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Microbiology Lecture > Chapter 7 > Flashcards

Chapter 7 Flashcards

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Biology 101 flashcards
1
Q

Cell division

A

for both prokaryotes and eukaryotes, there are two common ways that cells divide. During cell division each daughter cell receives genetic material and sufficient copies of all other constituents to exist as an independent cell.

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2
Q

Binary fission

A

cell gets roughly twice its size and then divides the gentic material and cytoplasm equally between the two cells.

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3
Q

Budding

A

a piece of the cell, containing the gentic material but only a little cytoplasm, pinches off to form a new cell. it will then grow bigger

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4
Q

Terminus

A

site at which replication is terminated, located opposite of the origin

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5
Q

replisome

A

group of proteins needed for dna synthesis

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6
Q

chromosome partitioning

A

replisome pushes or condensation of daughter chromosomes o opposite ends. MreB-an actin homolog, plays role in determination of cell shape as spiral inside cell periphery, and chromosome segregation.

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7
Q

Plasmid segregation

A

Plasmids replicate independently and acrry proteins necessary for segregation. E coli plasmid produces three proteins essential for its inheritance. ParM-similar to MreB, actin homolog forms long filaments. ParR(repressor) and ParC(centromere like) both bind to origins and link to ParM., ParM filaments elongate and sepreate plasmids to opposite ends of cell.

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8
Q

cytokinesis-septation

A

septation-formation of cross walls between daughter cells. Several steps directed by several enzymes. selection of site for septum formation. Assembly of Z ring. Linkage of Z ring to plasma membrane. Assembly of cell wall synthesizing machinery. Constriction of cell and septum formation.

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9
Q

Microbial growth

A

increase in cellular constituents that may result in: increase in cell size, increase in cell number. Growth usually refers to population growth rather than growth of individual cells.

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10
Q

Define dor synthetic media

A

all components and their concentrations are known

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11
Q

complex media

A

contain some ingredients of unknown composition and or concentration

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12
Q

peptones

A

potein hydrolysates prepared by partial digestions of various protein sources

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13
Q

extracts

A

aqueous extracts, usually of beef or yeast

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14
Q

agar

A

sulfated polysaccharide used to solidify liquid media, most microorganisms cannot degrade it

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15
Q

minimal medium

A

media containging minimal nutrional requirements for a particular microorganism, baries from microbe to microbe.

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16
Q

rich medium

A

medium containging much more than minimal, may have proteins, amino acids, starches, monosaccharides, ion, lipids

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17
Q

Selective

A

Favor the growth of some microorganisms and inhibit growth of others.
ex: MacConkey Agar. Selects for gram negative bacteria, crystal violet is inhibiting agent for gram+ bacteria

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18
Q

Pure culture

A

Population of cells arising from a single cell developed by Robert Koch. Allows for the study of single type of microorganism in mixed culture. Spread plate, streak plate, and pour plate are techniques used to isolate pure cultures.

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19
Q

Streak Plate

A

Involves techniques of spreading mixed cultures on an agar so that individual cells are well separated from each other.-> colonies

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20
Q

Spread Plate

A

Small volume of diluted mixture containging approximately 30-300 cells. Spread evenly with bent rod.

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21
Q

Pour Plate

A

Sample is sterily diluted, diluted samples are mixed with liquid agar. Mixture of cells and agar are poured into sterile culture dishes.

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22
Q

Growcurve

A

observed when microbes are cultivated in batch culture. Usually plotted as logarithm of cell number v. time. Has 3 or 4 distinct phases. (lag, exponential, stationary, senescence, death)

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23
Q

Lag phase

A

Does not always occur. Interval of time between when a culture is inoculated and when growth begins. Cell synthesizing new components. Ex-to replenish spent materials. To adapt to new medium or other conditions such as a change in temperature.

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24
Q

Exponential phase

A

Log phase. Cells growing exponentially. cell divisions>cell deaths bc plenty of space and nutrients and little waste, maximum growth rate

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25
Q

Stationary phase

A

Cell divisions=cell deaths. Growth rate of population is zero. Either an essential nutrient is used up or waste product of the organism accumulates in the medium, less space too.

Reasons: nutrient depletion, limited oxygen availability, toxic waste accumulation, critical pop density reached.

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26
Q

death phase

A

cell deaths>cell divisions. Too much waste and too little nutrients in medium

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27
Q

Starvation responses

A

Production of starvation proteins-increase cross linking in cell wall, Dps proteins protects DNA, chaperone proteins prevent protein damage. Cells are called persister cells long term survival and increased virulence.

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28
Q

Senescence and death phase hypotheses

A

cells are viable but not culturable-cells alive but dormant, capable of new growth when conditions are right. Programmed cell death- fraction of the population genetically programmed to die.

29
Q

Flow cytometry

A

Microbial suspension forced through small orifice with a laser light beam. Movement of microbe through orifice impacts electric current that flows through orifice. Instances of disruption of current are counted. Specific antibodies can be used to determine size and internal complexity.

30
Q

membrane filter technique

A

Bacteria from aquatic samples are trapped on membranes. Membrane soaked in culture media. Colonies grow on membrane. Colony count determines # of bacteria in sample.

31
Q

Measurement of Cell Mass

A

Dry weight- time consuming and not very sensitive. Quantity of a particular cell constituent- (ex: protein, DNA, ATP< chlorophyll) useful if amount of substance in each cell is constant. Turbidometric measures (light scattering) quick easy and sensitive.

32
Q

Chemostat

A

Device for continuous culture. Rate of incoming medium= rate of removal of medium from vessel (with wastes and cells). An essential nutrient is in limiting quantities.

33
Q

Extremophiles

A

grow under harsh conditions that would kill most other organisms/

34
Q

Changes in osmotic Concentration in the env. may affect microbial cells

A 
Hypotonic solution (lower osmotic concentration)-cells are hypertonic. Water enters the cell and cell swells may burst.
Hypertonic solution (higher osmotic concentration) cells are hypotonic. Water leaves the cell. Membrane shrinks from the cell wall (plasmolysis) may occur.
35
Q

Microbes adapt to changes in osmotic concentrations

A

reduce osmotic concentrations of cytoplasm in hypotonic solutions (if cell too hypertonic). Mechanosensitive (MS) channels in plasma membrane allow solutes to leave. Increase internal solute conc. with compatible solutes to increase their internal osmotic conc. in hypertonic solutions.
Most cells try to stay slightly hypertonic to the env.

36
Q

Halophiles

A

grow optimally in the presence of NaCl or other salts at a concentration above or about 0.2M

37
Q

Extreme halophiles

A

Require salt concentrations of 2M and 6.2M. Extrememly high concentrations of potassium. Cell wall, proteins, and plasma membrane require high salt to maintain stability and activity.

38
Q

Acidophiles

A

Microorganisms that growth optimum between 0 and 5.5 (Mostly prokaryotes, many archaea)

39
Q

Neutrophiles

A

most microorganisms. Growth optimum between pH 5.5 and pH 7

40
Q

Alkaliphiles (basophiles)

A

Microorganisms growth optimum between pH 8.5 and pH 11.5 (mostly prokaryotes)

41
Q

pH

A

Most microorganisms maintain an internal pH near neutrality because pH extremes can denature proteins and nucleic acids and kill cells. They can do this by the plasma membrane is impermable to protons, exchange potassium for protons, buffers. Acidic tolerance response-pump protons out of the cell, some synthesize acid and heat shock proteins that protect proteins. Many microorganisms change the pH of their habitat by producing acidic or basic waste products.

42
Q

Temperature

A

Microorganisms are ambitherms and cannot regulate their internal temp. Enzymes have optimal temp. at which they function optimally. High temperatures may inhibit enzyme functioning and be lethal.

43
Q

Psychrophiles

A 
0-20 degrees C.
Lot temp (otimum temp below 15 and max of 20). organisms with cold temperature optima, the most extreme representatives inhabit permanently cold env.
44
Q

Psychrotrophs

A

0-35 degrees C

45
Q

mesophiles

A

20-45 degrees C. midrange temperature (optimum between 15 and 45).
Warm blooded animals, terrestial (soil) and aquatic env, temperate and tropical latitues.

46
Q

thermophiles

A

55-85 degrees C. high temp (above 45)

47
Q

Hyperthermophiles

A

85-113 degrees C. VERY HGIH

48
Q

Psychrophile adaptations

A

productuon of enzymes and transport proteins that function optimally in the cold, features that may provide more flexibility. More of alpha helices and beta sheets, mroe polar and less hydrophobic amino acids, fewer weak bonds, decreased interactions between protein domains.
Transport processes fucntion optimally at low temp due to modifications of cytoplasmic membranes. High unsaturated fatty acid content. Fewer hopanoids (to minimize van der waals forces)

49
Q

Adaptations of thermophiles

A

protein structure stabilized by a variety of means (ex: more H bonds, more disulfide bonds, more proline, chaperones). Histone-like proteins stabilize DNA, membrane stabilized by variety of means (more saturated, more branched and higher molecular weight lipids, ether linkages)

50
Q

Strict aerobes

A

Usually live at 20,21% oxygen and wil die in the absence of oxygen, can only do aerobic cellular respiration

51
Q

Microaerophiles

A

strict aerobes, but can use oxygen only when it is present at levels reduced from the air, live in environments with reduced oxygen content

52
Q

Anaerobes

A

organisms use some other method of energy metabolism, not aerobic cellular respiration or other oxygen requiring energy metabolism (do not require oxygen)

53
Q

Aerotolerant anaerobe

A

can tolerate oxygen and grow in its presence even though they cannot use it

54
Q

Strict anaerobes

A

organisms that will die in the presence of any oxygen

55
Q

Facultative anaerobe (aerobes)

A

Organisms that can live in the presence or absence of oxygen- they do aerobic cellular respiration when oxygen (o2) is present, and some other energy metabolism when oxygen is absent

56
Q

Toxic forms of oxygen

A

Singlet Oxygen (O-). Superoxide anion (O2-). Hydrogen peroxide (H2O2). Hydroxyl Radical (-OH). **These molecules can damage proteins and nucleic acids. They can lead to mutations and cause cell death when they get up above a certain threshold of protection and repair.

57
Q

Dealing with Toxic Forms of Oxygen

A

Aerobes and facultative aerobes have the most detoxifying enzymes. Microaerophiles and aerotolerant anaerobes have less but have some. Strict anaerobes- have no detoxifying enzymes.

58
Q

Strict Anaerobic Microbes

A

all strict anaerobic microorganisms lack or have very low quantities of superoxide dismutase and catalase. These microbes cannot tolerate O2. Anaerobes must be grown without O2, work station with incubator and gaspak anaerobic system.

59
Q

Pressure

A

Microbes that live on land and water surface live at 1 atmosphere (atm). Some bacteria and Achaea live in deep sea with very high hydrostatic pressures.

60
Q

Barotolerant

A

adversely affected by increased pressure, but not as severely as nontolerant organisms

61
Q

Barophilic

A

(Peizophilic) organisms. require or grow more rapidly in the presence of increased pressure.. Change membrane fatty acids to adapt to high pressures.

62
Q

Ionizing Radiation

A

Xrays and gamma rays, can cause mutations at low doses and death at higher doses (sterilization). Disrupts chemical structure of many molecules, including DNA-damaged may be repaired by DNA repair mechanisms if small dose. Deinococcus radiodurans- extremely resistant to DNA damag e.

63
Q

Ultraviolet radiation

A

wavelength most effectively absorbed by DNA is 260nm. Can cause mutations (lowdose)> death (higher dose). Causes formation of thymine dimers in DNA, requires direct exposure on microbial surface, DNA damage can be repaired by several repair mechanisms.

64
Q

Visible Light

A

At high intensities generates singlet oxygen (powerful oxidizing agent). Carotenoid pigments protect many light exposed microorganisms from photooxidation.

65
Q

Biofilms

A

Most microbes grow attached to surfaces (sessile) rather than free floating (planktonic). These attached microbes are members of complex, slime enclosed communities called a biofilm, biofilms are ubiquitous in nature in water, can be formed on any conditioned surface.

66
Q

Biofilm formation

A

microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substance. Additional polymers are produced as microbes reproduced and biofilm matures.

67
Q

Heterogeneity

A

differences in metabolic activity and locations of microbes.

68
Q

Cell to cell communications

A

Prokaryotic cells in biofilms communicate in a density-dependent manner called quorum sensing. Produce small proteins that increase in concentrations as microbes replicate and convert a microbe to a competent state

Microbiology Lecture (11 decks)

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