(credit: modification of work by Centers for Disease Control and Prevention) albicans has a morphology similar to that of coccus bacteria however, yeast is a eukaryotic organism (note the nuclei) and is much larger. It is the causative agent of vaginal yeast infections as well as oral thrush, a yeast infection of the mouth that commonly afflicts infants. Algae are also being developed as a possible source for biofuels.įigure 1.17 Candida albicans is a unicellular fungus, or yeast. Agar, a gel derived from algae, can be mixed with various nutrients and used to grow microorganisms in a Petri dish. A derivative of algae also plays a prominent role in the microbiology laboratory. Many consumer products contain ingredients derived from algae, such as carrageenan or alginic acid, which are found in some brands of ice cream, salad dressing, beverages, lipstick, and toothpaste. Because other organisms can use the waste products of all algae for energy, algae are important parts of many ecosystems. ![]() Cyanobacteria, a type of bacteria, is also considered an algae, but these organisms are bacterial prokaryotes and therefore have a peptidoglycan-based cell wall, unlike the cellulose-based cell wall of the algal protists. Algae are photosynthetic organisms that extract energy from the sun and release oxygen and carbohydrates into their environment. Algal protists are surrounded by cell walls made of cellulose, a type of carbohydrate. Some algae are protists and others are bacteria all protozoa are examples of protists.Īlgae (singular: alga) are mostly made up of protists that can be either unicellular or multicellular and vary widely in size, appearance, and habitat ( Figure 1.15). Protist s are an informal grouping of eukaryotes that are not plants, animals, or fungi. The major defining characteristic of eukaryotes is that their cells contain a nucleus. The domain Eukarya contains all eukaryotes, including uni- or multicellular eukaryotes such as protists, fungi, plants, and animals. Name some of the defining characteristics of each type.What are the two main types of prokaryotic organisms?.Some archaea live in the human body, but none have been shown to be human pathogens. Like bacteria, archaea are found in nearly every habitat on earth, even extreme environments that are very cold, very hot, very basic, or very acidic ( Figure 1.14). Unlike most bacteria, archaeal cell walls do not contain peptidoglycan, but their cell walls are often composed of a similar substance called pseudopeptidoglycan. Archaea and bacteria have different evolutionary histories, as well as significant differences in genetics, metabolic pathways, and the composition of their cell walls and membranes. Other types of bacteria are nonphotosynthetic, obtaining their energy from organic or inorganic compounds in their environment.Īrchaea are also unicellular prokaryotic organisms. Some bacteria are photosynthetic, such as oxygenic cyanobacteria and anoxygenic green sulfur and green nonsulfur bacteria these bacteria use energy derived from sunlight, and fix carbon dioxide for growth. They have a wide range of metabolic capabilities and can grow in a variety of environments, using different combinations of nutrients. (credit “Coccus”: modification of work by Janice Haney Carr, Centers for Disease Control and Prevention credit “Coccobacillus”: modification of work by Janice Carr, Centers for Disease Control and Prevention credit “Spirochete”: Centers for Disease Control and Prevention) Note how coccobacillus is a combination of spherical (coccus) and rod-shaped (bacillus). See Table 1.1 for units of length used in microbiology.įigure 1.13 Common bacterial shapes. ![]() ![]() Bacterial cells are typically about 1 µm, and viruses can be 10 times smaller than bacteria ( Figure 1.12). For some perspective, consider that a typical animal cell measures roughly 10 µm across but is still microscopic. An object must measure about 100 micrometers (µm) to be visible without a microscope, but most microorganisms are many times smaller than that. However, there are some unicellular microbes that are visible to the naked eye, and some multicellular organisms that are microscopic. Most microbes are unicellular and small enough that they require artificial magnification to be seen.
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