Transcript The Importance of Microorganisms

Chapter 1
What is microbiology
• Study of organisms too small to be seen
by the unaided eye – Microorganisms
• Relatively simple in their construction,
mostly unicellular
• No distinct tissues
The Importance of Microorganisms
• Microbes exceed every other groups of
organisms
• Found everywhere (ubiquitous) – ice capped
mountains, bottom of the ocean
• Air, water, soil
• Inside us – normal flora – gastrointestinal,
genitourinary, respiratory tract, on the skin
• Source of nutrients, some carry out
photosynthesis
• Unicellular algae – bottom of the food chain
• Aquatic environments. Unicellular algae
• bottom of the food chain.
• Unicellular algae > tiny fish > large fish >
shark.
• Algae are autotrophs. They use CO2 and
water to make sugar.
• Soil microbes are involved in recycling
chemical elements.
• Breakdown cellulose and release CO2.
• Making food products (yogurt, cheese,
bread). Yeast + flour > dough
• Small ball of dough -----large ball of dough
• Therapeutic substances – genetic
engineering is used to force E. coli to
make human insulin.
• Bioremediation – microbes are used to
clean up chemical pollutants (oil spills) in
the environment.
• Insecticide – BT toxin is sprayed on plants.
• Sewage treatment – breakdown organic
matter to produce methane.
• Harmful aspects
• Tuberculosis, Lyme disease
• Spoilage of food products.
Milk ----- sour. Lactose --- acids.
Members of the microbial world
•
•
•
•
Procaryotic cells – pre-nucleus
DNA is not surrounded by a membrane
Eucaryotic cell – true nucleus
DNA is surrounded by a membrane
Classification of organisms
•
•
•
•
•
1969 Robert whittaker
5 kingdom system
Classification based on
Cell type - prokaryotic/eukaryotic
Cellular organization –
unicellular/multicellular
• Nutritional requirements –
photosynthetic/nonphotosynthetic
Classification of organisms
• Prokaryotae (monera) – procaryotic
organisms – bacteria
• Protista - protozoa
• Fungi – Yeasts and molds
• Plant – ferns, trees, flowering plants
• Animal – worms, insects, vertebrates
•
•
•
•
•
•
3 domains
Ribosomal RNA sequence
Archaea, Bacteria, Eukarya
Bacteria – procaryotic
Normal flora, pathogens
Peptidoglycan
•
•
•
•
•
•
•
•
Archaea
Procaryotic
Unique ribosomal RNA sequence
Unusual, extreme environments
Salt lakes, dead sea
Do not have peptidoglycan cell wall
Pseudomurein
No pathogenic species known
viruses
•
•
•
•
Acellular
Obligate intracellular parasites
Either have DNA or RNA
No plasma membrane, cytoplasm
• History of microbiology
• 1665 Robert Hooke – plant materials
(leaves and stems). Little boxes – cells.
• 1673 – 1723 Anton van Leeuwenhoek
observed microbes under the microscope.
Discovery of Microorganisms
• Antony van
Leeuwenhoek (16321723)
– first person to observe
and describe
microorganisms
accurately
Figure 1.3 (a)
Figure 1.3 (b) and (c)
• Rain water, scrapings from his teeth.
• Called the microbes animalcules.
• Spontaneous generation theory – life
could arise from nonliving matter.
• Decaying meat could give birth to
maggots (larvae of flies)
The Conflict over Spontaneous
Generation
• spontaneous generation
– living organisms can develop from nonliving
or decomposing matter
• Francesco Redi (1626-1697)
– disproved spontaneous generation for large
animals
– showed that maggots on decaying meat came
from fly eggs
Fine net
No maggots
But could spontaneous generation be
true for microorganisms?
• John Needham (1713-1781)
– his experiment:
mutton broth in flasks  boiled sealed
– results: broth became cloudy and contained
microorganisms
• Lazzaro Spallanzani (1729-1799)
– his experiment:
broth in flasks sealed  boiled
– results: no growth of microorganisms
Needham 1745
Louis Pasteur (1822-1895)
• his experiments
–
–
–
–
placed nutrient solution in flasks
created flasks with long, curved necks
boiled the solutions
left flasks exposed to air
• results: no growth of microorganisms
CO 01
Pasteur’s experiment
S shaped curve
S shaped curveS shaped curve
S shaped curve
S shaped curve
Germ theory of disease
• Belief microbes could cause diseases
• Before Pasteur’s time people thought a disease
was a punishment for someone’s misdeeds.
• 1850s Pasteur discovered fermentation.
• Yeasts broke down sugars in grapes to release
alcohol and CO2
• If microbes could cause changes in grapes, they
could cause changes in humans and animals
• Robert Koch proved the germ theory of disease
Fig. 1.6
• Drew blood from the animals that had died
of the disease.
• Isolated a rod-shaped bacterium (isolate
#1)
• Grew bacterium in the lab and obtained a
pure culture of the bacterium.
• Injected bacterium into healthy animals.
• They got sick and died. He isolated rod
shaped bacterium from these animals
(isolate #2)
• Compared the 2 isolates and found that
they were identical.
• Anthrax. Bacillus anthracis.
• The above steps are known as Koch’s
postulates.
• They are used even today to determine
the causative agent of a mysterious
infectious disease.
Koch’s postulates
• The microorganism must be present in every
case of the disease but absent from healthy
individuals.
• The suspected microorganism must be
isolated and grown in a pure culture.
• The same disease must result when the
isolated microorganism is inoculated into a
healthy host.
• The same microorganism must be isolated
again from the diseased host.
The Development of
Techniques for Studying
Microbial Pathogens
• Koch’s work led to discovery or
development of:
– agar
– petri dish
– nutrient broth and nutrient agar
– methods for isolating microorganisms
Other developments…
• Charles Chamberland (1851-1908)
– developed porcelain bacterial filters used by Ivanoski
and Beijerinck to study tobacco mosaic disease
• determined that extracts from diseased plants had infectious
agents present which were smaller than bacteria and passed
through the filters
• Infectious agents were eventually shown to be viruses
Immunological Studies
• Edward Jenner (1798)
• used a vaccination procedure to protect
individuals from smallpox
Cowpox materials from cowpox lesions to protect
people from snallpox.
The Development of Industrial
Microbiology and Microbial
Ecology
• Louis Pasteur
– demonstrated that alcohol fermentations
and other fermentations were the result of
microbial activity
– developed the process of pasteurization to
preserve wine during storage
Additional Developments…
• Sergei Winogradsky (1856-1953) and Martinus
Beijerinck (1851-1931)
– studied soil microorganisms and discovered
numerous interesting metabolic processes (e.g.,
nitrogen fixation)
– pioneered the use of enrichment cultures and
selective media
The Scope and Relevance of
Microbiology
• importance of microorganisms
–
–
–
–
–
first living organisms on planet
live everywhere life is possible
more numerous than any other kind of organisms
global ecosystem depends on their activities
influence human society in many ways
Microbiology has basic and applied
aspects
• Basic aspects are concerned with
individual groups of microbes, microbial
physiology, genetics, molecular biology
and taxonomy
• Applied aspects are concerned with
practical problems – disease, water, food
and industrial microbiology
Microbiology actually represents
many fields of study
• Many specialties
• Examples
– medical microbiology is concerned with
diseases of humans and animals
– immunology is concerned with how the
immune system protects a host from
pathogens
More fields…
– microbial ecology is concerned with the
relationship of organisms with their
environment
– microbial genetics and molecular biology are
concerned with the understanding of how
genetic information functions and regulates
the development of cells and organisms
The Future of Microbiology:
Challenges and opportunities for future
microbiologists
• infectious disease
• new and improved industrial processes
• microbial diversity and microbial ecology
– less than 1% of earth’s microbial population has been
cultured
• Easier to grow
• Results can be obtained faster
• Easier to manipulate their environment
and their DNA
• Most of the concepts and processes in
biology are first discovered in microbes
• Gave foundation that helped scientists to
discover the processes in other organisms
including humans