Identifying Fungi & Actinomycetes in Microscopic Settings PDF

Identifying Fungi & Actinomycetes in Microscopic Settings In this lesson, learn how to identify various organisms by examining them under a microscope. This includes yeasts, mold, fungi, dermatophytes, and actinomycetes. Microscopic Identi!cation Microscopic organisms such as fungi and bacteria c...

Identifying Fungi & Actinomycetes in Microscopic Settings In this lesson, learn how to identify various organisms by examining them under a microscope. This includes yeasts, mold, fungi, dermatophytes, and actinomycetes. Microscopic Identi!cation Microscopic organisms such as fungi and bacteria can be identi!ed using a microscope. Identifying the organisms requires that you recognize features such as the shape and parts that come o" of the main body of the organism. We will look at some general features of yeast, mold, dimorphic fungi, dermatophytes, and actinomycetes. Identifying Yeast If you look at yeast under a microscope, you will see several oval shapes. The sample will often also include a food source (such as sugar), which will lead to fermentation with the yeast, so bubbles will also be visible. These bubbles are part of the characteristic appearance of the yeast but should not be confused with the yeast cells themselves. Di"erentiating between di"erent yeast strains is typically done macroscopically using di"erent food sources. Identifying Mold Under a microscope, mold can also have round or oval, smooth shapes, similar to yeasts, but these only represent the spore form of the mold. If only spores are present, then the mold can be very di#cult to identify, as it has not yes sporulated. Once it has sporulated. long !laments can be seen branching o" of the mold cell. Some important features of mold that help to identify di"erent strains include: Hyphae – branching, tube-like structures coming o" of the mold. These determine the thickness and length. Spores – the dormant phase of the mold that determines if the mold has spores or not, also determines the structure of the spores, including how the spores are grouped together. The spores are often smooth and round. Conidiophores – the reproduction method of mold which are often found at the ends of hyphae. These determine grouping patterns, shape, thickness, and length. Sometimes di"erent areas of the sample will need to be examined to determine di"erent conidiophore features. Surface walls – which determine the texture and color. Identifying Dimorphic Fungi A dimorphic fungus is a fungus that can be both a mold or yeast depending on which phase it is presenting. To identify the dimorphic fungi, both phases need to be identi!ed using the method used to individually identify molds and yeast. There are macroscopic methods of identi!cation that only require one of the phases to be presented. Dermatophytes and Actinomycetes Dermatophytes are a speci!c type of fungi that use keratin as a food source. A characteristic feature of dermatophytes is the shape of the macroconidia, which can include spindle versus clubbed shapes. It is also important to note the thickness, size, and cell wall features (such as thin, smooth, etc.) of the macroconidia. Actinomycetes are bacteria that act and look like a fungus. To view the actinomycetes, typically the sample is !rst stained using a Gram-positive stain. The bacteria will appear rod-shaped with hyphae branching through the sample. The hyphae are often very thin, threadlike structures. Lesson Summary Many fungi can be identi!ed microscopically. Yeasts are identi!ed by their characteristic oval or round shape. Mold is identi!ed using the characteristics of hyphae (branching, tube-like structures), spores (smooth and round, dormant phase), conidiophores (found at ends of hyphae), and surface walls. Dimorphic fungi (a fungus that alternates between mold and yeast phases) need to be identi!ed by identifying both the yeast and mold forms of the fungi. Dermatophytes (a type of fungus that uses keratin for food) are identi!ed using the characteristics of the macroconidia. Actinomycetes (a bacteria that acts like a fungus) are identi!ed by !rst using a Gram-positive stain and then identifying the rod-shaped bacteria with branching hyphae.  Like this lesson  Share Explore our library of over 88,000 lessons Search Search Courses & Lessons  Browse Browse by subject 