Chapter 1-5 Microbiology Study Guide Questions and Answers

Chapter 1-5 Microbiology Study Guide Questions and Answers In what ways are microorganisms important to humans? The oxygen we breathe is the result of microbial activities, as well as the water we drink, the health of our animals, etc. What is a bacterial colony and how is it formed? A macroscopically visible population of cells that is formed from a single cell that has divided many times. How can you get a pure culture of bacteria and why are pure cultures important? Pure cultures usually come from mixed cultures and are very important because they can be used for experiments that probe the fundamental processes of life. Where do you find microorganisms and do they typically live in a pure culture? Microorganisms are found everywhere. Pure cultures are usually set up to perform experiments. What cellular structures distinguish prokaryotic and eukaryotic cells? -Eukaryotic cells contain organelles, which includes, most prominently, the DNA-containing nucleus and also mitochondria and chloroplasts. -Prokaryotic cells have few internal structures, they lack a nucleus, and they typically lack organelles. What are some differences between a cell wall and a cell membrane? Cell walls are relatively permeable and much stronger than the cell membrane. In what types of organisms would you expect to find cell walls and or cell membranes? Cell walls are typically found in plant cells and most microorganisms but are not found in animal cells. Cell membranes can be found in all cells. How has the Earth changed over its history? How have microorganisms contributed to these changes? 80% of life's history was exclusively microbial; Cyanobacteria provided the greatest changes because they produced oxygen Name the three domains of life. Which of these contain eukaryotic life forms? How are they similar and different? The three domains of life are Eukarya, Bacteria, and Archaea. Eukarya and Archaea are more similar to each other than either is to Bacteria despite Eukarya appearing long after. Why were cyanobacteria so important in the evolution of life on Earth? Cyanobacteria are so important to the evolution of life on earth because they are responsible for oxygenating the earth. What is a genus name of a cyanobacterium and what is unique about these organisms? How do microbes contribute to the nutrition of animals such as humans and cows? They allow for the digestion of cellulose through fermentation in ruminant animals. Humans rely on gut microbiomes to break down complex carbohydrates. Describe several ways in which microorganisms are important in the food and agricultural industries. Although some microbes contribute to the spoilage of food and foodborne diseases, some are important for the preservation, safety, or even development of certain foods. What is wastewater treatment and why is it important? It is the treatment of water contaminated with human waste by using microbes so it can be safely reused or returned to the environment. It is essential to sanitization and human health. What is the difference between magnification and resolution? Magnification is the capacity of a microscope to enlarge an image. Resolution is the ability to distinguish two objects as distinct and separate. What is the function of staining in light microscopy? The function of staining is to either increase the contrast or to determine which type of cell is present (gram negative/ gram positive). What color will a gram-negative cell be after Gram staining by the conventional method? Gram positive? Why? Gram negative will be pink, while gram positive will be purple. Gram positive is purple because it has a thicker cell wall and layer of peptidoglycan which will keep the crystal violet dye. What are the steps of a gram stain and the function of each reagent? 1. flood heat-fixed smear with crystal violet for one minute (all cells purple) 2. Add iodine solution for one minute (all cells purple) 3. Decolorize w/ alcohol for 20 sec. (gram positive cells=purple, gram negative= colorless) 4. counterstain with safranin for one to two minutes (gram negative now pink) What major advantage does phase-contrast microscopy have over staining? Staining can kill cells or distort their features, so phase-contrast microscopy allows for viewing of live specimens. How can cells be made to fluoresce? They are made to fluoresce by illuminating them from above with light of a single color, and filters are used so only fluorescent light is seen. They either naturally fluoresce due to chlorophyll or artificially fluoresce by dyes. What are the major differences between electron microscopes and light microscopes? Electron microscopes have greater resolution because the wavelength of electrons is much shorter than visual light's wavelength. What type of microscope would be used to view the three-dimensional features of a cell? Of the internal parts of a cell? -3D: Scanning electron microscope -Internal parts: Transmission electron microscope Explain how Pasteur disproved spontaneous generation. Advocates of the theory declared that "fresh air" was necessary for spontaneous generation. Pasteur made a flask designed to allow air to reach the solution after being sterilized but prevented particulate matter and microorganisms from entering, preventing spoilage of the solution. Explain Koch's postulates. Koch's postulate is a set of criteria for proving that a given microorganism causes a given disease. What advantages do solid media offer for the isolation of microorganisms? When a solid surface was incubated in air, masses of microbial cells developed, each having a characteristic shape and color. What is an example of a solid bacteriological medium? Liquid growth medium? What is a pure culture? When a bacteria is isolated and grown away from other microorganisms in laboratory culture. Describe Griffith's transformation experiment. When the disease-causing strain (S) in the experiment was in the presence of the strain that didn't cause disease (R), it transformed the R strain into an S strain through genetic transfer. What is a phylogenetic tree and what does it tell you? A diagram that depicts the evolutionary history of an organism; it shows the evolutionary relationships between organisms and that everything has one common ancestor. What are the contributions to microbiology associated with Robert Hooke? First to use microscope on living things What are the contributions to microbiology associated with Antoni van Leeuwenhoek? First to observe bacteria and Protozoa What are the contributions to microbiology associated with Louis Pasteur? disproved spontaneous generation What are the contributions to microbiology associated with Robert Koch? postulate to prove that an organism causes disease What are the contributions to microbiology associated with Frederick Griffith? Bacteria can transfer genetic info through process known as transformation What are the contributions to microbiology associated with Carl Woese? Phylogenetic tree Define sterile in terms of microbiology. Sterile means to be free of all living organisms. Name at least two ways to sterilize microbiological media Aseptic techniques and enrichment culture techniques are two ways to sterilize. Why are Archaea more closely related to Eukarya than Bacteria are to Eukarya? Archaea possesses genes and several metabolic pathways that are more closely-related to those of eukaryotes. How do cocci and rods differ in morphology? Give an example of a bacteria with each morphology. Cocci (Staphylococcus epidermis) has a spherical/round shape while rods(Escherichia coli) have a cylindrical shape. Using a microscope, could you differentiate a coccus from a spirillum? A pathogen from a nonpathogen? Yes, you can differentiate coccus from spirillum, but no you cannot differentiate a pathogen from a non-pathogen. Why is the cytoplasmic membrane a good permeability barrier? Cytoplasmic membrane is a good barrier because it contains both hydrophobic and hydrophilic sections. How are the membrane lipids of Bacteria and Archaea similar, and how do they differ? They are structurally similar but chemically different. In the lipids of Bacteria and Eukarya, the hydrophobic fatty acid tails are bound to glycerol by ester linkages; in contrast, the lipids of Archaea have hydrophobic isoprenoid rails, which are bound to glycerol by ether bonds. Describe the major functions of the cytoplasmic membrane. -Cell's permeability barrier, preventing the passive leakage of solutes into or out of the cell -Anchors several proteins that catalyze a suite of key cell functions -Bacteria and Archaea's cytoplasmic membrane plays a major role in energy conservation and consumption Why do bacterial cells need cell walls? Do all bacteria have cell walls? To prevent cell lysis to internal osmotic pressure. Cell walls also confer shape, rigidity and strength. Not all bacteria have cell walls. Why is peptidoglycan such a strong molecule? Cross-linking by covalent peptide bonds between amino acids in the layer of peptidoglycan forms a strong mesh-like structure that provides structure to the cell. Describe the major differences between the cell walls of gram-negative and gram positive bacteria. Gram-positive cell walls are thicker than gram-negative cell walls and contain peptidoglycan. Explain whether you expect the enzyme lysozyme to be equally effective against Bacteria and Archaea. The enzyme lysozyme will only be effective against Bacteria and not Archaea. This is because Bacteria cell walls contain peptidoglycan, unlike Archaea, and lysozyme targets and destroys peptidoglycan. What do the enzyme lysozyme and the antibiotic penicillin have in common? -Lysozyme cleaves the glycosidic bond between N-acetylglucosamine and N-acetylmuramic, weakening the peptidoglycan and possibly causing cell lysis. They are present in human secretion and function as a major line of defense against bacterial infection. -Penicillin, on the other hand, blocks a key step in peptidoglycan's biosynthesis so that it cannot form; this also weakens the molecule and leads to osmotic lysis. Describe the major chemical components in the outer membrane of gram-negative bacteria. at least two layers: LPS and peptidoglycan 1. Small amount of total cell wall contains peptidoglycan. 2. Most of cell wall composed of outer membrane or the lipopolysaccharide (LPS) layer What is the function of porins and where are they located in a gram negative cell wall? Porins are proteins that function as channels in the outer membrane for the entrance and exit of solutes, making the outer membrane relatively permeable to small molecules. What component of the gram-negative cell has endotoxin properties? The LPS layer (AKA outer membrane), specifically lipid A, has endotoxin properties. What is pseudomurein and where is it found? Polysaccharide similar to peptidoglycan. N-acetyltalosaminuronic acid is different (instead of N-acetylmuramic acid). Beta 1-3 glycosidic bonds rather than B 1-4. Amino acids are all L-stereoisomer. Cannot be destroyed by lysozyme and penicillin. Found in cells walls of methanogenic Archaea What is the value of a cell having a capsule? Capsule assists in attachment to surfaces, plays a role in development and maintenance of biofilms, protects against phagocytosis, prevents dehydration/desiccation. What is the capsule composed of and where is it found. Made of polysaccharide layers and found outside of the cell membrane Name a bacterium that has a capsule. Acinetobacter, Rhodobacter capsulatus, Rhizobium trifolii How do fimbriae differ from pili? Fimbriae are shorter than pili, and mainly function to mediate attachment. Pili have many other functions, not just to mediate attachment. What is dipicolinic acid and where is it found? Found in endospores; confers heat resistance What is formed when an endospore germinates? Vegetative cells converted to non-growing, heat-resistant, light-refractive structure. What causes a cell to make endospores? Only occurs when growth ceases due to lack of essential nutrients such as C or N. Name two genera that produce endospores and how are the different? Bacillus (aerobic) and Clostridium (anaerobic) What is archaella and where are they found? Structure that imparts movement to the cell by rotating; found in Archaea What is positive and negative chemotaxis? When would you see each? -Positive chemotaxis occurs if the movement is toward a higher concentration of the chemical in question. -Negative chemotaxis occurs if the movement is in the opposite direction What is the gram reaction, morphology and arrangement of E. coli? negative, rod-shaped, single-cell or in clumps What is the gram reaction, morphology and arrangement of Bacillus? positive, rod-shaped, small chains, clumps, or single cell What is the gram reaction, morphology and arrangement of Staphylococcus? positive, cocci in clusters What is the gram reaction, morphology and arrangement of Micrococcus? positive, cocci in tetrads What is the gram reaction, morphology and arrangement of Streptococcus? positive, cocci in chains What is the gram reaction, morphology and arrangement of Vibrio? negative, curved, rod-shaped What is the gram reaction, morphology and arrangement of Treponema? negative, spiral How big is E. coli? How big is Staphylococcus? E. coli: 1 micrometer by 3 micrometers Staphylococcus: 1 micrometer in diameter Compare and contrast gram positive and gram negative cells. What components are unique to each? -Gram Positive— purple-violet, Thick PG, teichoic acids, retains CV-I -Gram Negative— Thin PG, outer membrane (phospholipid bilayer and LPS (liposaccharide), loses the CV-I and retains safranin What value do gas vesicles give to bacteria? buoyancy What is the function of flagella? What are flagella made of? The function of flagella is to help with movement; they are made of a filamentous protein called flagellin Compare and contrast a prokaryotic and a eukaryotic cell. Prokaryotic cells lack membrane bound organelles while eukaryotic cells have membrane bound organelles such as a nucleus. How do prokaryotic and eukaryotic cells differ when it comes to reproduction? Prokaryotes reproduce by binary fission while eukaryotes use mitosis In general how do bacteria, fungi (molds and yeast), plants and animals reproduce? Explain endosymbiosis. symbiosis in which one of the symbiotic organisms lives inside the other Do bacteria have cilia? No they have fimbriae or pili How do bacterial endospores differ from fungal spores in function? bacterial endospores are not reproductive while fungal spores are reproductive What is phototaxis? movement in response to light How does a chemoorganotroph differ from a chemolithotroph? Chemoorganotrophs obtain their energy and reducing power from organic molecules, while chemolithotrophs obtain their energy and reducing power from inorganic molecules. How does a chemotroph differ from a phototroph? Phototrophs obtain energy for metabolism from light, while chemotrophs obtain energy for metabolism from chemical reactions. What does troph mean? How does an autotroph differ from a heterotroph? -Autotrophs make their own food (obtain carbon from CO2) -Heterotrophs obtain energy by eating other organisms What are enzymes made of? Why is that important when it comes to high temperatures? Enzymes are made of proteins. Higher temperatures disrupt the shape of the active site, which will reduce its activity, or prevent it from working, a process called denaturation. Where on the enzyme does the substrate bind? The active site What is the energy of activation? The minimum energy required to bring the substrate of an enzyme to the reactive state How is catabolism different from anabolism? -Catabolism is an exergonic process in which cells generate free energy by transforming reactants into products. -Anabolism is an endergonic process in which the synthesis of cellular material from simple precursors requires an input of energy. How is respiration different from fermentation? -Respiration is a form of aerobic or anaerobic catabolism in which an electron donor, which can be either organic or inorganic, is oxidized using an external electron acceptor. -Fermentation is a form of anaerobic catabolism in which organic compounds both donate electrons and accept electrons, and redox balance is achieved without the need for external electron acceptors. What are some of the end products of fermentation? Ethanol and CO2 (yeast), lactic acid (lactic acid bacteria) What yeast is commonly used for fermentations? Saccharomyces cerevisiae What happens in glycolysis? Glycolysis is the breakdown of glucose to two pyruvate molecules. The result is a net yield of 2 molecules of ATP, 2 molecules of NADH,, and 2 molecules of pyruvate per molecule of glucose. How does glucose get into a cell? Facilitated diffusion through glucose transporter proteins Where is the most ATP produced: Glycolysis, Kreb's cycle or in the ETC? ETC What is the final electron acceptor in aerobic respiration and what does it form? O2, which forms 6 molecules of water and 6 molecules of carbon dioxide What is the final electron acceptor in anaerobic respiration? Not O2 What is the carbon source for autotrophic organisms? Energy source? Inorganic carbon (CO2), and energy source is the sun