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| 209990910 | Antony van Leeuwenhoek (1632-1723) | constructed microscopes and was the first person to observe and describe microorganisms accurately | |
| 209990911 | Francesco Redi (1626-1697) | challenged this concept by showing that maggots on decaying meat came from fly eggs deposited on the meat, and not from the meat itself | |
| 209990912 | John Needham (1713-1781) | showed that mutton broth boiled in flasks and then sealed could still develop microorganisms, which supported the theory of spontaneous generation | |
| 209990913 | Lazzaro Spallanzani (1729-1799) | showed that flasks sealed and then boiled had no growth of microorganisms, and he proposed that air carried germs to the culture medium; he also commented that external air might be needed to support the growth of animals already in the medium; the latter concept was appealing to supporters of spontaneous generation | |
| 209990914 | Louis Pasteur (1822-1895) | trapped airborne organisms in cotton; he also heated the necks of flasks, drawing them out into long curves, sterilized the media, and left the flasks open to the air; no growth was observed because dust particles carrying organisms did not reach the medium, instead they were trapped in the neck of the flask; if the necks were broken, dust would settle and the organisms would grow; in this way Pasteur disproved the theory of spontaneous generation | |
| 209990915 | John Tyndall (1820-1893) | demonstrated that dust did carry microbes and that if dust was absent, the broth remained sterile-even if it was directly exposed to air; Tyndall also provided evidence for the existence of heat-resistant forms of bacteria | |
| 209990916 | Agostino Bassi (1773-1856) | showed that a silkworm disease was caused by a fungus | |
| 209990917 | M. J. Berkeley (ca. 1845) | demonstrated that the Great Potato Blight of Ireland was caused by a fungus | |
| 209990918 | Louis Pasteur (1822-1895) | showed that the péine disease of silkworms was caused by a protozoan parasite | |
| 209990919 | Joseph Lister (1872-1912) | developed a system of surgery designed to prevent microorganisms from entering wounds; his patients had fewer postoperative infections, thereby providing indirect evidence that microorganisms were the causal agents of human disease; his published findings (1867) transformed the practice of surgery | |
| 209990920 | Robert Koch (1843-1910) | established the relationship between Bacillus anthracis and anthrax | |
| 209990921 | Koch's Postulates | 1.) The microorganisms must be present in every case of the disease but absent from healthy individuals 2.) The suspected microorganisms must be isolated and grown in pure culture 3.) The same disease must result when the isolated microorganism is inoculated into a healthy host 4.) The same microorganism must be isolated again from the diseased host | |
| 209990922 | Robert Koch (1843-1910) | developed techniques, reagents, and other materials for culturing bacterial pathogens on solid growth media; these enable microbiologists to isolate microbes in pure culture | |
| 209990923 | Charles Chamberland (1851-1908) | constructed a bacterial filter that removed bacteria and larger microbes from specimens; this led to the discovery of viruses as disease-causing agents | |
| 209990924 | Edward Jenner (ca. 1798) | used a vaccination procedure to protect individuals from smallpox | |
| 209990925 | Louis Pasteur (1822-1895) | developed other vaccines including those for chicken cholera, anthrax, and rabies | |
| 209990926 | Emil von Behring (1854-1917) | and Shibasaburo Kitasato (1852-1931) induced the formation of diphtheria toxin antitoxins in rabbits; the antitoxins were effectively used to treat humans and provided evidence for humoral immunity | |
| 209990927 | Elie Metchnikoff (1845-1916) | demonstrated the existence of phagocytic cells in the blood, thus demonstrating cell-mediated immunity | |
| 209990928 | Louis Pasteur (1822-1895) | demonstrated that alcoholic fermentations were the result of microbial activity, that some organisms could decrease alcohol yield and sour the product, and that some fermentations were aerobic and some anaerobic; he also developed the process of pasteurization to preserve wine during storage | |
| 209990929 | Sergei Winogradsky (1856-1953) | worked with soil bacteria and discovered that they could oxidize iron, sulfur, and ammonia to obtain energy; he also studied anaerobic nitrogen fixation and cellulose decomposition | |
| 209990930 | Martinus Beijerinck (1851-1931) | isolated aerobic nitrogen-fixing bacteria, a root-nodule bacterium capable of fixing nitrogen, and sulfate reducing bacteria | |
| 209990931 | Beijerinck and Winogradsky | pioneered the use of enrichment cultures and selective media | |
| 209990932 | Procaryotes | have a relatively simple morphology and lack a true membrane-delimited nucleus | |
| 209990933 | Eucaryotes | are morphologically complex and have a true, membrane-enclosed nucleus | |
| 209990934 | five kingdoms | the Monera or Procaryotae, Protista, Fungi, Animalia, and Plantae | |
| 209990936 | What kingdoms are Microbiologists' concerned with? | the Monera or Procaryotae, Protista, Fungi and viruses which are not classified with living organisms | |
| 209990937 | three domains | Bacteria, Archaea, and Eucarya | |
| 209990939 | Microorganisms | were the first living organisms on the planet, live everywhere life is possible, are more numerous than any other kind of organism, and probably constitute the largest component of the earth's biomass | |
| 209990941 | The entire ecosystem depends on | the activities of microorganisms | |
| 209990943 | microorganisms influence | human society in countless ways | |
| 209990945 | Microbiology has an impact on many fields including | medicine, agriculture, food science, ecology, genetics, biochemistry, and molecular biology | |
| 209990946 | Microbiologists may be interested in specific types of organisms: | 1) Virologists-viruses 2) Bacteriologists-bacteria 3) Phycologists or Algologists-algae 4) Mycologists-fungi 5) Protozoologists-protozoa | |
| 209990948 | In the future microbiologists will be | 1) Trying to better understand and control existing, emerging, and reemerging infectious diseases 2) Studying the association between infectious agents and chronic diseases 3) Learning more about host defenses and host-pathogen interactions 4) Developing new uses for microbes in industry, agriculture, and environmental control 5) Still discovering the many microbes that have not yet been identified and cultured 6) Trying to better understand how microbes interact and communicate 7) Analyzing and interpreting the ever-increasing amount of data from genome studies 8) Continuing to use microbes as model systems for answering fundamental questions in biology 9) Assessing and communicating the potential impact of new discoveries and technologies on society | |
| 209990950 | Light is refracted (bent) when | passing from one medium to another | |
| 209990952 | Lenses | bend light and focus the image at a specific place known as the focal point | |
| 209990954 | the focal length | is the distance between the center of the lens and the focal point | |
| 209990956 | The bright-field microscope | produces a dark image against a brighter background | |
| 209990957 | Microscope resolution refers to | the ability of a lens to separate or distinguish small objects that are close together; magnification (total) is the product of the magnification of the objective lens and the magnification of the ocular (eyepiece) lens | |
| 209990958 | The major factor determining resolution is | the wavelength of light used | |
| 209990959 | The dark-field microscope | produces a bright image of the object against a dark background and is used to observe living, unstained preparations | |
| 209990960 | The phase-contrast microscope enhances | the contrast between intracellular structures that have slight differences in refractive index and is an excellent way to observe living cells | |
| 209990961 | The differential interference contrast microscope is similar to the phase-contrast microscope except | that two beams of light are used to form brightly colored, three-dimensional images of living, unstained specimens | |
| 209990962 | The fluorescence microscope | exposes a specimen to ultraviolet, violet, or blue light and shows a bright image of the object resulting from the fluorescent light emitted by the specimen | |
| 209990963 | Fixation | refers to the process by which internal and external structures are preserved and fixed in position and by which the organism is killed and firmly attached to the microscope slide | |
| 209990964 | Heat fixing is normally used for what? Why? | this preserves overall morphology but not internal structures | |
| 209990965 | Chemical fixing is used to | protect fine cellular substructure and the morphology of larger, more delicate microorganisms | |
| 209990966 | Dyes and simple staining are used to | make internal and external structures of the cell more visible by increasing the contrast with the background | |
| 209990967 | Differential staining is used to | divide bacteria into separate groups based on their different reactions to an identical staining procedure | |
| 209990968 | Gram staining is the most widely used differential staining procedure because | it divides bacterial species into two roughly equal groups-gram positive and gram negative | |
| 209990969 | How do you do a gram stain? | 1) The smear is first stained with crystal violet, which stains all cells purple 2) Iodine is used as a mordant to increase the interaction between the cells and the dye 3) Ethanol or acetone is used to decolorize; this is the differential step because gram-positive bacteria retain the crystal violet whereas gram-negative bacteria lose the crystal violet and become colorless 4) Safranin is then added as a counterstain to turn the gram-negative bacteria pink while leaving the gram-positive bacteria purple | |
| 209990970 | Acid-fast staining is a | differential staining procedure that can be used to identify two medically important species of bacteria-Mycobacterium tuberculosis, the causative agent of tuberculosis, and Mycobacterium leprae, the causative agent of leprosy | |
| 209990971 | Negative staining is widely used to | visualize diffuse capsules surrounding the bacteria; those capsules are unstained by the procedure and appear colorless against a stained background | |
| 209990972 | Spore staining | is a double staining technique by which bacterial endospores are left one color and the vegetative cell a different color | |
| 209990973 | Flagella staining | is a procedure in which mordants are applied to increase the thickness of flagella to make them easier to see after staining | |
| 209990974 | The electron microscope | focuses beams of electrons to produce an image | |
| 209990975 | In transmission electron microscopy (TEM) | electrons scatter when they pass through thin sections of a specimen; the transmitted electrons (those that do not scatter) are used to produce an image of the internal structures of the organism; TEM has a resolution about 1,000 times better than that of the light microscope (0.5 nm versus 0.2 mm) | |
| 209990976 | Specimen preparation for the electron microscope | involves procedures for cutting thin sections, chemical fixation, and staining with electron-dense materials (analogous to the procedures used for the preparation of specimens for light microscopy); other preparation methods include shadowing or freeze-etching | |
| 209990977 | The scanning electron microscope (SEM) | uses electrons reflected from the surface of a specimen to produce a three-dimensional image of its surface features; many SEM have a resolution of 7 nm or less | |
| 209990978 | The confocal microscope | is often used to examine fluorescently stained specimens | |
| 209990979 | The confocal microscope | 1) It uses a focused laser beam to illuminate just one point on the specimen 2) A detector measures the amount of illumination from each point, creating a digitized signal 3) After examining many points (optical sections), a computer combines all the digitized signals to form a three-dimensional image with excellent contrast and resolution | |
| 209990980 | Scanning Probe Microscopy | 1) The scanning tunneling electron microscope uses a sharp probe to create an accurate three-dimensional image of the surface atoms of a specimen; the resolution is such that individual atoms can be observed 2) The atomic force microscope is similar to the scanning tunneling microscope in that it uses a scanning probe; however, in this microscope the probe maintains a constant distance from the specimen and is useful for surfaces that do not conduct electricity well | |
| 211488481 | cocci | spheres | |
| 211488482 | bacilli | rods | |
| 211488483 | coccobacilli | ovals | |
| 211488484 | vibrios | curved rods | |
| 211488485 | spirilla | rigid helices | |
| 211488486 | spirochetes | flexible helices | |
| 211488487 | tetrads | During the reproductive process, some cells remain attached to each other to form chains, clusters, square planar configurations | |
| 211488488 | sarcinae | During the reproductive process, some cells remain attached to each other to form chains, clusters,cubic configurations | |
| 211488489 | pleomorphic | A few bacteria are flat and some lack a single, characteristic form | |
| 211488490 | Procaryotic cells vary in size although they are generally smaller than most eucaryotic cells; recently, however, | several large prokaryotes have been discovered, which grow as large as 750mm in diameter and can be seen without the aid of a microscope | |
| 211488491 | Procaryotic cells contain a variety of internal structures, although | not all structures are found in every genus | |
| 211488492 | procaryotes are morphologically distinct from eucaryotic cells and | have fewer internal structures | |
| 211488493 | The plasma membrane of bacteria consists of | a phospholipid bilayer with hydrophilic surfaces (interact with water) and a hydrophobic interior (insoluble in water); such asymmetric molecules are said to be amphipathic; most bacterial membranes lack sterols | |
| 211488494 | Many archaeal membranes have a monolayer instead of a | bilayer | |
| 211488495 | he fluid mosaic model | is the most widely accepted model of membrane structure. | |
| 211488496 | peripheral | loosely associated and easily removed | |
| 211488497 | integral | embedded within the membrane and not easily removed | |
| 211488498 | The membrane is | highly organized, asymmetric, flexible, and dynamic | |
| 211488499 | The plasma membrane serves several functions | 1) It retains the cytoplasm and separates the cell from its environment 2) It serves as a selectively permeable barrier, allowing some molecules to pass into or out of the cell while preventing passage of other molecules 3) It is the location of a variety of crucial metabolic processes including respiration, photosynthesis, lipid synthesis, and cell wall synthesis 4) It may contain special receptor molecules that enable detection of and response to chemicals in the surroundings | |
| 211488500 | Mesosomes | are structures formed by invaginations of the plasma membrane that may play a role in cell wall formation during cell division and in chromosome replication and distribution; however, mesosomes may be artifacts generated during chemical fixation for electron microscopy | |
| 211488501 | Photosynthetic bacteria may have complex infoldings of the plasma membrane that increase | the surface area available for photosynthesis | |
| 211488502 | Bacteria with high respiratory activity may also have extensive infoldings that provide | a large surface area for greater metabolic activity | |
| 211488503 | Internal membranes may be aggregates | of spherical vesicles, flattened vesicles, or tubular membranes | |
| 211882601 | The cytoplasmic matrix is | the substance between the membrane and the nucleoid; | |
| 211882602 | The cytoplasmic matrix is | is featureless in electron micrographs but is often packed with ribosomes and inclusion bodies | |
| 211882603 | The cytoplasmic matrix is | although lacking a true cytoskeleton, the cytoplasmic matrix of bacteria does have a cytoskeleton-like system of proteins | |
| 211882604 | Inclusion Bodies | Many are granules of organic or inorganic material that are stockpiled by the cell for future use; some are not bounded by a membrane, but others are enclosed by a single-layered membrane | |
| 211882605 | List two Inclusion Bodies | Gas vacuoles and Magnetosomes | |
| 211882606 | Gas vacuoles | are a type of inclusion body found in cyanobacteria and some other aquatic forms; they provide buoyancy for these organisms and keep them at or near the surface of their aqueous habitat | |
| 211882607 | Magnetosomes | are inclusion bodies that contain iron in the form of magnetite; they are used by some bacteria to orient in the Earthís magnetic field | |
| 211882608 | Ribosomes | are complex structures consisting of protein and RNA and They are responsible for the synthesis of cellular proteins | |
| 211882609 | Procaryotic ribosomes are similar in structure to, but | smaller than, eucaryotic ribosomes | |
| 211882610 | The nucleoid is an | irregularly shaped region in which the chromosome of the procaryote is found | |
| 211882611 | In most procaryotes, the nucleoid contains a | a single circular chromosome, though some have more than one chromosome or have one or more linear chromosomes | |
| 211882612 | The nucleoid is not bounded by a membrane, but it is sometimes found to be associated with | the plasma membrane or with mesosomes | |
| 211882613 | The bacterial chromosome | an efficiently packed DNA molecule that is looped and coiled extensively | |
| 211882614 | In addition to the chromosome, many bacteria contain | plasmids | |
| 211882615 | plasmids | are usually small, closed circular DNA molecules | |
| 211882616 | plasmids | They can exist and replicate independently of the bacterial chromosome They are not required for bacterial growth and reproduction, but they may carry genes that give the bacterium a selective advantage (e.g., drug resistance, enhanced metabolic activities, etc.) | |
| 211882617 | The cell wall is a | rigid structure that lies just outside the plasma membrane; it provides the characteristic shapes of the various procaryotes and protects them from osmotic lysis | |
| 211882618 | The cell walls of most bacteria contain | peptidoglycan | |
| 211882619 | the cell walls of archaea lack peptidoglycan and instead are composed of proteins | glycoptoteins, or polysaccharides | |
| 211882620 | The cell walls of gram-positive bacteria and gram-negative bacteria differ greatly, but both have | periplasmic space | |
| 211882621 | periplasmic space | usually contains a variety of proteins | |
| 211882622 | The protiens in the periplasmic space | these proteins can be involved in nutrient acquisition, electron transport, peptidoglycan synthesis or in modification of toxic compounds | |
| 211882623 | Peptidoglycan (murein) | is a polysaccharide polymer found in bacterial cell walls; it consists of polysaccharide chains cross-linked by peptide bridges | |
| 211882624 | Gram-positive cell walls-consist of | a thick layer of peptidoglycan and large amounts of teichoic acids | |
| 211882625 | Gram-negative cell walls | They consist of a thin layer of peptidoglycan surrounded by an outer membrane composed of lipids, lipoproteins, and a large molecule known as lipopolysaccharide (LPS). LPS can play a protective role and can also act as an endotoxin, causing some of the symptoms characteristic of gram-negative bacterial infections; there are no teichoic acids in gram-negative cell walls. The outer membrane is more permeable than the plasma membrane because of porin proteins that form channels through which small molecules (600-700 daltons) can pass | |
| 211882626 | The mechanism of Gram staining-involves | constricting the thick peptidoglycan layer of gram-positive cells, thereby preventing the loss of the crystal violet stain during the brief decolorization step; the thinner, less cross-linked peptidoglycan layer of gram-negative bacteria cannot retain the stain as well, and these bacteria are thus more readily decolorized when treated with alcohol | |
| 211882627 | The cell wall and osmotic protection-the cell wall prevents | swelling and lysis of bacteria in hypotonic solutions | |
| 211882628 | in hypertonic habitats, the plasma membrane | shrinks away from the cell wall | |
| 211882629 | plasmolysis | the plasma membrane shrinks away from the cell wall | |
| 211882630 | glycocalyx | are layers of polysaccharides lying outside the cell wall ie:Capsules and slime layers | |
| 211882631 | Capsules and slime layers (also known as glycocalyx protect and aid in what way | the bacteria from phagocytosis, desiccation, viral infection, and hydrophobic toxic materials such as detergents; they also aid bacterial attachment to surfaces and gliding motility | |
| 211882632 | Capsules | are well organized b. Slime layers are diffuse and unorganized | |
| 211882633 | Slime layers | are diffuse and unorganized | |
| 211882634 | S layers | are regularly structured layers of protein or glycoprotein observed in both bacteria and archaea, where it may be the only structure outside the plasma membrane | |
| 211882635 | S layers protect against | ion and pH fluctuations, osmotic stress, hydrolytic enzymes, or the predacious bacterium Bdellovibrio | |
| 211882636 | Pili and fimbria | are short, thin, hairlike appendages that mediate bacterial attachment to surfaces (fimbriae) or to other bacteria during sexual mating (pili) | |
| 211882637 | Flagella | are threadlike locomotor appendages extending outward from the plasma membrane and cell wall | |
| 211882638 | Monotrichous | a single flagellum | |
| 211882639 | Amphitrichous | a single flagellum at each pole | |
| 211882640 | Lophotrichous | a cluster (tuft) of flagella at one or both ends | |
| 211882641 | Peritrichous | a relatively even distribution of flagella over the entire surface of the bacterium | |
| 211882642 | The flagellum consists of | a hollow filament composed of a single protein known as flagellin. The hook is a short curved segment that links the filament to the basal body, a series of rings that drives flagellar rotation. | |
| 211882643 | Flagellar synthesis involves | many genes for the hook and basal body, as well as the gene for flagellin. New molecules of flagellin are transported through the hollow filament so that the growth of the flagellum is from the tip, not from the base. | |
| 211882644 | The mechanism of flagellar movement | appears to be rotation; the hook and helical structure of the flagellum causes the flagellum to act as a propeller, thus driving the bacterium through its watery environment Counterclockwise rotation causes forward motion | |
| 211882645 | spirochetes | axial filaments cause movement by flexing and spinning | |
| 211882646 | gliding motility | a mechanism by which they coast along solid surfaces; no visible structure is associated with gliding motility | |
| 211882647 | run | Counterclockwise rotation causes forward motion | |
| 211882648 | tumble | Clockwise rotation disrupts forward motion | |
| 211882649 | Chemotaxis | is directed movement of bacteria either towards a chemical attractant or away from a chemical repellent | |
| 211882650 | The concentrations of these attractants and repellents are detected by | chemoreceptors in the surfaces of the bacteria | |
| 211882651 | Directional travel toward a chemoattractant (biased random walk toward attractant) is caused by | lowering the frequency of tumbles (twiddles), thereby lengthening the runs when traveling up the gradient, but allowing tumbling to occur at normal frequency when traveling down the gradient | |
| 211882652 | The mechanism of control of tumbles and runs is complex, involving numerous proteins and several mechanisms (conformation changes, methylation, and phosphorylation) to modulate their activity | despite this complexity chemotaxis is fast, with responses occurring in as little as 200 meters/second | |
| 211882653 | The bacterial endospore | is a special, resistant, dormant structure formed by some bacteria, which enables them to resist harsh environmental conditions | |
| 211882654 | Endospore formation (sporulation) | normally commences when growth ceases because of lack of nutrients; it is a complex, multistage process | |
| 211882655 | Transformation of dormant endospores into active vegetative cells is also a complex, multistage process that includes | activation (preparation) of the endospore, germination (breaking of the endosporeís dormant state), and outgrowth (emergence of the new vegetative cell) |
