They are typically 1 to 3 microns in length and take the shape of a sphere or rod. Most bacteria consist of a ring of DNA surrounded by cellular machinery, all contained within a fatty membrane. They acquire energy from the same essential sources as humans, including sugars, proteins, and fats. Some bacteria live and multiply in the environment while others are adapted to life within human or animal hosts. Some bacteria can double in number every fifteen minutes, while others take weeks or months to multiply.
Bacteria cause many types of diseases, ranging from mild skin irritation to lethal pneumonia. Parasites are part of a large group of organisms called eukaryotes. Parasites are different from bacteria or viruses because their cells share many features with human cells including a defined nucleus.
Parasites are usually larger than bacteria, although some environmentally resistant forms are nearly as small. Some parasites only replicate within a host organism, but some can multiply freely in the environment. Parasites can be made of one cell, as in the case of Giardia , or many cells, as with parasitic worms. In developing countries unicellular parasites, such as Plasomdium , the cause of malaria, are a major sources of disease. Waterborne parasites, such as Giardia and Cryptosporidium are the most common causes of parasitic disease in the United States.
Procedures must be approved by an institutional review board. When working with patients, accurate record-keeping, honest communication, and confidentiality are paramount. Animals used for research must be treated humanely, and all protocols must be approved by an institutional animal care and use committee. These are just a few of the ethical principles explored in the Eye on Ethics boxes throughout this book. However, there is a high concentration of a particular protein, protein, in her CSF.
An electroencephalogram EEG of her brain function is also abnormal. CJD is an extremely rare disease, with only about cases in the United States each year. It is not caused by a bacterium, fungus, or virus, but rather by prions —which do not fit neatly into any particular category of microbe.
Like viruses, prions are not found on the tree of life because they are acellular. Prions are extremely small, about one-tenth the size of a typical virus. They contain no genetic material and are composed solely of a type of abnormal protein. CJD can have several different causes. It can be acquired through exposure to the brain or nervous-system tissue of an infected person or animal.
Consuming meat from an infected animal is one way such exposure can occur. There have also been rare cases of exposure to CJD through contact with contaminated surgical equipment [4] [5] and from cornea and growth-hormone donors who unknowingly had CJD.
Unfortunately for Cora, CJD is a fatal disease for which there is no approved treatment. Eight months later, Cora dies.
Her CJD diagnosis is confirmed with a brain autopsy. Algae is photosynthetic. Cyanobacterium is a prokaryotic microorganism. Viruses are acellular. Yeast is a type of fungal microorganism. Botany is not a subfield of microbiology. Skip to content An Invisible World. Learning Objectives List the various types of microorganisms and describe their defining characteristics Give examples of different types of cellular and viral microorganisms and infectious agents Describe the similarities and differences between archaea and bacteria Provide an overview of the field of microbiology.
How big is a bacterium or a virus compared to other objects? Check out this interactive website to get a feel for the scale of different microorganisms. Think about It What are the two main types of prokaryotic organisms? Name some of the defining characteristics of each type. Think about It Name two types of protists and two types of fungi. Think about It Are helminths microorganisms? Explain why or why not. How are viruses different from other microorganisms? Bioethics in Microbiology In the s, the U.
Key Concepts and Summary Microorganisms are very diverse and are found in all three domains of life: Archaea, Bacteria, and Eukarya. Archaea and bacteria are classified as prokaryotes because they lack a cellular nucleus.
Archaea differ from bacteria in evolutionary history, genetics, metabolic pathways, and cell wall and membrane composition. Archaea inhabit nearly every environment on earth, but no archaea have been identified as human pathogens.
Eukaryotes studied in microbiology include algae, protozoa, fungi, and helminths. Algae are plant-like organisms that can be either unicellular or multicellular, and derive energy via photosynthesis. Protozoa are unicellular organisms with complex cell structures; most are motile. Microscopic fungi include molds and yeasts. Helminths are multicellular parasitic worms. They are included in the field of microbiology because their eggs and larvae are often microscopic.
Viruses are acellular microorganisms that require a host to reproduce. The field of microbiology is extremely broad. Microbiologists typically specialize in one of many subfields, but all health professionals need a solid foundation in clinical microbiology. Multiple Choice Which of the following types of microorganisms is photosynthetic? Think about It Describe the differences between bacteria and archaea.
Name three structures that various protozoa use for locomotion. A virus is the simplest of germs—it is nothing but genetic material encased in protein. Researchers debate whether a virus is even "alive. By itself, a virus can accomplish nothing—it needs to enter a living thing to perform its only function, which is to replicate. When a virus gets inside a human body, it can hijack a person's cellular machinery to produce clones of itself, overtaking more cells and continuing to reproduce.
When the virus reproduces faster than the immune system can control it, it begins to destroy cells and harm the body. Viruses are also the smallest germ, making them generally the easiest to contract—they're so tiny they can spread through the air in a cough or a sneeze.
Some viruses also are spread by mosquitoes or through bodily fluid. Since each virus is very different, no one drug exists to attack whichever virus is in your body. Vaccines give preemptive protection from certain viruses by training the body's immune system to recognize and attack a specific virus. Common forms: Bacteria cause food poisoning, strep throat and urinary tract infections , as well as infections such as tuberculosis.
Bacteria are bigger and more complex than viruses, though they can still spread through the air. A bacterium is a single cell, and it can live and reproduce almost anywhere on its own: in soil, in water and in our bodies.
For the most part, we live peacefully with bacteria—the colonies in our guts are helpful to us and strengthen our immune system. But like viruses, bacteria can also harm us by replicating quickly in our bodies, killing cells. Some bacteria also produce toxins which can kill cells and cause an outsized, damaging immune reaction. Broad-spectrum antibiotics were developed to kill bacteria in our bodies and in the food supply by inhibiting their growth.
But bacteria are extremely adaptive and can quickly evolve to evade antibiotics. Bacteria share their antibiotic-resistant genes with each other, meaning more strains generate resistance to the drugs we use.
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