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BIO 111 > Chapter 4 > Flashcards

Chapter 4 Flashcards

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Biology 101 flashcards
1
Q

Microbial Growth

A

The growth of a population (increase in the number of cells not size) in a specific amount of time; lead by cell division

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2
Q

Binary Fission

A

A primitive form of cell division asexual reproduction) that does not use a spindle fiber apparatus:

  • Bacterial cell doubles in size
  • Replicates its chromosome (DNA)
  • Two chromosomes attach to separates sites (opposite ends) on the plasma membrane
  • A cell wall forms between the chromosomes and separates the cells, producing two daughter cells
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3
Q

Budding

A

A type of asexual reproduction in which a cell forms a bubble-like growth that enlarges and separates from the parent; a few bacteria and some eukaryotes (yeast) replicate this way

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4
Q

Phases of Growth (Closed System)

A

A microbial lab culture typically passes through 4 distinct, sequential phases of growth:
- Lag Phase
- Exponential Phase
- Stationary Phase
- Death Phase (phase of prolonged decline)
In the lab, cultures usually pass through all phases - not in nature

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5
Q

Lag Phase

A

Considerable metabolic activiity is occurring as the cells prepare to grow:

  • Enzymes and proteins are synthesized to efficiently break down substances in the environment and to construct new macromolecules and ribosomes
  • Length varies depending on species
  • No perceivable change in numbers
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6
Q

Exponential (Logarithmic) Phase

A

Cell numbers increase exponentially:

  • During each generation time, number of cells in a population increases by a factor of 2
  • Slowly at first, but then extremely rapidly
  • Lasts 4-10 hours; quickly use up most nutrients and metabolic byproducts accumulate to near toxic levels (oxygen depletion)
  • Cells are very virulent, easily cause infection or disease, but are also most susceptible to antibiotics
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7
Q

Stationary Phase

A

The number of cells doesn’t increase, but changes within cells occur:

  • Cells “realize” environmental conditions are turning detrimental to continued growth
  • Cells become smaller and produce structures the provide resistance (glycocalyx, endospores, cytoplasmic inclusions)
  • Signal to enter this phase may have to do with overcrowding (accumulation of metabolic byproducts, depletion of nutrients, etc.)
  • Important phase when treating infections with antibiotics
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8
Q

Death Phase

A

Cells begin to die out:

  • Occurs exponentially but at a low rate
  • Cells have depleted intracellular ATP resources
  • Not all necessarily die this way (phase of prolonged decline)
  • More fit cells survive using nutrients from dying cells
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9
Q

Continuous Culture of Microbes

A

In nature, nutrients continuously enter the cell’s environment at low concentrations, and populations grow continually at a low but steady rate:

  • Growth rate set by the concentration of the scarcest or limiting nutrient
  • Other microbes use metabolic byproducts for their own metabolism
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10
Q

Colony Growth of Microbes

A

Liquid or agar:

  • On agar, the position of the cell in the colony determines the environment it is in and what its phase is in the growth curve
  • Exponential on the edges, stationary in the middle, death in the center
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11
Q

Generation Time

A

The length of time it takes one cell to divide into two cells; varies greatly between bacteria:

  • Some bacteria can grow every 10 minutes if conditions are excellent
  • Some can take 24 hours to finish one division
  • The average can reproduce, under optimum conditions, about once every 30 minutes
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12
Q

Rate of Growth Formula

A

N+ = (No) x 2^n

  • N+ = total population of cells in a given amount of time
  • No = original number of cells
  • n= number of cell divisions in a given amount of time
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13
Q

Reasons Microbes Exist in Many Environments

A
  • Small size
  • Easily dispersed
  • Need only small quantities of nutrients
  • Diverse in their nutritional requirements
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14
Q

Moisture’s Influence on Bacterial Growth

A

Since they are free-living, independent cells get all their nutrients by diffusion from the surrounding environment, and therefore, need water in order to grow; very resistant to desiccation; dehydration preserves food (may not kill)

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15
Q

Minimum Temperature

A

Lowest temperature that permits growth and metabolism, but usually at a very slow pace; very cold temperatures do not usually denature proteins or destroy microorganisms

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16
Q

Maximum Temperature

A

Highest temperature that permits growth and metabolism, usually at depressed rates; going above, enzymes will become denatured and metabolism will stop, destroying the cell

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17
Q

Optimum Temperature

A

Typically covers a small range in which organism’s metabolic processes and growth are fastest; why fevers (even slight) can be helpful in fighting off bacterial infections

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18
Q

Psychophiles (Cold-Loving)

A

Bacteria that will grow in temperatures from 5’ C to 20’ C:

  • Will not cause infections in humans
  • Responsible for the spoiling of refrigerated, and some frozen, food (e.g., blood)
  • Perishable items must be frozen far below freezing to retard growth
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19
Q

Mesophiles (Middle-Loving)

A

Bacteria that will grow in temperatures from 20’ C to 50’ C:

  • Optimum temperatures from human pathogens are around 37’ C
  • Pathogenic bacteria
  • Different organisms will grow best in different regions of the body (e.g., Mycobacterium leprae grows best on the extremities - leprosy)
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20
Q

Thermophiles (Heat-Loving)

A

Bacteria that will grow in temperatures from 50’ C to 80’ C:

  • Found in natural hot springs, volcanic vents, etc.
  • The autoclave is used to isolate them in a culture
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21
Q

Hyperthermophiles

A

Bacteria that will grow in temperatures about 80’ C; found in compost heaps and in boiling hot springs

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22
Q

Acidophiles

A

Bacteria that live in very acidic environments; optimal pH is below 5.5, but some can live in environments close to 0 (e.g., Helicobacter pylori, which cause ulcers in the stomach; Lactobacillus, which ferments millk)

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23
Q

Neutrophiles

A

Bacteria that grow best in pHs of 6-8; most human pathogenic bacteria have an optimum pH near 7.3

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24
Q

Alkalinophiles

A

Bacteria that live in very alkaline environments; optimal pH is above 8.5, but some can live in environments of pHs close to 10 (bleach)

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25
Q

Antioxidants

A

Enzymes used by organisms to detoxify oxygen

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26
Q

Superoxide Dismutase (SOD)

A

Enzyme that detoxifies superoxide ions (O2-)

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27
Q

Catalase

A

Enzyme that detoxifies peroxides by converting them to water and oxygen; cause hydrogen peroxide to bubble (release oxygen) when poured into a wound

28
Q

Catalase Test

A

A clinical test used to determine if catalase is present; allows for a quick determination of an organisms capability of surviving in oxygen

29
Q

Obligate Aerobes

A

Bacteria that typically have both superoxide dismutase and catalase and, therefore, can tolerate an oxygen rich environment:

  • Conduct aerobic respiration and are totally dependent upon oxygenfor their metabolism
  • Without oxygen, the microorganism will not grow, and will die
  • e.g., most fungi, protozoans, some bacteria (Bacillus, Pseudomonas)
30
Q

Facultative Anaerobes

A

Bacteria that typically have superoxide dismutase and catalase:

  • Can conduct aerobic or anaerobic pathways to generate ATP
  • Grow best with oxygen present but can grow and reproduce without it (slower)
  • e.g., E. coli, Staphylococcus, Saccharomyces (yeast)
31
Q

Obligate Anaerobes

A

Bacteria that usually lack both enzymes necessary to live in an oxygen rich environment:

  • Conduct anaerobic pathways only (glycolysis, fermentation) to generate ATP used for growth
  • Can not grow if oxygen is present
  • Usually live in places that totally lack oxygen like deep mud, lakes, oceans, and the bodies of animals (the human body has many places relatively fee of oxygen - e.g., dental cavities, large intestine)
  • e.g., Clostridium
32
Q

Microaerophile

A

Bacteria that contain a small amount of catalase and superoxide dismutase, and so, can tolerate only small concentrations of oxygen (2 - 10%)

  • Large amounts of oxygen are inhibitory
  • Uses oxygen in catabolic pathways
  • Found within the mucous lining of the hollow organs
  • e.g., Helicobacter pylori (causes stomach ulcers)
33
Q

Aerotolerant Anaerobe (Obligate Fermenter)

A

Bacteria that don’t use oxygen, but it doesn’t harm them

34
Q

Hypertonic

A

Higher concentration of solute outside of a cell; high salt/sugar environments draw water out of the cell causing in to dry out

35
Q

Hypotonic

A

Lower concentration of solute outside of a cell; water will move into the cell
- Bacteria have cell walls that resist osmotic pressure; pump in K+ or produce amino acids that will keep the environment within the cell hypertonic as compared to the environment

36
Q

Halotolerant

A

Bacteria that can tolerate moderate concentrations of salt up to 10% NaCl; Stahylococcus on salty skin

37
Q

Halophiles (Obligate Halophile)

A

Specialized bacteria that require high levels of NaCl to live; 15-30% NaCl to live, grow, and maintain their cell walls; inhabit oceans, salt lakes

38
Q

Osmophiles

A

Bacteria that grow in environments where sugar concentrations are high

39
Q

Hydrostatic Pressure

A

Pressure exerted by standing water (lakes, oceans, etc.):

  • Some bacteria can only survive in these types of environments (ocean valleys in excess of 7000 meters)
  • Necessary to keep their enzymes in the proper 3-dimensional shape; if lose shape and denature, the cell dies
40
Q

Radiation

A

UV rays and gamma rays can cause mutations in DNA:

  • Rays may damage or kill microorganisms
  • Some bacteria have enzyme systems that can repair some mutations
41
Q

Nutritional (Biochemical) Growth Factors

A

Nutrients needed by microorganisms include:

  • Carbon
  • Nitrogen
  • Sulfur
  • Phosphorus
  • Vitamins
  • Certain trace elements: ex. copper, iron, zinc, sodium, chloride, potassium, calcium, etc.
42
Q

Media

A

A liquid or solid material used to grow bacteria

43
Q

Liquid Media (broth)

A

Media good for growing large numbers of bacteria in a short amount of time

44
Q

Agar

A

Solid media; a complex polysaccharide extracted from seaweed:

  • First used by Robert Koch
  • Primarily used to provide a solid surface for bacteria to grow on (isolated colonies)
  • Added to a liquid media at a 1.5% concentration
45
Q

Characteristics of Agar

A
  • Not a nutrient for most bacteria; gelatin (a protein), which can be used as a nutrient, was used prior
  • Melts at 100’ C and solidifies at 45’ C; bacteria can be inoculated in the liquid as it cools, before it solidifies, without killing the cells
  • Can be sterilized; heat at 121’ C for at least 15 minutes at 15psi; steam pressure kills cells and endospores
  • used in motility studies; added to a liquid media at a .4% concentration
46
Q

Defined (Synthetic) Medium

A

Prepared in the lab from materials of precise or reasonably well defined composition

47
Q

Complex Medium

A

Contains certain reasonably familiar materials but varies slightly in chemical composition from batch to batch (contains extract from beef, yeast, blood); ex. nutrient agar, nutrient broth

48
Q

Selective Medium

A

Encourages the growth of some bacteria but suppresses the growth of others

49
Q

Differential Medium

A

Has an ingredient that causes an observable change when a particular biochemical reaction occurs (ex. a color or pH change)

50
Q

Pure Culture

A

Culture that contains only one species of an organism

51
Q

The Streak Plate Method

A
  • Bacteria are picked up on a sterile wire loop
  • Wire is moved lightly along the agar surface, depositing streaks of bacteria
  • The loop is flamed and a few bacteria are picked from the region already deposited and streaked into a new region
  • Fewer and fewer bacteria are deposited as the streaking continues
  • Individual organisms (cells) are deposited in the region streaked last
52
Q

Indirect Measurements

A

Measure a property of the mass of cells and then estimate the number of microbes

53
Q

Turbidity

A

Hold tube up to the light and look for cloudiness as evidence of growth (difficult to detect slight growth); not sensitive in terms of numbers of bacterial cells and not useful for detecting minor contaminations

54
Q

Spectrophotometer

A

A device that can measure how much light a solution of microbial cells transmits; the greater the mass of cells in the culture, the greater its turbidity (cloudiness) and the less light that will be transmitted

55
Q

Indirect Measurements Using Metabolic Activity

A
  • The rate of formation of metabolic products, such as gases or acids, that a culture produces
  • The rate of utilization of a substrate, such as oxygen, glucose, or ATP
  • The rate of reduction of certain dyes (ex. methylene blue becomes colorless when reduced)
56
Q

Direct Measurements

A

Give more accurate measurements of numbers of microbes than indirect methods

57
Q

Direct Counts

A

Methods that determine total numbers of cells; quick and give total count - dead and living cells

58
Q

Direct Microscope Count

A

Organisms are counted in a special glass slide under the light compound microscope

59
Q

Coulter Counter

A

Electronic counter; rapid and accurate only if bacterial cells are the only particles present in the solution; solutions must be diluted

60
Q

Viable Cell Count

A

Determine total number of organisms that can grow under certain conditions

61
Q

Standard Plate Count

A

Bacterial colonies are viewed through the magnifying glass against a colony-counting grid (Quebec colony counter):

  • Use serial dilutions to decrease cell numbers before counting
  • Ideal number of colonies on final plate is 30-300 colonies
  • Multiply colonies by serial dilutions
62
Q

Filtration

A

A known volume of liquid or air is drawn through a membrane filter by vacuum; the pores in the filter do not allow microbial cells to pass through; the filter is placed on a solid medium and incubated; the colonies that develop are the number of viable microbial cells in the volume of liquid that was filtered; great technique for concentrating a sample

63
Q

Candle Jars

A

Inoculated tube or plate is placed in a jar and a candle is lit before the jar is sealed

64
Q

Thioglycollate Medium

A

Oxygen-binding agent added to the medium to prevent oxygen from exerting toxic effects on anaerobes; media is usually dispensed in sealed screw-cap tubes

65
Q

Anaerobic Chamber (Brewer Jar)

A

A catalyst is added to a reservoir in the lid of the jar; water is added to the gas-pak; water is converted to hydrogen gas and carbon dioxide; the hydrogen gas can then bind with any oxygen in the jar to form water

BIO 111 (15 decks)

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