Chapter 1: Microorganisms and Microbiology Flashcards
Microbiology revolves around two themes:
- Understanding basic life processes
• Microbes are excellent models for understanding cellular processes in
unicellular and multicellular organisms - Applying that knowledge to the benefit of humans
• Microbes play important roles in medicine, agriculture, and industry
The Importance of Microorganisms
• 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
What is a cell
A dynamic entity that forms the fundamental unit
of life
Cytoplasmic (cell) membrane
Barrier that separates the inside of the cell from the
outside environment
Cell wall
Present in most microbes, confers structural strength
Characteristics of Living Systems
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
Properties of all cells
Compartmentalization and metabolism
Growth
Evolution
Properties of some cells
Motility
Differentiation
Communication
Enzymes:
protein catalysts of the cell
that accelerate chemical reactions
Transcription:
DNA produces RNA
Translation:
RNA makes protein
Growth
The link between cells as machines and
cells as coding devices
microbial
communities
microorganisms exist in nature in populations of
interacting assemblages
habitat
the environment in which a microbial population
lives
refers to all living organisms plus
physical and chemical constituents of their
environment
ecosystem
the study of microbes in
their natural environment
microbial ecology
true or false
Diversity and abundances of microbes are controlled by resources
(nutrients) and environmental conditions (e.g., temp, pH, O2)
Microbes also interact with their physical and chemical environment
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
Last universal common ancestor (LUCA)
common ancestral
cell from which all cells descended
Evolution and the Extent of
Microbial Life
• 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
true or false
most microbial cells are found in oceanic and terrestrial subsurfaces
Many aspects of agriculture depend
on microbial activities (positive and negative impacts)
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
Microorganisms and Food (positive and negative impacts)
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)
Bioremediation
Microbes cleaning up pollutants
Microorganisms and Their Genetic Resources
• 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)
Robert Hooke (1635-1703)
first to describe microscope
Antoni van Leeuwenhoek (1632–1723)
The first to describe bacteria
• Further progress required development of
more powerful microscopes
Ferdinand Cohn (1828–1898)
founded the
field of bacterial classification and
discovered bacterial endospores
Louis Pasteur (1822–1895)
• 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
Robert Koch (1843–1910)
• 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
Koch’s Postulates
- The suspected pathogen must be present in all cases of the disease and absent from healthy animals
- The suspected pathogen must be grown in pure culture
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
- The suspected pathogen must be reisolated and shown to be the same as the original
Koch and the Rise of Pure Cultures
• 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
Microbial Diversity
• Field that focuses on nonmedical aspects of
microbiology
• Roots in 20th century
Martinus Beijerinck (1851–1931)
• Developed enrichment culture technique
• Microbes isolated from natural samples in a highly
selective fashion by manipulating nutrient and incubation
conditions (Example: nitrogen-fixing bacteria)
Sergei Winogradsky (1856–1953) and the Concept of Chemolithotrophy
• Demonstrated that specific bacteria are linked to specific biogeochemical
transformations (e.g., S & N cycles)
• Proposed concept of chemolithotrophy
chemolithotrophy
oxidation of inorganic compounds linked to energy conservation
In the 20th century, microbiology developed in
two distinct directions
Applied and basic
Molecular microbiology
Fueled by the genomics revolution
Major Subdisciplines of Applied Microbiology
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
Basic Science Subdisciplines in Microbiology
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
Basic Science Subdisciplines in Microbiology
Microbial biochemistry
• Study of microbial enzymes and chemical reactions
Bacterial genetics
• Study of heredity and variation in bacteria
Virology
• Study of viruses
Molecular Microbiology
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
