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In 1674, Anton van Leeuwenhoek
discovered a world of millions of tine
“animalcules”. About 100 years later,
Otto Muller, the Danish biologist,
extended Leeuwenhoek’s studies and
organized bacteria into genera and
species according to a classification
method Carolus Linnaeus. This was the
beginning of the taxonomic classification
of microbes.
Robert Koch and Louis Pasteur- 1870s and
1880s with a series of experiments that
microorganisms were responsible for
causing anthrax, rabies, plague, cholera,
and tuberculosis.
Others proved they were also responsible
for causing human disease. This is pretty
much the germ theory of disease.
Etiology - is the study
of the causation of
disease.
gram-staining - developed in the 1880s and is
still used today to differentiate bacteria into two
categoriesgram-positive
gram-negative
cowpox-based vaccine for preventing smallpox
began interest in the studies in the field of
immunology by Jenner.
Ehrlich laid the foundation for the field of
chemotherapy by his search of “magic bullets”-
Microbes can be subdivided into the following
four groups
Viruses
Fungi
Bacteria
Parasites
•Smallest infectious particles from 18-300 nanometers
•Consist of DNA or RNA and may contain protein for replication
and pathogenesis; components are then enclosed in a protein
coat with or without a lipid membrane coat.
•Parasites- requiring host cell to replicate
•The cells they infect and the host response to the infectious
dictate the nature of the clinical manifestation.
•Infection can lead to rapid reproduction and destruction of the
cell or to a long-term chronic relationship with possible
integration of the viral genetic information into the host
genome.
•Prokaryotic organisms
•Simple unicellular organisms with
•no nuclear membrane, mitochondria, Golgi bodies, or
endoplasmic reticulum•reproduce by asexual means.
•Consist of two basic formsgram-positive cell wall - thick peptidoglycan layer
gram-negative- thin peptidoglycan layer and an
overlying outer membrane.
•The human body is inhabited by thousands of different
bacterial species.
•Many things surrounding us are also inhabited by bacteria.
•Disease result from the toxic effects of bacterial products
(toxins) or when bacteria inhabit normally sterile body sites
•Eukaryotic
•Well-defined nucleus
• mitochondria
•Golgi bodies
•endoplasmic reticulum
can exist in either unicellular (fungi) that
can replicate asexually or in a filamentous
form (mold) that can replicate asexually or
sexually.
•Some can assume either morphology and
are known as dimorphic fungi.
•Most complex
•All are considered eukaryotic
• unicellular
•multicellular
•Life cycles are very complex
•Difficulty is not just understanding the spectrum of
disease caused by parasites, but also an appreciation
of the epidemiology of these infections.
Microbiology now a days is more used on
answering questions regarding biochemistry
which is the study of metabolism. This
extends toward the cell function at the
molecular level.
From applied knowledge through basic
research, scientist can answer questions also
regarding recombinant DNA technology and
gene therapy.