Noadswood Science, 2011

To understand how micro-organisms cause illness

Wednesday, April 19, 2023

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…

1 2 4 8 16 32 64 128 256 512 1024 2048

Bacterial ReproductionBacterial Reproduction 4096 8192 16384 32768 65536 131072 262144 524288 1048576 2097152 4194304 8388608

16777216 33554432 67108864 1.34x108

2.68x108

5.37x108

1.07x109

2.15x109

4.29x109

8.59x109

1.72x1010

3.44x1010

6.87x1010

1.37x1011

2.75x1011

5.5x1011

1.1x1012

2.2x1012

4.4x1012

8.8x1012

1.76x1013

3.52x1013

7.04x1013

1.41x1014

2.81x1014

5.63x1014

1.13x1015

2.25x1015

4.5x1015

9.01x1054

1.8x1016

3.6x1016

7.21x1016

1.44x1017

2.88x1017

5.76x1017

Bacterial ReproductionBacterial Reproduction 1.15x1018

2.31x1018

4.61x1018

9.22x1018

1.84x1019

3.69x1019

7.38x1019

1.48x1020

2.95x1020

5.9x1020

1.18059x1021

2.36118x1021

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 665x10-15 grams (0.000000000000665 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 ReproductionBacterial 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 NumbersExponential 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

Bacteria Viruses

1/1000th mm in size 1/1’000’000th mm in size

Living (some are harmless)Genetic information stored within

a protein coat

Reproduce quickly Replicate quickly within host cell

Affected by antibiotics Not 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 ExamplesMicro-organism Examples