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Biology of microorganisms (PowerPoint) by pptfiles

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									Chapter 1

Microorganisms and Microbiology

Chapter outline
1.1 What is a microbe? 1.2 The importance of Microbiology 1.3 Microbes in our lives 1.4 The history of microbiology 1.5 Important events in the development of microbiology

• Microorganisms are responsible for many of the changes observed in organic and inorganic matter (e.g., fermentation and the carbon, nitrogen and sulfur cycles that occurred in nature. • The development of microbiology as a scientific discipline has depended on the availability of the microscope and the ability to isolate and grow pure cultures of microorganisms. • Microbiology is a large discipline, which has a great impact on other areas of biology and general human welfare

1.1 What is a microbe?
The word microbe (microorganism) is used to describe an organism that is so small that can not be seen without the use of a microscope. Viruses, bacteria, fungi, protozoa and some algae are all included in this category.

Our world is populated by invisible creatures too small to be seen with the unaided eye. These life forms, the microbes or microorganisms, may be seen only by magnifying their image with a microscope.

Microbial world

Infectious agents (non-living) viruses viroids prions

Prokaryotes (unicellular)




Algae (unicellular or multicellular)

Fungi Protozoa Other (unicellular (unicellular) (multicellular or organisms) multicellular)

The size and cell type of microbes
Most of the bacteria, protozoa, and fungi are single-celled microorganisms, and even the multicelled microbes do not have a great range of cell types. Viruses are not even cells, just genetic material surrounded by a protein coat and incapable of independent existence.

The size and cell type of microbes
Microbe Approximate range of sizes Viruses Bacteria Fungi 0.01-0.25µm 0.1-10µm 2µm->1m Cell type Acellular Prokaryote Eukaryote


1µm-several meters


1.2 The importance of microbiology
Microbes impinge on all aspects of life, just a few of these are listed below:

The environment



• The environment • Medicine • Food • Biotechnology • Research
Press here to continue

Microbes are responsible for the geochemical cycles. They are found in association with plants in symbiotic relationships. Some microbes are devastating plant pathogens, but others may act as biological control agents against diseases.

The disease-causing ability of some microbes is well known. However, microorganisms have also provided us with the means of their control in the form of antibiotics and other medically important drugs.

Microbes have been used to produce food, from brewing and wine making, through cheese production and bread making, to the manufacture of soy sauce. But microbes are also responsible for food spoilage.

Traditionally microbes have been used to synthesize important chemicals. The advent of genetic engineering techniques has led to the cloning of polypeptides into microbes.

Microbes have been used as model organisms for the investigation of biochemical and genetical processes. Millions of copies of the same single cell can be produced very quickly and give plenty of homogeneous experimental material. Most people have no ethical objections to experiments with these microorganisms.

1.3 Microbes in our lives
• Microorganisms as Disease Agents

• Microorganisms and Agriculture

• Microorganisms and the Food Industry
• Microorganisms, Energy, and the Environment • Microorganisms and the Future

Microbial physiology
Microbial genetics Microbial Morphology



Branches of Microbiology

Protozoology Microbial ecology


Microbial taxonomy

Molecular biology

Phycology or Algology

The future of microbiology is bright
Microbiology is one of the most rewarding of professions, because it gives its practitioners the opportunity to be in contact with all the other natural science and thus to contribute in many different ways to the betterment of human life.

1.4 The history of microbiology

In the field of observation, chance favors only prepared minds.

------ Louis Pasteur

The discovery of microorganisms The spontaneous generation conflict The recognition of microbial role in disease The discovery of microbial effects on organic and inorganic matter The development of microbiology in this century

The discovery of microorganisms
Antony van Leeuwenhock (1632-1723)

The first person to accurately observe and describe microorganisms

The first person to observe and describe microorganisms was the amateur microscopist Antony van leeuwenhoek of Delft, Holland. Leeuwenhock made his simple, single-lens microscope which could amplify the object being viewed 50 – 300 times. Between 16731723, he wrote a series of letters to the Royal Society of London describing the microbes he observed from the samples of rainwater, and humam mouth.

Object being viewed adjusting screws

A drawing of one of the microscopes showing the lens a; mounting pin b; and focusing screws c and d.
Leeuwenhoek’s drawings of bacteria from the human mouth.

Louis Pasteur (1822 – 1895)
Pasteur’s contributions: • Pasteur (1857) demonstrated that lactic acid fermentation is due to the activity of microorganisms • Pasteur (1861) conflict over spontaneous generation – birth of microbiology as a science • Pasteur (1881) developed anthrax vaccine Louis Pasteur working in his laboratory • Pasteurization

The spontaneous generation conflict
Spontaneous generation – that living organisms could develop from nonliving or decomposing matter.

Pasteur’s swan neck flasks used in his experiments on the spontaneous generation of microorganisms

Conclusion: Microorganisms are not spontaneously generated from inanimate matter, but are produced by other microorganisms

Robert Koch (1843 – 1910)
The recognition of microbial role in disease

Robert Koch in his laboratory

Koch’s demonstration of special organisms cause special diseases

Koch’s postulates
• The microorganisms must be present in every case of the disease but absent from healthy organisms. • The suspected microorganisms must be isolated and grown in a pure culture. • The disease must result when the isolated microorganisms is inoculated into a healthy host. • The same microorganisms must be isolated again from the diseased host

The Golden age of microbiology
• Koch and pure cultures

• Fermentation and Pasteurization
• Germ theory of disease • Vaccination

The discovery of microbial effects on organic and inorganic matter
• The Russian microbiologist Winograsky discovered that soil bacteria could oxidize iron, sulfur and ammonia to obtain energy, and also isolated nitrogen–fixing bacteria.
• Beijerinck made fundamental contributions to microbial ecology. He isolated Azotobacter and Rhizobium.

Alexander Fleming (1881-1955)

Sir Alexander Fleming discovered the antibiotic penicillin. He had the insight to recognize the significance of the inhibition of bacterial growth in the vicinity of a fungal contaminant.

1.5 Important events in the development of microbiology
Microbiological History Leeuwenhoek discovers "animalcules" Pasteur shows that lactic acid fermentation is due to a microorganism 1861 Pasteur shows that microorganisms do not arise by spontaneous generation 1867 Lister publishes his work on antiseptic surgery 1869 Miescher discovers nucleic acids 1876-1877 Koch demonstrates that anthrax is caused by Bacillus anthracis 1880 Laveran discovers Plasmodium, the cause of malaria 1881 Koch cultures bacteria on gelatin Pasteur develops anthrax vaccine Date 1676 1857


1887 1889 1899
1921 1923 1928 1929 1933 1935

Koch's postulates first published Metchnikoff describes phagocytosis Gram stain developed Petri dish (plate) developed by Richard Petri Beijerinck isolates root nodule bacteria Beijerinck proves that a virus particle causes the tobacco mosaic disease Fleming discovers lysozyme First edition of Bergey's Manual Griffith discovers bacterial transformation Fleming discovers penicillin Ruska develops first transmission electron microscope Stanley crystallizes the tobacco mosaic virus


Avery shows that DNA carries information during transformation Waksman discovers streptomycin Watson and Crick propose the double helix structure for DNA 1961-1966 Cohen et al use plasmid vectors to clone genes in bacteria 1980 Development of the scanning tunneling microscope 1983-1984 The polymerase chain reaction developed by Mullis 1990 First human gene-therapy testing begun 1997 Discovery of Thiomargarita namibiensis, the largest known bacterium Escherichia coli genome sequenced 2000 Discovery that Vibrio cholerae has two separate chromosomes

1.How did Pasteur's famous experiment defeat the theory of spontaneous generation? 2.How can Koch's postulates prove cause and effect in a disease? 3.Who was the first person to use solid culture media in microbiology? What advantages do solid media offer for the culture of microorganisms?

4.What is the enrichment culture technique and why was it a useful new method in microbiology?
5.When and how Alexander Fleming discovered antibiotics?

1. Pasteur's experiments on spontaneous generation were of enormous importance for the advance of microbiology, having an impact on the methodology of microbiology, ideas on (he origin of life, and the preservation of food,to name just a few. Explain briefly how the impact of his experiments was felt on each of the topics listed.

2. Describe the various lines of proof Robert Koch used to definitively associate the bacterium Mycobacterium tuberculosis with the disease tuberculosis. How would his proof have been flawed if any of the tools he developed for studying bacterial diseases had not been available for his study of tuberculosis?

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