Introduction to Cultivating Microbial Growth - Online Tutor, Practice Problems & Exam Prep

Cultivating microbial growth involves using culture media, which can be solid (agar) or liquid (broth), to provide essential nutrients for microorganisms. Aseptic techniques are crucial to prevent contamination during this process. Various types of culture media, including slants and petri dishes, facilitate different growth methods. Techniques such as the streak plate, pour plate, and spread plate methods are employed for isolating and counting cells, while biomass can be measured using spectrophotometry. Understanding these methods is vital for effective microbiological practices.

Introduction to Cultivating Microbial Growth

In this video, we're going to begin our introduction to cultivating microbial growth. Studying microorganisms in a laboratory requires growing the microorganisms on culture medium. Culture medium, sometimes referred to as just media, is either going to be a solid or a liquid preparation of nutrients that are used to grow microorganisms. A solid preparation of these nutrients is referred to as agar, and a liquid preparation of the nutrients is referred to as broth. Recall from our previous lesson videos that a pure culture refers to a population of cells that started from just a single colony of viable cells.

If we take a look at our image down below, notice on the left-hand side, we are showing you an image of agar, which is a solid growth medium found inside one of these petri dishes. This petri dish, with its red color, represents the culture media in a solid form, referred to as agar. You can see that the microorganisms are capable of growing on this solid culture media. The culture media provides the nutrients and acts as food. The bacteria are able to grow on this agar medium, which provides the nutrients and food it needs.

On the right-hand side, notice that we're showing you a liquid broth, which is just a liquid growth medium. The container is going to be different in order to store a liquid. All of this red that you see here is really just the liquid culture media, which again acts as a nutrient and a food source for these organisms. The organisms are going to be able to grow inside the liquid broth. We're able to grow microorganisms on solid agar media or liquid broth media.

Now it is also important to note here that when cultivating microbes, it's extremely important to avoid contamination by using what's known as aseptic technique. Aseptic technique is a specific series of techniques that are very important when working with microbes, cultivating microbes in the lab. Aseptic technique can be defined as standard practice in a lab and medical procedures that ultimately prevents contamination. The main goal behind aseptic technique is that you perform very careful techniques to make sure that your culture media does not get contaminated from any unwanted microorganisms. You only want to be growing the microorganisms of interest. Aseptic technique helps to ensure that.

This here concludes our brief introduction to cultivating microbial growth, and we'll be able to get some practice applying these concepts and learn more as we move forward in our course. So I'll see you all in our next video.

Map of Techniques for Cultivating Microbes

In this video, we're going to introduce our map of the lesson on techniques for cultivating microbes, which is down below right here. This image represents a map or an outline of our lesson moving forward. As always, we're going to be following the map by following the leftmost branches first and then zooming out and covering the other branches in this order that you see right here. What's important to note about the techniques for cultivating microbes is that whenever you are cultivating microbes, it's really important to make sure that you're performing aseptic technique, which recall is just a specific series of techniques that helps to prevent contamination. It could include things such as using a Bunsen burner to help prevent contamination or using gloves to help prevent contamination as well. Aseptic technique is going to be important for all of these other techniques down below as well.

Now, over here on the far left, what we're showing you are types of culture media, and we'll talk more about these moving forward in our course. This includes things like slants, deeps, and petri dishes. After we cover the types of culture media, we'll move on to plating methods. We'll talk about specific plating methods such as the streak plate method, the pour plate method, and the spread plate method.

Last but not least, we'll move on to counting cells. There are direct cell counts such as microscopic counts and cell counters, and there are also viable cell counts like plate counts, membrane filtration, and most probable number or MPN. Then, of course, there is measuring biomass using a spectrophotometer or by direct weight. We'll be able to talk more about all of these different techniques as we move forward in our course. Again, this is really just an outline of our lesson. We'll start off by talking about the types of culture media. So I'll see you all in that lesson video.

Here’s what students ask on this topic:

What is the difference between agar and broth in microbial culture media?

Agar and broth are two types of culture media used to grow microorganisms. Agar is a solid medium, typically found in petri dishes, and provides a surface for microorganisms to grow on. It contains nutrients essential for microbial growth and is solidified using a substance called agar-agar. Broth, on the other hand, is a liquid medium that also contains nutrients but allows microorganisms to grow throughout the liquid. Both media types are essential for different experimental needs, with agar being useful for isolating colonies and broth being ideal for growing large quantities of microorganisms.

Why is aseptic technique important in cultivating microbial growth?

Aseptic technique is crucial in cultivating microbial growth to prevent contamination from unwanted microorganisms. This technique involves a series of practices, such as using a Bunsen burner, wearing gloves, and sterilizing equipment, to ensure that only the microorganisms of interest are grown. Contamination can lead to inaccurate results and potentially hazardous situations, especially in medical and laboratory settings. By following aseptic techniques, researchers can maintain the purity of their cultures and ensure the reliability of their experimental outcomes.

What are the different types of culture media used in microbiology?

In microbiology, various types of culture media are used to grow microorganisms. These include slants, deeps, and petri dishes. Slants are agar media solidified in test tubes at an angle, providing a large surface area for growth. Deeps are agar media solidified in an upright position, used for growing anaerobic bacteria. Petri dishes contain agar media in a flat, shallow dish, ideal for isolating colonies. Each type of media serves specific purposes, allowing researchers to cultivate and study different microorganisms effectively.

What are the common methods for plating microorganisms?

Common methods for plating microorganisms include the streak plate, pour plate, and spread plate methods. The streak plate method involves spreading a small amount of microbial sample across the surface of an agar plate to isolate individual colonies. The pour plate method involves mixing the microbial sample with molten agar and pouring it into a petri dish, allowing colonies to grow both on the surface and within the agar. The spread plate method involves spreading a diluted microbial sample evenly across the surface of an agar plate using a sterile spreader. Each method is used for different purposes, such as isolating colonies or quantifying microbial populations.

How is microbial biomass measured in a laboratory setting?

Microbial biomass can be measured using several methods, including spectrophotometry and direct weight measurement. Spectrophotometry involves measuring the optical density of a microbial culture at a specific wavelength, which correlates with the concentration of cells in the culture. Direct weight measurement involves filtering the microbial culture, drying the biomass, and weighing it to determine the total mass of microorganisms. Both methods provide valuable information about the growth and concentration of microbial populations in a laboratory setting.