Question 1: Salmonella is a type of bacteria that can cause food poisoning in humans. It is often transmitted through contaminated food or water. Understanding how Salmonella infects and spreads is essential for preventing outbreaks.

Answer: Salmonella is a bacteria that causes food poisoning, transmitted mainly via contaminated food or water.

Question 1: Define Salmonella and describe its main characteristics.

Answer: Salmonella is a genus of bacteria characterised by rod-shaped cells that can cause gastrointestinal illness in humans. It is gram-negative, motile, and can survive in both oxygen-rich and oxygen-poor environments.

Question 2: Explain the mechanism by which Salmonella bacteria cause illness in humans.

Answer: Salmonella bacteria infect the human digestive system by attaching to the intestinal lining, where they invade cells and multiply. This causes inflammation, leading to symptoms such as diarrhoea, fever, and abdominal cramps. The bacteria release toxins that further damage the intestinal lining.

Question 1: If a population of Salmonella bacteria doubles every 30 minutes, how many bacteria will there be after 3 hours if you start with 1,000 bacteria? Show your working.

Answer: Number of divisions = 3 hours / 0.5 hours = 6 divisions; total bacteria = 1000 × 2^6 = 1000 × 64 = 64,000 bacteria.

Question 1: Describe two safety precautions that must be taken when handling Salmonella bacteria in a laboratory setting.

Answer: Wearing protective gloves and lab coats; sterilising equipment and disposing of waste properly.

Question 2: Identify the variables involved in an experiment testing the effect of temperature on Salmonella growth and specify which should be controlled.

Answer: Variables include temperature (independent variable), bacterial growth rate (dependent variable), and the type of nutrient medium, pH, and incubation time (controlled variables).

Question 1: A study reports that in a contaminated water sample, Salmonella was detected at a concentration of 500 bacteria per millilitre. After boiling the water, no Salmonella was detected. Explain what this indicates about the effect of boiling on Salmonella.

Answer: Boiling effectively kills Salmonella bacteria, reducing their presence to zero in the sample.

Question 1: Describe the process by which Salmonella contaminates food and how it causes illness in humans. Include the role of food handling and storage.

Answer: Salmonella contaminates food primarily through contact with infected animals or contaminated water during processing. Improper handling, such as inadequate cooking or cross-contamination, allows bacteria to survive on food surfaces. When ingested, Salmonella bacteria attach to the intestinal lining, invade cells, and multiply, producing toxins that cause symptoms like diarrhoea, fever, and cramps. Proper storage, cooking, and hygiene are vital to prevent infection.

Question 2: Calculate the bacterial growth after 4 hours if the initial population is 2,000 bacteria and the bacteria divide every 45 minutes.

Answer: Number of divisions = 4 hours / 0.75 hours = 5.33, approximately 5 divisions; total bacteria = 2000 × 2^5 ≈ 2000 × 32 = 64,000 bacteria.

Question 1: Discuss how understanding Salmonella's characteristics has helped develop food safety regulations and treatments.

Answer: Knowledge of Salmonella's ability to survive in certain conditions has led to regulations on cooking temperatures, hygiene practices, and food storage. It also aids in developing vaccines and antibiotics to treat infections.

Question 2: Explain how advances in technology can help detect Salmonella outbreaks faster in the food industry.

Answer: Developments such as rapid DNA sequencing, PCR testing, and biosensors enable quicker identification of Salmonella presence in food samples, allowing faster response to outbreaks and reducing public health risks.