Microorganisms Reading Week 3
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Questions and Answers

What is a common characteristic of Proteobacteria?

  • Stain Gram-positive
  • Contain an outer membrane with LPS (correct)
  • Have a thick cell wall
  • Are exclusively lithotrophs

    • Which group of Proteobacteria includes sulfur and iron reducers?

  • Betaproteobacteria
  • Alphaproteobacteria
  • Deltaproteobacteria (correct)
  • Gammaproteobacteria

    • Which bacteria can be isolated from various environmental sources like sewage and marine water?

  • Rhodospirillum
  • Salmonella
  • Bdellovibrios (correct)
  • Neisseria gonorrhoeae

    • What is a characteristic of Epsilonproteobacteria?

    <p>Pathogens that cause gonorrhea</p> Signup and view all the answers

    What role do Deltaproteobacteria play in the ecosystem?

    <p>Breaking down sulfur and iron</p> Signup and view all the answers

    What is the main benefit of the mutualism between plants and nitrogen-fixing rhizobia?

    <p>Rhizobia fix more nitrogen than plants absorb, increasing the soil's nitrogen content.</p> Signup and view all the answers

    How do host plants and rhizobial bacteria recognize each other as suitable partners?

    <p>Through the exchange of signaling molecules like flavonoids</p> Signup and view all the answers

    What is the role of Nod factors in the symbiotic relationship between legumes and rhizobia?

    <p>They help establish species specificity between bacterium and host.</p> Signup and view all the answers

    What happens to bacteroids once they are surrounded by the plant cell envelope?

    <p>They are unable to reproduce.</p> Signup and view all the answers

    Why do farmers often alternate crops like corn with soybeans?

    <p>To restore nitrogen to the soil</p> Signup and view all the answers

    What is the main limiting nutrient for primary productivity in many natural ecosystems and forms of agriculture?

    <p>Nitrogen</p> Signup and view all the answers

    Which process involves the conversion of ammonia (NH3) to nitrite (NO2-) and nitrate (NO3-)?

    <p>Nitrification</p> Signup and view all the answers

    What is the main avenue for the entry of nitrogen into the biosphere?

    <p>Bacterial and archaeal nitrogen fixation</p> Signup and view all the answers

    What is the form of nitrogen that is assimilated into biomass by microbes and plants?

    <p>Ammonium ion (NH4+)</p> Signup and view all the answers

    Which microbial reaction involves the oxidation of ammonia to nitrite or nitrate?

    <p>Nitrification</p> Signup and view all the answers

    Why is nitrogen fixation considered energy-intensive?

    <p>The need to exclude oxygen during the process</p> Signup and view all the answers

    What is the major reason why nitrogen remains limiting in ecosystems despite being ubiquitous?

    <p>Insufficient fixation rate to meet ecosystem demand</p> Signup and view all the answers

    Which process contributes to the acidification of soil during nitrogen fixation?

    <p>Nitrification</p> Signup and view all the answers

    What role does denitrification play in terms of nitrate reduction in ecosystems?

    <p>Converts nitrate back to nitrogen gas (N2)</p> Signup and view all the answers

    What is the consequence of heavy fertilization leading to excess nitrate in ecosystems?

    <p>Increased global warming due to N2O production</p> Signup and view all the answers

    What type of media favours the growth of one organism over another?

    <p>Selective media</p> Signup and view all the answers

    Which type of media exposes biochemical differences between two species that grow equally well?

    <p>Differential media</p> Signup and view all the answers

    Why is a medium containing bile salts and crystal violet considered selective?

    <p>It favors the growth of Gram-negative over Gram-positive bacteria</p> Signup and view all the answers

    When is a differential medium needed in microbiology?

    <p>To distinguish between organisms that differ in their ability to grow</p> Signup and view all the answers

    What is the primary purpose of selective and differential media in clinical microbiology?

    <p>To promote the growth of specific organisms and highlight biochemical differences</p> Signup and view all the answers

    Where is anaerobic Photosystem 1 (PS1) found?

    <p>Chlorobia and Chloroflexi</p> Signup and view all the answers

    Which organisms contain bacteriorhodopsin and proteorhodopsin, which are light-driven proton pumps?

    <p>Haloarchaea</p> Signup and view all the answers

    What do chlorophylls and bacteriochlorophylls do in photosynthesis?

    <p>Absorb light and transfer energy to an ETS</p> Signup and view all the answers

    What is the function of the antenna complex in chlorophyll-based photosynthesis?

    <p>Absorb light for transfer to the reaction center</p> Signup and view all the answers

    Where are thylakoids found?

    <p>Within phototrophic bacteria or chloroplasts</p> Signup and view all the answers

    What is the source of electrons for Photosystem 1 (PS1)?

    <p>H2S</p> Signup and view all the answers

    What does Photosystem 2 (PS2) use to generate ATP?

    <p>$H_2O$</p> Signup and view all the answers

    What is the primary product of oxygenic photosynthesis?

    <p>$O_2$</p> Signup and view all the answers

    What is the primary energy source for Aquificae members?

    <p>Hydrogen gas</p> Signup and view all the answers

    Where was Thermotoga maritima originally isolated from?

    <p>Vulcano, Italy</p> Signup and view all the answers

    What type of bacteria are Chloroflexus species?

    <p>Photoheterotrophs</p> Signup and view all the answers

    Which bacteria are informally known as 'green nonsulfur bacteria'?

    <p>Chloroflexi</p> Signup and view all the answers

    What is a notable characteristic of Deinococcus species?

    <p>High resistance to radiation</p> Signup and view all the answers

    What specialized cells do cyanobacteria form to exclude oxygen for nitrogen fixation?

    <p>Heterocysts</p> Signup and view all the answers

    Which structures enable cyanobacteria to float in the water column?

    <p>Gas vesicles</p> Signup and view all the answers

    What is the specific purpose of carboxysomes in cyanobacteria?

    <p>Fixing CO2</p> Signup and view all the answers

    Which strategy do cyanobacteria use to maintain anaerobic biochemistry while producing oxygen?

    <p>Alternating between photosynthesis and nitrogen fixation</p> Signup and view all the answers

    In what way do cyanobacterial filaments and colonies resemble multicellular organisms?

    <p>By differentiating into heterocysts for nitrogen fixation</p> Signup and view all the answers

    What is the defining characteristic of methanotrophs?

    <p>Ability to grow on methane</p> Signup and view all the answers

    Which family of bacteria includes widely studied species like Escherichia coli?

    <p>Enterobacteriaceae</p> Signup and view all the answers

    What is a common feature of many Enterobacteriaceae strains regarding oxygen?

    <p>They can grow with or without oxygen</p> Signup and view all the answers

    Which bacterial group includes pathogens that can infect both plants and animals?

    <p>Gammaproteobacteria</p> Signup and view all the answers

    Which feature is characteristic of Xanthomonas species among agricultural pathogens?

    <p>Colonization of a wide range of agricultural plants</p> Signup and view all the answers

    What is a distinctive feature of the spirochete cell structure?

    <p>Long, tight spiral that is flexible like an old-style telephone cord</p> Signup and view all the answers

    How does spirochete motility differ from regular bacterial motility?

    <p>Propelled by flexing motion caused by rotating periplasmic flagella</p> Signup and view all the answers

    What is the primary energy source for spirochetes?

    <p>Fermentation</p> Signup and view all the answers

    Where are the periplasmic flagella located in a spirochete cell?

    <p>In the periplasmic space around the plasma membrane</p> Signup and view all the answers

    What is unique about the rotation of periplasmic flagella in spirochetes?

    <p>Forces the entire cell to twist around in a corkscrew motion</p> Signup and view all the answers

    What enzyme is required for nitrogen fixation in cyanobacteria like Anabaena?

    <p>Nitrogenase</p> Signup and view all the answers

    How do heterocysts enable cyanobacteria like Anabaena to fix nitrogen anaerobically?

    <p>By creating a low-oxygen environment</p> Signup and view all the answers

    What is the term for the specialized cells developed by Anabaena to fix nitrogen?

    <p>Heterocysts</p> Signup and view all the answers

    Why is the enzyme nitrogenase sensitive to oxygen?

    <p>Because it produces oxygen as a by-product of its function</p> Signup and view all the answers

    What physiological activities do cyanobacteria like Anabaena carry out simultaneously due to heterocyst development?

    <p>Nitrogen fixation and photosynthesis</p> Signup and view all the answers

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