Micro-organisms, Disease and Biotechnology

Fast breeders, for good and ill

This unit looks like several unconnected topics: germs, the immune system, vaccines, antibiotics, and then, oddly, bread and yoghurt. They are not unconnected. One fact about micro-organisms ties the whole unit together. ⭐⭐ Micro-organisms multiply FAST. Given warmth, food and moisture, a few become a great many in a short time. That single power is what makes them both dangerous and useful, depending only on WHERE they are doing it. Inside a body, fast multiplication is a threat. A pathogen that gets in can build up quickly and spread from person to person, which is why the body has to fight back, why we can train its defences in advance with a vaccine, and why we sometimes attack the invader with an antibiotic. Inside a fermenter, the very same fast multiplication is a gift. A vat of microbes given the right conditions makes a useful product quickly and cheaply, which is how we brew, bake, make yoghurt and cheese, and even make the antibiotics themselves. ⭐ So the two halves of this unit are one idea seen twice. A microbe is not a friend or an enemy by nature. What matters is whether it is multiplying IN us, which is disease to control, or FOR us, which is biotechnology to harness. ⚠️ Carry that question through everything that follows: is this microbe multiplying in a host, or working in a fermenter?

Threat, fight, and harness

The whole unit fits into three columns. The first is the problem, the second is what we do about it, and the third is the same microbes put to work.

Tap the two ways it spreads

Tap the TWO ways a COMMUNICABLE disease can spread from one person to another.

• Breathing in tiny droplets coughed or sneezed into the air by an infected person.
• Drinking water that has been contaminated with a pathogen.
• Inheriting it in the genes passed on from a parent.
• Eating too much sugar over many years.

Why antibiotics miss a cold

A common cold is caused by a virus. A doctor will not prescribe antibiotics for it. What is the reason?

• Antibiotics kill bacteria, and a cold is caused by a virus, which antibiotics have no effect on
• Because a cold is too mild to bother treating
• Because antibiotics are too expensive to give out
• Because the virus is too strong for any antibiotic

Words for the microbe unit

Six terms this unit turns on. The first two are the disease, the next three the fight, and the last the harness.

Match each defence to its job

Two that are true of vaccines

Select the TWO statements that correctly describe how vaccination works.

• A vaccine shows the immune system a harmless form of a pathogen, so it can respond fast if the real one arrives
• When enough people are vaccinated, a disease struggles to spread, which protects the wider population
• A vaccine works by killing viruses directly in the same way an antibiotic kills bacteria
• A vaccine gives you the full disease so you build up strength

The response, and the resistance

Two mechanisms are worth getting exactly right, because questions turn on them. ⭐ First, why a vaccine works and why a second infection is beaten faster. The first time the body meets a pathogen, it takes time to make the right antibodies. But it keeps MEMORY of it. So the next time, the response is faster and stronger, and you may not even feel ill. A vaccine simply gives the body that first, safe meeting in advance. ⚠️ Second, antibiotic resistance, which is a real and growing problem. Antibiotics kill bacteria, not viruses, so taking them for a cold does nothing but harm. And whenever antibiotics are used, any bacteria that happen to survive are the resistant ones, and they multiply. Overusing antibiotics, or not finishing a course, breeds bacteria the antibiotic can no longer kill. Using them only when needed, and finishing the course, slows that down. ⭐⭐ And notice the loop that ties the unit together. The antibiotics we use against bacteria are themselves MADE by micro-organisms grown in fermenters. The same fast multiplication that is a threat in the body is put to work in the vat. How to answer. When a question is about disease, follow the pathogen: how it gets in, how it spreads, and how the body or a medicine stops it. When it is about biotechnology, follow the product: which microbe, what conditions, what it makes. Keep the two halves clear and say which one you are in.

Order the immune response

Put the steps of the body response to a NEW pathogen into the order they happen.

• A pathogen gets past the barriers and enters the body
• White blood cells detect the pathogen as foreign
• They make antibodies that lock onto that particular pathogen
• The marked pathogens are destroyed and the person recovers
• Memory cells remain, so a second infection is beaten faster

Build why a vaccine protects

Assemble the sentence that explains why a vaccinated person is protected against a disease.

The microbe unit run

Five quick decisions about micro-organisms, disease and biotechnology. Three lives.

A rumour through a school

Leave biology aside for a screen. A false rumour starts in one class of a school and begins to travel. Nobody organises it; each person who hears it simply tells a couple of friends, who tell a couple more. ⭐ Because each teller passes it to several others, it grows fast. One person becomes a handful, a handful becomes half the year, and soon it feels as though everyone has heard it. That is the shape of anything that jumps from person to person: slow at first, then suddenly everywhere. ⭐⭐ Now think about how you would stop it. Chasing it once it has spread is almost hopeless. But suppose that BEFORE it started, a teacher had quietly told the class the true facts. Then when the rumour reached them, they would recognise it as false and simply not pass it on. They were made ready in advance. And here is the clever part. You would not need to prepare every single pupil. If enough of them refused to pass it on, the rumour would keep hitting dead ends and fizzle out, so even the few who were never told would probably never hear it. ⚠️ Hold that picture. Something that jumps from person to person grows fast and is hard to chase once loose, but preparing people in advance, and preparing enough of them, can stop it before it starts.

Complete the microbe unit facts

A micro-organism that causes disease is a _____. A disease that can spread from one person to another is a _____ disease. White blood cells defend the body partly by making _____, which lock onto a particular pathogen and mark it for destruction. Being given a harmless form of a pathogen so the immune system can learn to fight it in advance is called _____. Medicines that kill bacteria, but have no effect on viruses, are _____. Using micro-organisms to make useful products, such as yeast making bread rise, relies on _____.

Advise on three infections

A clinic sees three cases in a morning and wants advice grounded in how microbes and the body work.

• A patient with a heavy cold, which is caused by a virus, asks for antibiotics to clear it up quickly.
• A patient with a bacterial infection is prescribed antibiotics and says they will stop taking them as soon as they feel better.
• A healthy person asks why they should bother being vaccinated against a disease that is currently rare in their area.

Explain how the body meets a microbe

Explain how a communicable disease spreads and how the body and medicine deal with it, using the ideas of pathogens, the immune response, vaccination and antibiotics. You may use any disease you know.

• Explain what a pathogen is and give one way a communicable disease spreads
• Explain how white blood cells respond, including antibodies and memory
• Explain how a vaccine prepares the body in advance, and why it uses a harmless form
• Explain what antibiotics do and why they do not work on viruses
• Finish by explaining why finishing a course of antibiotics matters for antibiotic resistance