Human and the
Microbial World
Chapter 1
Preview
• History of microbiology
– microscope, spontaneous generation
• Applications of microorganism/microbiology
– Bioremediation, disease treatment and prevention,
genetic engineering, model system to study
• Classification and nomenclature of
microorganisms
– Three domains and major characteristics
– Binominal system
Introduction
• What is Microbiology?
• Includes several sub-disciplines
– Bacteriology
- Virology
– Mycology
- Parasitology
– Food microbiology
– Environmental microbiology
– Forensic microbiology
Introduction
• Microbiology born as a science in 1674
– Anthony van Leeuwenhoek
• Dutch drapery merchant
• First glimpses of microbial world
– Called organisms “animalcules”
– Robert Hook
• Looked at cork
The Origin of Life
• Theory of Spontaneous
Generation
“Organisms can arise from
decaying non-living organic
matter”
mice
maggots
People contributed to disproving
the theory
– Francesco Redi
– Louis Pasteur
– John Tyndall
Francesco Redi
• Demonstrated worms can not be
spontaneously generated from rotten
meat.
– Covered with fine gauze
– No eggs – no worms
“spontaneous generation”
Louis Pasteur
• father of modern microbiology
• Design swan neck bottle-proved that bacteria
growth in the infusion was due to contamination
from air
John Tyndall
• Explained discrepancies
– Different infusions require different boiling
time.
– Suggest heat resistant form of life cause
contamination.
– German botanist Ferdinand Cohn discovered
endospores in the same year
– Robert Koch established endospore role in
disease transmission
Origin of Microorganism
unsolved mystery
What is spontaneous generation theory?
Who were the scientists disproved it?
How did they disproved it?
Applications of Microorganism
• Microbes have enormous impact on human
existence
– Responsible for the production and recycle of
oxygen and nitrogen
• Key elements for all living organisms
– Decomposers
• breakdown of wide variety of material
Such as cellulose from plants
Applications of Microorganism
• Food production
– Fermentation to produce numerous products
• Bioremediation
– Use organisms to degrade environmental
waste
• Degrade PCB’s, DDT
• Clean up oil spills
• Treat radioactive waste
Applications of Microorganism
• Bacteria can synthesize numerous
products
– Ethanol
– Pesticides
– Antibiotics
– Dietary amino acids
Applications of Microbiology
• Genetic engineering
– Definition: introduce genes of one organism
into an unrelated organism to confer new
properties on the organism
• to produce medically important products and
vaccines
• Engineered plants resist disease
• Potentially therapeutic
– Gene therapy
Application of Microbiology
• Microorganisms are wonderful model for
study
– Metabolic and genetic properties similar to
higher forms of life.
– Building blocks of macromolecules same as
other life forms
– “What is true for an elephant is also true for a
bacteria”
– Much simpler system
– High growth rate
Applications of Microbiology
• Better treatment and prevention of
disease.
– Microbes are important causes of morbidity
and mortality
• More people died worldwide of influenza in the
1918 epidemic than died in WWI, WWII, Korean
War and Vietnam combined
– Modern sanitation, vaccination and effective
antimicrobial treatments have reduced
incidence of the worst diseases
Application of Microbiology
•understanding how they cause disease can help prevent disease
Per 100,000
Present and Future Challenges
• Infectious disease remains a threat
– 750 million cases each year in US
• 200,000 deaths
• Tens of billions of dollars spent on health care
Present and Future Challenges
• Emerging diseases
– with increased occurrence and wider
distribution
• Seemingly new diseases
• include
–
–
–
–
–
Mad cow disease
AIDS
West Nile virus disease
Severe Acute Respiratory Syndrome (SARS)
Swine flu
• Factors associated with emerging disease
– Changing lifestyles
– Genetic changes in organisms
Present and Future Challenges
• Resurgence of old diseases
– Diseases thought to be “defeated” increasing
in frequency
• Often more serious
• usually resistant to treatment
• Reasons for resurgence
– Increased travel
– Unvaccinated individuals susceptible to infection
Present and Future Challenges
• Chronic disease caused by bacteria
– Many disease once thought caused by
environmental stressors actually caused by
bacteria
• Example: gastric ulcers
– Causative agent – Helicobacter pylori
Host-Bacterial Interactions
• Estimated 500 – 1000 species of bacteria reside
in and on the human body
• Bacteria out number cells in the body 10:1
• compete with other organisms for food and
space
– Keep disease causing organisms from breaching host
defenses
– Help digest food in intestine.
• Some bacteria and viruses use the human body
as a habitat for multiplication, persistence and
transmission
Classification
Classification - process of arranging organisms into similar or related groups,
primarily to provide easy identification and study
•Domain - a collection of similar kingdoms
•Kingdom - a collection of similar phyla or classes
•Phylum/division - a collection of similar classes
•Class - a collection of similar orders
•Order - a collection of similar families
•Family - a collection of similar genera
•Genus - a collection of related species
•Species - a group of related isolates or strains
The Microbial World
• All living things can be
classified in three domains
– Bacteria
– Archaea
– Eucarya
• Organisms in each domain
share certain properties
The Microbial World
• Bacteria and Archaea
– single-celled organisms
– Contain no membrane bound nucleus
• Termed prokaryotes = pre nucleus
– Pro = pre
– karyote = nucleus
– Do not contain any other organelles
– Cytoplasm is surrounded by rigid cell wall
Domain Bacteria
• Most common type in human infection
• Members widely diverse
• Most prominent features include:
– Specific shapes
• Rod-shaped, spherical and spiral
– Rigid cell walls
• Responsible for cell shape
– Multiply by binary fission
• One cell divides into two
• Each cells is genetically identical to the first
– Some bacteria are motile
• Move by means of flagella
Domain Archaea
• Demonstrate a number of
same attributes as Bacteria
– Same shapes
– Multiply through binary fission
– Move by means of flagellum
• Archaea exhibit significant
difference
– Chemical composition of cell
wall differs from organisms in
other domain
– Organisms of Archaea domain
found in extreme
environments
• Extreme temperatures
• Environments with high
concentrations of salts
Domain Eucarya
• Eucarya
– Organisms contain membrane bound nucleus
• Termed eukaryote = true nucleus
– Eu = true
– karyote = nucleus
– Contains internal organelles
• Making organism more complex
– Example = mitochondria
• May be single or multicellular
Domain Eucarya
• Microbial world includes:
– Algae
– Fungi
– protozoa
Domain Eucarya
• Algae
– Usually found near surface waters
– All contain chlorophyll
• Pigments used to absorb light to be used as
energy source
– Some contain other pigments
– Have rigid cell wall
• Distinct from bacterial cell walls
Domain Eucarya
• Fungi
– Diverse single celled and multicellular
organisms
• Single celled = yeast
• Multicellular = molds
– Gain energy from organic materials
– Found mostly on land
Domain Eucarya
• Protozoa
– Found in water and on land
– Much larger than prokaryote
– Do not have a rigid cell wall
– Gain energy from organic matter
– Most are motile
• Means of motility diverse and a feature of their
classification
What is the major difference between bacteria
and eukaria?
Nomenclature
• Binomial naming system
– Two word naming system
• First word is genus name
– Always capitalized
• Escherichia
• Second word is species name
– Not capitalized
• coli
• When writing full name genus usually abbreviated
– E. coli
• Full name always italicized
– Or underlined
Bacillus anthracis
Bacillus cereus
Bacillus anthracis
Nomenclature
Modern human
Homo Sapiens
Domestic dog
Canis familiaris
•Genus - a collection of related species
•Species - a group of related isolates or strains
Wolf
Canis lupus
Viruses, Viroids, Prions
• Non-living elements (agents)
– Not organisms
– obligate intracellular parasites
• Must have host machinery to replicate
• Inactive outside of host
Viruses, Viroids, Prions
• Usually consist of only a few molecules found in
living cells
– protein coat surrounding nucleic acid
• Essentially protein bag of nucleic acid
• All forms of life can be infected by viruses
• Viruses frequently kill host cells
– Some live harmoniously with host
Viruses, Viroids, Prions
• Viroids are simpler than viruses
– Still require host cell for replication
• Consist of a single short piece of RNA
– Contains no protective protein coat
• Viroids smaller than viruses
• Generally cause plant diseases
Viruses, Viroids, Prions
• Prions are infectious proteins
– Contains no nucleic acid
• Responsible for six neurodegenerative
diseases
• Scrapie in sheep
• Mad cow disease in cattle
• Kuru in human
Size in the Microbial World
• Tremendous range in size
– Smallest virus approximately 1/1,000,000th size of
largest eukaryotic cell
Scientist found a microorganism that is 10um
long. Which domain it belongs to?