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Chapter 1
Introduction
• Ubiquitous – they are everywhere • Air, water, Soil ( microbes are all around
us)• Normal flora – found in the gastrointestinal
tract, genitourinary tract, respiratory tract, skin.
• Beneficial aspects and harmful aspects• Normal flora protect us from diseases.
They suppress the growth of pathogens.• E. coli in the large intestine makes vitamin
K – used for blood clotting.
• Aquatic environments. Unicellular algae – bottom of the food chain.
• Unicellular algae > tiny fish > large fish > shark.
• Algae are autotrophs. They use CO2 and water to make sugar.
• Soil microbes are involved in recycling chemical elements.
• Breakdown cellulose and release CO2.• Making food products (yogurt, cheese,
bread). Yeast + flour > dough
• Small ball of dough -----large ball of dough
• Therapeutic substances – genetic engineering is used to force E. coli to make human insulin.
• Bioremediation – microbes are used to clean up chemical pollutants (oil spills) in the environment.
• Insecticide – BT toxin is sprayed on plants.
• Sewage treatment – breakdown organic matter to produce methane.
• Harmful aspects
• Tuberculosis, Lyme disease
• Spoilage of food products.
Milk ----- sour. Lactose --- acids.
• History of microbiology
• 1665 Robert Hooke – plant materials (leaves and stems). Little boxes – cells.
• 1673 – 1723 Anton van Leeuwenhoek observe microbes under the microscope.
• Rain water, scrapings from his teeth.
• Called the microbes animalcules.
• Spontaneous generation theory – life could arise from nonliving matter.
• Decaying meat give birth to maggots (larvae of flies)
Fine net
No maggots
Needham 1745
• Rudolph Virchow – theory of biogenesis.
• Life could arise only from pre-existing living cells.
• 1861 Louis Pasteur disproved the spontaneous generation theory.
Pasteur’s experimentS shaped curve
S shaped curveS shaped curve
S shaped curve
• Microbes are found in the air, in liquids and on solids.
• Foundation for the aseptic procedure used in the lab to prevent contamination
• 1857 – discovered fermentation.
• Yeast converted sugars in the grapes to alcohol and CO2 in the absence of O2.
• 1864 – came up with pasteurization. Beverages such as milk are heated enough to kill microbes without destroying the flavor of the beverages.
Germ theory of disease
• A belief microbes could cause diseases.
• 1860s Joseph Lister treated surgical wounds with disinfectant.
• 1876 Robert Koch proved the germ theory of disease.
• Animals such as cattle were dying of a disease.
• Drew blood from the animals that had died of the disease.
• Isolated a rod-shaped bacterium (isolate #1)
• Grew bacterium in the lab and obtained a pure culture of the bacterium.
• Injected bacterium into healthy animals.
• They got sick and died. He isolated rod shaped bacterium from these animals (isolate #2)
• Compared the 2 isolates and found that they were identical.
• Anthrax. Bacillus anthracis.
• The above steps are known as Koch’s postulates.
• They are used even today to determine the causative agent of a mysterious infectious disease.
• 1928 Alexander Fleming discovered penicillin.
• Naming organisms
• 1735 Carolus Linnaeus – binomial
• Genus and species
• Latin – describe the organism, honor a scientist.
• Staphylococcus aureus
• Escherichia coli
Diversity of Microorganisms
• Bacteria – prokaryotic
• Pre-nucleus – DNA is NOT surrounded by a membrane
• Unicellular
• Heterotroph – get energy from organic molecules.
• Cell walls - peptidoglycan
• Fungi – yeasts and molds
• Eukaryotic – true nucleus
• Unicellular/multicellular
• Cell walls – chitin
• All are heterotrophs
• Protozoa – eukaryotic
• Unicellular
• Heterotophs
• Algae – eukaryotic
• Unicellular/multicellular
• Autotrophs - photosynthesize
• Viruses – acellular
• Either have DNA or RNA
• Obligate intracellular parasites
• Helminths – multicellular
• Worms
• Eggs are microscopic
Classification of organisms
• 1969 Robert whittaker
• 5 kingdom system
• Classification based on
• Cell type - prokaryotic/eukaryotic
• Cellular organization – unicellular/multicellular
• Nutritional requirements – photosynthetic/nonphotosynthetic
Classification of organisms
• Prokaryotae (monera) – prokaryotic organisms – bacteria
• Protista - protozoa
• Fungi – Yeasts and molds
• Plant – ferns, trees, flowering plants
• Animal – worms, insects, vertebrates
• 3 domains
• Ribosomal RNA sequence
• Archaea, Bacteria, Eukarya
• Bacteria – prokaryotic
• Normal flora, pathogens
• Peptidoglycan
• Archaea
• Prokaryotic
• Unusual, extreme environments
• Salt lakes, dead sea
• Do not have peptidoglycan cell wall
• pseudomurein
• Eukarya
• All the eukaryotic organisms
• Protozoa, fungi, plants and animals