Unit 3 Flashcards
Which 4 elements are necessary for growth?
Carbon
Hydrogen
Oxygen
Nitrogen
What 5 elements do proteins contain?
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
DNA is a macromolecule that contains which 5 elements?
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
How do animal cells reproduce asexually?
Mitosis
What 5 environmental factors do scientists have to take into consideration when growing cells in culture?
Temperature
pH
Osmotic pressure
Water pressure
Oxygen levels
What 2 macromolecules is the cell membrane composed of?
Lipids (phospholipids, steroids)
Proteins
What results when a single bacterium reproduces?
Two genetically identical daughter cells
When bacterial cells divide, what is the first event to occur?
Replication of the chromosome
Which step of binary fission is the reason for genetically identical daughter cells?
Replication of the bacterial chromosome
Where does the copy of bacteria attach before the cell splits
Cell membrane
How are bacterial cells different from eukaryotic cells during replication? (binary fission vs. mitosis)
Bacteria do not need to dissolve a nuclear membrane or assemble a mitotic spindle
What happens to the cell after the bacteria is replicated? (step 2)
It elongates;
since the chromosomes are attached to different parts of the cell membrane they separate from each other
What is the third step of binary fission?
The bacterium pinches off at the center and forms a septum
What is a septum?
A separating wall between the two compartments of the cell
What is the last step of binary fission?
Separation: The cell splits into two new daughter cells;
fully mature bacteria that can grow, and if conditions are right, continue the binary fission process
What enables the copied chromosomes to separate during binary fission?
The elongation of the cell
How long does it take for the daughter cells to initiate or start the next round of replication?
No time is required;
They are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right.
Put the following steps of bacterial replication in the correct order, starting from a parent cell:
- Septum formation
- Cell elongation
- Separation of daughter cells
- Chromosome replication
4 Chromosome replication
2 Cell elongation
1 Septum formation
3 Separation of daughter cells
What would happen if the septum did not form during binary fission?
The parent cell will not divide into daughter cells
What is an example of a biofilm?
Bacteria growing in plaque on teeth;
Plaque is an accumulation of a sticky polysaccharide (dextran) and an assortment of other oral bacteria
What is an example of a bacteria that has an affinity for the heart valves?
S. mutans;
Streptococcus spp. have an affinity for the heart valves and joints.
Which nutrient is responsible for the development of cavities in teeth?
Sucrose;
S. mutans organisms use sucrose to produce dextran and lactic acid, which directly contribute to dental caries
What term is likely to describe optimal growing conditions for Streptococcus mutans?
Mesophile;
Because it can survive in body temp (heart valves, and joints)
Fermented foods such as sauerkraut or pickles are kept from spoiling by the effects of what?
acidic pH;
produced during fermentation
During which growth phase are bacteria more susceptible to antimicrobial drugs?
Log phase;
because they are actively growing making them more vulnerable to these drugs
What are each of these growth phases?
Lag phase
Log phase
Stationary phase
Death Phase (Decline Phase)
Lag Phase:
- The initial phase after inoculation
- Bacteria adapt to new environment & prepare for growth.
- Little to no cell division occurs; cells are metabolically active
Log Phase (Exponential Phase)
- Bacteria divide at constant & rapid rate
- Population doubles at regular intervals (generation time).
- Cells most susceptible to antibiotics
Stationary Phase:
- The growth rate slows and stabilizes as resources become limited.
- Number of new cells produced = number of dying cells.
- Cells may produce secondary metabolites, including antibiotics
Death Phase (Decline Phase):
- The number of viable cells decreases as nutrients are exhausted and waste products accumulate.
- Death rate exceeds the growth rate
- Cells may enter a state of dormancy or death
These phases represent the typical growth cycle of bacterial populations in a closed system
What does halophilic mean?
It means the organism is salt-loving ;
Halophiles tolerate high levels of sodium chloride
What does the term facultative anaerobe mean?
Facultative anaerobes can grow with or without oxygen;
More growth is evident when oxygen is present because of ATP.
What does the term mesophile mean?
Mesophiles are microorganisms that thrive at moderate temperatures (body temperature)
(Boils in Locker room)
Which organism is most likely to be responsible for the boils?
S. aureus;
is a halophilic, Gram-positive coccus that produces yellow colonies and ferments mannitol
What is a boil?
A boil is a red lump in the skin that may be warm and painful to the touch.
It is a localized accumulation of pus and tissue debris;
Boils often start in an infected hair follicle
What does selective/differential medium do?
Allows you to visually distinguish between different organisms based upon metabolic or biochemical differences
What does CNA medium contain?
Colistin and naladixic acid (antibiotics);
inhibit gram -
selects for gram +
What does colistin and naladixic acid do?
Colistin: disrupts the outer membrane
Naladixic acid: blocks DNA replication in gram negative bacteria
If bacteria grows on the CNA medium what type is it? (potentially)
Gram positive;
because this medium inhibits gram negative bacterial growth
What does Mannitol salt agar (MSA) contain?
7.5% NaCl;
Phenol red
What is MSA selective for?
Halophiles;
Bacteria that can grow in this high salt concentration
ex. Staphylococcus
If the bacteria can ferment mannitol (MSA) then what color does it turn?
Yellow;
only certain bacteria can ferment mannitol if not then it stays red
What does MacConkey medium contain?
Bile salts
Crystal violet
Lactose (as carbohydrate source);
Neutral red as a pH indicator; detects acid fermentation of lactose
What does the MacConkey medium inhibit?
Inhibits gram + bacteria;
selects for gram -
if it grows pink this means that the bacteria can ferment lactose
no color = no fermentation
What does EMB (methylene blue agar) contain?
Lactose
Sucrose
(carbohydrates)
Eosin Y
&
methylene blue
What does EMB contents inhibit?
Inhibits gram +
selects for gram -
(Eosin Y & methylene blue)
EMB Fast fermentation vs. slow fermentation colors?
Fast fermentation: metallic green
Slow fermentation: dark purple
EMB Non fermenters that are gram negative will be what color?
Colorless
What does Blood agar contain?
5% sheeps blood & peptones for energy
What grows in Blood agar?
All organisms;
but it differentiates according to the species hemolytic reaction
What does the hemolytic reaction of Blood agar depend on?
Whether the bacterial species secretes exotoxins called hemolysins
What do hemolysins break down?
Red blood cells (hemoglobin)
What are the 3 different reactions of Blood agar?
- Beta hemolysis: complete breakdown of the hemoglobin and lysis of the red blood cells (clearing around colony)
- Alpha hemolysis: partial breakdown of the hemoglobin; oxidation of iron in hemoglobin
(brownish green color) - Gamma Hemolysis: no hemolysis and no clearing
What observation would suggest that a plate was inoculated with a pure (axenic) culture?
Isolated colonies are all white in color and about the same size
Imagine that you forgot to flame the loop before streaking the inoculum from the first quadrant into the second quadrant. What is the most likely consequence of this error?
Too much bacterial growth outside the first quadrant
When making a T-streak method of streak isolation, how many times would you flame your loop?
4
When making a T-streak method of isolation, how many times would you obtain fresh culture from your source tube?
Once
A selective medium:
Maximizes the growth of one group of bacteria while minimizing the growth of the other group
C.N.A. is supposed to select for Gram ____, while EMB and MacConkey are supposed to select for Gram _____.
positive; negative
Amy has tried to isolate Gram negative bacilli from a mixed culture using EMB. She retrieves her plates from the incubator and finds several colonies growing on her plate. Her classmate tells her she can assume that these colonies are her Gram negative unknown. She is not so sure and thinks it might be possible for some Gram positives to grow…just not as well. Is Amy or Amy’s classmate correct?
Amy is correct that EMB selects for (i.e., favors) Gram negatives, but does not necessarily eliminate all Gram positives. Some Gram positives have been known to grow on EMB, just not very well.
Blood agar is:
(type of medium)
Differential and Enrichment;
Differential: allows us to see whether the organism is hemolytic or not.
Enrichment: because it contains extra nutrients for the growth of fastidious bacteria
To distinguish between the three types of hemolysis, what would you do first?
Look to see whether there is a different-looking area around the colony;
You would do this first to see whether there is hemolysis (alpha or beta) or not (gamma). Then, if there is, you’d look to see whether the zone is transparent (beta) or not (alpha)
Mannitol Salt Agar selects for ____ and differentiates ____.
Halophiles ; mannitol fermenters
If a bacterium can ferment mannitol and grow on Mannitol Salt Agar, what will you see?
Colonies (but no specific color)
Yellow medium around the colonies
Selenite broth allows enteric bacteria to compete better with the other more numerous microbes found in the intestinal tracts of animals. Based upon this description, what is the best term for selenite broth?
Enrichment
