Flashcards in Chapter 1: The Microbial World Deck (133):
the total compliment of microbial cells in and on your body
life forms too small to be seen by the human eye
where microorganisms typically live
a collection of cells that have been grown in or on a nutrient medium
liquid or solid nutrient mixture that contains all of the nutrients required for a microorganism to grow
increase in cell number as a result of cell division
a visible colony happens after....
a single microbial cell is place on a solid nutrient medium that grows and divides.
the cells permeability barrier
aqueous mixture of macromolecules ( proteins, lipids, nucleic acids, polysaccharides), small organic molecules, various inorganic ions, and ribosomes.
structures responsible for protein synthesis in all cells
some cells have a ____ _____ that lends structural strength for the cell
T/F plant cells and most microorganisms have cell walls, whereas animal cells typically do not
what are the two major structural classes of cells:
eukaryotic cells are found in the _______ domain ______.
(includes plants and animals as well as diverse microbial eukaryotes such as algae, protozoa, and fungi.)
membrane enclosed cytoplasmic structures are called:
prokaryotic cells are found in the domains ____ and _____
How are prokaryotic cells different than eukaryotic cells?
They are much simpler and have few internal structures.
- contain plasmids
- have no nucleus
-typically lack organelles
what is the genome?
the complement of all genes in a cell.
the living blueprint of an organism; the characteristics, activities and very survival of a cell are governed by its genome.
what is a gene?
a segment of DNA that encodes a protein or an RNA molecule.
How do the genomes differ in prokaryotic cells vs eukaryotic cells?
Prokaryotic cells: the genomes are typically closed circular chromosomes (some prokaryotes have linear genomes), within the nucleoid.
Eukaryotic cells: the DNA is situated as several linear molecules within the membrane enclosed nucleus.
a mass visible with a microscope in prokaryote cells is referred to as the
t/f most prokaryotic cells only have a single chromosome but many also contain one of more small circles of DNA distinct from that of the chromosome
what is a plasmid?
small circles of DNA in prokaryotic cells that is distinct from the chromosome.
fun fact: plasmids typically contain genes that are not essential and confer some special property on the cell (unique metabolism or antibiotic resistance of some kind)
proteins that have catalytic activity
when are enzymes and other proteins synthesized?
during gene expression in the sequential process of transcription and translation
all cells show some form of ________ by taking up nutrients from the environment and transforming them into new cell materials and waste products.
What is transcription?
the process by which the information on DNA is copied into an RNA molecule.
What is translation?
the process whereby the information on an RNA molecule is used by a ribosome to synthesize a protein.
microbial growth requires replication through the process of ____ _________.
self-propulsion is another word for
some cells undergo the process of differentiation which results in:
the formation of modified cells specialized for growth, dispersal, or survival.
All cells have these 3 properties:
-metabolism (catalytic & genetic)
Only some cells have these 4 different properties:
the ability for cells to be "aware" of their neighbors and act accordingly:
the process of horizontal gene transfer occurs when
some prokaryotic cells exchange genes with neighboring cells, either of the same or a different species.
the term used what genes in a population of cells change in sequence and frequency over time, leading to descent with modification
t/f microorganisms evolve very very slowly compared to the evolution of plants and animals.
false, they evolve much quicker than plants and animals
History of earth and microbial cells:
-Earth is 4.6 billion years old
-first microbial cells appeared between 3.8 and 4.3 billion years ago
-1st 2 billion years of earth's existence was anoxic.
- anaerobic phototrophic microorganisms evolved
- cyanobacteria (aerobic phototrophs) evolved
- after oxygenation of earth, multicellular life forms began to exist
-plants and animals have only existed for about half a billion years.
where did early phototrophs live? do these structures still exist today?
microbial mats; yes
t/f 80% of lifes history was exclusively microbial
t/f all known cellular organisms belong to 1/3 major domains. What are these domains?
bacteria, archaea, and the eukarya
fun fact: approximately 60 genes are universally present in cells of all 3 major domains
all three domains have descended from what?
the last universal common ancestor (LUCA)
what is the estimated about of microbial cells on earth?
2 x 10^30
what are extremophiles?
microbes that are abundant in habitats that are much too harsh for other forms of life.
name 3 examples of places extremophiles live:
-volcanic hot springs
-high salt environments
-areas of extreme pressure
the consideration of the ways in which microorganisms affect animals, plants and the entire global ecosystem:
at the beginning of the 20th century, the major cause of death was:
the extremophile that can live in high heat is termed:
the extremophile that can live in very cold temperatures is termed:
the extremophile that can survive at an extremely low pH:
the extremophile that can survive at an extremely high pH:
the extremophile that can survive at extremely high pressure is:
the extremophile that lives in salt is called
what are some examples of foods that are improved and aided by microbes?
microbes help agriculture how?
how do microbes aid in human nutrition?
being present in the gut microbiome to help aid in digestion of complex carbohydrates and synthesize vitamins and other nutrients that are essential to host nutrition.
what are microbes that grow on submerged surfaces called?
where can biofilms be found?
-factories and pipelines
-implanted medical devices
How does industrial microbiology produce valuable products?
Naturally occurring microorganisms are grown on a massive scale to make thins such as antibiotics, enzymes, and chemicals at low cost in mass amounts.
How does biotechnology produce valuable products?
Biotechnology employs genetically engineered microorganisms to make products of high value such as insulin, human proteins etc. (low scale)
What is a biofuel?
a microorganism engineered fuel. Examples include:
- methane (CH4)
-Ethyl Alcohol (ethanol)
t/f microorganisms can convert waste material, such as animal wastes, cellulose and domestic refuse into biofuels
In what other ways can microorganisms be beneficial?
-wastewater treatment: battling cholera and typhoid
-bioremediation: process of cleaning up industrial pollution
Who was the inventor of the microscope and the first person to see bacteria?
Antoni van Leeuwenhoek
What type of microscope did Leeuwenhoek invent?
light microscope with a simple lens that could magnify an image at least 266x
what term describes the capacity of a microscope to enlarge and image?
what term refers to the ability to distinguish two adjacent objects as distinct and separate?
What governs our ability to see the very small?
what is the limit of resolution for a light microscope?
about .2 micrometers.
this means that two objects that are closer together than .2 micrometers cannot be resolves as distinct and separate.
what are the 5 types of light microscopy?
-differential interference contrast
fun fact: with the modern compound light microscope, light from a light source is focused on the specimen by the condenser, this light passes through the sample and is collected by the lenses
what are the two types of lenses and what are their magnifications?
-ocular: magnifies 10-30x
-objective: magnify 10-100x
what is the total magnification of a microscope?
the producct of the magnification of its objective and ocular lenses.
fun fact: 1000x is required to resolve objects .2 micrometers in diameter. this is the limit. magnification beyond this provides little improvement
lenses on which oil is used are called ___ _______ _____
oil immersion lenses
Immersion lenses work by ____
increasing the light gathering ability of a lens, which means it increases the amount of light that is collected and viewed by the lens.
specimen are visualized because of differences in _____ that exist between them and their surroundings
How does contrast result in bright-field microscopy?
contrast results when cells absorb or scatter light differently from their surroundings.
Why are bacterial cells difficult to see in bright-field microscopy?
because bacterial cells typically lack contrast, that is, their optical properties are similar to the surrounding medium, which makes them difficult to see with this microscope.
How do we increase the contrast when viewing bacteria with a bright-field microscope?
What is a basic dye?
Positively charge dyes.
what are three examples of basic dyes?
How do basic dyes work?
-by binding strongly to negatively charged cell components such as nucleic acids and acidic polysaccharides.
- these dyes also stain the surfaces of cells because cell surfaces are typically negatively charged
what is the procedure for staining cells for observation?
1. Preparing a smear:
- spread culture in thin film over slide
- dry in air
2. Heat fixing and staining
-pass slide through flame to heat fix
-flood slide with stain; rinse and dry
-place drop of oil on slide; examine with 100x objective lens
what are differential stains?
stains that render different kinds of cells different colors.
what are the two major groups bacteria can be divided into based on their reaction to gram staining?
what color do gram positive bacteria appear after staining?
what color do gram negative bacteria appear after staining?
why do color differences occur in gram positive/negative bacteria after staining?
because of differences in the cell wall structure of the different types of bacteria
what is the procedure for gram staining?
1. flood heat fixed smear with crystal violet
3. add alcohol to remove color from gram negative cells.
4. add safranin to make gram negative cells red
why is ethanol used in gram staining?
to decolorize gram negative cells but not gram positive cells
how can the gram stain be reduced to a one step procedure?
fluorescent microscopy because gram positive and gram negative cells can fluoresce different colors when treated with a special chemical
what is a common drawback with staining in light microscopy?
it often kills cells and can distort their features
what are the two forms of light microscopy that improve contrast without staining?
which microscope in particular is widely used for the observation of living samples?
what is the purpose of the phase ring in phase-contrast microscopy
the phase ring amplifies the contrast resulting in a dark image on a light background
what does the phase ring consist of?
a phase plate that amplifies the variation in phase to produce the higher-contrast image
instead of light passing through the specimen, what occurs during dark-field microscopy?
light is directed from the sides of the specimen and only light that is scattered when it hits the specimen can reach the lens
how does the specimen appear in dark-field microscopy?
light on a dark background
what microorganisms is the dark-field microscope very good at viewing?
motile microbes such as flagella
the fluorescence microscope visualizes specimens that ________
t/f all cells viewed in fluorescence microscopy must be naturally fluorescent
false, they can be made to fluoresce artificially through using DAPI.
what is DAPI? how is it used?
a fluorescent dye that stains cells bright blue. it can be used to visualize cells in their natural habitats and is used widely in ecology
name the 2 methods of light microscopy that produce 3d images:
-differential interference contrast microscopy
-confocal scanning laser microscopy
fun fact: DIC is especially helpful in viewing eukaryotic structures such as the nucleus, or endospores and vacuoles.
fun fact: Confocal scanning laser microscopy involves the microscopes laser scanning up and down through the lasers of each sample and using a computer to generate a 3d image of the sample
what do electron microscopes use that differs from the visible light in light microscopes?
what is a photograph taken by an electron microscope called?
what two types of electron microscopy are in routine use in microbiology?
-transmission electron microscopy
- scanning electron microscopy
describe the pros and cons of the transmission electron microscope:
-very powerful resolution
-must use thin slides
-can view things at the molecular level
describe the pros and cons for scanning electron microscopy:
-fairly large specimens can be observed
-typically only the surface is visualized
-produced in black and white imagery
what is the technique that refers to a collection of practices that allow for the preparation and maintenance of sterile?
what are pure cultures?
those that contain cells from only a single type of microorganism and are of great value for the study of microorganisms
what are enrichment culture techniques?
techniques which allow for the isolation from nature of microbes having particular metabolic characteristics.
why are enrichment culture techniques important?
they facilitate the discovery of diverse microorganisms
what did Louis Pasteur discover about optical isomers?
microorganisms could distinguish between these optical isomers which were in the crystals he was studying that had different molecular structures that influenced their properties
optical isomers led louis pasteur to what discovery?
many reactions thought to be chemical were actually catalyzed by specific microoorganisms
what is the term for the idea that life arose spontaneously from nonliving materials?
what was the purpose of Pasteur's swan necked flask?
it could let fresh air into the reaction but prevent microorganisms from getting in and putrefying.
who introduced aseptic techniques for surgeries?
which diseased did pasteur develop vaccines for?
pasteur also helped to solidify what theory?
the germ theory of disease
how did pasteur's discoveries aid the food industry?
his principles were adapted in milk production where they heat it to preserve it. this is called pasteurization
who instituted handwashing?
what did Koch's postulates demonstrate?
the cause and effect in an infectious disease
what are koch's 4 postulates?
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 re-isolated and shown to be the same as the original.
what other accomplishments did Robert Koch have?
-discovered and proved the cause of tuberculosis
-found the cause of cholera
-developed methods to diagnose infection of tb. (tuberculin skin test)
what contribution did Martinus Beijerinck make to microbiology?
-developed the enrichment culture technique
-described the first virus and the basic principles of virology
what contribution did sergei winogradsky make to microbiology?
-proposed the concept of chemolithotrophy
-was the first to demonstrate nitrogen fixation
what is meant by the term chemolithotrophy?
this is the oxidation of inorganic compounds to yield energy