Microbial Control Methods and Practices
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Questions and Answers

What is the primary goal of sterilization?

  • To disinfect living tissues
  • To reduce microbial counts
  • To inhibit the growth of bacteria
  • To eliminate all microbial life (correct)

    • Which process specifically targets pathogenic materials?

  • Bacteriostasis
  • Asepsis
  • Degerming
  • Disinfection (correct)

    • What does bacteriostasis mean?

  • Complete destruction of bacteria
  • Inhibition of bacterial growth (correct)
  • Reduction of microbial counts to safe levels
  • Removal of bacteria from surfaces

    • Which of the following is NOT considered a physical control method for microbes?

    <p>Chemical disinfection</p> Signup and view all the answers

    What does the Thermal Death Point (TDP) determine?

    <p>Lowest temperature needed to kill microorganisms in 10 minutes</p> Signup and view all the answers

    In what time frame does autoclaving effectively kill microorganisms at 121°C?

    <p>15 minutes</p> Signup and view all the answers

    Which method is used for pasteurization and reduces microbial count effectively?

    <p>High Temperature Short Time</p> Signup and view all the answers

    What occurs when the membrane permeability of a microbial cell is altered?

    <p>Loss of nutrients from the cell</p> Signup and view all the answers

    Which group of Archaea is characterized by requiring high salt concentrations for growth?

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

    What type of reproduction do extreme halophilic archaea primarily use?

    <p>Binary fission</p> Signup and view all the answers

    Which of the following characteristics is NOT associated with extreme halophiles?

    <p>Possess chlorophyll</p> Signup and view all the answers

    Which domain is highly diverse and can occupy extreme environments?

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

    Which of the following is a significant challenge that extreme halophiles face?

    <p>Maintaining positive water balance</p> Signup and view all the answers

    What is the primary method of microbial control employed by HEPA filters?

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

    Which process is characterized by growth inhibition without killing the microbes?

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

    What is the most lethal wavelength for DNA damage by UV radiation?

    <p>260 nm</p> Signup and view all the answers

    What effect does refrigeration have on microorganisms?

    <p>Slows down the growth of psychrotrophs</p> Signup and view all the answers

    Which method of microbial control uses a hypertonic environment for preservation?

    <p>Osmotic pressure</p> Signup and view all the answers

    Which type of radiation is known to cause mutations that can lead to lethality in microorganisms?

    <p>Gamma rays</p> Signup and view all the answers

    What is a critical factor that affects the efficacy of chemical disinfectants?

    <p>Concentration and contact time</p> Signup and view all the answers

    What is the role of microwaves in microbial control?

    <p>Primarily generate heat to kill microorganisms</p> Signup and view all the answers

    What is the primary action of macrolides in bacterial treatment?

    <p>Inhibit protein synthesis</p> Signup and view all the answers

    Which type of drug action is primarily linked to polymyxin B?

    <p>Injury to the plasma membrane</p> Signup and view all the answers

    Which type of resistance involves the inactivation of a drug?

    <p>Destruction of the drug</p> Signup and view all the answers

    Which process involves the synthesis of RNA from DNA?

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

    What is the function of RNA polymerase during transcription?

    <p>To synthesize RNA</p> Signup and view all the answers

    In the context of gene expression, what does an inducer do?

    <p>Turns on transcription of a gene</p> Signup and view all the answers

    Which type of codons specifically signal the end of protein synthesis?

    <p>Nonsense codons</p> Signup and view all the answers

    Which mechanism of drug resistance prevents penetration at the target site?

    <p>Prevention of target site penetration</p> Signup and view all the answers

    What remains a characteristic of mutagens?

    <p>They directly or indirectly induce mutations.</p> Signup and view all the answers

    What is the function of light repair enzymes in the context of DNA damage?

    <p>They separate thymine dimers using light.</p> Signup and view all the answers

    Which of the following best describes an auxotroph?

    <p>A cell that requires specific nutrients not needed by its parent.</p> Signup and view all the answers

    What type of bacteria is known to be metabolically diverse and significant in medicine?

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

    In microbial classification, serological tests are based on what characteristic?

    <p>Antigenic nature of bacterial strains.</p> Signup and view all the answers

    How do chemical mutagens typically affect mutation rates?

    <p>They can increase mutation rates by 10 to 100 times.</p> Signup and view all the answers

    Which group of proteobacteria contains bacteria that can perform anoxygenic photosynthesis?

    <p>Purple phototrophic bacteria</p> Signup and view all the answers

    Which bacteria are known as methanogens?

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

    Which of the following procedures is NOT typically used in microbial identification?

    <p>Sanger Sequencing</p> Signup and view all the answers

    What is the main characteristic of Pseudomonas species?

    <p>They use organic compounds as a carbon energy source.</p> Signup and view all the answers

    Which of the following is true about enteric bacteria?

    <p>They are Gram-negative and may have pathogenic strains.</p> Signup and view all the answers

    What is the role of nitrogen-fixing bacteria in agriculture?

    <p>They fix atmospheric nitrogen making it available for plants.</p> Signup and view all the answers

    Which type of proteobacteria is known for its ability to survive in contaminated water?

    <p>Gamma proteobacteria</p> Signup and view all the answers

    Which of these bacteria primarily oxidize hydrogen?

    <p>Hydrogen oxidizing bacteria</p> Signup and view all the answers

    What is a common trait of Rickettsias?

    <p>They are obligate intracellular parasites.</p> Signup and view all the answers

    What distinguishes sheathed proteobacteria?

    <p>They possess long tubes containing swarmer cells.</p> Signup and view all the answers

    Study Notes

    Sterilization and Disinfection

    • Sterilization: Complete destruction or elimination of all microbial life
    • Disinfection: Control of destroying pathogenic material
    • Antisepsis: Disinfection of living tissue
    • Degerming: Mechanical removal of microbes
    • Sanitization: Reduction of microbial count to safe levels (public health standards)
    • Bacteriostasis: Inhibition of microbial growth, not killing
    • Asepsis: Absence of significant microbial contamination

    Physical Microbial Control Methods

    • Heat:
      • Moist heat (e.g., boiling, steam under pressure): Kills via protein coagulation.
        • Boiling kills vegetative pathogens in 10 minutes
        • Autoclaving (steam under pressure) provides reliable sterilization (121°C, 15 minutes)
      • Dry heat: Kills by oxidation (e.g., incineration, hot-air sterilization).
        • Hot-air sterilization: 170°C for 2 hrs
    • Filtration: Removal of microbes by straining through a filter
      • HEPA filters are used to remove particulate matter.
      • Membrane filtration removes microbes over 0.22 um
    • Low Temperature: Slows microbial growth (refrigeration, freezing)
      • Refrigeration slows microbial growth, but it may not kill all pathogens
      • Freezing often does not kill, but it preserves for long-term storage.
    • High Pressure: Inactivates microbes by disrupting their cellular structures
    • Dessication: Inhibits microbial growth by removing water
    • Osmotic Pressure: Inhibition of microbial growth by increasing solute concentration, drawing water out of cells .
    • Radiation:
      • Ionizing radiation (e.g., gamma rays, X-rays): Damages DNA, effective on many microbes and materials
      • Non-ionizing radiation (e.g., UV): Damages DNA, less penetrating than ionizing radiation, effectively sterilizes surfaces
      • Microwave radiation (though used for cooking) has limited direct effect on microbes.

    Chemical Microbial Control (Disinfectants)

    • Phenols: Injure plasma membranes
    • Bisphenols: Broad-spectrum biocides, injure plasma membranes
    • Biguanides: Broad-spectrum biocides, injure plasma membranes
    • Halogens: Strong oxidizing agents, killing agents
      • Iodine (e.g. tincture of iodine): used as antiseptics for skin
      • Chlorine: oxidizing agent
    • Alcohols: Denature proteins, effective against bacteria, fungi, viruses (not endospores).
    • Heavy Metals: Denature proteins (e.g., silver nitrate, mercury chloride), good antiseptics/disinfectants.
      • Silver nitrate: common topical antiseptic.
    • Surface-active agents (surfactants): e.g. soaps, detergents
    • Other chemicals: Ethylene oxide, glutaraldehyde, peracetic acid

    Antimicrobial Drugs

    • Mechanism of Action
      • Inhibition of cell wall synthesis
      • Inhibition of protein synthesis
      • Disruption of cell membranes
      • Inhibition of nucleic acid synthesis
      • Inhibition of metabolic pathways

    Microbial Classification/Phylogeny

    • Classification systems categorize microorganisms based on evolutionary relationships. Criteria include morphology, physiology, and genetic characteristics.
    • Bacteria, Archaea, and Eukarya are the three domains that microorganisms fall into.

    Genetic Information Flow in Bacteria

    • Replication: Duplication of DNA molecules
    • Transcription: Production of RNA molecules from a DNA template (mRNA, rRNA, tRNA)
    • Translation: Synthesis of proteins from mRNA codons.
    • Regulation of gene expression: includes induction and repression.

    Microbial Growth and Environmental Factors

    • Environmental conditions affect microbial growth (temperature, pH, water activity, oxygen).
    • Mutation = alteration in DNA base sequence, often caused by mutagens; can be neutral, beneficial, or detrimental.
    • Microbial growth is affected by multiple factors and determines the growth environment. 

    Domain Bacteria (Specific Groups)

    • There are numerous specific types of bacteria discussed (Proteobacteria, Firmicutes etc) within the domain Bacteria. Specific notes and characterization details are provided in the text.
    • Phylogeny and classification schemes can use either phenotypic properties or genetic characteristics.

    Domain Archaea (Specific Groups)

    • There are numerous groups of Archaea discussed (e.g., methanogens, extreme halophiles etc). Specific notes and detailed characterization are provided in the text.

    Other concepts

    • General definitions of terms and processes regarding microbial control methods and classification are included in the notes.

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    Description

    This quiz delves into sterilization and disinfection techniques vital for microbial control. You will explore methods such as heat application, filtration, and understanding the concepts of asepsis and sanitization. Test your knowledge on how these practices ensure public health and safety.

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