Growth and Culturing of Bacteria

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How is microbial growth defined?

Increase in cell size

Increase in cell number (correct)

Both A and B

None of the above

What usually happens to the 'mother cell' before it divides?

It shrinks in size

It duplicates in size and contents (correct)

It remains the same

It divides into multiple daughter cells

What is the process of cell division in bacteria called?

Binary fission

Meiosis

Budding

a and c (correct)

What occurs in binary fission that leads to cell division?

Formation of a transverse septum Signup and view all the answers

When does DNA synthesis occur in continuously dividing cells?

Before the cell divides Signup and view all the answers

What special cell arrangements can result from incomplete separation of cells?

Tetrads, sarcinae, streptococci Signup and view all the answers

How does cell division occur in yeast ?

Budding Signup and view all the answers

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. Signup and view all the answers

What is the result of budding in terms of cell production?

One genetically identical cell and a smaller new cell Signup and view all the answers

What is the ultimate outcome of microbial growth and cell division?

Increase in the number of cells Signup and view all the answers

What characterizes the lag phase of bacterial growth?

Metabolic activity without cell division Signup and view all the answers

What activities occur during the lag phase?

All of the above Signup and view all the answers

What factors influence the length of the lag phase?

Both A and B Signup and view all the answers

In which phase do bacteria grow at an exponential rate?

Log phase Signup and view all the answers

What is the generation time?

Time taken for one generation of bacteria to double Signup and view all the answers

What is the typical range for generation time in bacteria?

20 minutes to 20 hours Signup and view all the answers

How does the population size change in each generation time during the log phase?

It doubles Signup and view all the answers

What is the defining characteristic of synchronous growth?

All cells divide precisely together after each generation time. Signup and view all the answers

What is the result of non-synchronous growth?

A smooth curve in bacterial growth. Signup and view all the answers

What follows the log phase in bacterial growth?

Stationary phase. Signup and view all the answers

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. Signup and view all the answers

What can maintain log bacterial growth in a controlled environment?

Chemostat. Signup and view all the answers

What happens in the stationary phase of bacterial growth?

Cell division decreases to a rate equal to that of cell death. Signup and view all the answers

What characterizes the decline (death) phase of bacterial growth?

all of the above Signup and view all the answers

How does growth occur in colonies on a solid medium?

A small colony forms, containing all descendants of the original cell. Signup and view all the answers

What is a colony-forming unit (CFU)?

The descendants of the original bacterial cell in a colony. Signup and view all the answers

What is the result of continuous addition of fresh medium in a chemostat?

Maintenance of log bacterial growth. Signup and view all the answers

What determines the duration of the decline (death) phase?

Genetic characteristics of the organism. Signup and view all the answers

How is the enumeration of bacteria measured?

By estimating the number of cells through binary fission Signup and view all the answers

What is the principle behind the serial dilution and standard plate count method?

Only living bacteria will form visible colonies on an agar plate Signup and view all the answers

Which method involves a series of dilutions followed by transferring 0.1ml to an agar plate?

Serial dilution and standard plate count Signup and view all the answers

What is the pour plate method?

add diluted culture to melted nutrient agar Signup and view all the answers

What is a disadvantage of the pour plate method?

a and b Signup and view all the answers

How is the spread plate method performed?

By placing a sample on the surface of cool solidified agar medium Signup and view all the answers

How is the concentration of bacterial cells in the original suspension calculated?

By multiplying the number of colonies by the dilution factor Signup and view all the answers

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 Signup and view all the answers

What are the other methods mentioned for bacterial enumeration?

Simple observation, gas production, acid production, and turbidity Signup and view all the answers

How is turbidity measured in bacterial enumeration?

By using a spectrophotometer or colorimeter Signup and view all the answers

What is the purpose of shaking tubes before sampling in bacterial enumeration?

To improve accuracy in colony counting Signup and view all the answers

What is the significance of the 30-300 CFU range in bacterial enumeration?

It represents the range of statistically representative colonies Signup and view all the answers

What are the reasons microorganisms exist almost everywhere on earth?

They need only small quantities of nutrients Signup and view all the answers

What are the physical factors influencing the type of organisms and their growth rates?

Temperature and pH Signup and view all the answers

Which classification of microorganisms is based on their tolerance to acidity or alkalinity?

Acidophiles, Neutrophiles, Alkaliphiles Signup and view all the answers

At what pH range do acidophiles typically grow best?

0.1-5.4 Signup and view all the answers

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 Signup and view all the answers

What protects the cell membrane of organisms that tolerate extreme pH levels?

Impervious cell walls Signup and view all the answers

What is the optimal temperature range for psychrophiles?

15-20°C Signup and view all the answers

What is the classification of bacteria that can grow both below and above 20°C?

Facultative psychrophiles Signup and view all the answers

What is the temperature range for thermophiles?

50-80°C Signup and view all the answers

Which group of bacteria includes those that can adjust and tolerate different environments?

Facultative bacteria Signup and view all the answers

What type of bacteria cannot grow over 20°C?

Obligate psychrophiles Signup and view all the answers

Which factor does NOT influence bacterial growth?

Genetic diversity Signup and view all the answers

What are the three classifications of bacteria based on their temperature preferences?

Psychrophiles, Mesophiles, Thermophiles Signup and view all the answers

What are the biochemical factors influencing bacterial growth?

Availability of C, N, S, P, trace elements, and vitamins Signup and view all the answers