Introduction to Microbiology
 Microbiology is the study of microorganisms, a large and diverse group
of microscopic organisms which must be viewed with a microscope that
exist as single cells or cell clusters; it also includes viruses, which are
microscopic but not cellular .
Importance of microbiology
 The importance of microbiology includes: used in biomedical research,
creation of medicines, environmental applications and new research tools.
 Bacteria are important for fixing N2 in a usable form for plants.
 Bacteria and some fungi are important in decomposition and recycling
of materials.
 Industry applications of microbiology: waste management, food
industry, mining, medicine, research and biotechnology.
History of Microbiology
The history of microbiology can be summarized in the
following:
 1660’s Robert Hooke observed microorganisms for the first time with
a microscope and coined the term “cell”.
 1632-1723 Anton van Leeuwenhoek having observed the first
bacteria.
 1796 First scientific Small pox vaccination by Edward Jenner.
 1828-1898 Ferdinand Cohn developed the first classification scheme
based on bacterial shape. Cohn detailed and described the life cycle of
Bacillus, and he put the first classification system of bacteria called
Cohn’s Classification System divided into four groups:




Sphaerobacteria are spherically shaped.
Microbacteria are rod shaped
Desmobacteria are filamentous
Spirobacteria are spiral shaped
 1822-1895 Louis Pasteur Defined pasteurization to prevent spoilage
of food by bacteria, develop Rabies vaccination and disproved the
scientific dogma of “Spontaneous Generation”. He defined “Germ
Theory” and demonstrated that germs were responsible for disease.
 1843-1910 Robert Koch identified anthrax and developed agar growth
medium. Koch’s postulates was a systematic method to establish the
microbial cause of disease.
 Ignaz Semmelweis was the first to recognize the need for good
hygiene during medical procedures. The first to identify nosocomial
infections and advocated washing hands to stop the spread of disease.
 1827-1912 Joseph Lister developed antiseptic methods for use in
surgery and medicine.
 1854-1915 Paul Ehrlich developed chemotherapy to cure infectious
diseases and discovers antibiotics to treat sleeping sickness and syphilis
with the developed the acid-fast stain.
 Invented Petri Dish by R.J. Petri.
 Developed Gram Stain by Christian Gram.
 Recognized viral dependence on cells for reproduction by Martinus
Beijerinck.
 1881-1951 Alexander Fleming discovered penicillin and lysozyme.
 1864-1920 Dmitri Ivansvski discovered the first virus which is known
as the tobacco mosaic virus (TMV).
 1952 Hershey & Chase Experiments identified that DNA was the
genetic material of bacteriophages.
 Hershey Case Experiment: using phage radioactively labeled with
P32 (DNA) or S35 (protein) they infected bacteria cells. They found the
P32 inside the bacteria not S35.
 1977 Developed a method to sequence DNA by W. Gilbert & F.
Sanger.
 1983 Polymerase Chain Reaction invented by Kary Mullis.
 1995 First microbial genomic sequence published by H. influenzae.
Anatomy of bacteria
The bacterial cell is a prokaryote cell which is simpler, and therefore
smaller, than a eukaryote cell, lacking a nucleus and most of the other
organelles of eukaryotes. Nuclear material of prokaryotic cell consist of a
single chromosome which is in direct contact with cytoplasm. Here the
undefined nuclear region in the cytoplasm is called nucleoid.
A
prokaryotic
cell
has
three
architectural
regions:
• On the outside, flagelig and pilli project from the cell’s surface. These
are structures (not present in all prokaryotes) made of proteins that
facilitate
movement
and
communication
between
cells;
• Enclosing the cell is the cell envelope — generally consisting of a cell
wall covering a plasma membrane though some bacteria also have a
further covering layer called a capsule. The envelope gives rigidity to the
cell and separates the interior of the cell from its environment, serving as
a protective filter. Though most prokaryotes have a cell wall, there are
exceptions such as Mycoplasma (bacteria) and Thermoplasma (archaea).
The cell wall consists of peptidoglycan in.bacteria, and acts as an
additional barrier against exterior forces. It also prevents the cell from
expanding and finally bursting (cytolysis) from osmotic pressure against
a hypotonic environment.
Diagram of a typical prokaryotic cell