MGY 277 Unit 5

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Questions and Answers

What is the primary state of bacteria in traditional culturing methods?

Rapid growth as fast growing single cells (correct)

Stationary phase with limited multiplication

Specialized roles and cooperation for health

Cooperative behavior for the greater good

What is the style of growth called when bacteria grown in a liquid media in a flask are fast growing single cells behaving as individuals?

Planktonic growth (correct)

Aggregated growth

Colonial growth

Biofilm growth

In what phase do bacteria spend most of their life, according to the text?

Death phase after rapid growth

Stationary phase – not multiplying (correct)

Lag phase before rapid growth

Exponential growth phase

How do planktonic E. coli cells behave, according to the text?

All cells are similar and behave as individuals Signup and view all the answers

Which type of disinfectant is suitable for destroying fungi, vegetative bacteria, and enveloped viruses?

Intermediate-level disinfectant Signup and view all the answers

What is the main consideration when selecting appropriate germicidal chemicals?

Toxicity Signup and view all the answers

Which class of germicidal chemical denatures essential proteins and damages lipid membranes?

Alcohols Signup and view all the answers

What is the main purpose of selecting an appropriate germicidal chemical?

Weighing benefits against risks Signup and view all the answers

Which type of instrument is suitable for disinfection using a high-level disinfectant?

Critical instruments (scalpels) Signup and view all the answers

Which type of germicidal chemical is relatively non-toxic and does not leave residue?

Alcohols Signup and view all the answers

What is the activity of alcohols in the presence of organic material?

Inactivated and less effective Signup and view all the answers

Which type of germicidal chemical is sometimes dissolved in alcohol and called tinctures?

Iodine Signup and view all the answers

Which method can be used to determine oxygen requirements for microbial growth?

Shake tube method Signup and view all the answers

What are the harmful by-products of aerobic respiration that damage cellular components?

Reactive oxygen species (ROS) Signup and view all the answers

Which enzymes do most organisms produce to protect against reactive oxygen species (ROS)?

Superoxide dismutase and catalase Signup and view all the answers

What is crucial for microbial growth, with high salt and sugar inhibiting growth?

Water availability Signup and view all the answers

Which principle of microbial control involves destroying, removing, or inhibiting contaminating microbes?

Sterilization Signup and view all the answers

What methods are included in routine control of microorganisms in daily life?

$H_2O$ monitoring and regulation Signup and view all the answers

Why is minimizing microbial population crucial in hospitals and healthcare facilities?

To prevent healthcare-associated infections Signup and view all the answers

What do microbiology laboratories require rigorous methods for?

Controlling microbial growth and preventing contamination Signup and view all the answers

What is necessary for food and food production facilities to retain quality?

Low microbial population or inhibition of contaminating microbes Signup and view all the answers

What do biosafety levels in laboratories range from BSL-1 to BSL-4 based on?

Pathogenicity of the microbes involved Signup and view all the answers

What is the most common and reliable mechanism for altering the flavor and appearance of products?

Heat treatment Signup and view all the answers

What is approved for treating certain foods, while chemical additives can prevent spoilage?

Irradiation Signup and view all the answers

Who regulates the use of irradiation and chemical additives due to the risk of toxicity?

CFIA/FDA Signup and view all the answers

What must facilities do to avoid contamination of large quantities of product?

Keep surfaces clean and relatively free of microbes Signup and view all the answers

What is traditionally used to disinfect water, but can form disinfection byproducts (DBPs) linked to long-term health risks?

Chlorine Signup and view all the answers

Which organism is resistant to traditional chemical disinfectants and causes diarrhea?

Cryptosporidium parvum Signup and view all the answers

What factors complicate the selection of an antimicrobial procedure?

Type of contaminating microbes Signup and view all the answers

What requires more rigorous treatment if potentially contaminated with highly resistant microbes?

Medical instruments Signup and view all the answers

What gauges commercial effectiveness in terms of time for heat or chemicals to kill?

Decimal reduction time (D value) Signup and view all the answers

What can interfere with heat penetration and the action of chemicals in microbial control?

Dirt, grease, and body fluids Signup and view all the answers

How are medical instruments categorized according to the risk for transmitting infectious agents?

By the risk for transmitting infectious agents Signup and view all the answers

What are biofilms?

Organized communities of bacteria and fungi living on surfaces Signup and view all the answers

What makes cells in biofilms more resistant to antibiotics and disinfectants?

They have different physiological properties than planktonic cells Signup and view all the answers

What is the medical implication of biofilms?

Causing dental plaque and tissue infections Signup and view all the answers

What is the process involved in the formation of a biofilm?

Bacteria adhering to a surface, multiplying, and producing extracellular polymeric substances (EPS) Signup and view all the answers

What is quorum sensing in bacteria?

A mode of regulation involving production and sensing of chemicals that control social behaviors Signup and view all the answers

How do prokaryotes interact with other species in mixed microbial communities?

They can be cooperative or competitive, influencing their growth and survival Signup and view all the answers

What influences the growth of prokaryotes?

Factors such as temperature, atmosphere, pH, and water availability Signup and view all the answers

Where are psychrophiles commonly found?

Arctic regions Signup and view all the answers

How do proteins of thermophiles resist denaturing?

Due to their amino acid sequence Signup and view all the answers

What are the varying oxygen requirements of microbes?

Microbes have varying oxygen requirements including aerobes requiring oxygen for respiration, facultative anaerobes being versatile, and obligate anaerobes unable to use or tolerate oxygen. Signup and view all the answers

What are the industrial implications of biofilms?

Accumulations in pipes and drains, associated with dental plaque, tissue infections, and medical device-related infections. Signup and view all the answers

Which method of microbial control is less effective than moist heat and requires longer times and higher temperatures?

Dry heat Signup and view all the answers

What is the purpose of using biological indicators like G. stearothermophilus in autoclaves?

To ensure proper functioning Signup and view all the answers

Which type of radiation is used to sterilize heat-sensitive materials and approved for use on various foods by the FDA?

γ rays Signup and view all the answers

What is the main purpose of using germicidal chemicals?

To disinfect and sterilize surfaces Signup and view all the answers

Which method is used in commercial foods to avoid problems with high temperature pasteurization?

δ radiation Signup and view all the answers

Study Notes

Biofilms and Microbial Communities

Biofilms are organized communities of bacteria and fungi that live on surfaces, encased in polysaccharide/protein.
Cells in biofilms have different physiological properties than planktonic cells and are more resistant to antibiotics and disinfectants.
Biofilms have medical implications, including causing dental plaque, tissue infections, and being problematic on medical devices such as contact lenses and catheters.
The formation of a biofilm involves bacteria adhering to a surface, multiplying, and producing extracellular polymeric substances (EPS).
Quorum sensing, a mode of regulation in bacteria, involves the production and sensing of chemicals called autoinducers that control social behaviors.
Prokaryotes interact with other species in mixed microbial communities, which can be cooperative or competitive, influencing their growth and survival.
Prokaryotes inhabit a wide range of environments, including harsh conditions, and their growth is influenced by factors such as temperature, atmosphere, pH, and water availability.
Different temperature requirements exist for prokaryotes, with psychrophiles found in Arctic regions, thermophiles in hot springs, and hyperthermophiles in hydrothermal vents.
Proteins of thermophiles resist denaturing due to their amino acid sequence, and temperature influences food preservation and the growth of disease-causing microbes.
Microbes have varying oxygen requirements, with aerobes requiring oxygen for respiration, facultative anaerobes being versatile, and obligate anaerobes unable to use or tolerate oxygen.
Biofilms have industrial implications, such as accumulations in pipes and drains, and are associated with dental plaque, tissue infections, and medical device-related infections.
The interactions of mixed microbial communities can be cooperative or competitive, influencing the growth and survival of different species.

Methods of Microbial Control

Biological indicators like G. stearothermophilus are used to ensure the proper functioning of autoclaves, where a color change in the media after autoclaving indicates survival of bacterial spores.
Commercial canning processes aim to reduce endospores to only 1 (12 D process), critical for preventing the germination of endospores in canned foods.
Dry heat is less effective than moist heat and requires longer times and higher temperatures, with incineration being a method of dry heat sterilization.
Filtration methods, including membrane and depth filters, are used for heat-sensitive solutions like beer and involve the application of vacuum or pressure to aid liquid flow.
Radiation methods include ionizing (X rays, gamma rays) and non-ionizing (UV light) radiation, with ionizing radiation being used to sterilize heat-sensitive materials and approved for use on various foods by the FDA.
Ultraviolet radiation is used to destroy microbes in air, water, and on surfaces, with limitations in penetrating solids or turbid liquids.
High pressure, or pascalization, is used in commercial foods to avoid problems with high temperature pasteurization, maintaining color and flavor associated with fresh food.
Germicidal chemicals are used to disinfect and sterilize surfaces, acting by irreversibly binding proteins, DNA, cytoplasmic membranes, or viral envelopes.
Germicidal chemical formulations are less effective than heat but are useful for treating countertops, surfaces, bathroom fixtures, doorknobs, and heat-sensitive items.
Sterilants destroy all microbes, including endospores, while disinfectants cannot destroy all microbes, including endospores.
Germicidal chemicals typically contain several antimicrobial chemicals and other chemicals, such as buffers, with their exact mechanisms of action often poorly understood.
These methods are aimed at destroying microorganisms and viruses and play a critical role in ensuring the safety and quality of various products and environments.

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Description

Learn about common mechanisms for treating food and water such as heat treatment, irradiation, and chemical additives. Understand the regulations and risks associated with using these methods to ensure safety and quality of products.