Microbiology: Study of microbes What is a microbe? - haspi

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20 Φεβ 2013 (πριν από 4 χρόνια και 3 μήνες)

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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 multi
-
cellular 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