Noadswood Science, 2011
To understand how micro-organisms cause illness Monday, September 07, 2015
A disease is any condition where the body isn’t working as it should – this could be caused by a malfunction in the body (as with diabetes) or it could be caused by a pathogen (a microbe that causes disease) Pathogens are micro-organisms that cause infectious disease: bacteria and viruses are the main pathogens What diseases are spread by bacteria / viruses, and how can their spread be reduced?
Microbes are micro-organisms that can cause diseases, entering the body in a number of ways: - Eyes Genitals Skin Mouth Cuts Nose Ears A number of these places where microbes can enter the body are defended
One easy way to defend the body against illness is by keeping it clean and hygienic as microbes can spread very quickly in unhygienic conditions The spreading of microbes is known as transmission As soon as a virus or bacterium enters the body, we are termed infected (not the same as being ill – illness results from the effects these microbes have on our body Bacteria and viruses have the ability to produce poisons known as toxins
There are two types of outbreaks: - ◦ An epidemic – a local outbreak of disease ◦ A pandemic – a global outbreak of disease
Bacteria are microscopic organisms – they come in many shapes and sizes, but even the largest are only 10 micrometres long (10 millionths of a metre) Bacteria are living cells and, in favourable conditions, can multiply rapidly – once inside the body, they release poisons or toxins that make us feel ill Diseases caused by bacteria include: - ◦ Food poisoning ◦ Cholera ◦ Typhoid ◦ Whooping cough ◦ Gonorrhoea (STI)
Bacteria can multiply rapidly – around every twenty minutes… If you started with one bacteria how many would you have at the end of the day? Bacteria replicate every 20 minutes, which means there are 72 replications available in the course of a day… 1 > 2 > 4 in one hour 8 > 16 > 32 by second hour etc…
11 22 44 88 16 32 64 128 256 512 1024 2048 Bacterial Reproduction 4096 8192 1.34x10 8 2.68x10 8 5.37x10 8 1.07x10 9 2.15x10 9 4.29x10 9 8.59x10 9 1.72x10 10 3.44x10 10 6.87x10 10 1.37x10 11 2.75x10 11 5.5x10 11 1.1x10 12 2.2x10 12 4.4x10 12 8.8x10 12 1.76x10 13 3.52x10 13 7.04x10 13 1.41x10 14
2.81x10 14 5.63x10 14 1.13x10 15 2.25x10 15 4.5x10 15 9.01x10 54 1.8x10 16 3.6x10 16 7.21x10 16 1.44x10 17 2.88x10 17 5.76x10 17 Bacterial Reproduction 1.15x10 18 2.31x10 18 4.61x10 18 9.22x10 18 1.84x10 19 3.69x10 19 7.38x10 19 1.48x10 20 2.95x10 20 5.9x10 20 x10 21 x10 21
2’361’183’241’434’820’000’000 bacterial from 1 original are replicated in 24 hours!!! This number is otherwise known as 2 sextrillion! Mass of one bacterium is around 665x grams ( grams) This means, with an infinite amount of energy and no bacteria dying potentially one bacteria could replicate to form 1’570’186 kilograms of bacteria in 24 hours! Bacterial Reproduction
When the creator of chess showed his invention to the emperor, the emperor was so pleased that he gave the inventor the right to name his prize for the invention. The man, who was very wise, asked the emperor for this: that for the first square of the chess board, he would receive one grain of rice, two for the second one, four on the third one, and so forth, doubling the amount each time. The emperor, arithmetically unaware, quickly accepted the inventor's offer, even getting offended by his perceived notion that the inventor was asking for such a low price, and ordered the treasurer to count and hand over the wheat to the inventor However, when the treasurer took more than a week to calculate the amount of wheat, the emperor asked him for a reason for his tardiness. The treasurer then gave him the result of the calculation, and explained that it would be impossible to give the inventor the reward. The emperor then, to get back at the inventor who tried to outsmart him, cut off the inventor's head to discourage such trickery – the amount of rice grains needed would have been 18,446,744,073,709,551,615 (18.4 quintillion) or 100’000kg or rice!!! Exponential Numbers
Viruses are significantly smaller than the smallest bacterium (among the smallest organisms known) Viruses consist of a fragment of genetic material inside a protective protein coat Viruses can only reproduce inside host cells, and they damage the cell when they do this – if a virus can get inside a cell it can take it over and make hundreds of thousands of copies of itself Eventually the virus copies fill the whole host cell and burst it open – the viruses are then passed out in the bloodstream, the airways, or by other routes
Diseases caused by viruses include: - ◦ Influenza (flu) ◦ Colds ◦ Measles ◦ Mumps ◦ Rubella ◦ Chicken pox ◦ AIDS
Viruses need a host cell to reproduce within – this is a body cell, which will provide the machinery, and chemicals the virus requires to make copies of it Host cell (e.g. human body cell) Virus
The virus not only infects the body – it also infects the body cells Approach – the virus approaches the cell Attachment – the virus secures itself to the host cell surface
Insertion – the virus injects its genetic material through the injection tube and into the host cell Replication – the genetic material makes multiple copies of itself
It is at this stage that the viruses within the host cell can remain dormant (virus remains within the cell without killing it or breaking out) – in some viruses, such as HIV, this period can last a number of years Assembly – new viruses are assembled using chemicals from the host cell (the original virus dies and breaks down)
The host cell splits open (cell lysis) and dies and viruses escape and release toxins Each virus will then start another round of replication… Virus Toxin
BacteriaViruses 1/1000 th mm in size1/1’000’000 th mm in size Living (some are harmless) Genetic information stored within a protein coat Reproduce quicklyReplicate quickly within host cell Affected by antibioticsNot affected by antibiotics
When a microbe enters the body it begins releasing toxins which can damage body tissue and prevent body systems working properly The body could probably cope with a small amount of poison, but microbes quickly reproduce themselves The microbes may be able to reproduce, with more microbes increasing the levels of toxins The bodies normal state of ‘well being’ is affected We are said to be ‘diseased’
Toxin Levels Presence of microbes Person is infected - microbe levels are low and the toxin levels are low Person is well - microbe levels are very low and the toxin levels are very low Person is ill and diseased - microbe levels are high and the toxin levels are high
Micro-organism Examples