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Questions and Answers

Which of the following is a nutrient required in minute amounts for microbial growth?

Turbidity

Viable counting

Macronutrients

Trace metals (correct)

What is used as a measure of microbial cell numbers based on its cloudiness?

Cell nutrition

Growth media

Turbidity (correct)

Viable counting

What is the main topic of Microbiology Lecture 4?

Chemical makeup of a microbial cell

Microbial periodic table of the elements

Cell nutrition

Dynamics of microbial growth (correct)

Which method provides information on viable cell counts?

Serial dilutions on solid media Signup and view all the answers

What is the main limitation of microscopic cell counting?

It cannot distinguish reproducing cells from dormant cells Signup and view all the answers

What does serial dilutions for viable counts involve?

Creating a series of successive ten-fold dilutions Signup and view all the answers

In which fields are applications of viable counts commonly found?

Food, dairy, medical, and aquatic microbiology Signup and view all the answers

What are turbidity measurements commonly used for?

Estimating cell density Signup and view all the answers

What does generation time refer to in microbial growth?

The time required for microbial cells to double in number Signup and view all the answers

Which phase is not part of the typical growth curve in a culture of fixed volume?

Reproductive phase Signup and view all the answers

What is a chemostat culture?

A continuous culture with constant addition and removal of medium Signup and view all the answers

What is involved in biofilm growth?

Planktonic and sessile growth, as well as the formation of biofilms Signup and view all the answers

What terms are used in describing microbial growth?

Binary fission, generation time, and growth curve Signup and view all the answers

What does spectrophotometric measurement of microbial growth involve?

Optical density (OD) and the growth cycle Signup and view all the answers

What is a key characteristic of biofilm growth?

Formation of a complex, multi-layered community Signup and view all the answers

What is the approximate dry weight of E. coli?

184 fg Signup and view all the answers

Which elements make up 96% of the dry weight of E. coli?

Carbon, oxygen, nitrogen, phosphorus, and sulfur Signup and view all the answers

What is the purpose of solid media prepared with agar in microbial culture?

To culture microbes and enable the observation of colony morphology Signup and view all the answers

What are the essential macronutrients for microbes?

Carbon, nitrogen, oxygen, phosphorus, and sulfur Signup and view all the answers

Which technique is used to transfer cultures without contamination and to count live cells using vital dyes and counting chambers?

Aseptic techniques Signup and view all the answers

What is the function of trace elements and growth factors in microbial growth?

Enzyme activation and precursor synthesis Signup and view all the answers

Which type of media requires prior knowledge of microbial nutrition requirements and is used for genetic studies involving prototrophic mutants?

Defined media Signup and view all the answers

What is the approximate water content in E. coli cell weight?

75% Signup and view all the answers

What is the purpose of differential media in microbial culture?

To distinguish between different types of microorganisms based on their growth and appearance Signup and view all the answers

Which technique is used to observe microbial cell numbers but can be prone to technical errors and lack reproducibility?

Staining cells with dyes and counting under a microscope Signup and view all the answers

What is the purpose of enriched media in microbial culture?

To provide additional nutrients to support the growth of fastidious microorganisms Signup and view all the answers

What is the main component of solid media used for microbial culture?

Agar Signup and view all the answers

Study Notes

Microbial Nutrition and Culturing Techniques

E. coli cell weight is approximately 1 pg, with 75% of its weight being water and a dry weight of 184 fg.
Carbon, oxygen, nitrogen, phosphorus, and sulfur make up 96% of the dry weight of E. coli.
Macronutrients for microbes include carbon, nitrogen, oxygen, phosphorus, and sulfur, obtained from various sources such as organic polymers, carbon dioxide, proteins, and inorganic phosphate.
Trace elements and growth factors are essential for microbial growth, serving various functions such as enzyme activation and precursor synthesis.
Different classes of culture media for microbial growth include nutrient solutions, defined media, complex media, selective media, differential media, and enriched media.
Complex media can grow a range of bacteria, while defined media require prior knowledge of microbial nutrition requirements and are used for genetic studies involving prototrophic mutants.
Solid media, prepared with agar, are used to culture microbes and enable the observation of colony morphology, aiding in microorganism identification and purity determination.
Aseptic techniques, like streak plate technique and counting microbial cell numbers with microscopes, are used to transfer cultures without contamination and to count live cells using vital dyes and counting chambers.
Staining cells with dyes and counting under a bright-field microscope or phase-contrast microscope can be used to determine microbial cell numbers, but this method can be prone to technical errors and lack reproducibility.

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Test your knowledge of microbial nutrition and culturing techniques with this quiz. Explore topics such as E. coli cell composition, macronutrients, culture media, aseptic techniques, and microbial cell counting methods.

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