Microbiology Cultivation and Growth

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Questions and Answers

What are the three primary mechanisms by which microorganisms generate metabolic energy?

The three primary mechanisms for generating metabolic energy in microorganisms are fermentation, respiration, and photosynthesis.

List two fundamental goals of microbiological cultivation.

Two fundamental goals are to raise a crop of cells of a particular species and to determine the number and type of organisms present in a given material.

Explain the significance of isolating microorganisms in pure culture.

Isolation in pure culture enables the study of a single species without interference from other organisms, allowing for detailed analysis of its properties and behavior.

Describe the plating method for isolating microorganisms.

The plating method involves spreading a dilute sample of microorganisms onto a solidified medium, where each cell forms a distinct colony. Signup and view all the answers

Explain the principle behind the dilution method for isolating microorganisms.

Serial dilution progressively reduces the density of microorganisms in a sample, making it possible to isolate individual cells for pure culture. Signup and view all the answers

What is the purpose of controlling factors like pH, temperature, and aeration during microbial cultivation?

Controlling these factors ensures optimal growth conditions for the target organisms, promoting their survival and reproduction. Signup and view all the answers

What is meant by 'metabolically accessible form' when discussing nutrients for microorganisms?

This refers to nutrients being presented in a form that microorganisms can readily absorb and utilize for their metabolic processes. Signup and view all the answers

Why is the population of microorganisms in the biosphere roughly constant?

The balance between growth and death maintains a relatively stable population size, ensuring ecological equilibrium. Signup and view all the answers

What is the primary factor determining the survival of a microbial group within its environment?

The survival of a microbial group depends on its ability to maintain a pool of living cells and to successfully compete for nutrients. Signup and view all the answers

Explain the meaning of 'growth' in the context of unicellular microorganisms.

In unicellular organisms, growth refers to an increase in the number of individuals within a population through cell division. Signup and view all the answers

Describe the significance of the lag phase in the bacterial growth curve.

The lag phase is a period of adaptation where bacteria prepare for active division by synthesizing essential components for growth. Signup and view all the answers

What are the key processes occurring during the exponential phase of bacterial growth?

During the exponential phase, bacteria actively replicate their DNA, synthesize proteins, and engage in high metabolic activity, leading to rapid population increase. Signup and view all the answers

How does the stationary phase differ from the exponential phase in terms of cell growth?

The stationary phase is characterized by a balance between cell division and cell death, resulting in a stable population size, unlike the exponential phase where cell growth is rapid. Signup and view all the answers

What are the main factors contributing to the decline phase in bacterial growth?

Nutrient depletion and accumulation of toxic waste products lead to an exponential decrease in bacterial populations during the decline phase. Signup and view all the answers

Explain how bacteria can be maintained in the exponential phase.

Repeated transfer of bacteria to fresh medium of identical composition while they are still growing exponentially allows for continued exponential growth. Signup and view all the answers

Why are bacteria most susceptible to antibiotics during the exponential phase?

Bacteria in the exponential phase are most susceptible to antibiotics due to their active metabolism and rapid growth, making them more vulnerable to antibiotic action. Signup and view all the answers

Study Notes

Cultivation of Microorganisms

Cultivation is the process of growing organisms by providing the necessary environmental conditions.
Organisms need energy to make complex molecules and maintain chemical balance across their membranes.
Essential nutrients must be provided in usable forms.
Growth factors like nutrients, pH, temperature, aeration, salt and ionic strength of the medium affect the organism’s growth.
Organisms use fermentation, respiration or photosynthesis to generate energy.

Cultivation Methods

To cultivate microorganisms, suitable mediums and isolating them in pure culture are necessary.
Fundamental goals include growing cells of a specific species, determining the number and types of organisms in a sample, and isolating a specific species from a natural source.
A single cell is isolated and cultivated to ensure progeny remain isolated.

Isolation in Pure Culture

Plating method: Placing a small number of cells on a gelled medium like agar allows each cell to grow into an isolated colony. Agar is a polysaccharide extracted from certain red algae.
Dilution method: Reducing the concentration of microorganisms in a sample through serial dilution and plating allows single cells to grow into pure colonies. Samples of each dilution are plated or streaked on a solid medium.

Survival of Microorganisms in the Natural Environment

The population of microorganisms in the biosphere is relatively stable; growth is balanced by death.
Survival depends on maintaining a viable population and access to sufficient nutrients.
Competition and deprivation of resources strongly influence their survival.

The Meaning of Growth

Growth is the increase in the total components of a single-celled or multicellular organism, with an increase in its size or mass over time, due to the increase in cellular components.
In single-celled microorganisms like bacteria, growth involves cell duplication, resulting in an increased number of cells in a population.

The Growth Curve

The growth curve describes the population dynamics of bacteria growing in a closed system.
Distinct phases are observed: lag phase, exponential phase, stationary phase, and death phase.
Lag phase: Cells adapt to new environment and prepare for division with minimal growth.
Exponential phase: Rapid cell division and growth.
Stationary phase: Cell division rate equals the death rate.
Death phase: Nutrient depletion and accumulation of waste products lead to cell death.

The Phases of Growth

Lag phase: Bacteria adapt to the new environment. Metabolic activity increases, but little cell division occurs. This is influenced by the organism and available nutrients and environmental conditions.
Exponential phase: Cells divide at a constant rate, resulting in a population doubling with each generation time.
Stationary phase: Growth slows and the population size stabilizes because the rate of new cell production equals the cell death rate.
Death phase: Nutrient exhaustion and toxic waste accumulation cause cell death at an exponential rate. Some bacteria can survive by forming spores.

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Description

This quiz covers key concepts related to microbial energy generation, cultivation processes, and growth dynamics. It includes questions on isolation techniques, nutrient accessibility, and factors influencing microbial populations. Test your understanding of microbiological principles through various aspects of microbial life.