful are known as pathogens.

Different types of bacteria

• Bacteria come in all shapes from spheres & spirals to rod shaped.

Structure of Bacteria• Bacterium cells differ from those of other living things:

No clearly defined nucleusHas a single closed loop chromosomeCells are very small (0.5 to 2 μm)

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.

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.

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

Harmful or pathogenic bacteria

• Many bacteria cause disease and infections in both humans, other animals and plants.