Chat with AIExam 6: Growth and Culturing of Bacteria
What is sporulation? What triggers sporulation? In bacteria that form endospores generally only a fraction of the total population sporulate and the process takes over eight hours. Explain why it would be harmful for the whole population to sporulate. Is it better to continuously form spores or wait to sporulate when conditions become unfavorable.
(82) 
VerifiedSporulation is the formation of endospores which are not metabolically active and are very resistant to extreme conditions and stress. The endospore cannot divide but can wake up when conditions for growth are restored. Endospores are generally triggered during the stationary phase in response to environmental,metabolic and cell cycle signals.
It would be harmful for the whole population to sporulate if the conditions changed rapidly or not predictably,if for example within those eight hours the nutrients were restored then the whole population would be unable to respond as they would still be sporulating. Also if there were a false alarm it would also be harmful for the whole population to sporulate.
An advantage to continuously forming spores is mainly in rapidly changing or unpredictable conditions as there will always be a safety net (spores)already formed. A disadvantage to continuously forming spores is that spores are not dividing,therefore they do not contribute to increasing the size of the bacteria population (ie fitness)and could be seen as diverted resource.
Draw and label a standard growth curve. Describe each of the 4 phases. Why do you think bacteria don't continue to double indefinitely? You sample a culture that has reached the fourth phase after 2 days,can you think of one reason why the culture would begin to increase on day 4?
(76) VerifiedGrowth curve should have a flat lag phase,followed by an upward sloping log phase,then a flat stationary phase and lastly a downward sloping decline or death phase. The four phases are : 1)lag phase -the organisms are metabolically active but not increasing in number; 2)log phase -organism divides; 3)stationary phase -number of new cells produced equals number of cells dying; 4)decline phase -where many cells have lost their ability to divide.
Bacteria cannot increase exponentially forever as the amount of nutrients will always eventually be consumed/limited. Also toxic byproducts of metabolism would eventually build up.
One reason for the culture to increase again on day 4 is scavenging; in this case the dying cells release their cell components as nutrients that the remaining cells can use to grow. Another could be the production of spores. Or there could be a mutation that arises that allows the bacteria to grow on a new nutrient.
Sporulation usually occurs in response to
(71) VerifiedA
A culture that contains only a single species of organism is known as a
(61) Which of the following does not contribute to an endospore's resistance to unfavorable conditions?
(71) The type of cell reproduction in which a small,new cell develops from the surface of an existing cell and then separates from the parent cell is known as ________ and is the normal mode of replication in _____ .
(74) When a bacterial cell divides into two new cells,the new cells are called
(86) A growth medium consisting of only known amounts of water,magnesium,calcium chloride,potassium and glucose would be considered
(64) Which type of cell will generally shift to aerobic metabolism when oxygen is available but will carry on fermentation otherwise?
(87) Within a bacterial endospore,the spore is most closely surrounded by the
(85) Bacteria that ferment lactose grow as red colonies on MacConkey agar while those that do not ferment lactose are pink. MacConkey agar can best be described as being
(76) Sabourard's agar has a low pH which encourages the growth of molds and discourages the growth of bacteria. Sabourard's agar could best be described as being
(79) All of the following are ways microorganisms adapt to limited nutrients except:
(87) Starch would be broken down to maltose by which of the following exoenzymes?
(69) Which of the following bacterial counting techniques relies on a statistical estimate to determine the number of bacteria in a culture?
(73) 
Filters
- Essay(0)
- Multiple Choice(0)
- Short Answer(0)
- True False(0)
- Matching(0)