54 Questions
How is microbial growth defined?
Increase in cell number
What usually happens to the 'mother cell' before it divides?
It duplicates in size and contents
What is the process of cell division in bacteria called?
a and c
What occurs in binary fission that leads to cell division?
Formation of a transverse septum
When does DNA synthesis occur in continuously dividing cells?
Before the cell divides
What special cell arrangements can result from incomplete separation of cells?
Tetrads, sarcinae, streptococci
How does cell division occur in yeast ?
Budding
What is the main difference between binary fission and budding?
Binary fission involves the division of the parent cell, while budding involves the development of a new cell on the surface of an existing cell.
What is the result of budding in terms of cell production?
One genetically identical cell and a smaller new cell
What is the ultimate outcome of microbial growth and cell division?
Increase in the number of cells
What characterizes the lag phase of bacterial growth?
Metabolic activity without cell division
What activities occur during the lag phase?
All of the above
What factors influence the length of the lag phase?
Both A and B
In which phase do bacteria grow at an exponential rate?
Log phase
What is the generation time?
Time taken for one generation of bacteria to double
What is the typical range for generation time in bacteria?
20 minutes to 20 hours
How does the population size change in each generation time during the log phase?
It doubles
What is the defining characteristic of synchronous growth?
All cells divide precisely together after each generation time.
What is the result of non-synchronous growth?
A smooth curve in bacterial growth.
What follows the log phase in bacterial growth?
Stationary phase.
Why is the log phase limited in time in a flask or test tube?
Nutrients and O2 are used up, waste materials accumulate, and living space is limited.
What can maintain log bacterial growth in a controlled environment?
Chemostat.
What happens in the stationary phase of bacterial growth?
Cell division decreases to a rate equal to that of cell death.
What characterizes the decline (death) phase of bacterial growth?
all of the above
How does growth occur in colonies on a solid medium?
A small colony forms, containing all descendants of the original cell.
What is a colony-forming unit (CFU)?
The descendants of the original bacterial cell in a colony.
What is the result of continuous addition of fresh medium in a chemostat?
Maintenance of log bacterial growth.
What determines the duration of the decline (death) phase?
Genetic characteristics of the organism.
How is the enumeration of bacteria measured?
By estimating the number of cells through binary fission
What is the principle behind the serial dilution and standard plate count method?
Only living bacteria will form visible colonies on an agar plate
Which method involves a series of dilutions followed by transferring 0.1ml to an agar plate?
Serial dilution and standard plate count
What is the pour plate method?
add diluted culture to melted nutrient agar
What is a disadvantage of the pour plate method?
a and b
How is the spread plate method performed?
By placing a sample on the surface of cool solidified agar medium
How is the concentration of bacterial cells in the original suspension calculated?
By multiplying the number of colonies by the dilution factor
What is the principle of the filtration method for bacterial enumeration?
A known volume of fluid is drawn through a filter with pores smaller than bacteria
What are the other methods mentioned for bacterial enumeration?
Simple observation, gas production, acid production, and turbidity
How is turbidity measured in bacterial enumeration?
By using a spectrophotometer or colorimeter
What is the purpose of shaking tubes before sampling in bacterial enumeration?
To improve accuracy in colony counting
What is the significance of the 30-300 CFU range in bacterial enumeration?
It represents the range of statistically representative colonies
What are the reasons microorganisms exist almost everywhere on earth?
They need only small quantities of nutrients
What are the physical factors influencing the type of organisms and their growth rates?
Temperature and pH
Which classification of microorganisms is based on their tolerance to acidity or alkalinity?
Acidophiles, Neutrophiles, Alkaliphiles
At what pH range do acidophiles typically grow best?
0.1-5.4
Why do microorganisms usually not grow well at pH values significantly above or below their optimum pH?
Due to enzyme denaturation and interference with ion pumping
What protects the cell membrane of organisms that tolerate extreme pH levels?
Impervious cell walls
What is the optimal temperature range for psychrophiles?
15-20°C
What is the classification of bacteria that can grow both below and above 20°C?
Facultative psychrophiles
What is the temperature range for thermophiles?
50-80°C
Which group of bacteria includes those that can adjust and tolerate different environments?
Facultative bacteria
What type of bacteria cannot grow over 20°C?
Obligate psychrophiles
Which factor does NOT influence bacterial growth?
Genetic diversity
What are the three classifications of bacteria based on their temperature preferences?
Psychrophiles, Mesophiles, Thermophiles
What are the biochemical factors influencing bacterial growth?
Availability of C, N, S, P, trace elements, and vitamins
Test your knowledge of microbial growth and cell division with this quiz. Explore questions about the definition of microbial growth, the process of cell division in bacteria, DNA synthesis in continuously dividing cells, and special cell arrangements resulting from incomplete separation.
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