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Chapter 1
Introduction to Microbes and Their Building Blocks
Microorganisms are defined as “living organisms too small to be seen with the naked
eye.” Members of this huge group of organisms are prokaryotes (bacteria and archaea),
algae, protozoa, fungi, parasitic worms (helminths), and viruses. Microorganisms live
nearly everywhere and influence many biological and physical activities on earth. There
are many kinds of relationships between microorganisms and humans; most are
beneficial, but some are harmful. Microbes and the Planet Groups of organisms
constantly evolve to produce new forms of life. Microbes are crucial to the cycling of
nutrients and energy necessary for all life on earth.
Humans have learned how to manipulate microbes to do important work for them in
industry, medicine, and in caring for the environment. In the last 120 years,
microbiologists have identified the causative agents for many infectious diseases. They
have discovered distinct connections between microorganisms and diseases whose
causes were previously unknown. Our current understanding of microbiology is the
cumulative work of thousands of microbiologists, many of whom literally gave their lives
to advance knowledge in this field. The microscope made it possible to see
microorganisms and thus to identify their widespread presence, particularly as
agents of disease. Medical microbiologists developed the germ theory of disease
and introduced the critically important concept of aseptic technique to control the spread
of disease agents.
Excluding the viruses, there are two types of microorganisms: prokaryotes, which are
small and lack a nucleus and organelles, and eukaryotes, which are larger and have
both a nucleus and organelles. Viruses are not cellular and are, therefore, sometimes
called particles rather than organisms. They are included in microbiology because of
their small size and close relationship with cells.
Macromolecules are very large organic molecules (polymers) usually built up by
polymerization of smaller molecular subunits (monomers). Carbohydrates are biological
molecules whose polymers are monomers linked together by glycosidic bonds. Their
main functions are protection and support (in organisms with cell walls), and also
nutrient and energy stores. Lipids are biological molecules, such as fats, that are
insoluble in water. Their main functions are as cell components, and
nutrient and energy stores. Proteins are biological molecules whose polymers are
chains of amino acid monomers linked together by peptide bonds. Proteins are called
the “shapers of life” because of the many biological roles they play in cell structure and
cell metabolism. Protein structure determines protein function. Structure and shape are
dictated by amino acid composition and by the pH and temperature of the protein’s
immediate environment. Nucleic acids are biological molecules whose polymers are
chains of nucleotide monomers linked together by phosphate–pentose sugar covalent
bonds. Double-stranded nucleic acids are linked together by hydrogen bonds. Nucleic
acids are information molecules that direct cell metabolism and reproduction.
Nucleotides such as ATP also serve as energy-transfer molecules in cells. As the atom
is the fundamental unit of matter, so is the cell the fundamental unit of life.
The taxonomic system has three primary functions: naming, classifying, and identifying
species. The major groups in the most advanced taxonomic system are (in descending
order): domain, kingdom, phylum or division, class, order, family, genus, and species.
Learning Objectives
1.1 Microbes: Tiny but Mighty
1. List the various types of microorganisms.
1.2 Microbes and the Planet
2. Describe the role and impact of microbes on the earth.
3. Explain the theory of evolution and why it is still called a theory.
1.3 Microbes and Humans
4. Explain the ways that humans manipulate organisms for their own uses.
5. Summarize the relative burden of human disease caused by microbes.
1.4 Microbes in History
6. Make a timeline of the development of microbiology from the 1600s to today.
7. List some recent microbiology discoveries of great impact.
1.5 What Are They Exactly?
8. Differentiate between prokaryotic and eukaryotic microorganisms.
9. Identify a third type of microorganism.
10. Compare and contrast the relative sizes of the different microbes.
1.6 Macromolecules: Superstructures of Life
11. Name the four main families of biochemicals.
12. Provide examples of cell components made from each of the families of
biochemicals.
13. Explain primary, secondary, tertiary, and quaternary structure as seen in proteins.
14. List the three components of nucleic acids.
15. Name the nucleotides of DNA and RNA.
16. List the three components of ATP.
17. Point out three characteristics all cells share.
1.7 Naming, Classifying, and Identifying Microorganisms
18. Differentiate among the terms nomenclature, taxonomy, and classification.
19. Create a mnemonic device for remembering the taxonomic categories.
20. Correctly write the binomial name for a microorganism.
21. Draw a diagram of the three major domains.
22. Explain the difference between traditional and molecular approaches to taxonomy.
Key Terms and Phrases
Emerging diseases
Pathogens
Bioremediation
Genetic engineering
Algae
Macroscopic
Adaptability
Immunology
Epidemiology
Biotechnology
Infectious
Prokaryote
Eukaryote
Parasites
Hosts
Spontaneous generation
Abiogenesis
Biogenesis
Scientific methods
Hypotheses
Ubiquitous
Helminths
Sterilization
Aseptic techniques
Germ theory of disease
Binomial system of
nomenclature
Taxonomy
Taxa
Classification
Identification
Domain
Kingdom
Phylum
Division
Class
Order
Family
Genus
Hierarchies
Species
Scientific names
Evolution
Theory of Evolution
Morphology
Physiology
Genetics
Microbiology
Microscopic
Microorganisms
Microbes
Starch
Macromolecules
Carbohydrate
Hexose
Glycerol
Amino acid
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
Nitrogen base
Pentose sugar
Phosphate
Deoxyribose
Cell
Living
Atom
Molecule
Covalent bond
Ionize
Oxidation
Hydrogen bond
Synthesis reaction
Solution
Hydrated
Acidic
Metabolism
Glycogen
Proton
Compound
Nonpolar
Cation
Reduction
Chemical formula
Decomposition reaction
Solute
Hydrophilic
Basic
Inorganic compounds
Polymerization
Monosaccharide
Pentose
Lipid
Bacteria
Viruses
Fungi
Protozoa
Phospholipid
Peptide
Antibodies
Replication
Genome
Mitosis
Mitochondria
Cytoplasmic membrane
Elements
Biochemical
Neutron
Isotope
Chemical bond
Polar
Anion
Reducing agent
Reactant
Exchange reaction
Solvent
Hydrophobic
pH scale
Organic compounds
Polymer
Disaccharide
Glycosidic bond
Triglyceride
Cholesterol
Polypeptide
Deoxyribonucleic acid
Adenosine triphosphate
Chromosome
Selective permeability
Ions
Hydrogen ion
Cellulose
Hydrolysis
Peptide bond
Enzyme
Nucleotides
Nucleus
Endoplasmic reticulum
Cell wall
Matter
Electron
Orbital
Valence
Ionic bond
Electrolyte
Oxidizing agent
Product
Reversible reaction
Concentration
Neutralization reaction
Functional groups
Polysaccharide
Peptidoglycan
Fatty acid
Protein
Disulfide bond
Ribonucleic acid
Organelles
Ribose
Oxidation-reduction
Chemical equations
Dehydration synthesis
Monomer
Photosynthesis
Recombinant DNA
technology
Topics for Discussion
Did you know?

Life as we know it would not exist without microorganisms!

Plants depend on microorganisms to help obtain nitrogen for survival.

Animals such as goats, cows, and sheep need microorganisms in order to
digest the cellulose in plant-based diets.

All our ecosystems rely on microorganisms to support life which includes
enriching soil and degrading wastes.

Microorganisms play important roles in human lives to make many delicious
foods such as cheese and wine, as well as to develop vaccines and antibiotics.

Besides its role in baking and making alcoholic beverages, the yeast
Saccharomyces cerevisiae is an important tool for scientists in the study of cells.

Some nutrionists and gastroenterologists are examining Saccharomyces
cerevisiae as a probiotic in the treatment of diarrhea and colitis, and other
gastrointestinal diseases.

Viruses are microbes (not cells) that exist at a level of complexity somewhere
between large molecules and cells.

Viruses are highly dependent on a host cell’s machinery for their activities, also
known as obligate intracellular parasites.

A common soil bacterium Acetobacter xylinum can be used for its strong
bacterial cellulose for medical applications such as skin replacement for severe
burn patients, repairing small blood vessels, or use as a dressing impregnated
with antibiotics on wounds.

Some microorganisms live in humans and other animals, and are required to
maintain good health!

In gene therapy, viruses are used to carry replacements for defective or missing
genes into human cells.

Genetically modified bacteria are used in agriculture to protect plants from frost
and insects, as well as to improve the shelf life of produce.

Recombinant DNA techniques have resulted in insertion of the gene for insulin
production into bacteria which can inexpensively produce human insulin.

About 26 elements are commonly found in living cells.

Water is a reactant in many of the decomposition reactions of digestion.

Microorganisms have an ecological importance in maintaining balance in the
environment by recycling chemical elements such as carbon and nitrogen
between the soil and the atmosphere.

The chemistry of microbes is one of the most important concerns of
microbiologists.

Haemophilus influenzae does not cause the flu, but it received its name because
it was once thought to be the cause.

An emerging infectious disease (EID) is a new or changing disease showing an
increase in incidence in the recent past or a potential to increase in the near
future.