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Questions and Answers
What is the primary purpose of antiseptics?
Which physical method of microbial control involves cell wall injury?
Which type of enzyme inhibition is reversible?
What distinguishes a facultative anaerobe from an obligate aerobe?
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What role do vitamins play in microbial metabolism?
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What is the effect of chemical agents on DNA?
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Which microbial control agent is not used for living tissues?
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What is necessary for active transport in cells?
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What is the primary energy source for phototrophic microbes?
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Which of the following is a characteristic of chemotrophs?
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What is the difference between microbicidal and microstatic effects?
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Which agent would be classified as an antiseptic?
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What does lysis of the cell wall in microbes lead to?
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What is the result of denaturation of cytoplasmic proteins in microbes?
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What type of inhibition occurs when a natural substrate competes for the active site of an enzyme?
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Which physical method of microbial control involves interference with the structure of DNA?
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What indicates a positive completed test for E-coli in the lactose broth?
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Which chemical agent is used as a disinfectant on non-living materials?
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What is implied by the presence of a zone of inhibition around a disinfectant disc?
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In the antiseptic susceptibility test, what does absence of a zone of inhibition suggest?
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What characteristics define antiseptics in microbiological control?
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During the control experiment, what color is associated with chlorine bleach discs?
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The degree of effectiveness of a chemical agent is indicated by what?
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What is the role of forceps treated with alcohol in the experiment?
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Study Notes
Microbial Growth Control
- Two types of bioenergetics microbes exist: phototrophs using radiant energy and chemotrophs depending on oxidation of chemical compounds.
- Chemotrophs utilize organic molecules like glucose or inorganic compounds like H2S (hydrogen sulfide) and NaNO2 (sodium nitrite).
- Control of microorganisms is crucial in various fields, including home, business, industry, and medical settings, for disease prevention, treatment, and food spoilage inhibition.
- Chemical and physical agents are used for microbial control.
- Microbicidal Effect - Kills microbes immediately.
- Microstatic Effect - Inhibits reproduction and maintains a constant microbial population size.
Chemical Methods of Control
- Antiseptics: Chemical substances used on living tissue to kill bacteria.
- Disinfectants: Chemical substances used on non-living materials/surfaces.
- Chemotherapeutic Agents: Chemical substances that inhibit growth in living tissues.
Physical Methods of Control
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Cell Wall Injury:
- Lysis of the cell wall weakens cells, forming protoplasts.
- Inhibition of cell wall synthesis also produces protoplasts.
- Cell Membrane Damage: Lysis leads to immediate cell death.
- Alteration of Colloidal State of Cytoplasm: Certain agents denature cytoplasmic proteins, inactivating enzymes and causing cell death due to broken molecular bonds.
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Inactivation of Cellular Enzymes:
- Competitive Inhibition: A chemically similar molecule competes with the natural substrate for the active site on the enzyme surface, blocking end product creation. This is reversible.
- Non-competitive Inhibition: Physical agents like mercuric chloride (HgCl2) uncoil the protein molecule, rendering it biologically inactive. This is irreversible.
- Interference with Structure and Function of DNA: DNA is the cell's control center and a target for destruction or inhibition. Some agents bind to DNA, causing breakage or distortion, interfering with its role in replication and protein synthesis.
Microbial Growth Requirements
- Vitamins: Serve as co-enzymes required for enzyme systems, particularly B vitamins. Some microbes don't require vitamins.
- Oxygen: Many life forms require oxygen for aerobic respiration. Aerobes extract more energy from nutrients than anaerobes (microbes that don't use or need oxygen). There are different types of anaerobes: obligate aerobes, facultative anaerobes, aerotolerant anaerobes, and microaerophiles.
- Water: All cells require distilled water for nutrient transport across the cell membrane.
- Energy: Necessary for active transport, biosynthesis, and biodegradation within cells.
Week-7 Experiment: Disinfectants and Antiseptics
- This experiment requires heavy inoculation of an agar plate with the test organism.
- Sterile, color-coded filter-paper discs are impregnated with different antiseptics and placed on the inoculated agar plate.
- Zones of inhibition (areas of no microbial growth) surrounding the discs indicate microbicidal activity against an organism.
- The absence of a zone of inhibition means the chemical was ineffective.
- The size of the zone of inhibition does not reflect the chemical agent's effectiveness.
- Students use four TSA plates per group and label them with group number, organism, and 12, 3, 6, and 9 o'clock positions.
- They aseptically inoculate the plates by streaking them with a sterile swab in vertical and horizontal directions, and around the edge.
- Color-coded Sensi-discs are used for different chemical agents: red for chlorine bleach, ______ for tincture of iodine, ______ for 3% Hydrogen Peroxide (H2O2), and ______ for 70% Isopropyl Alcohol.
- Using sterilized forceps, four discs of the same color are exposed to one of the chemical solutions.
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Description
This quiz covers the fundamental concepts of microbial growth control, focusing on bioenergetics microbes, their classification into phototrophs and chemotrophs, and the significance of controlling microorganisms in various settings. It also explores chemical methods such as antiseptics, disinfectants, and chemotherapeutic agents, highlighting their roles and effects.
