Download Microbiology: Study of microbes What is a microbe?

Microbiology: Study of microbes
What is a microbe?
• Typically microbes are small and most
cannot be seen without the aid of a
microscope
• Microbes are comprised of prokaryotes and
eukaryotes
• Most microbes classified as bacteria,
archaea, fungi, protozoa or algae
• Is a virus a microbe?
Bacteria and Archaea
• Prokaryotes -- single-celled
organisms without nuclei
• Typically very small
• Usually have cell walls and
membranes
• Live in many different
environments
• Many bacteria cause disease
(pathogenic)
• Most haploid and reproduce
asexually
Fungi -- Molds and Yeasts
• Eukaryotic organisms either
multi- or unicellular,
pathogenic or beneficial
• Many are microscopic
• Fungi contain cell walls but
are not photosynthetic
• Molds are typically multicellular and have sexual and
non-sexual reproduction by
spores
• Yeasts are unicellular and
reproduce asexually by
budding or via sexual spores
Protozoa
• Eukaryotic single-celled
organisms similar to
animal cells
• Most are motile and are
classified by means of
locomotion (cilia,
flagella or pseudopodia)
• Many species are
pathogenic
Algae
• Unicellular or multi-cellular
eukaryotes
• All are photosynthetic
• Have cell walls
• Classification based on cell
wall composition and
composition of their
photosynthetic proteins
• Large multi-cellular forms
include seaweed and kelp
• Diatoms contain silicates
(glassy) in cell walls
Highlights of a History of Microbiology
• Leeuwenhoek -- the microscope (1670’s)
• Redi, Needham, Spallanzani and Pasteur -spontaneous generation debunked
• Germ theory of disease
• Koch’s postulates
• Development of aseptic techniques and
vaccination
• Molecular microbiology
Antoni van Leeuwenhoek (1632-1723)
• First to view
(1674)“animalcules”
(protozoa) in drops of
water
• Reported the existence
of bacteria in 1676
• Spent 50 yrs. observing
and reporting on
microbes, but didn’t
share techniques
The question of spontaneous generation
• Embraced for 1900 yrs. since the time of Aristotle, at least
for small organisms
• Late 17th century: Francesco Redi demonstrated that
maggots appearing “spontaneously” on old meat required
the presence of flies
18th century experiments on spontaneous
generation: Needham vs. Spallanzani
• Needham’s
experiments used
boiled beef gravy and
corked vials
• Microbes grew readily
• Spontaneous
generation supported
• Spallanzani used
boiled infusions and
heat-sealed glass vials
• No microbial growth
occurred
• Spontaneous
generation does not
occur
Louis Pasteur (1822-1895)
Father of Microbiology
• Disproved spontaneous generation by carefully
demonstrating under what conditions microbes
appear
Other contributions by Pasteur
• Demonstrated anaerobic fermentation by both bacteria and
yeasts (bacteria produce acid and yeast produce alcohol)
• Developed pasteurization to prevent spoilage of wine by
bacteria
• Began field of industrial microbiology when he added
yeast to sterilized grape juice to make wine
• Bacterial spoiling of wine led to Germ theory of Disease
(1857)
Koch’s postulates drive search for disease
causative agents
• Examined patients blood and
identified bacteria associated with
different diseases
• Postulates: (1) Disease agent must be
present in every patient and absent in
others; (2) Agent is isolated and
when introduced into healthy person,
causes the disease; (3) Disease agent
can be reisolated from
experimentalhost
Disease prevention
Cleaner is better
• Nosocomial infections were rampant through mid
19th century
• Semmelweis demonstrated that hand washing
could significantly lesson childbirth-related
fatalities in mid-1800’s
• Lister demonstrated 2/3 reduction in patient death
by sterilizing equipment with phenol in early 20th
century
• Florence Nightingale introduced antiseptic
techniques into nursing practices in mid 1850’s
Modern microbiology
• Biochemical basis of life
• Microbial genetics
• Recombinant DNA and biotechnology