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Asked by Fanta to Ceri, Marikka, Matt, Rob, Sally on 15 Nov 2014.
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Sally Cutler answered on 15 Nov 2014:
This is a rather complicated question. Bacteria can attack by forming toxins in something that we eat, so a bit like poisoning. The toxins can cause all kinds of damage like giving you diarrhoea. Live bacteria can also get into our bodies and directly invade various sites causing direct damage. They get in when we breathe, eat, get bitten by an insect, or have sexual contact. Some bacteria will just stay in one place, but produce toxins that can damage us in distant sites in the body. Others make our immune system that is supposed to protect us turn on us and cause immune-mediated damage. Viruses need to live inside a host cell to multiply and will end up bursting out of that cell to infect adjacent cells. Often bacteria and viruses will target certain places in our bodies where they are best suited to multiply and spread.
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Marikka Beecroft answered on 17 Nov 2014:
Bacteria and viruses can attack the body in many different ways. It all depends on what type of bacteria or virus it is and what does it attack in our bodies.
Bacteria can attack us with toxins, their own proteins or our cells directly. For example the Pseudomonas aeruginosa is a bacteria that can damage the lungs of people who have too much snot in their lungs (cystic fibrosis). It releases a toxin that breaks down the elastic parts of your lungs, but the bacteria that causes tuberculosis invades your white blood cells and multiplies within them which hurts your lungs because it causes large balls to form.
Viruses are a bit different, they invade your cell and then burst from it when there is enough of them. Though different viruses can target different cells in your body. HIV targets white blood cells but papillloma viruses just attacks your skin cells.
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Robert Hampson answered on 17 Nov 2014:
Viruses are little protein cases containing a few bits of DNA and some enzymes. The little protein case attaches to a host cell and injects the enzymes and DNA. The enzymes cut the host DNA and add the virus DNA. The virus DNA then proceeds to hijack the cell and create loads more viruses. At some point, it pops the host cell producing millions more viruses.
Bacteria can act in many different ways. They don’t need to hijack a host cell like a virus does. However, some of them do choose to live inside cells to hide from the host immune system. In a classical infection, the bacteria grow and divide inside human tissue somewhere using any food they can find. If at some point they cannot find food, they start to release enzymes and food which destroy host cells so they can get more space and more food. However, gut bacteria for example are a bit different in that they normally happily live in the gut, it is only when one bacteria start to outnumber others that nasty bacteria can cause a problem. At this point they release toxins, because this can stimulate an environment that further reduces their competition (by things like diarrhoea). These toxins aren’t very good for us though and can make us very ill.
Most of the time though we have countless bacteria living all over us and inside us and they don’t cause a problem. In fact most of the time, they are actually very useful!
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Ceri Dare answered on 17 Nov 2014:
The other scientists have already given you good answers.
Bacteria and viruses want to make more of themselves, so they try to hijack your body. Viruses hijack your cells directly, and turn them into virus-making factories. Bacteria mostly like being inside you because there is lots of food and it is a nice temperature for them.
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