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