Chapter 1: Microorganisms and Microbiology

Question 1

Microbiology revolves around two themes:

Answer 1

1. Understanding basic life processes
   • Microbes are excellent models for understanding cellular processes in
   unicellular and multicellular organisms
2. Applying that knowledge to the benefit of humans
   • Microbes play important roles in medicine, agriculture, and industry

Question 2

The Importance of Microorganisms

Answer 2

• Oldest form of life
• Largest mass of living material on Earth
• Carry out major processes for biogeochemical cycles
• Can live in places unsuitable for other organisms
• Other life forms require microbes to survive

Question 3

What is a cell

Answer 3

A dynamic entity that forms the fundamental unit
of life

Question 4

Cytoplasmic (cell) membrane

Answer 4

Barrier that separates the inside of the cell from the
outside environment

Question 5

Cell wall

Answer 5

Present in most microbes, confers structural strength

Question 6

Characteristics of Living Systems

Answer 6

Metabolism: chemical transformation of nutrients
Reproduction: generation of two cells from one
Differentiation: synthesis of new substances or structures that
modify the cell (only in some microbes)
Communication: generation of, and response to, chemical signals
(only in some microbes)
Movement: via self-propulsion, many forms in microbes (only in
some microbes)
Evolution: genetic changes in cells that are transferred to offspring

Question 7

Properties of all cells

Answer 7

Compartmentalization and metabolism
Growth
Evolution

Question 8

Properties of some cells

Answer 8

Motility
Differentiation
Communication

Question 9

Enzymes:

Answer 9

protein catalysts of the cell
that accelerate chemical reactions

Question 10

Transcription:

Answer 10

DNA produces RNA

Question 11

Translation:

Answer 11

RNA makes protein

Question 12

Growth

Answer 12

The link between cells as machines and
cells as coding devices

Question 13

microbial
communities

Answer 13

microorganisms exist in nature in populations of
interacting assemblages

Question 14

habitat

Answer 14

the environment in which a microbial population
lives

Question 15

refers to all living organisms plus
physical and chemical constituents of their
environment

Answer 15

ecosystem

Question 16

the study of microbes in
their natural environment

Answer 16

microbial ecology

Question 17

true or false

Answer 17

Diversity and abundances of microbes are controlled by resources
(nutrients) and environmental conditions (e.g., temp, pH, O2)

Question 18

Microbes also interact with their physical and chemical environment

Answer 18

Ecosystems greatly influenced (if not controlled) by microbial activities
• Microorganisms change the chemical and physical properties of their
habitats through their activities
• For example, removal of nutrients from the environment and the excretion of waste
products

Question 19

Last universal common ancestor (LUCA)

Answer 19

common ancestral
cell from which all cells descended

Question 20

Evolution and the Extent of
Microbial Life

Answer 20

• Earth is 4.6 billion years old
• First cells appeared between 3.8 and 3.9 billion
years ago
• The atmosphere was anoxic until ~2 billion years
ago
• Metabolisms were exclusively anaerobic until evolution of oxygen-producing phototrophs
(Cyanobacteria)
• Life was exclusively microbial until ~1 billion years ago

Question 21

true or false

Answer 21

most microbial cells are found in oceanic and terrestrial subsurfaces

Question 22

Many aspects of agriculture depend
on microbial activities (positive and negative impacts)

Answer 22

Positive impacts
•nitrogen-fixing bacteria
• cellulose-degrading microbes in
the rumen
• regeneration of nutrients in soil
and water
Negative impacts
• diseases in plants and animals

Question 23

Microorganisms and Food (positive and negative impacts)

Answer 23

Negative impacts
• Food spoilage by microorganisms requires specialized preservation of many foods
Positive impacts
• Microbial transformations (typically fermentations) yield
• dairy products (e.g., cheeses, yogurt, buttermilk)
• other food products (e.g., sauerkraut, pickles, leavened breads, beer)

Question 24

Bioremediation

Answer 24

Microbes cleaning up pollutants

Question 25

Microorganisms and Their Genetic Resources

Answer 25

• Exploitation of microbes for production of antibiotics, enzymes,
and various chemicals
• Genetic engineering of microbes to generate products of value to
humans, such as insulin (biotechnology)

Question 26

Robert Hooke (1635-1703)

Answer 26

first to describe microscope

Question 27

Antoni van Leeuwenhoek (1632–1723)

Answer 27

The first to describe bacteria
• Further progress required development of
more powerful microscopes

Question 28

Ferdinand Cohn (1828–1898)

Answer 28

founded the
field of bacterial classification and
discovered bacterial endospores

Question 29

Louis Pasteur (1822–1895)

Answer 29

• Discovered that living organisms discriminate between optical
isomers
• Discovered that alcoholic fermentation was a biologically
mediated process (originally thought to be purely chemical)
• Disproved theory of spontaneous generation (Figure 1.16)
• Led to the development of methods for controlling the growth of
microorganisms (aseptic technique)
• Developed vaccines for anthrax, fowl cholera, and rabies

Question 30

Robert Koch (1843–1910)

Answer 30

• Demonstrated the link between
microbes and infectious diseases
• Identified causative agents of
anthrax and tuberculosis
• Koch’s postulates (Figure 1.19)
• Developed techniques (solid
media) for obtaining pure
cultures of microbes, some still in
existence today
• Awarded Nobel Prize for
Physiology and Medicine in 1905

Question 31

Koch’s Postulates

Answer 31

1. The suspected pathogen must be present in all cases of the disease and absent from healthy animals
2. The suspected pathogen must be grown in pure culture
3. Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
4. The suspected pathogen must be reisolated and shown to be the same as the original

Question 32

Koch and the Rise of Pure Cultures

Answer 32

• Discovered that using solid media provided a simple way of
obtaining pure cultures
• Began with potato slices, but eventually devised uniform and
reproducible nutrient solutions solidified with gelatin and agar

Question 33

Microbial Diversity

Answer 33

• Field that focuses on nonmedical aspects of
microbiology
• Roots in 20th century

Question 34

Martinus Beijerinck (1851–1931)

Answer 34

• Developed enrichment culture technique
• Microbes isolated from natural samples in a highly
selective fashion by manipulating nutrient and incubation
conditions (Example: nitrogen-fixing bacteria)

Question 35

Sergei Winogradsky (1856–1953) and the Concept of Chemolithotrophy

Answer 35

• Demonstrated that specific bacteria are linked to specific biogeochemical
transformations (e.g., S & N cycles)
• Proposed concept of chemolithotrophy

Question 36

chemolithotrophy

Answer 36

oxidation of inorganic compounds linked to energy conservation

Question 37

In the 20th century, microbiology developed in
two distinct directions

Answer 37

Applied and basic

Question 38

Molecular microbiology

Answer 38

Fueled by the genomics revolution

Question 39

Major Subdisciplines of Applied Microbiology

Answer 39

Medical microbiology and immunology
• Have roots in Koch’s work
Agricultural microbiology and industrial microbiology
• Developed from concepts developed by Beijerinck and Winogradsky
Aquatic microbiology and marine microbiology
• Developed from advances in soil microbiology
Microbial ecology
• Emerged in 1960s–70s

Question 40

Basic Science Subdisciplines in Microbiology

Answer 40

Microbial systematics
• The science of grouping and classifying microorganisms
Microbial physiology
• Study of the nutrients that microbes require for metabolism and growth
and the products that they generate
Cytology
• Study of cellular structure

Question 41

Basic Science Subdisciplines in Microbiology

Answer 41

Microbial biochemistry
• Study of microbial enzymes and chemical reactions
Bacterial genetics
• Study of heredity and variation in bacteria
Virology
• Study of viruses

Question 42

Molecular Microbiology

Answer 42

Biotechnology
• Manipulation of cellular genomes
• DNA from one organism can be inserted into a bacterium and the
proteins encoded by that DNA harvested
Genomics: study of all of the genetic material
(DNA) in living cells
• Transcriptomics: study of RNA patterns
• Proteomics: study of all the proteins produced by cell(s)
• Metabolomics: study of metabolic expression in cells