Microbes in Our Lives

      Microorganisms are organisms that are too small to be seen with the unaided eye

      Germ refers to a microbe

o   Bacteria

o   Fungi

o   Protozoa

o   Viruses


Microbes in Our Lives

      A few are pathogenic (disease-causing)

      Decompose organic waste

      Are producers in the ecosystem by photosynthesis

      Produce industrial chemicals such as ethanol
and acetone

      Produce fermented foods such as vinegar, cheese,
and bread

      Produce products used in manufacturing
(e.g., cellulase) and treatment (e.g., insulin)


Designer Jeans: Made by Microbes?

      Stone-washing: Trichoderma (fungus)

      Cotton: Gluconacetobacter (bacterium)

      Bleaching: Mushroom peroxidase

      Indigo: E. coli (bacteria)

      Plastic: Bacterial polyhydroxyalkanoate


Microbes in Our Lives

      Knowledge of microorganisms

o   Allows humans to

      Prevent food spoilage

      Prevent disease occurrence

o   Led to aseptic techniques to prevent contamination in medicine and in microbiology laboratories


Naming and Classifying Microorganisms

      Linnaeus established the system of scientific nomenclature

      Each organism has two names:

o    Genus (capitalized)

o    specific epithet (not capitalized)

      Example:  Homo sapiens (human)


Scientific Names

      Are italicized or underlined. The genus is capitalized, and the specific epithet is lowercase.

      Are Latinized and used worldwide.

      May be descriptive or honor a scientist.

      May see an abbreviation of the individual who classified and/or named the organism after the scientific name

o    Thiomargarita namibiensis Schultz

      Gr. Theion/Thio (sulfur) + L. margarita (pearl) because it looks like a string of pearls

      Namibia honored as location of origin


Thiomargarita namibiensis

      Thiomargarita namibiensis Schulz

o    Gr. Theion/Thio (sulfur) + L. margarita (pearl) because it looks like a string of pearls

o    Namibia honored as location of origin


Escherichia coli

      Escherichia coli

o    Honors the discoverer, Theodor Escherich

o    Describes the bacteriums habitat—the large intestine, or colon


Staphylococcus aureus

      Staphylococcus aureus

o    Describes the clustered (staphylo-) spherical (cocci) cells

o    Describes the gold-colored (aureus) colonies


Scientific Names

      After the first use, scientific names may be abbreviated with the first letter of the genus and the specific epithet:

o    Escherichia coli and Staphylococcus aureus are found in the human body. E. coli is found in the large intestine, and S. aureus is on skin.

o    T. namibiensis is found in the sulfur-rich coastal sediments of Namibia (Africa).


Types of Microorganisms




      Peptidoglycan cell walls

      Binary fission

      For energy, use organic chemicals, inorganic chemicals, or photosynthesis




      Lack peptidoglycan

      Live in extreme environments


o    Methanogens

o    Extreme halophiles

o    Extreme thermophiles




      Chitin cell walls

      Use organic chemicals for energy

      Molds and mushrooms are multicellular, consisting of masses of mycelia, which are composed of filaments called hyphae

      Yeasts are unicellular




      Absorb or ingest
organic chemicals

      May be motile via pseudopods, cilia,
or flagella




      Cellulose cell walls

      Use photosynthesis for energy

      Produce molecular oxygen and organic compounds




      Consist of DNA or RNA core

      Core is surrounded by a protein coat

      Coat may be enclosed in a lipid envelope

      Viruses are replicated only when they are in a living host cell


Multicellular Animal Parasites


      Multicellular animals

      Parasitic flatworms and roundworms are called helminths.

      Microscopic stages in life cycles.


Classification of Microorganisms

      Three domains

o    Bacteria

o    Archaea

o    Eukarya







A Brief History of Microbiology

      Ancestors of bacteria were the first life on Earth, some 3.6 billion years ago

      Humans first evolved about 200,000 years ago

      The first microbes were observed about 230 years ago, in 1673


The First Observations

      1665: Robert Hooke reported that living things were composed of little boxes, or cells

      1858: Rudolf Virchow said cells arise from preexisting cells (biogenesis)

      Cell theory: All living things are composed of cells and come from preexisting cells

      1673-1723: Anton van Leeuwenhoek described live microorganisms


The Debate over Spontaneous Generation

      Spontaneous generation: The hypothesis that living organisms arise from nonliving matter; a vital force forms life

      Biogenesis: The hypothesis that the living organisms arise from preexisting life


Evidence Pro and Con

      1668: Francesco Redi filled 6 jars with decaying meat

      1745: John Needham put boiled nutrient broth into covered flasks

      1765: Lazzaro Spallanzani boiled nutrient solutions in flasks

      1861: Louis Pasteur demonstrated that microorganisms are present in the air


The Theory of Biogenesis

      Pasteurs S-shaped flask kept microbes out but let air in


The Golden Age of Microbiology


      Beginning with Pasteurs work, discoveries included the relationship between microbes and disease, immunity, and antimicrobial drugs


Fermentation and Pasteurization

      Pasteur showed that microbes are responsible for fermentation

o    Fermentation is the conversion of sugar to alcohol to make beer and wine

      Microbial growth is also responsible for spoilage of food

o    Bacteria that use alcohol and produce acetic acid spoil wine by turning it to vinegar (acetic acid)

      Pasteur demonstrated that these spoilage bacteria could be killed by heat that was not hot enough to evaporate the alcohol in wine

      Pasteurization is the application of a high heat for a short time


The Germ Theory of Disease

      1835: Agostino Bassi showed that a silkworm disease was caused by a fungus

      1865: Pasteur believed that another silkworm disease was caused by a protozoan

      1840s: Ignaz Semmelweis advocated hand washing to prevent transmission of puerperal fever from one OB patient to another

      1860s: Applying Pasteurs work showing that microbes are in the air, can spoil food, and cause animal diseases, Joseph Lister used a chemical disinfectant to prevent surgical wound infections

      1876: Robert Koch proved that a bacterium causes anthrax and provided the experimental steps, Kochs postulates, to prove that a specific microbe causes a specific disease



      1796: Edward Jenner inoculated a person with cowpox virus, who was then protected from smallpox

o    Vaccination is derived from vacca, for cow

o    The protection is called immunity


The Birth of Modern Chemotherapy

      Treatment with chemicals is chemotherapy

      Chemotherapeutic agents used to treat infectious disease can be synthetic drugs or antibiotics

      Antibiotics are chemicals produced by bacteria and fungi that inhibit or kill other microbes


The First Synthetic Drugs

      Quinine from tree bark was long used to treat malaria

      Paul Erlich speculated about a magic bullet that could destroy a pathogen without harming the host

      1910: Ehrlich developed a synthetic arsenic drug, salvarsan, to treat syphilis

      1930s: Sulfonamides (sulfa drugs) were synthesized


A Fortunate Accident—Antibiotics

      1928: Alexander Fleming discovered the first antibiotic

      Fleming observed that Penicillium   fungus made an antibiotic, penicillin, that killed S. aureus

      1940s: Penicillin was tested clinically and mass produced


Modern Developments in Microbiology

      Bacteriology is the study of bacteria

      Mycology is the study of fungi

      Virology is the study of viruses

      Parasitology is the study of protozoa and parasitic worms

      Immunology is the study of immunity. Vaccines and interferons are being investigated to prevent and cure viral diseases.

      The use of immunology to identify some bacteria according to serotypes was proposed by Rebecca Lancefield in 1933.


Recombinant DNA Technology

      Microbial genetics: The study of how microbes inherit traits

      Molecular biology: The study of how DNA directs protein synthesis

      Genomics: The study of an organisms genes; has provided new tools for classifying microorganisms

      Recombinant DNA: DNA made from two different sources.

o    In the 1960s, Paul Berg inserted animal DNA into bacterial DNA, and the bacteria produced an animal protein

      1941: George Beadle and Edward Tatum showed that genes encode a cells enzymes

      1944: Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA was the hereditary material

      1961: Francois Jacob and Jacques Monod discovered the role of mRNA in protein synthesis


Nobel Prizes for Microbiology Research

      * The first Nobel Prize in Physiology or Medicine.

1901* von Behring = Diphtheria antitoxin

1902   Ross = Malaria transmission

1905   Koch = TB bacterium

1908   Metchnikoff = Phagocytes

1945   Fleming, Chain, Florey = Penicillin

1952   Waksman = Streptomycin

1969   Delbrck, Hershey, Luria = Viral replication

1987   Tonegawa = Antibody genetics

1997   Prusiner = Prions

2005   Marshall & Warren = H. pylori & ulcers


Microbial Ecology

      Bacteria recycle carbon, nutrients, sulfur, and phosphorus that can be used by plants and animals



      Bacteria degrade organic matter in sewage

      Bacteria degrade or detoxify pollutants such as oil and mercury


Biological Insecticides

      Microbes that are pathogenic to insects are alternatives to chemical pesticides in preventing insect damage to agricultural crops and disease transmission

      Bacillus thuringiensis infections are fatal in many insects but harmless to other animals, including humans, and to plants



      Biotechnology, the use of microbes to produce foods and chemicals, is centuries old

      Recombinant DNA technology, a new technique for biotechnology, enables bacteria and fungi to produce a variety of proteins including vaccines and enzymes

o    Missing or defective genes in human cells can be replaced in gene therapy

o    Genetically modified bacteria are used to protect crops from insects and from freezing


Normal Microbiota

      Bacteria were once classified as plants, giving rise to use of the term flora for microbes

      This term has been replaced by microbiota

      Microbes normally present in and on the human body are called normal microbiota


Normal Microbiota

      Normal microbiota prevent growth of pathogens

      Normal microbiota produce growth factors such as folic acid and vitamin K

      Resistance is the ability of the body to ward off disease

      Resistance factors include skin, stomach acid, and antimicrobial chemicals



      Microbes attach to solid surfaces and grow into masses

      They will grow on rocks, pipes, teeth, and medical implants


Infectious Diseases

      When a pathogen overcomes the hosts resistance, disease results

      Emerging infectious diseases (EIDs): New diseases and diseases increasing in incidence


Avian influenza A

      Influenza A virus (H5N2)

      Primarily in waterfowl and poultry

      Sustained human-to-human transmission has not occurred yet



      Methicillin-resistant Staphylococcus aureus

      1950s: Penicillin resistance developed

      1980s: Methicillin resistance

      1990s: MRSA resistance to vancomycin reported

o    VISA: Vancomycin-intermediate-resistant S. aureus

o    VRSA: Vancomycin-resistant S. aureus


West Nile Encephalitis

      Caused by West Nile virus

      First diagnosed in the West Nile region of Uganda
in 1937

      Appeared in New York City in 1999


Bovine Spongiform Encephalopathy

      Caused by a prion

o    Also causes Creutzfeldt-Jakob disease (CJD)

      New variant CJD in humans is related to cattle fed sheep offal for protein


Escherichia coli O157:H7

      Toxin-producing strain of E. coli

      First seen in 1982

      Leading cause of diarrhea worldwide


Ebola Hemorrhagic Fever

      Ebola virus

      Causes fever, hemorrhaging, and blood clotting

      First identified near Ebola River, Congo

      Outbreaks every few years



      Cryptosporidium protozoa

      First reported in 1976

      Causes 30% of diarrheal illness
in developing countries

      In the United States, transmitted via water



Acquired immunodeficiency syndrome (AIDS)

      Caused by human immunodeficiency virus (HIV)

      First identified in 1981

      Worldwide epidemic infecting 30 million people; 14,000 new infections every day

      Sexually transmitted infection affecting males and females

      HIV/AIDS in the U.S.: 30% are female, and 75% are African American