A Brief History of Microbiology - PowerPoint Presentation

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A Brief History of Microbiology

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The Early Years of MicrobiologyWhat Does Life Really Look Like?Antoni van Leeuwenhoek

Began making and using simple microscopes

Often made a new microscope for each specimen

Examined water and visualized tiny animals, fungi, algae, and single-celled protozoa: "animalcules

"

By end of 19th century, these organisms were called

microorganisms

; now they are also called

microbes

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Figure

1.1 Antoni

van Leeuwenhoek.

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Lens

Specimen holder

Figure

1.2 Reproduction

of

Leeuwenhoek

'

s

microscope.

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Figure

1.3 The

microbial world.

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The Early Years of Microbiology

How Can Microbes Be Classified?

Carolus Linnaeus developed taxonomic system for naming plants and animals and grouping similar organisms together

Leeuwenhoek

'

s microorganisms are now grouped into six categories:

Bacteria

ArchaeaFungiProtozoaAlgae Small multicellular animals

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The Early Years of Microbiology

How Can Microbes Be Classified?

Bacteria and Archaea

Prokaryotic (lack nuclei)

Much smaller than eukaryotes

Found everywhere there is sufficient moisture; some have been isolated from extreme environments

Reproduce asexually

Bacterial cell walls contain peptidoglycan; some lack cell wallsArchaeal cell walls are composed of polymers other than peptidoglycan

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Prokaryotic

bacterial cells

Nucleus of

eukaryotic cheek cell

Figure

1.4 Cells

of the bacterium

Streptococcus

(dark blue) and two human cheek cells.

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The Early Years of Microbiology

How Can Microbes Be Classified?

Fungi

Eukaryotic (have membrane-bound nucleus)

Obtain food from other organisms

Possess cell walls

Include

Molds – multicellular; grow as long filaments; reproduce by sexual and asexual sporesYeasts – unicellular; reproduce asexually by budding; some produce sexual spores

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Spores

Hyphae

Budding cells

Figure

1.5 Fungi

.

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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 byPseudopods – cell extensions that flow in direction of travelCilia – numerous short protrusions that propel organisms through environmentFlagella – extensions of a cell that are fewer, longer, and more whiplike than cilia

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Pseudopods

Nucleus

Cilia

Flagellum

Figure

1.6 Locomotive

structures of protozoa.

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The Early Years of MicrobiologyHow Can Microbes Be Classified?Algae

Unicellular or multicellular

Photosynthetic

Simple reproductive structures

Categorized on the basis of pigmentation and composition of cell wall

Scientists and manufacturers use many algae-derived products

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Figure

1.7 Algae

.

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The Early Years of MicrobiologyHow Can Microbes Be Classified?Other Organisms of Importance to Microbiologists

Parasites

Viruses

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Red blood cell

Figure

1.8 An

immature stage of a parasitic worm in blood.

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Virus

Bacterium

Viruses

assembling

inside cell

Figure

1.9 A

colorized electron microscope image of viruses infecting a bacterium.

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The Early Years of MicrobiologyTell Me WhyOther Organisms of Importance to Microbiologists

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The Golden Age of MicrobiologyScientists searched for answers to four questionsIs 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 MicrobiologyDoes Microbial Life Spontaneously Generate?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

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The Golden Age of MicrobiologyDoes Microbial Life Spontaneously Generate?Redi

'

s experiments

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

Meat exposed to flies was soon infested

As a result, scientists began to doubt Aristotle

'

s theory

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Figure

1.10 Redi

'

s

experiments.

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The Golden Age of MicrobiologyDoes Microbial Life Spontaneously Generate?Needham

'

s experiments

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

Needham

'

s experiments with beef gravy and infusions of plant material reinforced this idea

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The Golden Age of Microbiology

Does Microbial Life Spontaneously Generate?

Spallanzani

'

s experiments

Results contradicted Needham

'

s findingsConcluded thatNeedham failed to heat vials sufficiently to kill all microbes or had not sealed vials tightly enoughMicroorganisms exist in air and can contaminate experimentsSpontaneous generation of microorganisms does not occurThe debate continued until the experiments conducted by Louis Pasteur

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Figure

1.11 Louis

Pasteur.

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The Golden Age of MicrobiologyDoes Microbial Life Spontaneously Generate?Pasteur

'

s experiments

Performed investigations of spontaneous generation

When the "swan-necked" flasks 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

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Figure

1.12 Pasteur

'

s

experiments with

"swan

-necked flasks

."

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The Golden Age of Microbiology

Does Microbial Life Spontaneously Generate?

The scientific method

Debate over spontaneous generation led in part to development of scientific method

Observation leads to question

Question generates hypothesis

Hypothesis is tested through experiment(s)

Results prove or disprove hypothesisAccepted hypothesis can lead to theory/lawDisproved hypothesis is rejected or modified

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Figure

1.13 The

scientific method, which forms a framework for scientific research.

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The Golden Age of MicrobiologyWhat Causes Fermentation?

Spoiled wine threatened livelihood of vintners

Some believed air caused fermentation; others insisted living organisms caused fermentation

Vintners funded research of methods to promote production of alcohol and prevent spoilage during fermentation

This debate also linked to debate over spontaneous generation

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Figure

1.14 How

Pasteur applied the scientific method in investigating the nature of fermentation.

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The Golden Age of MicrobiologyWhat Causes Fermentation?Pasteur

'

s experiments

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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The Golden Age of MicrobiologyWhat Causes Fermentation?Buchner

'

s experiments

Demonstrated fermentation does not require living cells

Showed enzymes promote chemical reactions

Began the field of biochemistry

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The Golden Age of MicrobiologyWhat Causes Disease?Pasteur developed germ theory of disease

Robert Koch studied disease causation (etiology)

Anthrax

Examined colonies of microorganisms

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Figure

1.15 Robert

Koch.

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The Golden Age of Microbiology

What Causes Disease?

Koch

'

s experiments

Simple staining techniques

First photomicrograph of bacteria

First photomicrograph of bacteria in diseased tissueTechniques for estimating CFU/mlUse of steam to sterilize mediaUse of Petri dishesTechniques to transfer bacteriaBacteria as distinct species

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Bacterium 1

Bacterium 2

Bacterium 3

Bacterium 4

Bacterium 5

Bacterium 6

Bacterium 7

Bacterium 8

Bacterium 9

Bacterium 10

Bacterium 11

Bacterium 12

Figure

1.16 Bacterial

colonies on a solid surface (agar).

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The Golden Age of MicrobiologyWhat Causes Disease?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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Gram-positive

Gram-negative

Figure

1.17 Results

of Gram staining.

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The Golden Age of MicrobiologyHow Can We Prevent Infection and Disease?Many great advances in disease prevention came after it was shown that microbes can cause disease

Modern principles of hygiene not widely practiced in the mid-1800s

Healthcare associated infections were common

Six health care practitioners were instrumental in changing health care delivery methods

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The Golden Age of MicrobiologyHow Can We Prevent Infection and Disease?

Semmelweis and handwashing

Ignaz Semmelweis required medical students to wash their hands in chlorinated lime water

Resulted in higher patient survival rates

Lister

'

s antiseptic technique

Joseph Lister advanced antisepsis in health care settingsSprayed wounds, surgical incisions, and dressings with carbolic acid (phenol)

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The Golden Age of MicrobiologyHow Can We Prevent Infection and Disease?

Nightingale and nursing

Florence Nightingale introduced cleanliness and antiseptic techniques into nursing practice

Advocated for hospital and public health policy reform

Snow and epidemiology

John Snow mapped cholera epidemic in London in 1854

His work was the foundation for infection control and epidemiology

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Figure

1.18 Florence

Nightingale.

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The Golden Age of MicrobiologyHow Can We Prevent Infection and Disease?

Jenner

'

s vaccine

Edward Jenner developed a vaccine against smallpox

Demonstrated the validity of vaccination

Began the field of immunology

Ehrlich's "magic bullets"Paul Ehrlich worked to identify "magic bullets" that would destroy pathogens but not harm humans

Discoveries began the field of chemotherapy

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Figure

1.19 Some

of the many scientific disciplines and applications that arose from the pioneering work of scientists just before and around the time of the Golden Age of Microbiology.

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The Golden Age of MicrobiologyTell Me WhySome people consider Pasteur or Koch to be the Father of Microbiology, rather than Leeuwenhoek. Why might they be correct?

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The Modern Age of MicrobiologyWhat Are the Basic Chemical Reactions of Life?

Biochemistry

Study of metabolism: the chemical reactions that occur in living organisms

Began with Pasteur

'

s work on fermentation and Buchner

'

s discovery of enzymes in yeast extractKluyver and van Niel proposed basic biochemical reactions shared by all living thingsMicrobes used as model systems for biochemical reactions

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The Modern Age of MicrobiologyWhat Are the Basic Chemical Reactions of Life?

Biochemistry

Practical applications

Design of herbicides and pesticides

Diagnosis of illnesses and monitoring of patients

'

responses to treatment

Treatment of metabolic diseasesDrug design

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The Modern Age of MicrobiologyHow Do Genes Work?Genetics: scientific study of inheritance

Many advances in the discipline made through the study of microbes

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The Modern Age of MicrobiologyHow Do Genes Work?Microbial genetics

Avery, MacLeod, and McCarty determined that genes are contained in molecules of DNA

Beadle and Tatum established that a gene

'

s activity is related to protein function

Explained translation of genetic information into protein

Investigated rates and mechanisms of genetic mutation

Determined how cells control genetic expression

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The Modern Age of Microbiology

How Do Genes Work?

Molecular biology

Explanation of cell function at the molecular level

Pauling proposed that gene sequences could

Provide understanding of evolutionary relationships and processes

Establish taxonomic categories to reflect these relationships

Identify existence of microbes that have never been culturedWoese determined that cells belong to domains Bacteria, Archaea, or EukaryaCat scratch disease caused by unculturable organism

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The Modern Age of MicrobiologyHow Do Genes Work?Recombinant DNA technology

Genes in microbes, plants, and animals manipulated for practical applications

Production of human blood-clotting factor by

E. coli

to aid hemophiliacs

Gene therapy

Inserting a missing gene or repairing a defective one in humans by inserting desired gene into host cells

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The Modern Age of MicrobiologyWhat Role Do Microorganisms Play in the Environment?Bioremediation uses living bacteria, fungi, and algae to detoxify polluted environments

Recycling of chemicals such as carbon, nitrogen, and sulfur

Most microbes in the environment are not pathogenic

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The Modern Age of Microbiology

How Do We Defend Against Disease?

Serology

The study of blood serum

Von Behring and Kitasato – presence in the blood of chemicals and cells that fight infection

Immunology

The study of the body

's defenses against specific pathogensChemotherapyFleming discovered penicillinDomagk discovered sulfa drugs

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Fungus colony

(

Penicillium

)

Zone of inhibition

Bacteria

(

Staphylococcus

)

Figure

1.20 The

effects of penicillin on a bacterial

"lawn"

in a Petri dish.

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The Modern Age of MicrobiologyWhat Will the Future Hold?Microbiology is built on asking and answering questions

The more questions we answer, the more questions we have

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The Modern Age of MicrobiologyTell Me WhyWhy are so many modern questions in microbiology related to genetics?