Introduction to Microbiology

• Microbiology is the study of microorganisms, a large and diverse group of microscopic organisms existing as single cells or cell clusters

Groups Included

• Bacteria which relates to Bacteriology
• Fungi (yeasts and molds) which relates to Mycology
• Protozoa and microscopic algae which relates to Parasitology and Phycology
• Viruses which relates to Virology

Microbes

• Microorganisms are often called germs or microbes
• Germ originates from the Latin word "germen," meaning to sprout from or germinate
• Latin word "germen," was first used in the 19th century to explain rapidly growing cells that caused the disease.
• Microbes are minute living things usually too small to be seen with the unaided eye
• Microbes include bacteria, fungi (yeasts and molds), protozoa, microscopic algae, and viruses
• Viruses, which are noncellular entities, are sometimes regarded as straddling the border between life and nonlife.

Importance of Microbes

• Microorganisms are important in maintaining Earth's ecological balance through photosynthesis
• Some microorganisms live in humans and other animals, aiding in maintaining good health by synthesizing some B vitamins
• Microbiota is the term for the trillions of microbes that live in humans
• Some microorganisms produce foods and chemicals like vitamins, organic acids, enzymes, and alcohols
• Some microorganisms cause diseases like Tuberculosis

History of Microbiology

• In 1665, after observing a thin slice of cork with a crude microscope, Robert Hooke reported that life's smallest structural units were "little boxes" or cells
• Hooke's discovery marked the beginning of cell theory, which posits that all living things are composed of cells
• Anton van Leeuwenhoek observed live microorganisms through the magnifying lenses of over 400 microscopes he constructed between 1673 and 1723

First Golden Age of Microbiology

• The period from 1857 to 1914 is named the first golden age of Microbiology

Louis Pasteur

• In 1861, Louis Pasteur demonstrated that microorganisms are present in the air, which can contaminate sterile solutions, and that air itself does not create microbes
• Pasteur boiled beef broth in short-necked flasks, left some open to cool, and observed contamination with microbes in a few days

Pasteur's Experiment

• Pasteur's experiment disproved the theory of spontaneous generation, which stated that life could arise spontaneously from nonliving matter (e.g., dead corpses and soil)
• According to the theory of spontaneous generation life can arise spontaneously from nonliving matter, such as dead corpses and soil
• Pasteur poured beef broth into a long-necked flask and heated the flask's neck, bending it into an S-shape, then boiled the broth
• Microorganisms did not appear in the cooled solution, even after long periods, because the bend prevented microbes from entering the flask, proving that microbes are present in the air

Fermentation & Pasteurization

• Pasteur found that yeasts ferment sugars to alcohol and that bacteria can oxidize alcohol to acetic acid

Pasteurization

• Pasteurization is heating used to kill bacteria in some alcoholic beverages and milk

Germ Theory of Disease

• Robert Koch proved microorganisms cause disease, using a sequence of procedures called Koch's postulates (1876), still used today to prove that a particular microorganism causes a particular disease

Vaccination

• In 1798, Edward Jenner demonstrated that inoculation with cowpox material provides humans with immunity to smallpox

Vaccine for Fowl Cholera

• Around 1880, Pasteur discovered that a virulent bacteria could be used as a vaccine for fowl cholera.

Antimicrobial Agent

• Paul Ehrlich introduced an arsenic-containing chemical called salvarsan to treat syphilis (1910), known as chemotherapy

Antibiotics Discovery

• Alexander Fleming observed that the Penicillium fungus inhibited the growth of a bacterial culture and named the active ingredient penicillin (1928), known as antibiotics

Chemotherapeutics

• In 1910, Paul Ehrlich found a chemotherapeutic agent called salvarsan, an arsenic derivative effective against syphilis
• By the late 1930s, sulfonamides (sulfa drugs) were synthesized

Molecular Genetics

• Microbial genetics studies the mechanisms by which microorganisms inherit traits, and molecular biology looks at how genetic information is carried in molecules of DNA
• In the 1950s, James Watson and Francis Crick proposed a model for the structure and replication of DNA
• In the early 1960s, François Jacob and Jacques Monod discovered messenger RNA

Microbes & Human Welfare

• Bacteria convert chemical elements like carbon, nitrogen, oxygen, sulfur, and phosphorus into forms that plants and animals can use

Sewage Treatment

• Bacteria are used to convert organic material into by-products such as carbon dioxide, nitrates, phosphates, sulfates, ammonia, hydrogen sulfide, and methane

Bioremediation

• Bioremediation uses microbes to remove toxins from underground wells, chemical spills, toxic waste sites, and oil spills

Biotechnology

• Commercial use of microorganisms to produce foods and chemicals

Gene Therapy

• Gene therapy involves inserting a missing gene or replacing a defective one in human cells.

Second Golden Age of Microbiology

• Fleming, Chain, and Florey discovered penicillin around the 1940-1950's
• Waksman discovered Streptomycin around the 1940-1950's
• H. Krebs created the chemical steps of the Krebs cycle around the 1940-1950's
• Enders, Weller, and Robbins cultured poliovirus in cell cultures around the 1940-1950's
• Beadle and Tatum discovered genetic control of biological reactions around the 1940-1950's
• Medawar discovered acquired immune tolerance around the 1960's
• Sanger and Gilbert created techniques for sequencing DNA around the 1980's
• Jerne, Köhler, and Milstein discovered a technique for creating monoclonal(single pure) antibodies around the 1980's
• Tonegawa discovered Genetics of antibody production around the 1980's
• Bishop and Varmus discovered cancer-causing genes around the 1980's

Third Golden Age of Microbiology

• Murray and Thomas found the first successful transplants using immunosuppressive drugs around the 1990's
• Fischer and E. Krebs discovered enzymes that regulate cell growth(protein kinases) around the 1990's
• Roberts and Sharp discovered genes can be present in separated segments of DNA around the 1990's
• Mullis discovered polymerase chain reactions that amplify DNA around the 1990's
• Doherty and Zinkernagel discovered cell-mediated immunity around the 2000's
• Agre and MacKinnon discovered water and ion channels of plasma membranes around the 2000's
• Marshall and Warren discovered Helicobacter pylori as the cause of peptic ulcers around the 2010's
• Barré-Sinoussi and Montagnier co-discovered HIV around the 2010's
• Ramakrishnan, Steitz, and Yonath discovered the detailed struture and function of ribosomes around the 2010's
• Beutler, Hoffmann, and Steinman found and studied innate immunity, dendritic cells in adaptive immunity around the 2010's
• Tu invented a treatment for malaria around the 2010's
• César Milstein fused cancerous cells with antibody-producing cells to create a hybrid cell that grows continuously and produces therapeutic antibodies.
• Françoise Barré-Sinoussi discovered and studied a virus in a patient with swollen lymph nodes, known as human immunodeficiency virus
• Youyou Tu extracted artemisinin from a Chinese sage plant which later acted to inhibit the malaria parasite

Microorganisms and the Human Body

• Normal microbiota are microorganisms on and inside bodies, making up the normal flora.
• Normal Microbiota live on your skin, mucus membrane, in the oral cavity, in the large and small intestine and in the lacrimal gland

Roles of Normal Flora

• Inhibit disease from harmful microbes
• Microbes produce helpful substances such as vitamin K and some B vitamins
• Normal microbiota can make us sick or infect people

Biofilms

• Microorganisms may exist as single cells that float or swim independently in a liquid or attach to each other and/or some usually solid surface
• Biofilms are bacterial communities that form slimy layers on surfaces with roles to protect mucous membranes from harmful microbes, also to cause infections as endocarditis or clog medical implants, also to play in antibiotic resistance

Infectious Disease

• Pathogens invade a susceptible host, humans or animals, and the pathogen carries out its life cycle inside host, and disease results (e.g., malaria)

Emerging Infectious Dieases

• New or changing disease showing increased indicidence and potential increase in near future

Factors That Contribute To The Development of EIDs

• Evolutionary changes in existing organisms (e.g.,Vibrio cholerae)
• The spread of known diseases to new geographic regions/populations by modern transportation (e.g., West Nile virus)
• Increased human exposure to new, unusual infectious agents in areas that are undergoing ecologic changes (e.g., Venezuelan hemorrhagic virus, H1N1 influenza, SARS)
• Antimicrobial resistance (e.g.,vancomycin-resistant S. aureus)

Carl Woese classification system in 1978

• Bacteria, whose cell walls contain a protein-carbohydrate complex called peptidoglycan
• Archaea, whose cell walls lack peptidoglycan
• Eukarya, which includes protists (slime molds, protozoa, and algae), fungi (unicellular yeasts, multicellular molds, and mushrooms), plants (mosses, ferns, conifers, and flowering plants), and animals (sponges, worms, insects, and vertebrates)

Nomenclature Of Microorganisms

• Established in 1735 by Carolus Linnaeus
• Scientific names are latinized
• Scientific nomenclature assigns each organism two names: Genus (plural: genera) is the first name and is always capitalized
• Specific epithet (species name) follows and is not capitalized

Salmonella Enterica

• The genus name "Salmonella" honors public health microbiologist Daniel Salmon
• The specific name indicates that it is found in the intestines (entero-)

Streptococcus pyogenes

• "Streptococcus" references the appearance of cells in chains (strepto-)
• "pyogenes" describes how it forms pus (pyo-)

Saccharomyces cerevisiae

• "Saccharomyces" references that it is a Fungus (-myces) that uses sugar (saccharo-)
• Specific name "cerevisiae" describes how it makes beer (cerevisia)

Penicillium chrysogenum

• The genus name "Penicillium" refers to the paint brush like appearance microscopically
• The specific name "chrysogenum" references how it produces a yellow pigment

Trypanosoma cruzi

• The genus name "Trypanosoma" references how it is corkscrew-(trypano-borer; soma-, body)
• The specific name "cruzi" references how it honors epidemiologist Oswaldo Cruz