Bacterial Diseases (AQA GCSE Biology: Combined Science)

• Bacterial pathogens are cells that can infect plants and animals, causing disease
• Not all bacteria are harmful (so not all bacteria are pathogens) – both the skin and large intestine, in particular, are home to hundreds of different bacterial species that play a vital role in maintaining our health
  • Bacteria on the skin act as competitors to harmful pathogens
  • Bacteria in the large intestine digest substances we can’t in food (such as cellulose) and provide essential nutrients (such as Vitamin K)

• Bacterial pathogens produce toxins that cause damage to cells and tissues directly
• In certain optimum conditions, some bacteria can reproduce rapidly (with the fastest being once every 20 minutes for some species of coli)
  • Optimum conditions usually involve warmth, moisture and a supply of nutrients

The graph shows the exponential growth of bacteria due to binary fission

• Salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions
• It is found in the gut of many different animals

Salmonella table

• Gonorrhoea is a sexually transmitted disease (STD) – these diseases are also called sexually transmitted infections (STI)
• In 2018 it had the largest increase (26%) of infections in the UK (a total of 56,259 cases!). It was the cause of 13% of diagnosed STDs

Gonorrhoea table