Microbial Growth Flashcards

1
Q

population growth

A

Populations of unicellular microorganisms increase exponentially by geometric progression (2n)

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2
Q

exponential growth

A

asynchronous culture
synchronous culture (will finally become asychronous)

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3
Q

Growth rate or doubling time or Generation time

A

period required for a cell to enlarge, divide, and produce two daughter cells

-variable between different bacteria
-all cell in one population have the same doubling time
-varies with the nutrient availability:

-Less nutrients, doubling time increases
-Accumulation of toxic metabolic compounds, doubling time increases
-E. coliin the lab (18 mins) vsin the gut (12 hours)
-When nutrients are all consumed growth stops

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4
Q

Growth curve or phases of growth

A

lag phase
exponential or log phase
stationary phase (plateau)
Death phase

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5
Q

Lag phase

A

time for cells (stationary or death phase) to adjust to fresh or new medium, start or adjust their metabolism (protein synthesis, DNA replication), and start dividing

A longger lag phase will cause by:
*Inoculum taken from an old culture
*Inoculum taken from a rich medium and added to a poorer one
* No Lag occurs when growing cells are transferred from a poor to a richer medium
*Inoculum taken from a chemically different medium
*Inoculum taken from refrigerated cells
*Cells inoculated into a cold medium

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6
Q

log phase

A

period where nutrients are not in limiting amounts and where cells divide at their maximum speed (lowest doubling time)

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7
Q

Stationary phase (plateau)

A

The culture gradually switch from the log to the stationary phase when nutrient concentration is limiting and toxic waste accumulates, cells divide slower and eventually stop (doubling time increases gradually)

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8
Q

Death phase

A

nutrients where completely consumed, cells stopped growing (stationary phase), and now cells are starting to burst and die (exponentially), not all cells die

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9
Q

Continuous culture in a chemostat

A

*Concentration of one of the nutrient should be provided in limiting amounts to reduce growth rate
*All nutrients (culture medium) should be provided continuously at the same rate to the growing culture
*Some of the growing culture (cells and waste products) should be removed continuously at the same rate

Growth rate is constant and equals loss rate, same amounts of cells actively growing

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10
Q

Uses of continuous culture

A

*Provide a constant supply of cells in balanced growth (exponential phase) and growing at a known growth rate
*Study bacterial growth at variable and very low nutrient concentrations, resemble the environment bacteria encounter in nature
*Facilitate research in microorganism interactions and ecological situations
*Allow industrial production of food and metabolites continuously (antibiotics, vitamins, ethanol)

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11
Q

Parameters affecting bacterial growth

A
  1. temperature
  2. hydrogen ion concentration (pH)
  3. gas environment
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12
Q

temperature

A

Hyperthermophiles (95°C)
Thermophiles (65°C)
Mesophiles (37°C)
Psychrotrophs(25°C)
Psychrophiles (10°C)

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13
Q

pH

A

Neutrophiles (pH around 7.0)
Acidophiles (pH below 7.0)
Alkalophiles(pH above 7.0

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14
Q

Gas environment

A

Aerobes (need oxygen)
Anaerobes (need anaerobic conditions)
Facultative anaerobes (with or without oxygen)
Capnophiles (need oxygen and high CO2concentrations)

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15
Q

温度和growth rate趋势

A

最佳温度越高,最高的growth rate越高

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16
Q

Reactive Oxygen Species (ROS)

A

superoxide radical
hydrogen peroxide
hydroxyl radical

These can hydrolyze all of the molecules we can find in cells

16
Q

什么pH区间可以抑制生长

17
Q

Protective enzymes

A

Superoxide dismutase (SOD)
2O2- + 2H+——>O2 + H2O2

Catalase
Peroxidase

2H2O2——>2H2O + O2
H2O2 + NADH + H+——>H2O +NAD+

18
Q

Oxygen and bacterial growth
+SOD +catalase
+SOD +Catalase
+SOD -Catalase
-SOD -Catalase
+SOD +/- Catalase(low levels)

A

Obligate
Facultative anaerobe
Aerotolerant anaerobe
Strict anaerobe
Microaerophile

bacteria grow in liquid culture, put in agar

19
Q

The anaerobic jar

A

Rubber gasket seal
lid
Catalyst chamber (containing palladium pellet, 催化H2和O2生成水)
Gas generator envelop
anaerobic indicator strip(methylene blue)

20
Q

Growth on solid vs liquid media

A

In liquid cultures, all cells are in the same condition

On a petri dish cells in a colony face different conditions
-Cells in the center are in the stationary phase or death phase
-Cells on the edge are actively growing (exponential phase)
-Cells at the surface are in aerobic conditions
-Cells under the surface of the colony are in anaerobic conditions

21
Q

Mass measurement

A

Turbidity
colony number

22
Q

Mathematics of cell growth

A

Starting with a single cell, the total population number (Nt) at the end of a given time period would be

start with single cell
Nt= 1 x 2^n

start with more than one cell
Nt= N0x 2n
n = 3.3 (log Nt-log N0)

log2=0.301

23
Q

Gene vs. Genome vs. Genotype vs. Phenotype

A

DNA segment that codes for a protein, ribosomal RNAs (rRNAs), or transfer RNAs (tRNAs)

complete DNA sequence present in a cell or a virus

the specific set of genes of an organism

observable characteristics

24
Q

Prokaryote vs. Eucaryotic microorganisms

A

*Prokaryote: bacteria (haploid, one set of genes, 1N)

*Eucaryotic microorganisms: diploid 2N

25
Q

Experiments Prove DNA carry genetic info

A

1. Griffith’s Transformation Experiment
Streptococcus pneumoniae
S(die)M(alive)heat-killedS(alive)heatkilled s+live R(die)

2.Oswald T. Avery
-R cells 只有+ perified S cell DNA——> S colonies
加其他都是R colonies
-S cell extract +protease/RNase +R cells ——> S colonies

3. The Hershey-Chase Experiment
T2 bacteriophage
35S:found in environment
32P:found in cell

26
Q

The Central Dogma

A

Flow of genetic info
gene expression

27
Q

Nucleic Acids

A

Two types of nucleic acids DNA and RNA
–DeoxyriboNucleic Acid (DNA)
–RiboNucleic Acid (RNA)

*Nucleoside polymers (strings of beads)
*Nucleotides: ucleosides with one or more phosphate groups attached to the sugar

–DNA: Adenine, Cytosine, Guanine, Thymine (A, C, G, T)
–RNA: Adenine, Cytosine, Guanine, Uracil (A, C, G, U)

28
Q

Organization of DNA in Cells

A

Eukaryotes
-Inside the nucleus
-Genome of 10^9 bp
-Numerous linear chromosomes
-Highly compacted and organized (chromatin)
-Associated with small basic proteins (histones)
-Generally no plasmids

Prokayotes
-No nucleus, anchored to the cell membrane
-Genome of 10^6 bp
-One circular chromosome
-Only supercoiled (save space)
-Associated with small basic proteins (nonhistone)
-Contain plasmids (small circular DNA molecules)

29
Q

The Organization of DNA in Eukaryotic Cells

A

*Nucleosome (7 nm): histone octamer (8 histone) and 146 base pairs of DNA
*Histone H1 binds the linker regions (14 to >100 bp) and promotes the chromatin structure

30
Q

DNA in human and Bacteria

A

*DNA in the human genome is 1.8 meters long (≈ 6 feet)
*The cell nucleus is only 6 μM in diameters
*The DNA is condensed approximately 10,000 fold
*The bacterial chromosome measures 1 mm, 1,000 times longer than the cell