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MICR 201 Microbiology for Health Related Sciences

Lecture 1: The Microbial WorldEdith Porter, M.D.

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Lecture Outline

Definition of Microbiology Size dimensions Classification of microbial agents Microbial diversity Role of microbes in nature

Beneficial▪ Environment▪ Normal microbiota▪ Commercial use and industrial applications

Harmful▪ Disease causing

History of Microbiology

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What is Microbiology?

Micro Small (micrometer range) Not visible with the unaided eye

Bio Living Able to reproduce

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The Dimensions of Microorganisms and Smaller Agents

1 inch

1 cm

1 mm (1/10 of 1 cm)

1 mm (1/1000 of 1 mm)

1 nm (1/1000 of 1 mm)

Human Egg cell (almost 1 mm)

Erythrocyte (7 mm)

Bacterium (2 –4 mm)

Large Virus (200 nm)

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What do We Study in Microbiology?

Cellular organisms Eukaryotes (have a nucleus) Prokaryotes (do not have a

nucleus)

Acellular agents Viruses (nucleic acid + protein) Viroids (nucleic acid) Prions (protein)

Cell membrane

Nucleus with genetic material

Nuclear membrane

Cell membraneGenetic material in cytoplasm

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Classification of Cellular Organisms (Carl Woese 1978)

DomainBacteria

DomainArchaea

Domain Eukarya

Animals Helminths

Plants

Fungi

ProtozoaAlgae

Prokaryotes

Protists

Slimemolds

Eukaryotes

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The Prokaryotes in Microbiology

Bacteria Peptidoglycan cell walls Binary fission For energy, use organic

chemicals, inorganic chemicals, or photosynthesis

Some produce molecular oxygen

Archaea No peptidoglycan Often in extreme environments Diverse metabolic pathways Not known to cause disease

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Eukaryotes in Microbiology: Algae

Cellulose cell walls

Use photosynthesis for energy

Produce molecular oxygen and organic compounds

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Eukaryotes in Microbiology: Fungi

Chitin cell walls Use organic

chemicals for energy

Two forms Molds▪ Multicellular▪ Consisting of masses

of mycelia composed of filaments called hyphae

Yeasts▪ Unicellular

Dimorphic shift

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The Eukaryotes in Microbiology: Protozoa

Unicellular Absorb or ingest

organic chemicals

May be motile via pseudopods, cilia, or flagella

Eukaryotes in Microbiology: Multicellular Animal Parasites

Multicellular animals

Parasitic flatworms and roundworms are called helminths

Microscopic stages in life cycles

Dirofilaria immitis

Acellular Microbial Agents: Viruses

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

Consist of DNA or RNA core

Core is surrounded by a protein coat

Coat may be enclosed in a lipid envelope (from host cell)

Not all viruses are harmful!

Acellular Microbial Agents: Prions

Proteinaceous infectious particles

Consist of protein only Prions induce

conformation changes of normal counter parts

Body’s response leads to symptomatic disease

Neurodegenerative disorders CJD BSE

Brain section of animal with BSE

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How do we Name Microbes?

Genus name followed by species name

Typically relate to the discoverer, habitat, properties of the organism or its role

Genus name capitalized, species name lower case

In italic (or underlined)

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Some Examples for Microbial Name Giving

Escherichia coli or E. coli

Neisseria meningitidis or N. meningitidis

spaceDiscoverer was

Escherich

lives in colon

Discoverer was Neisser

causes meningitis

space

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Making Scientific Names Familiar

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The Role of Microbes in Nature:Mostly Beneficial

Plankton Geochemical cycling

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

Oxygen production Normal flora: digestion,

vitamin production etc Cellulose digestion by

protozoa in termite gut Vitamin K production by

human intestinal flora

Microbes on human tongue in a healthy

individual

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The Role of Microbes in Nature: Sometimes Harmful

A small percentage of all microorganisms are involved in diseases

Humans, animals and plants can be affected

Opportunistic and obligate pathogens

Diseases linked to microbial proliferation

(e.g. pus, pneumonia) toxic substances (e.g.

botulism, liver cancer)

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Multiple Choice #1

An organism that contains a nucleus and a cell membrane is:

a. Virusb. Prokaryotec. Helminthd. Archaea

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Multiple Choice #2

Choose the correct form of naming a microbe:

a. Pseudomonas maltophiliab. P. maltophiliac. Pseudomonas m.d. P. m.

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Brief History of Microbiology

Development of tools to study microbes

Microbes exist Microbes cause disease Humans have a defense system Drugs that kill microbes can be

developed Microbes can be exploited to the

benefit of humans

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Tools to Study Microbes

For identification Optics (microscope) Glass slides Dyes Culture media, inoculation material Biochemical and molecular genetic assays

Advanced tools to study their role In vitro models Animal models

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Milestones in Microbiology: Microbes exist

~ 1600 Galilei: Lenses for use in a microscope

1665: Robert Hooke described cells

1676 Van Leeuwenhoek: first recorded description of microbes called “animacules”

17th/18th century: spontaneous generation Living things arise from non

living matter 1858 Virchow proposes

concept of biogenesis Cells arise from living cells

1861 Pasteur disproves theory of spontaneous generation (and proves concept of biogenesis)

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Pasteur’s Proof of Biogenesis

Fermentation, Pasteurization

Pasteur’s S-shaped flask kept microbes out but let air in

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Milestones in Microbiology: Microbes cause disease

1847 Semmelweis childbed fever

1867 Lister antiseptic surgery with

phenol 1876 Koch

First proof that microbes cause disease: Bacillus anthracis causes anthrax

1884 Gram stain developed, Koch’s postulates formulated

http://www.acponline.org/bioterro/anthrax/graphics/cutaneous.jpg

http://www.cdc.gov/ncidod/eid/vol7no2/images/cover_final_rgb.jpghttp://www.chemistryexplained.com/images/chfa_03_img0510.jpg

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Koch’s Postulates

Microbe must be present in every case of disease and not in the healthy one.

Microbe must be isolated in pure culture.

When inoculated into a healthy tissue the same disease must arise.

From this diseased tissue the same microbe must be re-isolated in pure culture.

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Koch’s Postulates

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Milestones in Microbiology: Humans have a defense system

1798 Jenner: cow pox vaccination

1884 Metchnikoff: phagocytosis

1890 Ehrlich: theory of antibodies

1921 Fleming: lysozyme

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Milestones in Microbiology: Drugs that kill microbes

End of 19th century: dyes

1910 Ehrlich: First chemotherapeuticum (salvarsan: arsenic compound to treat syphilis)

1928 Fleming: first antibiotic (penicillin) First successful

treatment in 1942

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Milestones in Microbiology: Microbes can be exploited

Food preparation (fermentation)

Bread, yogurt, kim-chi, cheese, beer, wine and many more

Production of Chemicals

acetone, butanol, alcohol, organic acids and many more

Drugs Antibiotics, some cancer

drugs

Biotechnology Bioremediation

Clean up of BP oil spill

Genetic engineering Recombinant drugs

Immunoassays Rebecca Lancefield:

serotyping of Streptococcus spec.

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Anything left to do for Microbiologists?

Emerging infectious diseases and topics Avian Flue (H5N1) and swine flu West Nile virus encephalitis Mad cow diseases (prions) E. coli O157:H7 Biofilm▪ On teeth, mucosal surfaces, rocks, medical devices▪ Hard to penetrate, source of recurrent infections

Emerging antibiotic resistance Vancomycin resistant staphylococci and enterococci Multidrug resistant tuberculosis strains Resistance among malaria strains

S. aureus Biofilm

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Important to Remember

Microbial agents include prokaryotes, eukaryotes and acellular agents

Prokaryotes are cells without nucleus Bacteria, archaea, fungi, algae, and

protozoa are in the MICROMETER range (mm)

Viruses, acellular agents, are in the NANOMETER range (nm)