Control of Microorganisms

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are obligate anaerobes and how do they interact with oxygen?

Obligate anaerobes are microorganisms that cannot use molecular O2 for energy and are harmed by its presence.

What role do organic growth factors play in microbial growth?

Organic growth factors are essential compounds that microorganisms cannot synthesize and must obtain from their environment, such as vitamins that function as coenzymes.

Describe the characteristics of solid media and its importance in microbiology.

Solid media contain a solidifying agent like agar, which allows for the growth of microbes while remaining solid at higher temperatures.

What are the key criteria that must be met for successful microbial culture growth?

Key criteria include providing the right nutrients, sufficient moisture, proper pH, suitable oxygen levels, incubation at the right temperature, and ensuring the medium is sterile. Signup and view all the answers

What is chemically defined media, and why is it significant for certain microorganisms?

Chemically defined media have a known exact chemical composition, which supports organisms requiring specific growth factors, such as Neisseria. Signup and view all the answers

What are the main components of defined media for E. coli cultivation?

The main components are glucose, ammonium phosphate, sodium chloride, magnesium sulfate, potassium phosphate, and water. Signup and view all the answers

How do complex media differ from defined media in terms of composition?

Complex media are made from nutrients like yeast extract or meat, and their exact chemical composition is not known. Signup and view all the answers

What is the purpose of anaerobic growth media?

Anaerobic growth media are used to cultivate anaerobic bacteria that could be harmed or killed by exposure to oxygen. Signup and view all the answers

Give an example of a bacterium that requires special culture techniques and explain why.

Mycobacterium leprae is an example that must be cultured in living animals like armadillos due to its specific growth requirements. Signup and view all the answers

What is the function of selective media in microbiology?

Selective media allow the growth of desired microbes while inhibiting the growth of undesired ones. Signup and view all the answers

What is the purpose of using enrichment culture in microbiology?

Enrichment culture is used to encourage the growth of a specific type of microbe within a mixed culture. This is particularly useful when the desired microbe exists in small numbers, such as in soil or fecal samples. Signup and view all the answers

Describe the principle behind the streak plate method for obtaining pure cultures.

The streak plate method aims to isolate individual colonies, originating from a single cell or spore, on a solid medium. A sterile inoculating loop is used to dilute the mixed culture by streaking it across the agar plate in a pattern. This spreads individual cells, allowing them to form colonies that are spatially separated and visible to the naked eye. Signup and view all the answers

What are the two main methods for long-term storage of bacterial cultures, and how do they differ?

Two methods for long-term storage are deep-freezing and lyophilization (freeze-drying). Deep-freezing involves quickly freezing the microbial suspension at $50^{\circ}C$ to $95^{\circ}C$, whereas lyophilization first quick-freezes the suspension at $54^{\circ}C$ to $72^{\circ}C$ and then removes water by a high vacuum. Signup and view all the answers

Explain how binary fission contributes to bacterial growth.

Binary fission is the primary method of bacterial cell division. During binary fission, a single cell divides into two identical daughter cells. This process leads to an increase in the number of bacteria, resulting in bacterial growth. Signup and view all the answers

What factors can influence generation time (GT) in bacterial populations?

The generation time of bacteria can vary depending on species and environmental factors. Important factors include the type of bacteria, nutrient availability, temperature, and oxygen concentration. Signup and view all the answers

What is the main difference between sterilization and disinfection?

Sterilization removes or kills all microbial life, while disinfection removes or kills only pathogens. Signup and view all the answers

Explain the importance of contact time in the effectiveness of disinfectants.

Contact time is essential because the disinfectant must remain in contact with the microbe for a sufficient duration to effectively deactivate or kill it. Signup and view all the answers

Describe the role of pH in microbial growth.

Most bacteria grow best near neutral pH (6.5 - 7.5), while acidophiles thrive at pH levels below 4.0. Signup and view all the answers

How does pasteurization differ from sterilization?

Pasteurization reduces microbial populations to safe levels but does not sterilize, unlike sterilization, which eliminates all microbes. Signup and view all the answers

What is the effect of temperature on microbial growth, and how do different organisms adapt?

Microbial growth is influenced by temperature, with psychrophiles thriving in colder conditions and thermophiles in hotter environments. Signup and view all the answers

Flashcards

Differential Media

Type of media that distinguishes among different organisms based on their characteristics.

Enrichment Culture

Method used to favor the growth of specific microbes in mixed cultures.