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Questions and Answers

What is the primary role of methanogens in the carbon cycle?

  • Decompose organic matter
  • Convert CO2 and H2 into methane (correct)
  • Photosynthesize using sunlight
  • Convert methane into carbon dioxide

    • Which group of microorganisms is strictly adapted to high pressure environments, such as deep sea waters?

  • Halophiles
  • Photosynthesizers
  • Methanogens
  • Barophiles (correct)

    • What chemical process involves the release of methane from the gastrointestinal tracts of ruminant animals?

  • Photosynthesis
  • Respiration
  • Fermentation (correct)
  • Carbon fixation

    • What is the consequence of synergistic relationships among microbes, such as in biofilms?

    <p>Enhanced growth and survival</p> Signup and view all the answers

    Which of the following is NOT one of the four major contributions to the carbon cycle?

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

    What effect does fluid flow have on microbial populations?

    <p>Enhances motility and attachment</p> Signup and view all the answers

    How do extreme halophiles differ from obligate halophiles?

    <p>Extreme halophiles can grow in higher salt concentrations than obligate halophiles</p> Signup and view all the answers

    What is a characteristic of non-photosynthesizing microbes when exposed to radiation?

    <p>They can become damaged by light</p> Signup and view all the answers

    What is the main function of antimicrobial agents that prevent nucleic acid synthesis?

    <p>Prevent replication and transcription of viral molecules</p> Signup and view all the answers

    Which of the following best describes the process of sterilization?

    <p>Destruction of all forms of microbial life</p> Signup and view all the answers

    What is a common method by which microbes can develop resistance to antimicrobials?

    <p>Horizontal gene transfer</p> Signup and view all the answers

    Which of the following cellular targets is affected by chemical disinfectants?

    <p>Cell Wall and Protein Function</p> Signup and view all the answers

    What distinguishes a microbicidal agent from a microbistatic agent?

    <p>Microbicidal agents kill microbes, while microbistatic agents inhibit their growth</p> Signup and view all the answers

    What is the primary role of nitrogen-fixing bacteria in the nitrogen cycle?

    <p>Convert atmospheric nitrogen to ammonia</p> Signup and view all the answers

    Which group of bacteria is primarily responsible for nitrification?

    <p>Nitrosomonas and Nitrobacter</p> Signup and view all the answers

    What is the main consequence of eutrophication in aquatic ecosystems?

    <p>Heavy surface growth of cyanobacteria and algae</p> Signup and view all the answers

    What is generated during glycolysis from one molecule of glucose?

    <p>2 NADH and 2 pyruvates</p> Signup and view all the answers

    How do rhizobia benefit legume plants?

    <p>By supplying reduced nitrogen (ammonia)</p> Signup and view all the answers

    What role do aerobic heterotrophs play in the process of eutrophication?

    <p>Deplete oxygen by decomposing organic matter</p> Signup and view all the answers

    What occurs during the Krebs cycle following the conversion of pyruvate?

    <p>Formation of acetyl-CoA</p> Signup and view all the answers

    What does metagenomic sampling primarily allow scientists to achieve?

    <p>Sequence entire microbial genomes</p> Signup and view all the answers

    Which statement correctly describes denitrification?

    <p>Transformation of nitrates back to atmospheric nitrogen</p> Signup and view all the answers

    Which form of nitrogen is most commonly utilized by higher plants?

    <p>Nitrate (NO3−)</p> Signup and view all the answers

    What is a significant impact of the 'One Health' approach?

    <p>Increases disease incidence due to environmental changes</p> Signup and view all the answers

    How many ATP are produced through one cycle of the Krebs cycle for each glucose molecule?

    <p>2 ATP</p> Signup and view all the answers

    What phenomenon occurs primarily due to the overabundance of nutrients in aquatic ecosystems?

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

    What is a key difference between anaerobic and aerobic respiration?

    <p>Anaerobic respiration uses a non-oxygen terminal electron acceptor.</p> Signup and view all the answers

    Which of the following accurately describes prokaryotic chromosomes?

    <p>They are usually circular and located in the cytoplasm.</p> Signup and view all the answers

    What process occurs during bacterial transcription?

    <p>RNA polymerase synthesizes mRNA from DNA.</p> Signup and view all the answers

    What distinguishes light-dependent reactions from light-independent reactions in photosynthesis?

    <p>Light-dependent reactions require sunlight to occur.</p> Signup and view all the answers

    Which of the following describes a precursor molecule?

    <p>A compound that serves as a source for another compound.</p> Signup and view all the answers

    What is a characteristic of co-transcriptional translation in prokaryotes?

    <p>Transcription and translation occur simultaneously in the cytoplasm.</p> Signup and view all the answers

    What defines an inducer in the context of an inducible operon?

    <p>A substrate that binds to the repressor and enables transcription.</p> Signup and view all the answers

    How does bacterial DNA replication differ from eukaryotic DNA replication?

    <p>Bacterial replication occurs semiconservatively.</p> Signup and view all the answers

    What role does ATP synthase play in cellular respiration?

    <p>It synthesizes ATP from ADP using a proton gradient.</p> Signup and view all the answers

    What happens during nucleotide elongation in bacterial translation?

    <p>A peptide bond forms between amino acids.</p> Signup and view all the answers

    What is an essential characteristic of amphibolism?

    <p>It integrates catabolic and anabolic pathways.</p> Signup and view all the answers

    What distinguishes fermentation from respiration?

    <p>Fermentation occurs regardless of oxygen availability.</p> Signup and view all the answers

    Where does the electron transport system (ETS) occur in eukaryotic cells?

    <p>In the inner mitochondrial membrane.</p> Signup and view all the answers

    Which of the following accurately represents the concept of phase variation?

    <p>Reversible changes in gene expression affecting phenotype.</p> Signup and view all the answers

    What is the main difference between F factor transfer and Hfr conjugation?

    <p>Hfr conjugation involves the integration of the F factor into the donor's chromosome.</p> Signup and view all the answers

    What characterizes a drug with a high therapeutic index?

    <p>It is safer to use, as it has a larger ratio of effective dose to toxic dose.</p> Signup and view all the answers

    Which type of antimicrobial drug is produced by chemically altering the structure of natural antibiotics?

    <p>Semi-synthetic antibiotics</p> Signup and view all the answers

    Which of the following describes a superinfection?

    <p>Overgrowth of previously low-number microbes leading to disease.</p> Signup and view all the answers

    What is a mechanism of action of beta-lactam antibiotics?

    <p>Inhibition of cell wall peptidoglycan synthesis.</p> Signup and view all the answers

    What characterizes broad-spectrum antimicrobials?

    <p>Effective against multiple groups of bacteria.</p> Signup and view all the answers

    Which of the following describes direct damage to tissues through drug toxicity?

    <p>Disruption of gut microbiota leading to diarrhea.</p> Signup and view all the answers

    What is the primary mechanism of action for fluoroquinolones?

    <p>Inhibition of DNA replication.</p> Signup and view all the answers

    Which antibiotic is used to treat Mycobacterium tuberculosis specifically?

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

    What is selective toxicity in antimicrobial drugs?

    <p>The ability to kill or inhibit microbes without harming host cells.</p> Signup and view all the answers

    Which type of bacteria-specific antibiotics target the ribosome?

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

    What is the primary function of polymyxins in antimicrobial treatment?

    <p>Disruption of cytoplasmic and outer membranes.</p> Signup and view all the answers

    Which of the following is a characteristic feature of narrow-spectrum antibiotics?

    <p>Target a specific group of bacteria.</p> Signup and view all the answers

    Study Notes

    Staphylococcus aureus

    • Staphylococcus aureus can grow in high salt concentrations (9-25% NaCl)

    Extreme Halophiles

    • Require salt and can grow in up to 36% NaCl
    • Found in inland seas, salt mines, and salted fish

    Hydrostatic pressure

    • Most microbes prefer atmospheric pressure.
    • Barophiles are adapted to deep-sea pressures up to 1000x atmospheric pressure.

    Radiation

    • Photosynthetic microbes use visible light as an energy source.
    • Non-photosynthetic microbes are damaged by light.
    • Radiation can be used as an antimicrobial treatment.

    Fluid flow

    • Fluid flow impacts microbe populations in terms of attachment, nutrient access, and motility.

    Other microbes

    • Microbes can have synergistic or antagonistic relationships.
    • Synergistic relationships involve microbes working together, such as in biofilms and quorum sensing.
    • Antagonistic relationships involve competition and toxin secretion.

    Chemicals

    • Microbes require specific nutrients for growth.
    • Antimicrobials are agents that kill microbes.

    The Carbon Cycle

    • Carbon exists predominantly in mineral form and in organic reservoirs within organisms.
    • Microbes play a key role in carbon recycling.

    Respiration

    • One of the four major contributions to the carbon cycle.

    Fermentation

    • One of the four major contributions to the carbon cycle.

    Carbon Fixation

    • One of the four major contributions to the carbon cycle.
    • Photosynthesis is the process of carbon fixation.

    Methane production

    • One of the four major contributions to the carbon cycle.
    • Produced by methanogens.

    Methanogen

    • Converts CO2 and H2 into methane (CH4).
    • Live in anaerobic ecosystems.
    • Belongs to the Archaea Domain.

    Nitrogen Cycle

    • Nitrogen gas (N2) accounts for nearly 80% of air volume.
    • Nitrogen cycle is complex, involving multiple reactions.
    • Higher plants utilize NO3- and NH4+.
    • Microorganisms use all forms of nitrogen.

    Nitrogen Fixation

    • Converts atmospheric nitrogen (N2) to ammonia (NH3).
    • Performed by bacteria.
    • Enzyme complex nitrogenase is involved.
    • Occurs in soil, both aerobic and anaerobic conditions.
    • Some bacteria are free-living, while others are symbiotic with plants.

    Ammonification

    • Decomposition of organic matter by bacteria, producing ammonia (NH4+).
    • Organic nitrogen (proteins, nucleic acids) is converted to NH4+.

    Nitrification

    • Converts ammonia to nitrate (NO3-).
    • Nitrate is the most oxidized form of nitrogen used by plants, fungi, and bacteria.
    • Carried out by obligate aerobic bacteria, in two steps:
      • Nitrosomonas oxidize ammonia (NH3) to nitrite (NO2-)
      • Nitrobacter oxidize nitrite (NO2-) to nitrate (NO3-)

    Denitrification

    • Converts nitrate (NO3-) or nitrite (NO2-) to atmospheric nitrogen (N2).
    • Carried out by many different species of bacteria.
    • Contributes to nitrogen loss in soils.

    Rhizobia and Legumes

    • Rhizobia are Gram-negative, motile, rod-shaped bacteria.
    • Colonize legume roots and form root nodules.
    • Supply reduced nitrogen (ammonia) to the plant.

    Microbial Ecosystem

    • Microbial ecology is the study of microbes in their natural habitats.
    • Ecosystems are collections of organisms with their surrounding physical and chemical factors.

    Aquatic and Soil Environments

    • Plankton are a floating community that drifts with waves and currents.
    • Phytoplankton are photosynthetic algae and cyanobacteria.
    • Zooplankton are microscopic consumers, including protozoa and invertebrates.

    Eutrophication

    • Excess nutrients in aquatic ecosystems can lead to eutrophication.
    • Heavy surface growth of cyanobacteria and algae depletes oxygen supply.
    • Aerobic heterotrophs further deplete oxygen by decomposing organic matter.
    • Strict aerobes (fish, invertebrates) die off, while anaerobic and facultative microbes survive.

    Metagenomic Sampling

    • DNA is obtained, fragmented, and sequenced.
    • Sequences are aligned to reveal entire genomes.

    Impact of Metagenomics on Microbiology

    • Revealed microbial abundance and diversity.
    • Identified microbes in new places.
    • Uncovered novel genes and traits in microbes.

    One Health

    • Microbes circulate among human hosts, animal hosts, and environmental reservoirs.
    • Changes in the environment can lead to the transmission of pathogens to previously unexposed animals and humans.
    • Pathogen evolution can increase disease incidence and geographic spread.

    Glycolysis

    • Converts glucose to pyruvic acid/pyruvate.
    • Occurs in the cytoplasm of bacteria and eukaryotes.
    • 9-step process.
    • Yields ATP, NADH, and 2 pyruvates per glucose molecule.

    Krebs Cycle

    • Occurs in the cytoplasm of bacteria or mitochondrial matrix of eukaryotes.
    • 8-step cycle, starting with pyruvate and converting it to acetyl-CoA.
    • Yields ATP, NADH, FADH2, and CO2.

    Electron Transport System (ETS)

    • Occurs in the inner mitochondrial membrane of eukaryotes.
    • Involves chemiosmosis to produce ATP via ATP synthase, using the proton gradient.
    • Bacteria may have simpler or branched chains and can use alternative respiratory pathways.

    Anaerobic Respiration

    • Does not require oxygen.
    • Uses a non-oxygen terminal electron acceptor, such as nitrate, sulfate, or carbonate.
    • Less ATP produced than aerobic respiration.

    Aerobic Respiration

    • Requires oxygen as the terminal electron acceptor.

    Aerobic Respiration in Eukaryotes vs Bacteria

    • Different locations for ETS and Krebs Cycle:
      • ETS: Bacteria = cell membrane; eukaryotes = mitochondrial membrane.
      • Krebs: Bacteria = cytoplasm; eukaryotes = mitochondrial matrix.
    • Different electron carriers in the membrane.
    • Bacteria produce more ATP than eukaryotes.

    Aerobic and Anaerobic Respiration: Net ATP Yield

    • 2 ATP from glycolysis
    • 2 ATP from Krebs cycle
    • 34 ATP from ETS
    • Total = 38 ATP

    Microbial Fermentation

    • Does not require oxygen.
    • Incomplete oxidation of glucose.
    • Uses organic compounds as terminal electron acceptors.
    • Produces NADH and regenerates NAD+.
    • Can produce alcoholic or acidic products.

    Amphibolism

    • The integration of catabolic and anabolic pathways.
    • Uses strategic molecular intermediates (precursor molecules) that can be diverted into other pathways.

    Precursor Molecule

    • A compound serving as a source of another.

    Photosynthesis

    • Light-dependent reactions:
      • Use light to produce ATP.
      • Only occur in the presence of sunlight.
      • Involve hydrolysis of water, producing oxygen.
      • Involve photosystems I and II.
      • Catabolic, energy-producing reactions.
      • Produces ATP and NADPH.
    • Light-independent reactions (Calvin Cycle):
      • Sunlight not required.
      • Anabolic, synthetic reactions.
      • Produce glucose.
      • Uses ATP, NADPH, and CO2.

    Eukaryotic Chromosomes

    • Located in the nucleus.
    • Vary in number.
    • Linear.
    • Can occur in pairs (diploid) or singles (haploid).
    • Larger.

    Bacterial Chromosomes

    • Located in the cytoplasm (nucleoid).
    • Usually one chromosome.
    • Typically circular.
    • Single copies.
    • Smaller.

    Bacterial DNA Replication

    • Semiconservative: Each daughter molecule is half parental and half newly synthesized.
    • Bidirectional replication starts at the origin of replication.
    • Replication proceeds in the 5’ to 3’ direction.

    Steps of Bacterial DNA Replication

    • Initiation: DNA unwinds and separates.
    • Elongation: DNA polymerase adds nucleotides to the new strand.
    • Termination: Replication is complete.

    Enzymes used in Bacterial DNA Replication

    • Helicase: unwinds DNA.
    • Topoisomerase: relieves tension in DNA.
    • Primase: synthesizes RNA primers.
    • DNA polymerase: adds nucleotides to the new strand.
    • Ligase: joins DNA fragments.

    Bacterial Transcription

    • DNA is transcribed into mRNA.
    • Involves three steps:
      • Initiation: RNA polymerase binds to the promoter.
      • Elongation: RNA polymerase adds nucleotides to the mRNA strand.
      • Termination: RNA polymerase reaches the terminator.

    Key factors used in Bacterial Transcription

    • RNA polymerase: synthesizes mRNA from DNA.
    • Promoter: DNA sequence recognized by RNA polymerase.
    • Terminator: DNA sequence that signals the end of transcription.

    Bacterial Translation

    • mRNA is translated into protein.
    • Involves three steps:
      • Initiation: Ribosome binds to the mRNA.
      • Elongation: tRNA molecules bring amino acids to the ribosome.
      • Termination: Stop codon is reached.

    Key factors used in Bacterial Translation

    • Ribosome: translates the mRNA into protein.
    • tRNA: carries the amino acids to the ribosome.

    Differences in Bacteria vs Eukaryotes for DNA Replication, Transcription & Translation:

    Bacterial DNA Replication

    • Occurs in the cytoplasm.
    • Replication starts at a single origin.

    Eukaryotic DNA Replication

    • Occurs in the nucleus.
    • Replication can start at multiple origins.

    Bacterial Transcription and Translation

    • Can occur simultaneously (co-transcriptional translation).

    Eukaryotic Transcription and Translation

    • Transcription occurs in the nucleus and translation occurs in the cytoplasm.
    • mRNA is processed before translation.

    Operon

    • Coordinate set of genes regulated and transcribed as a single unit.
    • Not present in eukaryotes.

    Repressible Operon

    • Genes are turned off by the product synthesized by the enzyme.
    • Typically anabolic.

    Inducible Operon

    • Genes are turned on by the substrate for which they encode.
    • Typically catabolic.

    Phase Variation

    • Reversible phenotypic changes due to bacteria turning on/off genes.

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