Lab assignment #1

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A Brief History of Microbiology

Prototype monocular microscope

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The Early Years of Microbiology

What Does Life Really Look Like?

Antoni van Leeuwenhoek

The birth of Microbiology (study of microbes)

began with the discovery of microscope by

a Dutch lens grinder, Antoni Van Leeuwenhoek

Leeuwenhoek made simple microscopes and examined pond water and other materials to visualized tiny animals such as fungi, algae and single-celled protozoa.

For the first time, he reported the existence of

protozoa in 1674 and bacteria in 1676 and were

called "animalcules“.

By the end of 19th century, these organisms were

called microorganisms. Because of his, Leeuwenhoek is known today as the father of Protozoology and Bacteriology.

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The Early Years of Microbiology

How Can Microbes Be Classified?

• Carolus Linnaeus developed taxonomic system for naming plants and animals. He grouped similar organisms together into either animal kingdom or plant kingdom.
• Leeuwenhoek's microorganisms now grouped into six categories as follows:
• Bacteria } Domain Bacteria
• Archaea } Domain Archaea
• Fungi
• Protozoa Domain Eukarya
• Algae
• Small multicellular animals
• Scientists later modified Linnaeus’s scheme by adding more categories to logically reflect the relationships among organisms

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The Early Years of Microbiology

• How can microbes be classified?

• Bacteria and Archaea
• Prokaryotic - unicellular microbes

and lack nuclei

• Much smaller than eukaryotes
• Found everywhere there is sufficient moisture; some isolated from extreme environments
• Reproduce asexually
• Bacterial cell walls contain peptidoglycan; some lack cell walls
• Archaeal cell walls composed of polymers other than peptidoglycan

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The Early Years of Microbiology

• How Can Microbes Be Classified?
• Fungi
• Eukaryotic (have membrane-bound nucleus)
• Unlike plants, obtain food from dead organic matter or other organisms (saprobes or parasites)
• Possess cell walls
• Include
• Molds – multicellular; grow as long filaments; reproduce by sexual and asexual spores
• Yeasts – unicellular; reproduce asexually by budding; some produce sexual spores

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The Early Years of Microbiology

• How Can Microbes Be Classified?
• Protozoa
• Single-celled eukaryotes
• Similar to animals in nutrient needs

and cellular structure

• Live freely in water; some live in animal

hosts

• Asexual (most) and sexual reproduction
• Most are capable of locomotion by
• Pseudopods – cell extensions that flow in direction of travel
• Cilia – numerous short protrusions that propel organisms through environment
• Flagella – extensions of a cell that are fewer, longer, and more whip-like than cilia

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The Early Years of Microbiology

• How Can Microbes Be Classified?
• Algae
• Unicellular or multicellular
• Eukaryotic
• Photosynthetic
• Simple reproductive structures
• Categorized on the basis of

pigmentation and composition

of cell wall

(b) diatoms

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The Early Years of Microbiology

• How Can Microbes Be Classified?
• Other organisms that microbiologists study
• Parasites
• Viruses

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The Golden Age of Microbiology

Scientists searched for answers to four questions:

Is spontaneous generation of microbial life possible?

What causes fermentation?

What causes disease?

How can we prevent infection and disease?

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The Golden Age of Microbiology

Theory of spontaneous generation (Abiogenesis)

Some philosophers and scientists of the past thought living things arose from three processes:

• Asexual reproduction
• Sexual reproduction
• Nonliving matter

Aristotle proposed spontaneous generation

• Living things can arise from nonliving matter
• Competition among scientist to answer these questions during the golden age of microbiology drove exploration and discovery and shaped the course of today’s microbiological research

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The Golden Age of Microbiology

Does life generate spontaneously?

Francesco Redi's experiments:

When decaying meat was kept isolated from flies, maggots never developed

• Meat exposed to flies was soon infested with maggots
• As a result, scientists began to doubt Aristotle's theory

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Does microbial life spontaneously generate?

Needham’s experiments

Scientists did not believe animals could arise spontaneously, but did believe microbes could

Boiled beef gravy and plant infusions in tightly corked vials to kill all life; later observed vials were cloudy and examinations revealed microscopic animals

Concluded that there must be a “life force” that causes inanimate matter to spontaneously come to life

Needham’s experiments with beef gravy and infusions of plant material reinforced this idea of theory of spontaneous generation

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Does microbial life spontaneously generate?

Spallanzani’s experiments

Boiled infusions in vials for almost an hour and sealed/closed the vials by melting their ends

Infusions remained clear unless he broke the seal and exposed the infusion to air, after which they became cloudy with microorganisms

Splallazini concluded that:

Needham failed to heat vials sufficiently to kill all microbes or had not sealed vials tightly enough

Microorganisms exist in air and can contaminate experiments

Spontaneous generation of microorganisms does not occur. All living things arise from other living things

Critics said, sealed vials did not allow enough air for organisms to thrive and that prolonged heating destroyed “life force”

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The Golden Age of Microbiology

Does microbial life spontaneously generate?

• Pasteur's experiments
• When the "swan-necked" flasks filled with boiled infusion remained upright, no microbial growth appeared
• When the flask was tilted, dust from the bend in the neck seeped back into the flask and made the infusion cloudy with microbes within a day.

Louis Pasteur

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The scientific method

Debate over spontaneous generation led to the development of the scientific method

A group of observations leads a scientist to ask question about a phenomenon

The scientist generates hypothesis (potential answer to question)

The scientist designs and conducts experiment to test hypothesis

Results prove or disprove hypothesis

Accepted hypothesis leads to theory/law

Reject or modify hypothesis

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The scientific method

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The Golden Age of Microbiology

What causes fermentation?

• Spoiled wine threatened livelihood of vintners
• Some believed air caused fermentation; others insisted living organisms caused fermentation. This debate is also linked to debate over spontaneous generation
• Vintners funded research of methods to promote production of alcohol and prevent spoilage during fermentation
• Others thought that yeasts are alive and were spontaneously generated during fermentation
• Still others asserted that yeasts were not only living, but also caused fermentation
• Some scientists proposed that yeasts observed in fermentation products were nonliving globules of chemicals and gases

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Pasteur's application of the scientific method

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The Golden Age of Microbiology

• What Causes Fermentation?
• Pasteur's experiments
• Showed that microbes (yeast) are responsible for fermentation
• Led to the development of pasteurization
• Process of heating liquids just enough to kill most bacteria
• Began the field of industrial microbiology
• Intentional use of microbes for manufacturing products

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Buchner’s experiments on fermentation

Buchner’s experiments on acellular fermentation

Earlier studies of fermentation began with the idea that fermentation reactions were strictly chemical and did not involve living organisms

Idea was supplanted by Pasteur’s work showing that fermentation proceed only when living cells were present

Eduard Buchner resurrected the chemical explanation, and showed that fermentation does not require living cells, but enzymes (cell produced proteins) that promote chemical reactions

His work began the field of biochemistry and the study of metabolism (sum of all chemical reactions within an organism)

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The Golden Age of Microbiology

• What Causes Disease?
• Pasteur developed germ theory of disease: that microorganisms are also responsible for diseases
• Robert Koch studied causative agents of disease (etiology)

Today it is known that some diseases are genetic, or caused by allergens or toxins in the environment; thus germ theory applies only to infectious diseases

Anthrax (Bovine disease caused by Bacillus anthracis)

Examined colonies of microorganisms

Robert Koch.

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• Koch's postulates
• Suspected causative agent must be found in every case of the disease and be absent from healthy hosts
• Agent must be isolated and grown

outside the host

• When agent is introduced into a

healthy, susceptible host, the host must get the disease

• Same agent must be found in the diseased experimental host

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The Golden Age of Microbiology

Koch's experiments and contributions

• Simple staining techniques
• First photomicrograph of bacteria
• First photomicrograph of bacteria

in diseased tissue

• Techniques for estimating CFU/ml
• Use of steam to sterilize media
• Use of Petri dishes
• Techniques to transfer bacteria
• Bacteria as distinct species
• Because of his achievements, he is considered father of the microbiological laboratory

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The Golden Age of Microbiology

• How Can We Prevent Infection and Disease?
• Ignaz Semmelweis (1818-1865) before germ theory was fully

understood, discovered the benefits of handwashing to prevent

disease in the medical setting.

• Joseph Lister (1827-1912) was the first surgeon to advance

the idea of antiseptic surgery with the use of phenol treated surgical instruments.

• Florence Nightingale (1820-1910) was an English nurse who introduced cleanliness and other antiseptic techniques into nursing practice.
• Edward Jenner (1749-1823) an English physician who spurred the field of immunology by discovering vaccination. He did so by intentionally inoculating a boy with pus collected from a milkmaid’s cowpox lesion. The boy became resistant to cowpox. He named the procedure vaccination after Vaccinia virus.

Florence Nightingale

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