Bacterial and Fungal Diseases

This lesson covers the bacterial and fungal diseases named on the AQA GCSE Biology specification. You need to know Salmonella and gonorrhoea as examples of bacterial diseases, and rose black spot as an example of a fungal disease. For each, you must learn the pathogen type, how it spreads, symptoms, and treatment or prevention.

---

How Bacteria Cause Disease

Bacteria are single-celled prokaryotic organisms. Most bacteria are harmless, but pathogenic bacteria cause disease by:

1. Reproducing rapidly inside the body — bacteria undergo binary fission (splitting in two) and can double in number every 20 minutes under ideal conditions
2. Producing toxins — these are poisonous chemicals that damage cells and tissues, causing the symptoms of disease

It is the toxins, not the bacteria themselves, that usually make you feel ill. For example, the toxins produced by Salmonella bacteria cause vomiting and diarrhoea.

graph TD
    A[Bacterium enters the body] --> B[Rapid reproduction by binary fission]
    B --> C[Large population of bacteria]
    C --> D[Toxins released]
    D --> E[Toxins damage cells and tissues]
    E --> F[Symptoms appear: fever, inflammation, pain]

---

Salmonella