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Summary Micro-organisms, diversity, nutrition and culturing
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Test Bank For Brock Biology of Microorganisms 15th Edition By Michael T. Madigan 2024 A+
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Test Bank for Brock Biology of Microorganisms, 15th Edition by Madigan, 9781292235103, Covering Chapters 1-33 | Includes Rationales
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HC4 Micro-organisms, diversity,Nutrition and Culturing (BOOK)
Chapter 1.1 – 1.5, 1.9 – 1.14 and 5.5 – 5.9
CH1 Exploring the Microbial World
1.1 Microorganims, Tiny Titans of the earth
Microorganisms, also called microbes typically live in complex microbial communities.
A microbial culture is a collection of cells that have been grown on a nutrient medium. A nutrient
medium is a liquid or solid nutrient mixture that contains all of the nutrients required for a
microorganism to grow. Growth refers to the increase in cell number as a result of cell division.
1.2 Structure and Acitivities of Microbial Cells
All cells have a cytoplasmic membrane that separates the cytoplasm from the outside.
Some cells do also have a cell wall that lends structural strength (plant and most microbes).
There are two major structural classes of cells:
- Prokaryotic (bacteria, archaea) – lack a nucleus and organelles
- Eukaryotic (animals, plants) – contain organelles
All cells contain a cytoplasmic membrane, ribosomes and DNA genome. However, the genome of
eukaryotic cells and prokaryotic cells are organised differently. In eukaryotes genome is present in
the nucleus and in prokaryotes the genomes are typically closed circular chromosomes —>
aggregate to form a nucleoid.
Most prokaryotic cells have only a singe chromosome, but many also contain plasmids that form
DNA distinct from that of the chromosomes.
Properties of microbial cells
, 1.3 Microorganisms and the Biosphere
Earth is about 4.6 billion years old, microbial cells first appeared between 3.8 and 4.3 billion years
ago. During the first 2 billion years of Earth’s existence its atmosphere was anoxic and only N2, CO2
and a few other gases were present.
Phototrophic organisms occurred within 1 billion years of the formation of the Earth, and the first
were anoxygenic (do not produce oxygen), and only 1 billion years after that oxygenic phototrophs
occurred.
As evolutionary events unfolded, three major lineages (domains) of microbes were distinguished:
- Bacteria
- Archaea
- Eukarya
All three domains have descended from a common ancestor, the last universal common ancestor
(LUCA).
1.4 The Impact of Microorganisms on Human Society
Agriculture benefits from the cycling of key plant nutrients by microorganisms.
The human GI lacks a rumen, but complex carbohydrates are digested by the gut microbiome.
Microbes often grow on submerged surfaces, forming biofilms.
In industrial microbiology, microorganisms are grown on a massive scale to make large amount of
products at relatively low costs. By contrast, biotechnology employs genetically engineered
microorganisms to synthesizer products of high value, usually on small scale.
In bioremediation microorganisms are used to transform environmentally toxic pollutants and
speeding op the cleanup process.
1.5 Light Microscopy and the Discovery of Microorganisms
Magnification describes the capacity of a microscope to enlarge an image. Resolution is the ability to
distinguish two adjacent objects as distinct and separate.
In light microscopy, specimens are visualised because of differences in contrast that exits between
them and their surroundings.
1.9 Pasteur and Spontaneous Generation
One of the thing that Pasteur discovered was that chemical identical substances can have optical
isomers, which have different molecular structures that can influence their properties. Another thing
is that he discovered that some processes depend on microorganisms (such as making alcohol).
The concept of sponteneous generation is the assumption that life arises spontaneously from non
living materials.
1.10 Koch, Infectious Diseases, and Pure Cultures
Koch formulated a set of rigorous criteria, Koch’s postulates:
1. The suspected pathogen must be present in all cases of the disease and absent from health
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
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