Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

MICROBIOLOGY CHAPTER 1 – A Brief History of Microbiology
THE EARLY YEARS OF MICROBIOLOGY
 What Does Life Really Look Like?
o 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 the end of 19th century, these organisms were called
microorganisms; now they are also called microbe
...

o Leeuwenhoek’s microorganisms are now grouped into six categories:
 Bacteria
 Archaea
 Fungi
 Protozoa
 Algae
 Small multicellular animals
o 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 cells walls are composed of polymers other than
peptidoglycan
o 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
o 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
o 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
o Other Organisms of Importance to Microbiologists
 Parasites
 Viruses
THE GOLDEN AGE OF MICROBIOLOGY
 Scientists searched for answers to four questions:
o Is spontaneous generation of microbial life possible?
o What causes fermentation?
o What causes disease?
o How can we prevent infection and disease?

 Does Microbial Life Spontaneously Generate?
o Some philosophers and scientists of the past thought living things arose
from three processes:
 Asexual reproduction
 Sexual reproduction
 Nonliving matter
o Aristotle proposed spontaneous generation
 Living things can arise from nonliving matter
o 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
o Needham’s experiments
 Scientists did not believe that animals could arise spontaneously, but
the microbes could
 Needham’s experiments with beef gravy and infusions of plant
material reinforced this idea
o 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
o 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
o 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
o Accepted hypothesis can lead to theory/law
o Disproved hypothesis is rejected or modified
 What Causes Fermentation?
o Spoiled wine threatened livelihood of vintners
o Some believed air caused fermentation; others insisted living organisms
caused fermentation
o Vintners funded research of methods to promote production of alcohol and
prevent spoilage during fermentation
o This debate also linked to debate over spontaneous generation
o 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
Some Industrial Uses of Microbes
Product or Process
Contribution of Microorganism
Foods and Beverages
Cheese
Flavoring and ripening produced by
bacterias and fungi; flavors dependent
on the source of milk and the type of
microorganism
Alcoholic beverages
Alcohol produced by bacteria or yeast
by fermentation of sugars in fruit juice
or grain

Soy sauce
Vinegar
Yogurt
Sour cream
Artificial sweetener
Bread

Other Products
Antibiotics
Human growth hormone, human
insulin
Laundry enzymes
Vitamins
Diatomaceous earth (in polishes and
buffing compounds)
Pest control chemicals
Drain opener

Produced by fungi fermentation of
soybeans
Produced by bacterial fermentation of
sugar
Produced by certain bacteria growing in
milk
Produced by bacteria growing in cream
Amino acids synthesized by bacteria
from sugar
Rising of dough produced by action of
yeast; sourdough results from bacteriaproduced acids
Produced by bacteria and fungi
Produced by genetically engineered
bacteria
Isolated from bacteria
Isolated from bacteria
Composed of cell walls of microscopic
algae
Insect pests killed or inhibited by
insect-destroying bacteria
Protein-digesting and fat-digesting
enzymes produced by bacteria

o Buchner’s experiments
 Demonstrated fermentation does not require living cells
 Showed enzymes promote chemical reactions
 Began the field of biochemistry
 What Causes Disease?
o Pasteur developed germ theory of disease
o Robert Koch studied disease causation (etiology)
 Anthrax
 Examined colonies of microorganisms
o Koch’s experiments
 Simple staining techniques

 First photomicrograph of bacteria
 First photomicrograph of bacteria in diseased tissue
 Techniques for estimation CFU/ml
 Use of steam to sterilize media
 Use of Petri dishes
 Techniques to transfer bacteria
 Bacteria as distinct species
o 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 introduces into a healthy, susceptible host, the host
must get the disease
 Same agent must be found in the diseased experimental host
 How Can We Prevent Infection and Disease?
o Many great advances in disease prevention came after it was shown that
microbes can cause disease
o Modern principles of hygiene not widely practiced in the mid-1800s
o Healthcare associated infections were common
o Six health care practitioners were instrumental in changing health care
delivery methods
o Semmelweis and hand washing
 Ignaz Semmelweis required medical students to wash their hands
in chlorinated lime water
 Resulted in higher patient survival rates
o Lister’s antiseptic technique
 Joseph Lister advanced antisepsis in health care settings
 Sprayed wounds, surgical incisions, and dressing with carbolic
acid (phenol)
o Nightingale and nursing
 Florence Nightingale introduced cleanliness and antiseptic
techniques into nursing practice
 Advocated for hospital and public health policy reform
o Snow and epidemiology

 John Snow mapped cholera epidemic in London in 1854
 His work was the foundation for infection control and
epidemiology
o Jenner’s vaccine
 Edward Jenner developed a vaccine against smallpox
 Demonstrated the validity of vaccination
 Began the field of immunology
o 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
Fields of Microbiology
Disciplines
Basic Research
Microbe Centered
Bacteriology
Phycology
Mycology
Protozoology
Parasitology
Virology
Process Centered
Microbial metabolism
Microbial genetics
Environmental microbiology

Applied Microbiology
Medical Microbiology
Serology
Immunology
Epidemiology

Subject(s) of Study

Bacteria and Archaea
Algae
Fungi
Protozoa
Parasitic protozoa and parasitic animals
Viruses
Biochemistry: chemical reactions within
cells
Functions of DNA and RNA
Relationships between microbes and
among microbes, other organisms, and
their environment

Antibodies in blood serum, particularly
as an indicator of infection
Body’s defenses against specific
diseases
Frequency, distribution, and spread of

Etiology
Infection control
Chemotherapy

disease
Causes of disease
Hygiene in health care settings and
control of nosocomial infections
Development and use of drugs to treat
infectious diseases

Applied Environmental Microbiology
Bioremediation
Public health microbiology

Use of microbes to remove pollutants
Sewage treatment, water purification,
and control of insects that spread disease
Agricultural microbiology
Use of microbes to control insect pests
Industrial Microbiology (Biotechnology)
Food and beverage technology
Reduction or elimination of harmful
microbes in food and drink
Pharmaceutical microbiology
Manufacture of vaccines and antibiotics
Recombinant DNA technology
Alteration of microbial genes to
synthesize useful products
 What Are the Basic Chemical Reactions of Life?
o 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
 Practical applications
 Design of herbicides and pesticides
 Diagnosis of illness and monitoring of patients’ responses to
treatment
 Treatment of metabolic diseases
 Drug design
 How Do Genes Work?
o Genetics: scientific study of inheritance

o Many advances in the discipline made through the study of microbes
o 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
o 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 uncultured organism
o Recombinant DNA technology
 Genes in microbes, plants, and animals manipulated for practical
applications
 Production of human blood-clotting factor by E

---