Growing a Pure Culture: Videos & Practice Problems

In microbiology, a pure culture is a population of cells containing only one species, typically initiated from a single colony of approximately 1,000,000 cells. This process begins with an inoculum, which is a colony added to a culture medium to grow the pure culture. Understanding these concepts is crucial for studying bacterial and archaeal cells, as they allow for the isolation and examination of specific microorganisms in a controlled environment.

Growing a Pure Culture

In microbiology, the concept of a pure culture is fundamental for studying bacterial and archaeal cells. A pure culture is defined as a population of cells that contains only one species. This is typically initiated from a single colony, which is a group of approximately one million cells. The process begins with a single bacterial cell that divides and replicates, leading to a population where all cells are genetically identical and belong to the same species.

To illustrate, when a single bacterial cell is cultured, it can multiply to form a colony, which is essential for establishing a pure culture. The colony represents a significant number of cells, all derived from that initial cell, ensuring that the culture is pure. This is crucial for accurate scientific analysis and experimentation.

Another important term in this context is inoculum, which refers to the colony of cells that is introduced into a culture medium to initiate the growth of a pure culture. By using an inoculum from a single species, researchers can effectively cultivate a pure culture, allowing for controlled studies and observations of that specific organism.

Understanding these concepts is vital for anyone working in a microbiology lab, as they form the basis for isolating and studying microorganisms in a controlled environment.

A pure culture of bacteria is made of…

• A. Around 1 million viable bacteria cells that are all of the same species.
• B. Around 1 million viable bacteria cells that are all descended from a single parent cell.
• C. Around 1 million viable bacteria cells that are a mixture of different bacterial species.
• D. Both A and B.
• E. Both A and C.
• F. Both B and C.

Answer: (D)

A bacterial culture grown in a _________________ will not continue to grow exponentially forever, but will stop once the limited nutrients have been consumed.

• A. Open system.
• B. Secure system.
• C. Closed system.
• D. Extended system.

Answer: (C)

Here’s what students ask on this topic:

What is a pure culture in microbiology?

A pure culture in microbiology is a population of cells that contains only one single species. This is typically achieved by starting with a single colony, which is a group of approximately 1,000,000 cells. The colony is used as an inoculum to inoculate a culture medium, allowing the cells to grow and replicate. The result is a controlled environment where only one species of microorganism is present, making it easier to study specific bacterial or archaeal cells without contamination from other species.

How is a pure culture initiated in a lab?

A pure culture is initiated in a lab by starting with a single colony of cells, which contains about 1,000,000 cells of the same species. This colony is used as an inoculum, which is added to a culture medium. The inoculum allows the cells to grow and replicate, forming a population of cells that all belong to the same species. This process ensures that the culture remains pure and uncontaminated by other microorganisms, facilitating accurate study and analysis.

What is an inoculum in the context of growing a pure culture?

An inoculum in the context of growing a pure culture is a colony of cells that is added to a culture medium to start the growth of a pure culture. The inoculum typically consists of about 1,000,000 cells of a single species. By using an inoculum, scientists can ensure that the resulting culture contains only one species of microorganism, which is crucial for accurate study and experimentation in microbiology.

Why is it important to use a pure culture in microbiology studies?

Using a pure culture in microbiology studies is important because it ensures that only one species of microorganism is present in the culture. This eliminates the risk of contamination from other species, allowing for more accurate and reliable results. Pure cultures are essential for studying the characteristics, behavior, and interactions of specific microorganisms, as well as for developing antibiotics and other treatments. They provide a controlled environment that is crucial for scientific research and experimentation.

What is a colony in microbiology?

In microbiology, a colony is a group of approximately 1,000,000 cells that originate from a single cell. Colonies are visible to the naked eye and are used to start pure cultures. Each colony consists of cells that are genetically identical, making them ideal for studying specific species of microorganisms. Colonies are essential for isolating and growing pure cultures, as they provide a starting point for the inoculum used in the culture medium.