Bacteria and Viruses

Transcription

1 Bacteria and Viruses 1 of 25 Boardworks Ltd 2012

2 2 of 25 Boardworks Ltd 2012

3 Comparing cell sizes 3 of 25 Boardworks Ltd 2012 Most plant and animal cells are between 10µm and 100µm in size around the diameter of a human hair and too small to see without a microscope. The largest cell in the human body is the female egg cell, at around 100µm in diameter. The smallest human cell is the sperm cell the head is around 5µm long. Bacteria are single celled organisms and are around 1µm in diameter, even smaller than sperm.

4 How big are micro-organisms? 4 of 25 Boardworks Ltd 2012

5 5 of 25 Boardworks Ltd 2012 Microscopes Due to advances in microscope technology, micro-organisms can be magnified, allowing us to see them in greater detail. Magnification is the measure of how many times bigger the image is than the object being studied. magnification = size of image actual size of the object When Antonie van Leeuwenhoek discovered single-celled organisms in 1676, his microscope could magnify an image up to 500 times. Now, with electron microscopes, scientists can attain a magnification as high as bacteria

6 Virtual microscope 6 of 25 Boardworks Ltd 2012

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8 What are bacteria? 8 of 25 Boardworks Ltd 2012 Bacteria can be classified according to their shape under a microscope: spherical spiral rod curved rod Bacteria lack mitochondria and chloroplasts. As they also have no distinct nucleus, their genetic material is contained within a coiled cluster of chromosomal DNA and a single circular strand of plasmid DNA.

9 What do bacteria contain? 9 of 25 Boardworks Ltd 2012

10 How do bacteria feed? 10 of 25 Boardworks Ltd 2012 A large number of different species of bacteria exist and exploit a very wide range of habitats. Different species of bacteria can survive on a range of energy sources: Using carbon dioxide and inorganic chemicals, such as ammonia and nitrate, to produce their own food. This method of obtaining food allows bacteria to survive extreme conditions, such as boiling sulphur-rich water. Using photosynthesis to produce their own food. Consuming organic compounds from the environment, e.g. from dead organisms, to obtain energy.

11 Energy from decaying substances 11 of 25 Boardworks Ltd 2012 Many species of bacteria can obtain energy from organic compounds through the process of decomposition or decay. A warm, moist, oxygen-rich environment is the most favourable for decay to occur. Which of the following might you expect to decay at a faster rate: cubes of bread that are kept in a dry environment cubes of bread that are exposed to moisture? The conditions in which bacteria reproduce and feed will therefore affect the rate of food spoilage.

12 Rates of decay experiment 12 of 25 Boardworks Ltd 2012

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14 How bacteria reproduce 14 of 25 Boardworks Ltd 2012 Bacteria can reproduce rapidly via asexual reproduction, where a single bacterium makes a copy of itself with exactly the same genetic code. In particular, bacteria use a special type of asexual reproduction called binary fission. This involves one bacteria splitting in two.

15 The growth rate of pathogens 15 of 25 Boardworks Ltd 2012

16 What do micro-organisms need to grow? 16 of 25 Boardworks Ltd 2012 growth rate Bacteria can be grown in a liquid broth or on solid agar. To reproduce at the optimum growth rate, bacteria need to be kept in ideal conditions, involving: a continuous supply of food the removal of products the optimum ph the optimum temperature. For example, when the ph or temperature is above the optimum, bacterial growth rates decline. optimum ph or temperature

17 Culturing bacteria 17 of 25 Boardworks Ltd 2012

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19 Virus fact file 19 of 25 Boardworks Ltd 2012 Micro-organism: Virus (e.g. flu virus and HIV) Size: They are smaller than bacteria and fungi, between 10 nm and 100 nm. Shape: Viruses have regular and geometric shapes. Structure: A virus is a simple organism that does not display all the characteristics of a living thing. It is made up of a protein coating and some genetic material. Reproduction: Viruses can only grow and reproduce within other living things.

20 Structure of a virus 20 of 25 Boardworks Ltd 2012

21 Using viruses 21 of 25 Boardworks Ltd 2012 A virus cannot read its own genes but it can make a host cell copy them and make the proteins. protein coat genetic material The virus on the right is a bacteriophage. It infects bacteria by injecting its genetic material down a special tube. Viruses can also attack some plant cells and some animal cells. injection tube

22 Human immunodeficiency virus (HIV) 22 of 25 Boardworks Ltd 2012 HIV is a virus that causes acquired immunodeficiency syndrome (AIDS) a deterioration of the immune system. In 2007, 33.2 million people were estimated to be living with HIV. There is currently no cure; however, antiviral drugs have been developed to help delay the onset of AIDS. The process of how the HIV infects a cell and reproduces within the living cell is typical of a virus.

23 How do viruses replicate? 23 of 25 Boardworks Ltd 2012

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25 Glossary 25 of 25 Boardworks Ltd 2012

26 Multiple-choice quiz 26 of 25 Boardworks Ltd 2012