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Bio 20N > Exam 2: Ch 10 > Flashcards

Exam 2: Ch 10 Flashcards

1
Q

Generation time in eukaryotic organisms

A

In eukaryotic cells, the generation time is typically 12 to 24 hours but can vary widely depending on the type of cell and conditions.
Eukaryotic cells undergo more complex processes such as mitosis (for somatic cells) or meiosis (for gametes), which generally take longer than prokaryotic binary fission

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2
Q

Generation time in prokaryotic organisms (bacteria and archaea)

A

Generally, the generation time in prokaryotic cells, like Escherichia coli (E. coli), can range from 20 minutes to several hours under optimal conditions.
Prokaryotes reproduce through binary fission, a simple form of asexual reproduction

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3
Q

Generation time of E. coli, M. tuberculosis, M. leprae

A
  • E. coli: 20 minutes
  • M. Tuberculosis: 15 to 20 hours
  • M. leprae: 14 days/2 weeks
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4
Q

Binary fission:

A

the process by which prokaryotic organisms, like bacteria, divide and reproduce
- The most common mechanism of cell replication in bacteria
- Essentially, it is a division of one cell into 2 daughter cells

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5
Q

Ftsz protein

A

directs cell division in prokaryotes
- forms Z ring

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6
Q

Divisome

A

a type of structure
- activates to produce a peptidoglycan cell wall and build a septum that divides the two daughter cells

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7
Q

Exponential division

A

STUDY THIS

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8
Q

Growth Curve

A

the reproducible growth pattern

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9
Q

Culture Density

A

the number of cells per unit volume, it is a measure of the number of cells in a population

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10
Q

Growth curve phases

A

4 phases
- lag phase
- log phase
- stationary phase
- death/decline phase

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11
Q

Lag Phase

A

the initial phase
* small number of cells, a.k.a. the inoculum, are added to a fresh culture medium
* in this phase there is no increase in number of living bacterial cells, although they do grow larger in size and are metabolically active

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12
Q

Log Phase

A

2nd phase
* also known as the exponential growth phase
* in this phase, the cells are actively dividing by binary vision, and their number increases exponentially
* cells are sensitive to adverse conditions
* antibiotics can be introduced and are effective

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13
Q

Stationary Phase

A

Third Phase
* the number of new cells created by cell division becomes equivalent to the number of dying cells
* cells switch to survival mode of metabolism
* synthesis of peptidoglycan, proteins, and nucleic acids slow down
* cells become less susceptible to antibiotics
* in bacteria which produce endospores, cells may undergo sporulation
* something about Persister cells

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14
Q

Death or Decline Phase

A

last phase
* Exponential decrease in number of living cells due to accumulation of toxic waste and nutrient exhaustion
* the number of dying cells exceeds the number of dividing cells
* Surviving cells maintain viability and form endospores
* Persister Cells

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15
Q

Batch culture

A

also known as a closed culture, in which no nutrients are added and most waste is not removed

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16
Q

Continuous Culture

A

open system, adding nutrients and removing an equal volume of culture medium. Keeps the system in the exponential growth phase for an extended period

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17
Q

Chemostat

A

a culture vessel fitted with an opening to add nutrients (feed) and an outlet to remove contents (effluent) , effectively diluting, toxic wastes, and dead cells
- the addition and removal of fluids is adjusted to maintain the culture in the log phase of growth
- if aerobic bacteria are grown, suitable oxygen levels are maintained

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18
Q

Persister Cells

A

cells with slow metabolic rate. These cells are important because they are associated with certain chronic infections, like tuberculosis, that do not respond to antibiotic treatment

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19
Q

Measurement of growth

A

bacterial count, which refers to the estimating of the number of bacterial cells in a sample (there are two types):

  • direct cell count: actually counting the cells in a liquid culture or colonies on a plate
  • easiest way to count bacteria is called the direct microscopic cell count
  • indirect methods: depend on the measurement of cell presence or activity without actually counting individual cells
  • measures turbidity (or cloudiness) of a sample of bacteria in a liquid
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20
Q

Methods of direct cell count

A
  • serial dilution
  • plate count
  • fluorescent stains and microscopy (or direct microscopic cell count)
  • using cell counters
  • using cytometer
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21
Q

Methods of indirect cell counts:

A
  • spectrophotometer (laboratory instrument used to measure turbidity): measures the light passing through the bacteria and converts it into percent transmission or absorbance value
  • measuring dry weight of a culture
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22
Q

Plate count

A

a count of viable or live cells
- it is considered a low estimate of the actual number of life cells due to several reasons
- it is based on the principle that viable cells replicate and give rise to visible colonies when incubated under suitable conditions for the specimen
Results are expressed as colony forming units per milliliter

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23
Q

Serial dilution

A
  • Serial dilution of a culture is the first step before proceeding to either the poor plate or spread plate method
  • Goal is to obtain plates with CFUs in the range of 30 to 300
  • The dilution is used to calculate the number of cells in the original cell culture
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24
Q

Statistically valid number of colonies

A
  • 30-300 colonies
  • samples with less than 30 colonies do not give statistically reliable numbers and are considered TFTC
  • samples with more than 300 colonies make it difficult to accurately count individual colonies and are considered TNTC
  • CFU = #of colonies/(amount plated x dilution)
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25
Biofilm formation
- Stage one: reversible attachment of platonic cells (attachment of platonic cells to a substrate where they become sessile or attached to a surface) SECONDS - Stage two: first colonizers become irreversibly attached (SECONDS, MINUTES) - Stage three: growth in cell division (HOURS, DAYS) - Stage four: production of EPS and formation of water channels (HOURS, DAYS) - stage five: attachment of secondary colonizers and dispersion of microbes two new sites (DAYS, MONTHS)
26
Biofilms
highly structured communities that provide a selective advantage to their constituent microorganisms * purpose: provides a protected environment in harsh conditions and aids colonization by microorganisms * Form on medical devices, resist routine, cleaning, and sterilization, and cause health acquired infections * Can form on teeth as plaque, in the lungs of patients with cystic fibrosis, and on the cardiac tissue of patients with endocarditis
27
Function of the extracellular polymeric substances (EPS) found in the matrix of the biofilm:
* EPS: is a hydrated gel composed primarily of polysaccharides and containing other macromolecules, such as proteins, nucleic acids, and lipids secreted by the organisms in the biofilm * The channels in the EPS allow movement of nutrients, waste, and gases throughout the biofilm, which keep the cells hydrated preventing desiccation * EPS also shelters organisms in the biofilm from predation by other microbes or cells (example: protozoans, white blood cells in the human body)
28
What is Quorum Sensing?
* the mechanism by which cells in a biofilm coordinate their activities in response to environmental stimuli * It enables microorganisms to detect their cell density through the release and binding of small, diffusible molecules called autoinducers
29
Gram-negative bacteria communicate mainly using??
N-actuated homoserine lactones NHL
30
Gram-positive bacteria communicate mostly using??
Small peptides
31
Pseudomonas aeruginosa
colonizes biofilms in the airways of patients with cystic fibrosis, causing chronic and sometimes fatal infections of the lungs
32
Reactive oxygen species
highly unstable ions and molecules derived from partial reduction of oxygen that can damage virtually any macromolecule or structure with which they come in contact * ingredients in bleach are an example of ROS
33
Obligate (strict) Aerobes:
* all the bacteria growth is seen at the top of the tube * cannot grow without an abundant supply of oxygen (they NEED oxygen) * use aerobic respiration
34
Examples of Obligate Aerobes:
- Mycobacterium tuberculosis: causes tuberculosis - Micrococcus luteus: a gram-positive bacterium that colonizes the skin - Neisseria meningitidis: agent of severe bacterial meningitis - Neisseria gonorrhoeae: agent of sexually transmitted gonorrhea
35
Obligate Anaerobes:
* bacteria growth is seen at the bottom of the tube * killed by oxygen * use anaerobic fermentation
36
Examples of Obligate Anaerobes:
* - Bacteroidetes: represent a large fraction of the microbes in the human gut * - Clostridium difficile: major cause of health acquired infections and inflammation of colon * - C. tetani and C. perfringens: causes gas gangrene (black dead skin)
37
Facultative Anaerobes:
* heavy growth at the top of the tube and growth throughout the tube * organisms thrive in the presence of oxygen, but also grow in its absence by relying on fermentation or anaerobic respiration * use both anaerobic and aerobic respiration
38
Examples of Facultative Anaerobes
- Staphylococci: found in the skin and upper respiratory tract - Enterobacteriaceae: found in the gut and upper respiratory tract but can spread to the urinary tract
39
Aerotolerant Anaerobes:
* indifferent to the presence of oxygen grow evenly distributed across the tube * do not use oxygen, but they usually have a fermentative metabolism, but they are not harmed by the presence of oxygen as obligate
40
Examples of Aerotolerant Anaerobes:
- Lactobacilli: found in oral microbiota - Streptococci: found in oral microbiota
41
Microaerophiles
* known as the “Goldilocks” culture * oxygen level has to be just right for growth, not too much and not too little * bacteria that requires a minimum level of oxygen for growth, about 1% to 10%s
42
Optimum oxygen concentration
the ideal concentration of oxygen for a particular organism
43
Minimum permissive oxygen concentration
lowest concentration of oxygen that allows growth
44
Maximum permissive oxygen concentration:
highest tolerated concentration of oxygen
45
Optimum growth pH:
the most favorable pH for the growth of an organism
46
Minimum growth pH
the lowest pH value that an organism can tolerate
47
Maximum growth pH
the highest pH value that an organism can tolerate
48
Neutrophils
grow optimally at a pH within one or two pH units of the neutral pH of 7 (pH around 5.5-8.5) * examples: Escherichia coli, staphylococci, and Salmonella spp.
49
Acidophiles
microorganism that grow at pH less than 5.55 (optimal growth is at about 3 pH) * examples: ferroplasma, lactobacillus (bacteria in vagina), * Helicobacter : causes stomach cancer
49
Alkaliphiles
microorganisms that grow best at pH between 8.0 and 10.5 * Examples: Vibrio Cholerae (pathogenic agent of cholera)
50
Optimum growth temperature:
temperature at which the growth rates of the organism are highest
51
Minimum growth temperature
lowest temperature at which organisms can survive and replicate
52
Maximum growth temperature:
the highest temperature at which growth can occur
53
Mesophiles
or “middle loving”, are adapted to moderate temperatures, with optimal growth temperature ranging from room temperature (20* C) to about 45*C * since the human body lies at 37*C, normal human microbiota and pathogens, like E.coli, Salmonella spp., and Lactobacillus) are mesophiles
54
Psychrotrophs
aka psychrotolerant, prefer cooler environments, from a high temperature of 25*C to refrigeration temperature about 4*C * found in many natural environments in temperature climates * responsible for the spoilage of refrigerated food * important decomposers in cold climates
55
Psychrophiles
aka “cold loving”, microorganisms that can grow at 0*C and below * optimum growth is 15*C * can not survive at temperatures above 20*C * found in deep waters of ocean * important decomposers in cold climates
56
Thermophiles
aka “heat loving”, have growth in optimum temperatures of 50*C to a maximum of 80*C * do not multiply at room temp * widely distributed in hot springs, geothermal soils, and manmade environments such as garden compost piles where the microbes break down kitchen scraps and vegetal material
57
Hyperthermophiles
characterized by growth ranges from 80*C to a maximum of 110*C * some can survive even higher temperatures
58
Halophiles
“salt loving”, require high salt concentration for growth * found in marine environments where salt concentrations hover at 3.5%
59
Halotolerant
do not need high concentrations of salt for growth but will survive and divide in the presence of high salt * Halotolerant pathogens are an important cause of food-borne illnesses because they survive and multiply in salty food. * For example, the halotolerant bacteria S. aureus, Bacillus cereus, and V. cholerae produce dangerous enterotoxins and are major causes of food poisoning
60
Barophiles
Microorganisms that require high atmospheric pressure for growth * not much is known about these organism because it’s difficult to get ahold of them * bacteria that live at the bottom of the ocean are great examples
61
If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?
* 1600 cells * 50*2*2*2*2*2 =1600
62
In which phase would you expect to observe the most endospores in a Bacillus cell culture?
Death phase
63
In which phase of the bacterial growth curve would you be able to introduce antibiotics
Log phase
64
In which phase of the bacterial growth curve would the number of dead cells be equal to the number of live cells?
Stationary phase
65
How much will a culture be diluted if 1 ml of the cell suspension is added to 999 ml of diluent?
1:1000
66
How much will a culture be diluted if 10 ml of the cell suspension is added to 90 ml of diluent
* 10^-1
67
A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?
Psychrotrophs
68
A thioglycollate medium culture tube is clear throughout the tube except for the dense growth at the bottom of the tube. What is your conclusion?
organisms are obligate anaerobes
69
Which of the following best describes how a microaerophile would grow in a thioglycollate tube culture?
* a short distance below the top of the medium, but not at the top
70
An experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through?
* 5 * 4*2*2*2*2*2=128
71
How much will a culture be diluted if 10 ml of the cell suspension is added to 990 ml of diluent?
* 10^-2
72
What is the function of the Z ring in binary fission?
forms contractile ring at the septum

Bio 20N (9 decks)

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