Cell Division in Prokaryotes

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Questions and Answers

What process do most prokaryotes use for division?

Fragmentation

Spore formation

Budding

Binary fission (correct)

How does binary fission contribute to genetic continuity?

It leads to genetically varied daughter cells

It creates two genetically identical daughter cells (correct)

It promotes genetic recombination

It requires the exchange of genetic material

What is the initial step that occurs before a cell undergoes binary fission?

Budding of a side branch

Chromosome duplication (correct)

Cell differentiation

Formation of a spore

Which of the following statements about budding is true?

An outgrowth forms on the original cell and eventually separates. Signup and view all the answers

What defines spore formation in bacteria?

Spore formation can occur asexually in bacteria. Signup and view all the answers

Which of the following factors can influence generation time in bacteria?

Species specificity and environmental conditions Signup and view all the answers

What structure forms during binary fission to complete cell division?

Septum Signup and view all the answers

Which scenario exemplifies the formation of biofilms?

Planktonic bacteria adhering to surfaces like catheters. Signup and view all the answers

What organisms thrive between pH 1 and pH 5?

Acidophiles Signup and view all the answers

Which group of microorganisms is associated with most pathogens?

Mesophiles Signup and view all the answers

Which microorganisms can tolerate high-salt environments but may not grow well?

Facultative halophiles Signup and view all the answers

What is the optimal pH range for most microorganisms?

5 to 8 Signup and view all the answers

Which microorganisms can withstand high-pressure environments in the deep sea?

Barophiles Signup and view all the answers

Which types of bacteria are associated with compost piles and hot springs?

Thermophiles Signup and view all the answers

What happens to normal cells in high-salt conditions due to osmosis?

They undergo plasmolysis Signup and view all the answers

At what temperature do psychrotrophs typically grow?

About 20 to 30°C Signup and view all the answers

Which oxygen classification is characterized by organisms that require oxygen for growth?

Obligate Aerobes Signup and view all the answers

In a plugged test tube with spherical cells clustered at the bottom, which type of organism is present?

Obligate Anaerobes Signup and view all the answers

What does the presence of growth throughout the medium in a thioglycolate tube indicate about the organism?

It is a facultative anaerobe. Signup and view all the answers

Which classification represents organisms that do not require oxygen but can tolerate it?

Aerotolerant Anaerobes Signup and view all the answers

Which type of organism would you expect to find floating in the middle of a thioglycolate tube?

Facultative Anaerobes Signup and view all the answers

In a growth medium that shows no growth in the presence of oxygen, which classification would be most appropriate?

Obligate Anaerobes Signup and view all the answers

What is the primary location of growth for microaerophiles in a thioglycolate medium?

Middle of the medium Signup and view all the answers

Which of the following statements about facultative anaerobes is true?

They prefer oxygen but can survive without it. Signup and view all the answers

Which method uses reducing agents to remove oxygen from media?

Thioglycate addition Signup and view all the answers

What is the primary purpose of aseptic techniques in healthcare settings?

To prevent contamination Signup and view all the answers

What is the function of nitrogen in an anaerobic chamber?

To displace oxygen Signup and view all the answers

Which of the following is NOT a critical step in collecting clinical samples?

Placing samples in sunlight Signup and view all the answers

What is essential to maintain sample integrity during transport?

Immediate freezing or refrigeration Signup and view all the answers

How should samples be collected to ensure they remain uncontaminated?

Wearing gloves at all times Signup and view all the answers

Which type of anaerobic media removes oxygen by creating oxygen-free conditions through chemical reactions?

Anaerobic jar Signup and view all the answers

What does proper hand washing prevent during clinical sample collection?

Contamination from the collector Signup and view all the answers

What is the environment like at the very top of the test tube?

Oxygen-rich Signup and view all the answers

What type of oxygen dependence do the cells exhibit at the bottom of the test tube?

No dependence Signup and view all the answers

Which of the following describes the oxygen usage in the middle of the test tube?

Oxygen usage is minimal. Signup and view all the answers

What type of metabolic adaptation do the cells exhibit?

Facultative anaerobes Signup and view all the answers

What primarily characterizes the bottom section of the test tube?

It is an anaerobic environment. Signup and view all the answers

How does the density of cell clusters change from the top to the bottom of the test tube?

Density increases towards the surface. Signup and view all the answers

Which statement about oxygen use in metabolism is accurate?

Some cells do not use oxygen at all. Signup and view all the answers

Which option best describes the range of oxygen availability in the test tube?

From oxygen-rich at the top to anaerobic at the bottom. Signup and view all the answers

What is the implication of the cell's capability to manage reactive oxygen species?

They can survive both aerobic and anaerobic conditions. Signup and view all the answers

What is a characteristic of the microscopic count method?

It involves a manual count of cells. Signup and view all the answers

Which method allows for the measurement of metabolic activity in a sample?

Spectrophotometer Signup and view all the answers

What does the Coulter counter measure?

The number of cells in a fluid. Signup and view all the answers

What can be inferred from a spectrophotometer that measures percent light transmitted?

It quantifies the concentration of a substance based on light absorption. Signup and view all the answers

Which indirect method assesses total dry weight?

Filtration and drying Signup and view all the answers

Which of the following methods does not allow for differentiation between living and dead cells?

All of the above Signup and view all the answers

What is a disadvantage of using a microscopic counting method?

It can be time-consuming and subjective. Signup and view all the answers

In indirect cell-counting methods, what does assessing metabolic activity imply?

Evaluating health and reproduction rates. Signup and view all the answers

Study Notes

Microbiology: Basic and Clinical Principles

Chapter 7 covers Fundamentals of Microbial Growth and Decontamination.
The chapter was presented by Janet Dowding, Ph.D., at St. Petersburg College.
A clinical case study, "The Case of the Sickly Soaker," is available to further explore microbial growth.
Students should be able to discuss differences in microbial growth in a lab versus in nature.
Define binary fission and compare to budding and spore formation.
Calculate generation time for a bacterium.
Outline the four stages of bacterial growth in a closed batch system.

Microbial Growth Basics

Microbes grow in size and divide when nutritional requirements are met.
Microbial growth is defined as cell division increasing the total cell population.
Most knowledge about bacteria comes from laboratory-grown types.
Only approximately 1% of all bacteria can be cultured in a lab.

Microbes Show Dynamic and Complex Growth in Nature, and Often Form Biofilms

Bacteria intermingle with archaea and eukaryotes in nature.
Environmental factors are important for bacterial life, metabolism, and structure.
Escherichia coli can change shape during urinary tract infections.
Biofilm communities collaborate to survive.
Biofilms are a concern in healthcare due to difficulty treating persistent, or recurring, infections.
Biofilm formation happens when free-floating bacteria cling to surfaces.
Indwelling devices (e.g., catheters, heart valves) can become homes for biofilms.

Bacteria Usually Divide by Binary Fission, but Some May Use Budding or Spore Formation

Binary fission is the typical prokaryotic cell division process.
Binary fission involves dividing a single cell into two cells.
Binary fission is an asexual process.
In budding, a small outgrowth from a parent cell develops and eventually separates.
Spore formation is a common asexual method in some fungi and bacteria.
Spore formation in fungi can be either sexual or asexual, but it's asexual in bacteria.
Streptomyces form spores that extend from hyphae.
Bacterial endospores are thick-walled, non-growing structures.

Generation Time

Generation time varies among different cell types.
The generation time is about 15 minutes to 24 hours and is species- and condition-dependent.
E. coli has a generation time of about 20 minutes, under certain conditions.
Mycobacterium tuberculosis has a slower generation time of 15–20 hours.
The nutrients available impact how quickly microbes reproduce.

Bacteria Have Four Distinct Growth Phases When Cultured Using a Closed Pure Batch System

Bacteria is isolated and grown in closed cultures in labs.
The distinct phases are characterized by observing the number of viable cells.
The four phases include lag phase, log phase, stationary phase, and death phase.
The lag phase is the adaptation to the new environment.
Log phase involves rapid exponential growth.
Stationary phase is when nutrients deplete and waste accumulates.
Death phase is marked by an exponential rate of cell death.
Maintaining cells in a specific growth phase is important in certain industries.
A chemostat is used to control the phase of growth by adding fresh medium and removing waste and cells.

Prokaryotic Growth Requirements

Optimal, minimum, and maximum are terms describing temperature and pH requirements for growth.
Psychrophiles thrive in very cold environments; psychrotrophs also thrive in cold environments but can grow at warmer temperatures; mesophiles thrive at moderate temperatures; thermophiles thrive in warm environments; and extreme thermophiles thrive in very warm environments.
Acidophiles, alkaliphiles, and neutralophiles are microbes that thrive in acidic, basic, or neutral pH ranges respectively.
Microbial survival in extreme pH relies on specific adaptations.
Halo-philes thrive in high-salt environments with high osmotic stress, and must adapt to maintain homeostasis.
Different microbes have various oxygen requirements, with a variety of classes: aerobic, microaerophilic, facultative anaerobic, aerotolerant anaerobic, and obligate anaerobic.

High-salt Conditions

Halophiles can tolerate up to 35% salt.
Facultative halophiles can tolerate higher salt but may not grow well in those conditions.
Bacterial cytoplasm is mainly water.
Normal cells undergo plasmolysis in high-salt environments.
Halophiles maintain high concentrations of organic materials and ions in their cytoplasm to combat high osmotic stress.

Oxygen Requirements

Many microbes thrive in low or no oxygen environments.
Most pathogens thrive in low-oxygen environments in the host body
Atmospheric oxygen easily diffuses across the cell plasma membrane.
Inside the cell, oxygen is converted to reactive oxygen species (ROS).
Aerobic microbes use antioxidants to detoxify ROS to maintain homeostasis.

Microbes Require Nutrients, Growth Factors, and a Source of Energy

Microbes acquire nutrients and ingredients to build structural components, enzymes, and other factors for cell division.

Essential Nutrients

Approximately 90% of a microbe's dry weight is oxygen, nitrogen, carbon, and hydrogen.
Other essential nutrients include sulfur, phosphorus, potassium, sodium, calcium, magnesium, chlorine, and various metal ions (e.g., copper, zinc, iron).
Macronutrients are needed in large amounts; micronutrients in very small amounts.
Heterotrophs require an external source of organic carbon.
Autotrophs produce their own organic carbon from inorganic carbon using carbon fixation.
Most nitrogen and phosphorus are taken from organic nutrients.
Some cells obtain nitrogen directly from the atmosphere (nitrogen fixation.)

Growth Factors

Some microbes cannot produce all their organic precursors.
Cells need to import these substances from their environment.
Growth factors are materials cells cannot produce, and must obtain.
Fastidious organisms require many growth factors in their environment.

Energy Sources

Phototrophs use light energy to produce their own compounds.
Chemotrophs break down chemical compounds to get energy.
There are four basic types of heterotrophs/chemotrophs differentiated by their carbon and energy source use: photoautotrophs, photoheterotrophs, chemoautotrophs, and chemoheterotrophs. Examples of each type of organism are provided.

Growing, Isolating, and Counting Microbes

Media come in three formats: liquid (broth), solid, and semisolid.
The choice of format depends on the application.
Media also have different compositions (complex or defined) depending on the purpose of the growth experiment.
Methods for culturing anaerobic microbes (microbes that don't need oxygen to survive) include specialized chambers, tubes, and media to allow for anaerobic growth conditions.
Aseptic techniques are required for collecting clinical samples to ensure sample integrity.
Streak plate technique isolates microbes by diluting a bacterial culture over the surface of an agar plate.
Direct and indirect methods can be used for cell enumeration.

Collecting Samples for Clinical Microbial Analysis

Collect samples aseptically to prevent contamination.
Use sterile materials for sampling.
Use appropriate collection containers for tests.
Proper hand washing is essential.
Wear gloves.
Quickly seal samples.
Take into account agent properties (pathogen) when performing sample collection.
Refrigerate or place on dry ice for shipping when necessary.

Isolating Microbes Using the Streak Plate Technique

The streak plate technique isolates bacteria by diluting a sample.
Individual cells are separated on the plates.
Bacterial colonies form as cells divide and multiply.

Methods for Counting Microbes

Counting microbes is important for various reasons such as food and beverage manufacturers, water treatment, clinical laboratories, etc.
Direct methods count individual cells (e.g., microscope, Coulter counter, viable plate count, flow cytometer).
Indirect methods use secondary reflections of overall population size to estimate cell numbers (e.g., turbidity, dry weight, and biochemical activity.)
Colony-forming units (CFUs) per milliliter or gram are used to represent numerical data for microbes.

Indirect Methods

Indirect methods estimate population size using secondary reflections.
Turbidity is a fast and reliable indirect method.
Spectrophotometer measures turbidity(cloudiness) by measuring light transmission or absorbance.
Other indirect methods include assessing the total dry weight of cells and determining the level of a microbial's metabolic activity.

Methods for Identifying Microbes

Identifying microbes is a critical step in diagnosis.
Physical analysis utilizes staining and microscopy to observe morphological features.
Biochemical analysis utilizes different growth media to assess metabolic properties.
Genetic methods use probes, polymerase chain reaction (PCR), DNA "fingerprinting," and electrophoresis separation methods.

Controlling Microbial Growth

Decontamination, sterilization, disinfection, microbiostatic, microbiocidal, disinfectant, and antiseptic are defined.
Different heat treatments for microbe control, such as decimal reduction time, thermal death point, and thermal death time , are defined.
Description of radiation and filtration controls used for microbial control.

Control Strategies

Strategies aim to reduce/eliminate microbial contamination in daily life, hospital settings, and industrial settings.
Decontamination reduces microbial populations, rendering objects safe for handling.
Sterilization eliminates all bacteria, viruses, and endospores.
Disinfection reduces microbial numbers, often used for surfaces and equipment.
Physical methods (temperature, radiation, filtration) or chemical methods (germicides) can destroy microbes.

Temperature Changes

Refrigeration (4°C.) and freezing (0°C) slow microbial growth and spoilage.
Heat treatments are used to denature microbe proteins and kill them.
Decimal reduction time (DRT or D-value) is the time needed to kill 90% of a microbial population at a specific temperature.
Autoclaving is a method that uses pressure and heat to sterilize items (sterilizing).
Boiling is used to kill pathogens but is not as effective for endospores.
Pasteurization uses moderate heat to kill microbes without affecting the qualities of liquids like milk.
Dry heat sterilization (high temperature/incineration flames or ovens) kills microbes through heat.

Radiation

lonizing radiation uses high-energy waves to kill microbes (sterilize).
Nonionizing radiation uses low-energy waves (e.g., UV light) to destroy microbes (disinfect surfaces.)
Radiation is used on food packaging material to inhibit microbial growth or contamination.
Radiation can disinfect surfaces or equipment.
Filtration can be used to remove viruses, or microbes, from liquid/air.
HEPA filters are important for air quality.
Membrane filters remove microbes from liquids.
"LifeStraws" are widely used water filtration tools to remove microbes from water

Germicides

Chemicals used to control microbial growth are called germicides.
Germicides are classified into two types: microbiocidal (kill microbes) and microbiostatic (inhibit growth.)
Disinfectants are for inanimate objects; antiseptics are for living tissue.
Germicides are ranked based on their ability to destroy microbes (low, intermediate, high level).
The correct type of germicide and its concentration depends on the intended use.
Factors (item, microbe, concentration) are important in selecting the correct germicide.

Different Control Methods Work for Different Microbes

Mycobacterium Species have cell walls that make them hard to kill/destroy.
Endospores form under unfavorable conditions. Endospores are highly resistant to most controls.
Viruses can be resistant to some measures.
Protozoa stages of life, often require different treatment measures.
Prions withstand almost all sterilization and decontamination measures.

Visual Summary: Fundamentals of Microbial Growth and Decontamination

Summary of microbial growth and control methods using visual representations and data.
Bacteria divide using binary fission, which increases populations exponentially in the log phase.
Environmental factors that impact microbe growth are presented (temperature, oxygen concentrations, etc.).
Isolation techniques (streak plate) and methods (pour plate, spread plate, etc.) are presented along side direct and indirect counting methods.
Different control strategies aimed at decontaminating objects include autoclaving, boiling, pasteurization, and dry heat.
The use of radiation and filtration to remove or destroy bacteria.

Think Clinically: Be S.M.A.R.T. About Cases

The cases of patients with upper ear cartilage infections are presented as a case study.
The symptoms, the investigation, and procedures taken by healthcare professionals are detailed for each case.
The role of aseptic techniques, different levels of germicides and their selection process, and the proper use of materials were identified during each case analysis.
Possible explanations and conclusions for each case presented are included.

Studying That Suits You

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Description

This quiz explores the process of binary fission in prokaryotes, detailing how it contributes to genetic continuity. Participants will learn the initial steps involved in this essential process of cell division.