Main Themes of
Microbiology
Chapter 1
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Learning Goals:
• Define microorganism and characterize the main
groups of microorganisms.
• Describe the basic cellular structure of microbes and
differentiate between prokaryotic and eukaryotic
cell.
• Explain the importance of studying microbes.
Describe the role and impact of microbes on the
Earth.
• Define the main branches of Microbiology
• Summarize the relative burden of human disease
caused by microbes.
What is Microbiology?
• micron = small and biologia = study of living things
• Microbiology = study of small living things
– How small is “small”?
– What do we really mean by living?
• Working definition: Study of entities too small to be
seen with the unaided human eye.
• (< 0.2 mm = 200 µm = 200,000 nm)
Size Range of Microbes
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1 mm
Range of
Human eye
Reproductive structure
of bread mold
Louse
Macroscopic
Microscopic
100mm
Colonial alga
(Pediastrum)
Range of
light microscope
10mm
1mm
White blood cell
Most bacteria fall between
1 to 10 mµ in size
Rod-shaped bacteria
Rickettsia bacteria
(Escherichia coli)
Mycoplasma
bacteria
100 nm
AIDS virus
1 nm
Require
special
microscopes
0.1 nm
(1 Angstrom)
Ameba
Red blood cell
200 nm
Range
10 nm
of
electron
microscope
Nucleus
Coccus-shaped bacteria
(Staphylococcus)
Poxvirus
Hepatitis B virus
Poliovirus
Flagellum
Large protein
Diameter of DNA
Amino acid
(small molecule)
Hydrogen atom
Relative Microbial Sizes
• If poliovirus (27 nm) was the size of a quarter…
• Staphylococcus aureus (0.8 µm)
• Escherichia coli (0.7 x 2.5 µm)
• Saccharomyces cerevisiae (5 µm)
• Paramecium caudatum (50 x 250 µm)
• Amoeba proteus (800 µm)
Beach ball
Adult human
Elephant
Large yard
(2.5 acres)
10 city blocks
(100 acres)
Major Groups of Microorganisms
•
•
•
•
•
•
Bacteria
Protozoa
Algae
Helminths
Fungi
Viruses
Cell Structure of Microorganisms
Bacteria
Algae
Protozoa
Helminths
Fungi
Viruses
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8
Characteristics of Living Organisms
• Metabolism – enzyme-catalyzed chemical reactions
Bacillus cereus – Yes
Bacteriophage T4 – No
• Reproduction – progeny formed sexually or asexually
Bacillus cereus – Yes
Bacteriophage T4 – Yes
• Differentiation – different cell types can occur
Bacillus cereus – Yes
Bacteriophage T4 – No
• Communication – signaling within and between cells
Bacillus cereus – Yes
Bacteriophage T4 – No
• Locomotion – relative movement of cell or organism
Bacillus cereus – Yes
Bacteriophage T4 – No
• Evolution – genetic change over time
Bacillus cereus – Yes
Bacteriophage T4 – Yes
Importance of
Microbes
• The earliest
organisms in the
fossil record
• Essential reactions
in the environment
• Can be harnessed
to work for us
• Infectious diseases
Branches of
Microbiology
• Medical Microbiology
• Public health
Microbiology and
Epidemiology
• Immunology
Branches of
Microbiology
• Industrial
Microbiology
• Agricultural
Microbiology
• Environmental
Microbiology
Biotechnology
• Genetic
Engineering and
Recombinant
DNA Technology:
genetically
modified
organisms
(GMOs)
• Bioremediation
Microbial Diseases
• Pathogens: microbes cause infectious diseases
Microbiology Disciplines by Organism
• Microbiologists are sometimes referred to by
the type of microbial system that they study
• Bacteriology: Study of prokaryotes
• Mycology: Study of fungi
• Phycology: Study of algae
• Protozoology: The study of protozoa
• Virology: The study of viruses
Conclusions:
• Microbiology studies living organisms “too
small to be seen by with the naked eye”. They
include bacteria, algae, protozoa, fungi,
helminths, and viruses.
• There are two types of cellular structure of
microorganisms: prokaryotes and eukaryotes.
Viruses are not cellular and can be considered
particles.
• Microorganisms have a crucial effect on the
life on Earth.
Conclusions:
• Humans manipulate microbes to do work for
them in industry, medicine, and in caring for the
environment.
• Microbiology is a complex discipline which
includes many branches studying different
aspects of microbes
• Infectious diseases are caused by microbes acting
as parasites. There are differences in infectious
diseases affecting developing and industrialized
countries
What Aspects of Microorganisms Will
We Study?
•
•
•
•
•
Cell Structure and Function
Cell Growth and Metabolism
Microbial Genetics
Taxonomy and Evolutionary History
Interaction with Living and Non-Living
Environment