Microbiology Ch 01 lecture_presentation

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Chapter 1


The Early Years of Microbiology

• What 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


Figure 1.1 Antoni van Leeuwenhoek.


Lens Specimen holderFigure 1.2 Reproduction of Leeuwenhoek's microscope.


Figure 1.3 The microbial world.



• 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• Archaea• Fungi• Protozoa• Algae• Small multicellular animals



• 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 walls

• Archaeal cell walls are composed of polymers other than peptidoglycan


Prokaryoticbacterial cells

Nucleus ofeukaryotic cheek cell

Figure 1.4 Cells of the bacterium Streptococcus (dark blue) and two human cheek cells.



• 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 spores

• Yeasts – unicellular; reproduce asexually by budding;

some produce sexual spores


SporesHyphae Budding cellsFigure 1.5 Fungi.



• 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 whiplike than cilia


PseudopodsNucleus Cilia

Flagellum

Figure 1.6 Locomotive structures of protozoa.



• How 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


Figure 1.7 Algae.



• How Can Microbes Be Classified?• Other Organisms of Importance to Microbiologists

• Parasites

• Viruses


Red blood cellFigure 1.8 An immature stage of a parasitic worm in blood.


Virus

Bacterium

Virusesassemblinginside cell

Figure 1.9 A colorized electron microscope image of viruses infecting a bacterium.



• Tell Me Why• Other Organisms of Importance to Microbiologists


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?



• Does 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



• Does 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


Figure 1.10 Redi's experiments.



• Does 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



• Does Microbial Life Spontaneously Generate?• Spallanzani's experiments

• Results contradicted Needham's findings• 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

• The debate continued until the experiments conducted by Louis Pasteur


Figure 1.11 Louis Pasteur.



• Does 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


Figure 1.12 Pasteur's experiments with "swan-necked flasks."



• 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 hypothesis

• Accepted hypothesis can lead to theory/law

• Disproved hypothesis is rejected or modified


Figure 1.13 The scientific method, which forms a framework for scientific research.



• What 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


Figure 1.14 How Pasteur applied the scientific method in investigating the nature of fermentation.



• What 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



• What Causes Fermentation?• Buchner's experiments

• Demonstrated fermentation does not require living cells

• Showed enzymes promote chemical reactions

• Began the field of biochemistry



• What Causes Disease?• Pasteur developed germ theory of disease

• Robert Koch studied disease causation (etiology)

• Anthrax

• Examined colonies of microorganisms


Figure 1.15 Robert Koch.



• What Causes Disease?• Koch's experiments

• 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


Bacterium 1

Bacterium 2

Bacterium 3

Bacterium 4

Bacterium 5Bacterium 6 Bacterium 7

Bacterium 8

Bacterium 9

Bacterium 10

Bacterium 11

Bacterium 12

Figure 1.16 Bacterial colonies on a solid surface (agar).



• What 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


Gram-positive Gram-negativeFigure 1.17 Results of Gram staining.



• How 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



• How 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 settings

• Sprayed wounds, surgical incisions, and dressings with

carbolic acid (phenol)



• How 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


Figure 1.18 Florence Nightingale.



• How 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


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.



• Tell Me Why• Some people consider Pasteur or Koch to be the Father

of Microbiology, rather than Leeuwenhoek. Why might

they be correct?


The Modern Age of Microbiology

• What 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 extract

• Kluyver and van Niel proposed basic biochemical reactions

shared by all living things

• Microbes used as model systems for biochemical reactions



• What 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 diseases

• Drug design



• How Do Genes Work?• Genetics: scientific study of inheritance

• Many advances in the discipline made through the study

of microbes



• How 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



• 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 cultured

• Woese determined that cells belong to domains Bacteria, Archaea, or Eukarya

• Cat scratch disease caused by unculturable organism



• How 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



• What 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



• 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

pathogens

• Chemotherapy• Fleming discovered penicillin

• Domagk discovered sulfa drugs


Fungus colony(Penicillium)

Zone of inhibition

Bacteria(Staphylococcus)

Figure 1.20 The effects of penicillin on a bacterial "lawn" in a Petri dish.



• What Will the Future Hold?• Microbiology is built on asking and answering questions

• The more questions we answer, the more questions we

have



• Tell Me Why• Why are so many modern questions in microbiology

related to genetics?


Important topics

Antoni van Leeuwenhoek’s and Semmelweis findings The general characteristics of bacteria, archaea, virus,

protozoa, fungus, algae To differentiate the prokaryotes and eukaryotes Enzyme, a protein that runs the chemical reactions in the

cell.

Microbiology Ch 01 lecture_presentation

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Transcript of Microbiology Ch 01 lecture_presentation