1. Main Themes of Microbiology
The Main Themes of Microbiology
Microbiology: A Systems Approach
Main Themes of Microbiology
Chapter 1
Copyright © The McGraw-Hill Companies, Inc) Permission required for reproduction or display.
Chapter 1, pages 1 to 26

2. 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.

3. The Main Themes of Microbiology
Microbiology: A Systems Approach
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)
Chapter 1, pages 1 to 26

4. The Main Themes of Microbiology
Size Range of Microbes
Microbiology: A Systems Approach
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 mm
Reproductive structure
of bread mold
Range of
Human eye
Louse
Macroscopic
Microscopic
100mm
Nucleus
Colonial alga
(Pediastrum)
Ameba
Range of
light microscope
Red blood cell
White blood cell
10mm
Most bacteria fall between
1 to 10 mµ in size
Rod-shaped bacteria
(Escherichia coli)
Coccus-shaped bacteria
(Staphylococcus)
1mm
Rickettsia bacteria
Mycoplasma bacteria
200 nm
Poxvirus
100 nm
AIDS virus
Hepatitis B virus
Range of
electron
microscope
10 nm
Poliovirus
Flagellum
Large protein
1 nm
Diameter of DNA
Require
special
microscopes
Amino acid
(small molecule)
0.1 nm
Hydrogen atom
(1 Angstrom)
Chapter 1, pages 1 to 26

5. Relative Microbial Sizes
If poliovirus (27 nm) was the size of a quarter…
Staphylococcus aureus (0.8 µm) Beach ball
Escherichia coli (0.7 x 2.5 µm) Adult human
Saccharomyces cerevisiae (5 µm) Elephant
Paramecium caudatum (50 x 250 µm) Large yard (2.5 acres)
Amoeba proteus (800 µm) 10 city blocks (100 acres)

6. Major Groups of Microorganisms
Bacteria
Protozoa
Algae
Helminths
Fungi
Viruses

7. Cell Structure of Microorganisms
Algae
Protozoa
Helminths
Fungi
Viruses
Bacteria

8. Page 26

9. Characteristics of Living Organisms
The Main Themes of Microbiology
Microbiology: A Systems Approach
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
Chapter 1, pages 1 to 26

10. Importance of Microbes
The earliest organisms in the fossil record
Essential reactions in the environment
Can be harnessed to work for us
Infectious diseases

11. Branches of Microbiology
Medical Microbiology
Public health Microbiology and Epidemiology
Immunology

12. Branches of Microbiology
Industrial Microbiology
Agricultural Microbiology
Environmental Microbiology

13. Biotechnology
Genetic Engineering and Recombinant DNA Technology: genetically modified organisms (GMOs)
Bioremediation

14. Microbial Diseases
Pathogens: microbes cause infectious diseases

15. Microbiology Disciplines by Organism
The Main Themes of Microbiology
Microbiology: A Systems Approach
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
Chapter 1, pages 1 to 26

16. 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.

17. 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

18. 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