Chapter 5: Microbial Growth Flashcards
what are the reproductive strategies of eukaryotic microbes?
asexual (mitosis) and sexual (meiosis), haploid or diploid
what is the reproductive strategy of bacteria and archaea?
haploid only,
asexual - binary fission, budding, filamentous
what is cell division?
each daughter cell receives genetic material and sufficient copies of all other cell constituents to exist as an independent cell
For both prokaryotes and eukayrotes, there two common ways cell division occurs. What are they and describe them
1.) Binary fission – cell gets roughly twice its size and then divides the genetic material and cytoplasm equally between the two cells.
2.) Budding – a piece of the cell, containing the genetic material but only a little cytoplasm, pinches off to form a new cell. It will then grow bigger
(slides 4 and 5)
what is the cell cycle?
sequence of events from formation of new cell through the next cell division
most bacteria divide by _________
binary fission
for the bacterial cell cycle, two pathways function during cycle. What are they?
- ) DNA replication and partition
2. ) Cytokinesis – division of cytoplasm and structures within
most bacterial chromosomes are____
circular
Most bacterial chromosomes have a ______ origin/s of replication – site at which replication begins
single
in regards to the bacterial chromosomes, what is the Terminus?
site at which replication is terminated, located opposite of the origin
in regards to the bacterial chromosomes, what is the Replisome?
group of proteins needed for DNA synthesis
True or False: DNA replication proceeds in both directions from the origin
true
slides 8 and 9
describe chromosome partitioning in bacteria (2)
1.) 2 daughter chromosomes are moved to opposite ends
2.) MreB (murein cluster B) – an actin homolog, plays role in chromosome segregation
-new origins associate with MreB tracks
-if MreB is mutated, chromosomes do not segregate
(slide 11)
what is Septation?
- formation of cross walls between daughter cells
- several steps directed by several enzymes
describe culture media (3)
Slide 14
- ) Need to grow, transport, and store microorganisms in the laboratory
- )Culture media is solid or liquid preparation
- ) Must contain all the nutrients required by the organism for growth
what are the three basis for classifications for culture media?
- chemical constituents from which they are made
- physical nature
- function
for the chemical composition basis for classification, what are the 2 types? describe them
- ) Defined or Synthetic
- All components and their concentrations are known - ) Complex
- Contain some ingredients of unknown composition and/or concentration
what is minimal medium?
media containing minimal nutritional requirements for a particular microorganism; varies from microbe to microbe
what is rich medium?
medium containing much more than minimal; may have proteins, amino acids, starches, monosaccharides, ion, lipids
for the function basis for classification, what are the 4 types?
Supportive
Enriched
Selective
Differential
describe Supportive or general purpose media
Support the growth of many microorganisms (rich media)
e.g., (TSA) tryptic soy agar (rich medium)
describe enriched media
general purpose media supplemented by blood or other special nutrients
e.g., blood agar (TSA + sheep blood)
describe selective media
Favor the growth of some microorganisms and inhibits growth of others (has inhibiting agent)
e. g., MacConkey agar
- selects for gram-negative bacteria
- Crystal violet is inhibiting agent for gram + bacteria
describe differential media
Media which allows different microorganisms to grow differently
i.e., blood agar
what is a pure culture?
what does it allow for?
what techniques are used?
- 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
describe a streak plate (2)
-Involves technique of spreading a mixture of cells on an agar surface so that individual cells are well separated from each other
(involves use of bacteriological loop_
-Each cell can reproduce to form a separate colony (visible growth or cluster of microorganisms)
(Slide 31)
what is a spread plate? (2)
-small volume of diluted mixture containing
-approximately 30–300 cells are transferred
spread evenly over surface with a sterile bent rod
(slide 33)
describe a pour plate (3)
-sample is serially diluted
-diluted samples are mixed with liquid agar
-mixture of cells and agar are poured into sterile culture dishes
(slide 34)
what is growth?
Increase in cellular constituents that may result in:
- increase in cell number
- increase in cell size
Growth refers to______ rather than _________
population growth; growth of individual cells
slides 36-39
Make sure to look at these slides!
Entry into stationary growth curve phase activates survival strategy. Name 3 things that happen
- ) morphological changes
e. g., endospore formation - ) Decrease in size, protoplast shrinkage, and nucleoid condensation
- ) RpoS protein assists RNA polymerase in transcribing genes for starvation proteins
for starvation response, Production of starvation proteins does what? (3 things)
increase cross-linking in cell wall
Dps protein protects DNA
chaperone proteins prevent protein damage
Cells in the starvation response stage are called what?
Persister cells
- long-term survival
- increased virulence
There are 2 alternate hypothesis regarding Senescence and Death Phase. What are they?
1.) cells are Viable But Not Culturable (VBNC)
-cells alive, but dormant, capable of new growth when conditions are right
2.) Programmed cell death
fraction of the population genetically programmed to die (commit suicide)
(slide 43)
describe Generation (doubling) time (3)
- Time required for the population to double in size
- Varies depending on species of microorganism and environmental conditions
- Range is from 10 minutes for some bacteria to several days for some eukaryotic microorganisms
What is exponential population growth?
Population is doubling every generation
slide 47-50
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