yr. 1 microbiology. lec

8/10/2019 Yr. 1 Microbiology. LEC

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Microbiology - Lecture 1

References:Brock, Biology of Microorganisms Ch 1Tortora, Microbiology an Introduction Ch 1

Each lecture will be accompanied by an audiorecording.

Underlined words are illustrated in separate slides that are hyper-linked just point to underlined words


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2Microbiology

1. Microbiology is the study of microscopic life, including:BacteriaVirusesFungi - moulds Some algaeSome parasites (worms, trypanosomes, malaria etc)

2. Cells of macroorganisms such as plants and animals cannotsurvive alone, exist as part of multicellular structures

Organs and tissues in animals, structures such as stems and leaves inplants, etc

3. Most microorganisms can survive, grow and replicate as singlecells

Q. What type of microbe is: influenza, tinea, red tide, giardia?

Q. Why is it important to know what type of microbe it is?


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3Why study microbiology?

1. All living cells on Earth have much in common,studying biochemical and genetic functions in bacterial cells hasgiven insight into the physical and chemical basis of life

2. Microbes play a large role in human health, both as causes of

disease and as producers of medicines such as penicillin

3. Microbes play a large role in agriculture, and are used in industryto produce foods such as wine, bread, cheese etc and to produceproteins such as insulin

4. Microbial cells can be grown rapidly to high densities, this allowsfor genetic and biochemical studies and industrial uses

Q. Why does the mould Penicillium produce penicillin?

Q. Why do we need Biotechnology to produce insulin?


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Microbes in agriculture1. Legume plants (eg lentils, peas) have bacteria present in their root

nodules that convert nitrogen from the atmosphere (N 2) into fixednitrogen the plants can use for growth (NH 3) Nitrogen cycling

2. Cows and sheep have bacteria in the rumen of their stomachs thatdigests cellulose from grass

3. Microorganisms also take part in other nutrient cycling, e.g. ofcarbon and sulfur, convert these elements into forms that can betaken up by plants Carbon dioxide sink

4. Some microorganisms will break down pollutants, such as oil,pesticides and solvents Bioremediation

Q. How do ruminants contribute to global warming?

Q. How do we win $25 million using microbes?*

*http://www.virginearth.com/


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5 Microorganisms as founders ofhigher life

1. The oxygen present in the atmosphere is due to microbial activity by photosynthetic cyanobacteria that first existed more than 3.5billion years ago Stromatolites

2. Microorganisms existed for billions of years before plants andanimals, because of this there is a much larger evolutionarydiversity of microorganisms compared with plants and animals

3. Some microorganisms can live in extreme environments, togetherthey have the capacity to metabolise a huge range of chemicals

Extremophiles

4. They form relationships with other higher organisms such asanimals, these can be beneficial or harmful

Q. Why do microbes cope better with global warming?

Q. Why are you really an alien?


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Microbial environments1. Microbes live in populations of cells in a particular

environment, usually several populations of microbesinteract in a microbial community Biofilms

2. Microbial ecology is the study of microorganisms in their natural

environment

3. Major microbial ecosystems include aquatic environments,terrestrial environments and in and on plants and animals

4. Estimated that the total number of bacterial cells on Earth is 5 X10 30

5. Most of these exist underground

Q. If many bacteria multiply ever 20 minutes why arewe not covered in slime?

Q. How far underground?


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8Prokaryote vs Eukaryote cells

Plant and bacterial cells have a cell wall, while animal cells have aninternal cytoskeleton

Wikipedia - Prokaryote Wikipedia - Eukaryote


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Viruses1. Viruses are a class of microorganism, but they are not cells

2. Viruses only replicate once they have infected another cell

3. They have no ribosomes and so rely on the host cell for proteinproduction

4. Viruses have very small genomes

5000 to 670,000 bases

Can consist of DNA or RNA, can besingle or double-stranded

Fig. 1.1e


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DNA arrangements in cells1. Most prokaryotes have a single, circular chromosome, and a

single copy of each gene, arranged in a nucleoid rather than anucleus

2. Many prokaryotes also have extrachromosomal circular DNAcalled plasmids, contain genes with particular properties, e.g.antibiotic resistance

3. In eukaryotes DNA is arranged in multiple linear chromosomes

4. E. coli bacteria have 4.68 million base pairs of DNA, containing4,300 genes

5. Human cells have 3 billion base pairs of DNA, containing 18,000to 30,000 genes


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11 The three domains of life1. By sequencing the ribosomal RNA from different cells, a

evolutionary tree of life has been established

2. From these results it can be seen that Archaea, whilst beingprokaryotes, are more closely related to eukaryotes than bacteria

Wikipedia Three domains


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Mitochondria and chloroplasts1. It is believed that the mitochondria and chloroplast organelles of

eukaryote cells were once free-living cells

2. Evidence for this includes: these organelles have their own circular

genome, and their own ribosomes

3. Through a process of endosymbiosis they came to be a permanent partof eukaryote cells, they produce energy used by the cell

4. Ribosomal RNA sequencing has shown that these organelles evolvedfrom bacteria

5. Some simple eukaryotes lack mitochondria/chloroplasts, cannot existalone and live as parasites of other organisms (e.g. giardia )


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13 Foundations of microbiology1. The existence of organisms too small to be seen by eye

had long been suspected, discovered with the inventionof the microscope

2. Robert Hooke first used microscopes todescribe cells when he published a picture

of mould in 1655.Van Leeuwenhoek was the first to drawbacteria in 1683.

Fig. 1.2


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Foundations of microbiology1. Before the existence of microorganisms, some believed that food

spoilage occurred because organisms spontaneously generated fromnon-living material

2. Louis Pasteur (1822-1895) opposed this theory, observed thatmicroorganisms present on spoiled food were similar to microbes presentin the air

3. Pasteur hypothesised that if he could sterilise food it would remain sterileunless contaminated

4. Some argued that the process of boiling changed the property of the airand prevented spontaneous generation

5. Pasteur used swan-necked flasks to show that when air without particlesentered the broth remained sterile


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Pasteurs experiment

Fig. 1.3


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Koch - the first medical microbiologist

1. Robert Koch (1843-1910) developed the germ theory of disease

2. First studied anthrax, caused by the bacteria Bacillus anthracis

3. Mostly occurs in cattle, Koch observed that Bacillus microbes werealways present in the blood of cattle with anthrax

4. He demonstrated that a small amount of blood from a mouse infectedwith anthrax could transfer the disease when injected into a healthymouse

5. He showed that the bacteria could be grown in culture for manygenerations, when injected it would still cause anthrax

6. He developed criteria, known as Kochs Postulates , for proving that aspecific microorganism causes a particular disease


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Fig 14-3


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Kochs experiments 1. Koch and subsequent microbiologists used these postulates to discover

the causes of many human and animal diseases

2. This led to the development of treatments for the prevention and cure ofmany infectious diseases

3. Koch developed methods of obtaining pure microbial cultures that are stillused now

He observed that bacteria grew on potato slices in colonies, and that eachcolony had specific characteristics, such as colour

He concluded that each bacterial colony represented a pure culture

4. This allowed the causative organisms of many diseases to be identified


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Kochs experiments 1. At the time of Kochs experiments, up to 14% of all human deaths were

due to tuberculosis

2. The causative organism, Mycobac ter ium tube rcu los i s , was difficult toidentify as it has a waxy cell wall that is difficult to stain, and is difficult togrow in culture

Koch developed a staining procedure for M. tuberculosis present in tissues

He cultured the bacteria on media containing coagulated serum

He used guinea pigs as a model of M. tuberculosis infection

3. For this work, he was awarded the Nobel prize for physiology or medicinein 1905

End of audio


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Microorganisms and biotechnology

Foreign DNA, e.g.human insulin gene

plasmid

AGGCCT

AGGCTT

DNA cut withrestrictionenzymes

The complementarypieces of DNA joined

with enzymes

Plasmid containingforeign gene introduced

into bacteria

Foreign proteinexpressed and

purified from bacteria

Return


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Stromatolites

Stromatolites growing in Shark Bay , Australia. Photo taken in March 2005. Source and creator:Photograph taken by Paul Harrison (Reading, UK)

Return
http://en.wikipedia.org/wiki/Stromatolitehttp://en.wikipedia.org/wiki/Shark_Bayhttp://en.wikipedia.org/wiki/Shark_Bayhttp://en.wikipedia.org/wiki/Stromatolite


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Plaque a biofilm of teethSource: Dental plaque - Wikipedia

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