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 (D)</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 (B)</p> Signup and view all the answers

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

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

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

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

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

<p>Haloarchaea (B)</p> Signup and view all the answers

What type of reproduction do extreme halophilic archaea primarily use?

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

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

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

Which domain is highly diverse and can occupy extreme environments?

<p>Archaea (C)</p> Signup and view all the answers

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

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

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

<p>Filtration (A)</p> Signup and view all the answers

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

<p>Dessication (D)</p> Signup and view all the answers

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

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

What effect does refrigeration have on microorganisms?

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

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

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

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

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

What is the role of microwaves in microbial control?

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

What is the primary action of macrolides in bacterial treatment?

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

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

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

Which type of resistance involves the inactivation of a drug?

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

Which process involves the synthesis of RNA from DNA?

<p>Transcription (B)</p> Signup and view all the answers

What is the function of RNA polymerase during transcription?

<p>To synthesize RNA (B)</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 (D)</p> Signup and view all the answers

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

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

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

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

What remains a characteristic of mutagens?

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

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

<p>Proteobacteria (D)</p> Signup and view all the answers

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

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

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

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

Which bacteria are known as methanogens?

<p>Archaea (B)</p> Signup and view all the answers

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

<p>Sanger Sequencing (A)</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. (C)</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. (C)</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. (D)</p> Signup and view all the answers

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

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

Which of these bacteria primarily oxidize hydrogen?

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

What is a common trait of Rickettsias?

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

What distinguishes sheathed proteobacteria?

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

Flashcards

Sterilization

Complete destruction or elimination of all microbial life.

Disinfection

Control that destroys pathogenic material.

Antisepsis

Disinfection of living tissue.

Thermal Death Point (TDP)

Lowest temperature at which all microorganisms will be killed in 10 minutes.

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Thermal Death Time (TDT)

Minimum time for all microorganisms to be killed at a given temperature.

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Decimal Reduction Time (DRT)

Time (minutes) at which 90% of microbes will be killed at a given temperature.

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Autoclave

Sterilization using steam under pressure, typically at 121°C.

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Pasteurization

Heat treatment that reduces microbial count, eliminating pathogens.

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Macrolides

Antibiotics that inhibit protein synthesis, particularly effective against Streptococcal and Staphylococcal infections.

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Polymyxin B

An antibiotic that targets bacterial cell membranes, specifically Gram-negative bacteria.

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Rifamycins

Antibiotics that disrupt mRNA synthesis and have good tissue penetration.

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Quinolones

Inhibits the activity of DNA gyrase, an essential enzyme for DNA replication in bacteria.

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Sulfonamides

Antibiotics that block the synthesis of essential bacterial metabolites.

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Drug Resistance

The ability of microorganisms to withstand the effects of antimicrobial drugs.

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Genotype

The genetic makeup of an organism, representing its potential characteristics.

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Phenotype

The observable characteristics of an organism, determined by its genotype and environmental factors.

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Dry Heat Sterilization

A method of sterilization using a dry oven at 170°C for 2 hours. It's suitable for materials that can't be sterilized with steam or other moist heat methods.

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HEPA Filter

A type of air filter that removes at least 99.97% of particles larger than 0.3 micrometers in diameter. It is a key component in many sterilization and ventilation systems.

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Membrane Filtration

A method of microbial control that uses a membrane filter with a pore size of 0.22 micrometers to trap and remove bacteria and other microorganisms.

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Refrigeration as Microbial Control

A low temperature method to control microbial growth by slowing down their metabolic processes. It doesn't always kill microbes, but inhibits their growth.

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High-Pressure Microbial Control

A method of microbial control that uses high pressure to rapidly inactivate vegetative cells. Endospores are more resistant to this method.

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Dessication as Microbial Control

A method of microbial control that removes water, inhibiting microbial growth and reproduction. It does not kill all microbes.

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Osmotic Pressure as Microbial Control

A method of microbial control that uses a hypertonic environment (high salt or sugar concentration) to draw water out of microorganisms, inhibiting their growth.

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Ionizing Radiation as Microbial Control

A method of microbial control that uses high-energy radiation (gamma rays, X-rays, electron beams) to damage DNA and kill microbes.

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What are halophiles?

Halophiles are a group of archaea that thrive in environments with extremely high salt concentrations. They require saline environments for growth and can be found in places like salt lakes and salt mines.

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What are some key characteristics of halophiles?

Halophiles are obligate aerobes, meaning they require oxygen for survival. They have a unique cell wall made of glycoprotein that helps them stabilize their internal environment in high salt concentrations. They also use a mechanism to pump potassium ions into their cells to maintain water balance.

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Where are halophiles found?

Halophiles are typically found in saline environments, such as salt lakes, salt mines, and hypersaline environments. These environments are often hot, dry, and have extremely high salt concentrations.

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What is the importance of potassium in halophiles?

Potassium plays a crucial role in maintaining water balance in halophiles. They pump large amounts of potassium into their cells to offset the high sodium concentration outside. This helps them maintain a positive water balance and survive in these extreme environments.

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What is the domain Archaea?

Archaea are a domain of single-celled organisms that are distinct from bacteria and eukaryotes. They are highly diverse in terms of their morphology, physiology, and ability to occupy extreme environments.

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Missense Mutation

A point mutation that changes a single codon, resulting in a different amino acid being incorporated into the protein sequence.

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Nonsense Mutation

A point mutation that introduces a premature stop codon, leading to an incomplete protein.

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Frameshift Mutation

A mutation caused by insertions or deletions of nucleotides in a DNA sequence, shifting the reading frame and altering the amino acid sequence.

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Spontaneous Mutation

A mutation that occurs naturally without any external factors, solely due to errors in DNA replication or repair.

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Mutagen

An environmental agent, either directly or indirectly, that causes mutations in DNA.

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Auxotroph

A mutant strain that has acquired a nutritional requirement not present in the parent organism.

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Phylogeny

The study of the evolutionary history of organisms, tracing their relationships and ancestry.

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Prokaryotic Species

A population of cells sharing similar characteristics, including genetic makeup and metabolic capabilities.

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Proteobacteria

A large and diverse group of bacteria that are classified into five main classes: Alpha, Beta, Gamma, Delta, and Epsilon. They exhibit a wide range of metabolic capabilities and are found in various environments.

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Alphaproteobacteria

A class of Proteobacteria that includes nitrogen-fixing bacteria, plant and human pathogens, and bacteria that can grow in low-nutrient environments.

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Gammaproteobacteria

The most abundant class of Proteobacteria, known for their diverse metabolic abilities, and containing bacteria that can survive in contaminated water.

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Nitrogen Fixation

The process by which atmospheric nitrogen gas is converted into a usable form, primarily by certain bacteria. This process is essential for plant growth and the nitrogen cycle.

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Nitrification

A process where ammonia (NH4+) is oxidized to nitrite (NO2-) and then to nitrate (NO3-) by certain bacteria.

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Purple Phototrophic Bacteria

Bacteria that perform anoxygenic photosynthesis, using bacteriochlorophyll and carotenoid pigments.

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Pseudomonas

A genus of bacteria known for their straight or curved rod shape, ability to use organic compounds as energy sources, and contain many pathogens.

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Acetic Acid Bacteria

Bacteria that are characterized by their high acid tolerance and incomplete oxidation of alcohols and sugars, leading to the production of acetic acid.

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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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