Bacterial Growth and Reproduction
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Questions and Answers

What characterizes synthetic or defined media?

  • They are made from natural substances.
  • They have a variable composition.
  • They contain yeast or plant tissues.
  • Their exact composition is known. (correct)

Which of the following media types is used to support the growth of fastidious bacteria?

  • Enriched media (correct)
  • Synthetic media
  • Nutrient broth
  • Basal media

What is an example of a complex media?

  • Lee's medium
  • Selenite F broth
  • Nutrient agar (correct)
  • Alkaline Peptone Water

What is the purpose of differential media?

<p>To distinguish between different bacterial species. (A)</p> Signup and view all the answers

Which medium is specifically used for the isolation of Salmonella and Shigella?

<p>Selenite F broth (B)</p> Signup and view all the answers

What is the indicative feature of Christensen's urease medium?

<p>It changes color to indicate urease activity. (B)</p> Signup and view all the answers

Which medium is selective for gram-negative bacteria?

<p>Mac Conkey's medium (D)</p> Signup and view all the answers

What type of media would be defined as 'basal media'?

<p>Media containing undefined natural extracts (A)</p> Signup and view all the answers

What is the primary purpose of High Efficiency Particulate Air Filters (HEPA)?

<p>To remove bacteria from air (D)</p> Signup and view all the answers

Which size of membrane filter is effective for filtering most bacteria?

<p>0.22 and 0.45 um pores (C)</p> Signup and view all the answers

What is the primary mechanism of genetic transfer among bacteria that involves the uptake of external DNA?

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

What effect does osmotic pressure have on cells?

<p>It can cause plasmolysis in certain bacteria (B)</p> Signup and view all the answers

Which type of transduction involves bacteriophages picking up any portion of the host's genome?

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

Ionizing radiation is primarily used for which of the following purposes?

<p>Sterilizing medical supplies (D)</p> Signup and view all the answers

What is a disadvantage of using ultraviolet light for disinfection?

<p>It causes genetic mutations in humans (B)</p> Signup and view all the answers

What does the presence of a conjugative plasmid indicate in a bacterial cell?

<p>The cell is male and can transfer DNA (B)</p> Signup and view all the answers

What is the primary consequence of horizontal genetic transference for bacteria in terms of human health?

<p>It results in the reappearance of previously eliminated diseases (B)</p> Signup and view all the answers

Which type of radiation is primarily absorbed by water molecules when used to heat food?

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

Which mechanism of genetic transfer requires direct contact between bacterial cells?

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

What is the role of alcohols in microbial control?

<p>To denature proteins and disrupt cell membranes (C)</p> Signup and view all the answers

What concentration of ethanol is considered optimal for disinfecting purposes?

<p>70% (C)</p> Signup and view all the answers

What distinguishes specialized transduction from generalized transduction?

<p>It can only transfer specific segments of bacterial DNA (D)</p> Signup and view all the answers

Which of the following is NOT a mechanism of horizontal genetic transference in bacteria?

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

What is the primary mechanism by which aldehydes inactivate proteins?

<p>By forming covalent crosslinks (A)</p> Signup and view all the answers

Which of the following disinfectants is commonly used to preserve biological specimens?

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

What technique can be used to encourage bacteria that typically lack natural DNA uptake to incorporate plasmids?

<p>Chemical methods or electroporation (A)</p> Signup and view all the answers

What is a common use for glutaraldehyde?

<p>Disinfecting hospital instruments (B)</p> Signup and view all the answers

What characteristic of chlorine makes it less effective when organic materials are present?

<p>It is easily inactivated (B)</p> Signup and view all the answers

What characteristic distinguishes lactose fermenters from non-lactose fermenters on Mac Conkey's medium?

<p>Lactose fermenters produce pink colonies. (B)</p> Signup and view all the answers

Which method is NOT used to generate anaerobiosis?

<p>Utilizing high temperatures. (D)</p> Signup and view all the answers

What is the primary function of iodine in antiseptic use?

<p>It combines with proteins and denatures them (B)</p> Signup and view all the answers

Which substance is known for its oligodynamic action in disinfecting?

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

What role does Durham's tube play in anaerobic media?

<p>It detects gas production by bacteria. (D)</p> Signup and view all the answers

Which statement is true regarding the indicators used in anaerobic conditions?

<p>Reduced methylene blue changes to colorless in the presence of oxygen. (B)</p> Signup and view all the answers

What is the main benefit of using iodophors compared to tincture of iodine?

<p>Slow release and reduced irritation (B)</p> Signup and view all the answers

Which of the following is described as sporicidal in 3 to 10 hours?

<p>2% solution of glutaraldehyde (D)</p> Signup and view all the answers

What is a common strategy employed during the identification of microorganisms?

<p>Using non-specific media to establish initial growth. (B)</p> Signup and view all the answers

Why are most microbial cells difficult to view under a microscope?

<p>Most cells are colorless. (C)</p> Signup and view all the answers

Which of the following factors may vary during the incubation of inoculated cultures?

<p>Agitation. (A), Oxygen level. (C)</p> Signup and view all the answers

What is generally a result of successful culturing and isolation techniques in microbiology?

<p>Establishment of pure cultures. (A)</p> Signup and view all the answers

What is a significant disadvantage of using Phenol as a disinfectant?

<p>It is a skin irritant and has a strong odor. (D)</p> Signup and view all the answers

Which chemical is known to be an effective liquid sporicide that kills bacteria and fungi within 5 minutes?

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

What is a primary concern regarding the use of Quaternary Ammonium Compounds (Quats) in hospital settings?

<p>They are easily neutralized by soaps. (D)</p> Signup and view all the answers

Why is Hydrogen Peroxide not recommended for open wounds?

<p>It is quickly broken down by catalase in human cells. (D)</p> Signup and view all the answers

What is a characteristic of Ethylene Oxide as a sterilizing agent?

<p>It can be explosive in its pure form. (B)</p> Signup and view all the answers

What is the primary function of Biphenols in medical settings?

<p>To act against gram-positive bacteria. (C)</p> Signup and view all the answers

Which of the following describes a major disadvantage of using Quaternary Ammonium Compounds?

<p>They can be ineffective against gram-negative bacteria. (D)</p> Signup and view all the answers

How long does Ethylene Oxide need to be in contact to effectively sterilize medical equipment?

<p>4 to 18 hours (C)</p> Signup and view all the answers

Which mechanism of horizontal gene transfer involves the uptake of free DNA from the environment by a recipient cell?

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

During conjugation, what is the role of the sex pilus?

<p>To connect the donor and recipient bacterial cells (D)</p> Signup and view all the answers

Which type of bacteria is primarily involved in the process of conjugation?

<p>Bacteria of the same species (B)</p> Signup and view all the answers

What is a common laboratory method to introduce plasmids into bacteria that lack natural DNA uptake ability?

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

Which term best describes bacteria's ability to rapidly adapt to new toxins or phages due to horizontal gene transfer?

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

What is the primary mechanism of genetic transfer that involves a virus bringing DNA from one bacterium to another?

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

What phase of bacterial growth occurs immediately after the lag phase?

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

During which stage does bacterial growth cease due to nutrient depletion or waste accumulation?

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

Which method is primarily used for direct microscopic total cell counting?

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

What is a key limitation of the total cell count method?

<p>It cannot distinguish between dead and living cells (A)</p> Signup and view all the answers

What does the turbidity of a microbial culture indicate?

<p>The concentration of cells (C)</p> Signup and view all the answers

Which aspect of measuring microbial growth is typically assessed using optical density (OD) measurements?

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

In viable counting methods, what does the spread-plate method primarily determine?

<p>Live cell count (A)</p> Signup and view all the answers

What is the primary purpose of including a standard curve in turbidity measurements?

<p>To correlate optical density with cell concentration (A)</p> Signup and view all the answers

Which type of radiation is known to cause mutations in DNA and produce peroxides?

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

Which of the following alcohol concentrations is considered optimal for disinfecting purposes?

<p>70% (A)</p> Signup and view all the answers

What is a major limitation of using ultraviolet light for disinfection?

<p>Does not penetrate paper and cloth (C)</p> Signup and view all the answers

What is the effect of osmotic pressure on bacterial cells?

<p>Leads to plasmolysis (A)</p> Signup and view all the answers

Which characteristic of HEPA filters makes them particularly useful in certain medical environments?

<p>Uniform pore size for consistent results (D)</p> Signup and view all the answers

Which type of microorganisms is most resistant to high osmotic pressure?

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

What is a significant disadvantage of using microwaves for killing bacteria in food?

<p>They may heat food unevenly (B)</p> Signup and view all the answers

What effect does desiccation have on microbial cells?

<p>May lead to dormancy (B)</p> Signup and view all the answers

What is the optimum temperature range for mesophiles?

<p>Between 30 and 37 ºC (D)</p> Signup and view all the answers

Which type of microorganism requires a pH environment close to neutral for optimal growth?

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

What defines extreme halophiles in terms of salt concentration?

<p>Require 15-30% NaCl (C)</p> Signup and view all the answers

Which classification of microorganisms can only survive in low oxygen levels?

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

What happens to microbial growth when the temperature exceeds the maximum tolerance level?

<p>Microbial cells may die (D)</p> Signup and view all the answers

What is the primary method used by early civilizations to control microbial growth in food?

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

How do halotolerant organisms differ from halophiles?

<p>They grow better without added solutes (C)</p> Signup and view all the answers

Which factor primarily facilitates the diffusion of water in and out of microbial cells?

<p>Concentration of dissolved solutes (A)</p> Signup and view all the answers

What is the primary action of aldehydes in disinfection?

<p>Forming covalent crosslinks with proteins (B)</p> Signup and view all the answers

Which antimicrobial is one of the few chemical disinfectants that can act as a sterilizing agent?

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

What is a major characteristic of iodine in its antiseptic use?

<p>Irritates mucous membranes (B)</p> Signup and view all the answers

Which halogen compound is commonly used as an active ingredient in bleach?

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

What is the primary reason chlorine is less effective in sanitation when organic materials are present?

<p>Chlorine reacts with organic compounds to form harmful byproducts (C)</p> Signup and view all the answers

Which of the following is a key advantage of using glutaraldehyde over formaldehyde?

<p>Less irritating to mucous membranes (A)</p> Signup and view all the answers

What is considered an oligodynamic action in antimicrobial activity?

<p>Very small amounts of substances are effective against microbes (C)</p> Signup and view all the answers

Which of the following is NOT an ingredient known for its antimicrobial properties?

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

What is a primary reason why Hydrogen Peroxide is not suitable for open wounds?

<p>It breaks down quickly due to catalase in human cells. (A)</p> Signup and view all the answers

Which of the following statements about Peracetic Acid is correct?

<p>It can kill endospores and viruses within 30 minutes. (B)</p> Signup and view all the answers

What disadvantage is associated with the use of Biphenols in medical settings?

<p>Excessive use in infants may cause neurological damage. (C)</p> Signup and view all the answers

Which of the following is a characteristic of Ethylene Oxide as a sterilizing agent?

<p>It requires a longer exposure time of 4 to 18 hours. (D)</p> Signup and view all the answers

What is a major concern regarding the use of Quaternary Ammonium Compounds (Quats) in hospitals?

<p>Pseudomonas strains may develop resistance to them. (A)</p> Signup and view all the answers

What was Phenol primarily used for by Lister in medical practice?

<p>As a common disinfectant for surgical instruments. (A)</p> Signup and view all the answers

Why is the use of Quaternary Ammonium Compounds limited despite their advantages?

<p>Organic matter interferes with their effectiveness. (B)</p> Signup and view all the answers

Which chemical is considered a strong antimicrobial agent effective against fungi, amoebas, and enveloped viruses?

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

Flashcards

Horizontal gene transfer

The transfer of genetic material between bacteria, which can occur through mechanisms like transformation, conjugation, transduction, and vesicles.

Transformation

The uptake of free DNA from the environment by a bacterial cell, which integrates into its own genome.

Conjugation

Direct transfer of genetic material from a donor to a recipient bacterial cell. The donor cell typically injects DNA through a pilus.

Transduction

The transfer of bacterial genes from one cell to another via a bacteriophage (a virus that infects bacteria).

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Generalized Transduction

A type of transduction where the phage can pick up any part of the bacterial DNA.

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Specialized Transduction

A type of transduction where the phage only picks up a specific portion of the bacterial DNA.

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Bacterial culture

The process of isolating bacteria and growing them in a controlled environment for studying and research.

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Electroporation/Chemical methods

Chemical or electrical methods used to force bacteria to take in DNA.

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Simple or Basal Media

A type of media used to grow a wide variety of microorganisms from the environment. It includes basic nutrients like peptone, meat extract, and sodium chloride.

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Complex Media

A type of media with added ingredients that provide special nutrients for specific microorganisms.

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Synthetic Media

A media prepared from pure chemical substances with a known and consistent composition. It doesn't contain any animal or plant tissue.

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Enriched Media

A type of media used to grow organisms with specific nutritional needs. It's enriched with substances like blood, serum, or egg.

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Selective media

A type of media used to isolate pathogens from a mixed culture. It contains inhibitory substances to suppress the growth of unwanted organisms.

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Differential Media

A type of media containing an indicator that changes color when a specific bacteria grows. This helps distinguish between different bacteria.

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Semi-solid Media

A semi-solid media, typically containing 0.5% agar, used to observe bacterial motility.

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Liquid Media

A type of liquid media used to grow bacteria. It doesn't contain agar and allows for free movement of bacteria.

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Desiccation

Removing moisture from a substance, usually by heat, to inhibit microbial growth.

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Membrane Filtration

A type of filtration that uses filters with pores of a specific size to remove bacteria, viruses, and other particles from liquids or gases.

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Osmotic Pressure

The pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.

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Plasmolysis

A process where the plasma membrane of a cell shrinks away from the cell wall due to loss of water.

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Ionizing Radiation

A method of sterilization that involves exposing objects to ionizing radiation, such as gamma rays or X-rays, to kill microbes by damaging their DNA.

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Ultraviolet Light

A method of disinfection that damages DNA by producing thymine dimers, causing mutations in microbes.

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Microwave Radiation

A type of radiation that heats food by causing water molecules to vibrate, which can kill vegetative cells but not endospores.

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Isopropanol

A type of alcohol that is commonly used as an antiseptic to kill bacteria and fungi on the skin.

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Differential Media: MacConkey's Agar

A medium that allows the growth of microbes while also providing visual differentiation based on their ability to ferment lactose. Lactose fermenting bacteria produce pink colonies, while non-fermenting bacteria remain colorless.

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Sugar Fermentation Media

Liquid media containing a specific sugar (like glucose, arabinose, lactose, or starch) at a concentration of 1% within a peptone water base. This medium is used to observe fermentation activity and gas production by bacteria.

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Durham's Tube

A small, inverted tube placed inside a culture tube to capture gas bubbles produced by bacteria during fermentation.

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Anaerobic Media

Growth conditions that lack oxygen. These conditions are necessary for the cultivation of anaerobic microbes.

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Anaerobic Culture Media

A medium specifically designed for growing anaerobic organisms. A common example is Robertson's Cooked Meat Medium.

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GasPak Anaerobe System

A commercially available system that uses a chemical reaction to generate hydrogen (H2) and carbon dioxide (CO2) gases, displacing oxygen and creating anaerobic conditions within a sealed environment. The reduction of the indicator methylene blue to a colorless state denotes the creation of anaerobic environment.

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Incubation Conditions

The conditions under which a culture is incubated, including temperature, gas composition, agitation, light availability, and humidity.

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Enrichment Culture Technique

A widely used strategy in microbial identification, where unknown organisms are initially grown on general, non-selective media. Subsequently, they are transferred to selective or differential media to favor the growth of specific species.

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Aldehydes

A type of chemical disinfectant known for its effectiveness in inactivating proteins by forming cross-links with various functional groups. Examples include formaldehyde and glutaraldehyde.

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Formaldehyde

A potent disinfectant that forms a 37% aqueous solution and preserves biological specimens, inactivates viruses and bacteria in vaccines. However, it has a strong odor and irritates mucous membranes.

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Glutaraldehyde

A less irritating and more effective alternative to formaldehyde. It's one of the few chemical disinfectants that sterilizes, commonly used in hospital settings. It's also used in mortuaries for embalming.

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Peroxygens

A group of chemical disinfectants that disrupt cell membranes and proteins by oxidizing their components. They act like tiny explosions, damaging microbial structures.

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Chlorine

A strong disinfectant used for disinfecting drinking water, pools, and sewage. It effectively works by disrupting microbial functions.

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Ozone

A specific type of peroxygen used in combination with chlorine to improve the effectiveness of water disinfection. A powerful oxidizer, effectively breaking down harmful molecules.

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Bactericidal

A type of antimicrobial agent that kills bacteria, but not necessarily their spores. Used for disinfecting surfaces and medical instruments

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Viricidal

A strong disinfectant effective against a wide range of microbes, including bacteria, fungi, and viruses. It works by attacking the cell membranes of these microorganisms.

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Disinfectant

A chemical used to kill or inhibit the growth of microorganisms. Disinfectants are typically used on inanimate objects.

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Antiseptic

An agent that kills bacteria, often used on the skin or in wounds.

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Sterilant

A chemical agent that can kill all forms of microbial life, including bacteria, viruses, fungi, and spores.

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Why isn't hydrogen peroxide good for open wounds?

Hydrogen peroxide is a common disinfectant and antiseptic. While effective against some microbes, it breaks down quickly in the presence of catalase, an enzyme found in human cells.

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What is Peracetic acid and what is it used for?

Peracetic acid is a potent sporicide, meaning it can kill even resistant bacterial spores. This makes it useful for disinfecting medical instruments and surfaces.

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What are Quats and what are their limitations?

Quaternary ammonium compounds (Quats) are cationic detergents widely used as disinfectants. They are effective against gram-positive bacteria and some fungi, but not against all microbes.

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What is Ethylene oxide used for?

Ethylene oxide is a gas used to sterilize medical equipment, mattresses, and other large items. It is highly effective but toxic and flammable.

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How do Alkylating agents work?

Alkylating agents are chemical sterilants that work by attaching alkyl groups to proteins, denaturing them and killing microbes. They are used in specialized sterilization chambers.

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Generation Time

The time it takes for a bacterial population to double in size.

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Lag Phase

The stage before bacterial growth begins, where cells are preparing for division by synthesizing new enzymes and molecules.

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Exponential Phase

The period of rapid bacterial growth where the number of cells doubles with each division. This is the fastest growth rate.

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Stationary Phase

When bacterial growth slows down and eventually stops due to limited nutrients or accumulation of waste products.

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Death Phase

A period where bacterial cells begin to die off due to lack of resources or accumulated toxins, leading to a decrease in the population.

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Total Cell Count

A technique for counting all cells in a sample, both living and dead, using a specialized counting chamber with a grid.

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Viable Count

A technique that uses a special media to count only living cells that can form colonies.

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Turbidity

Measuring the turbidity of a bacterial culture using a spectrophotometer to estimate cell density. A cloudy broth means more cells.

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Culture Methods

The use of specific media to grow a particular type of bacteria or microbe to study its growth and characteristics. This allows for the isolation and identification of specific microbial species.

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Optimum Temperature

The temperature at which a microorganism grows most rapidly. It's like the 'Goldilocks' temperature - not too hot, not too cold.

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Psychrophiles

Microorganisms that thrive in cold temperatures, with an optimum temperature range around 15 degrees Celsius. They're like the 'ice lovers' of the microbial world.

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Mesophiles

Microorganisms that prefer moderate temperatures, with an optimum temperature range around 37 degrees Celsius. Think of us humans, as we're 'mesophiles', too!

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Thermophiles

Microorganisms that love heat, with an optimum temperature range around 45 degrees Celsius. They're like the 'heat seekers' of the microbial world.

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Hyperthermophiles

Microorganisms that can tolerate extreme heat, with an optimum temperature range above 80 degrees Celsius. These are the 'super-heat lovers' of the microbial world.

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Neutrophiles

Microorganisms that can tolerate a range of pH levels, but grow best in a neutral pH environment (around 6-8). They're the 'pH balance' lovers.

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Halophiles

Microorganisms that thrive in environments with high salt concentrations, like seawater. They're like the 'saltwater lovers' of the microbial world.

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Osmosis

The process where water moves from an area of high concentration to an area of low concentration across a semipermeable membrane. It's like water always trying to even out.

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Phenol

A strong disinfectant that effectively kills bacteria and viruses, but can irritate skin and has a strong odor. It is used in some throat sprays and tablets and acts as a local anesthetic.

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Alkylating agents

A group of chemicals used to sterilize equipment. They work by attaching alkyl groups to proteins, changing their shape and preventing them from functioning.

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Ethylene oxide

A gas used to sterilize medical equipment, mattresses, and large items that cannot be sterilized using heat. It is effective but toxic and flammable.

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Gaseous sterilization

A type of disinfection technique that does not rely on heat. It involves exposing materials to a gas that kills microbes. Commonly used for sensitive items that can't be autoclaved.

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Peracetic Acid

A type of chemical disinfectant that is very effective against bacteria, fungi, and even viruses. It is used for disinfecting surfaces and medical instruments.

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Biphenols

An effective antimicrobial agent that kills bacteria, fungi, and enveloped viruses. They are widely used disinfectants, but can cause neurological damage in infants.

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Hydrogen Peroxide

A type of disinfectant commonly used to kill bacteria and viruses. It is effective against many microbes but breaks down quickly upon contact with human cells.

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Study Notes

Bacterial Growth and Control

  • The rate bacteria grow and divide depends on species (Escherichia coli 20 minutes, Mycobacterium tuberculosis 2 weeks) and the environment's nutritional status. Bacteria can adjust their growth speed to the conditions.
  • Bacterial reproduction is asexual, primarily by binary fission. In this process, the cell enlarges then divides into two new cells.

Unusual Division Patterns

  • Some bacteria grow larger than their starting size before dividing multiple times to produce offspring.
  • Some bacteria reproduce by budding, where a small cell forms and grows from the surface of the parent cell before detaching, forming a new, independent cell.
  • Some bacteria create internal offspring that develop within the mother cell's cytoplasm.

Genetic Changes in Bacterial Populations

  • Mutations, spontaneous or mutagen-induced, can change the DNA sequence. Point mutations involve additions, deletions, or substitutions of bases. Missense mutations alter single amino acids; nonsense mutations create stop codons; silent mutations don't change the amino acid sequence.
  • Horizontal gene transfer involves transposons, transformation, conjugation, transduction, and vesicles. These processes allow bacteria to exchange genetic material.

Bacterial Mutants

  • Antimicrobial resistant mutants can grow in the presence of antimicrobial agents, like AmpR mutations causing resistance to ampicillin.
  • Nutritional mutants have altered nutritional requirements, with prototrophic bacteria synthesizing their own nutrients and auxotrophic bacteria needing specific supplements.

Horizontal or Lateral Genetic Transfer

  • Bacteria can exchange genes through processes like transformation, conjugation, or transduction, crucial to adaptation to various environments and overcoming antimicrobials like in the 1990s tuberculosis antibiotic resistance cases. Gene exchange does not involve sexual reproduction (meiosis).

Bacterial Transformation

  • A donor DNA molecule is taken from the environment and incorporated into the recipient cell’s genome.
  • Bacteria may not have a natural ability to take up DNA but can be made to do so using chemical methods or electroporation (introducing DNA plasmids).

Bacterial Conjugation

  • DNA is passed directly from a donor bacterium to a recipient through a physical connection, like a "bridge," called a sex pilus.
  • A plasmid is typically transferred in this way.

Bacterial Transduction

  • Viruses (bacteriophages) transfer bacterial DNA from one bacterial cell to another; this piece of bacterial DNA can be incorporated into the new host's genome.
  • Two kinds exist - generalized (any part of the genome can be picked up) and specialized (only specific parts of the genome are transferred).

Culture Methods in Microbiology

  • Techniques to isolate and grow microorganisms include inoculation into suitable media, incubation under specific conditions, isolation, and inspection.
  • Identification methods include microscopic, biochemical, and genetic analyses.

Bacterial Growth Media

  • Solid media (e.g., agar) allows organisms to grow in colonies, while liquid media (e.g., broth) supports growth without separation. Agar is a gel-like substance derived from seaweed used to prepare solid culture media for bacteria.
  • Media are classified by consistency (solid, liquid, semi-solid) or based on chemical composition (simple, complex, synthetic/defined). Special media types include enriched, enrichment, selective, and indicator media, which support and distinguish specific types of microorganisms.

Culture Methods in Microbiology (continued)

  • Common classifications of media based on oxygen or nutritional requirements include aerobic, anaerobic, and growth media for different oxygen needs/species. This also includes types like enriched, selective, and differential.

Staining Procedures

  • Simple Stains: Use a single dye to visualize cell morphology and external structures.
  • Differential Stains: Use multiple dyes to distinguish different cell types (e.g., Gram stain to differentiate Gram-positive and Gram-negative bacteria). Acid-fast, spore, and special stains have other uses and techniques.
  • Special stains are important for identification of specific bacteria, fungi, or other microbes.

Population Growth of Bacteria

  • Population growth increases cell number. Growth rate is the change in cell number per unit time, and it is measured in generation time, or the time needed for a population to double.

Phases of Growth for Bacteria

  • During the lag phase, there is a delay in growth as bacteria adapt to the new medium, synthesizing essential enzymes.
  • Exponential growth occurs actively when the cell populations rapidly multiply.
  • Stationary phase happens when essential nutrients are depleted or waste products accumulate, inhibiting further growth.
  • Death phase happens when the harmful substances or lack of nutrients cause a cell population to die off.

Determination of bacterial growth

  • Several methods can be used to ascertain the size of bacterial populations including total cell count, viable cell count, and cell mass. Methods to enumerate bacterial growth include direct microscopic count, spread plate method, viable counts, absorbance methods, and cell-mass measurement.

Methods for Microbial Control

  • Physical methods involve heat (boiling, autoclaving, pasteurization, dry heat), low temperature, filtration, desiccation, and radiation.
  • Chemical methods use various agents including alcohols, aldehydes, biguanides, bisphenols, halogens, heavy metals, peroxygens, phenolics, and gaseous sterilizers (e.g., ethylene oxide).

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Microbial Growth and Control PDF

Description

Explore the fascinating processes of bacterial growth and reproduction in this quiz. Learn about the different division patterns, the effects of environmental conditions, and the genetic changes that can occur within bacterial populations. Test your knowledge on concepts like binary fission and mutations.

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