Microbiology is the scientific discipline focused on the study of microorganisms and of the effects they may have on other organisms. The term derives from the Greek words mīkros (meaning small), bios (meaning life), and logia (meaning study of). Generally, microorganisms are too small to be seen with the unaided eye. Microbiologists, scientists studying these small organisms, aid their observations with the use of such devices as microscopes (optical and electronic) and hand lenses.
Such organisms as bacteria, viruses, some algae and protozoa, and prions fall within the definition of microorganisms. Microorganisms constitute the majority of organisms; yet, only a very small percentage of the Earth's microbial species, populations and communities have been characterized scientifically.
Centers for Disease Control and Prevention
Yellow fever is a viral disease that is transmitted to humans...
Combating Hopping PestsLast Updated on 2015-02-28 18:55:12The Mormon cricket is a voracious feeder that wipes out acres of grasses and field crops in no time. When it’s young, it grows so fast that its immune system cannot keep up. ARS scientists are finding that this may be the best time to use biocontrol fungi to target the insect pest.
New Hopes for Combating Hopping Pests
For many Americans, summertime means warm, sunny days spent by the pool or exploring the country and the world. But for farmers, ranchers, scientists, and state pest control organizations in the western half of the country, summer also means a chance of infestations of hopping pests, particularly grasshoppers and Mormon crickets.
Each adult female grasshopper can lay multiple egg pods—each containing many eggs—in one summer, which could greatly increase the population the next summer, after the eggs hatch. This compounding effect could lead... More »
FungiLast Updated on 2015-02-15 18:00:24The word fungus usually invokes images of mushrooms and toadstools. Although mushrooms are fungi, the forms which a fungus may take are varied. There are over 100,000 species of described fungi and probably over 200,000 undescribed.
Most fungi are terrestrial, but they can be found in every habitat worldwide, including marine (about 500 species) and freshwater environments. Fungi are nonmotile, filamentous eukaryotes that lack plastids and photosynthetic pigments. The majority of fungi are saprophytes; they obtain nutrients from dead organic matter. Other fungi survive as parasitic decomposers, absorbing their food, in solution, through their cell walls.
Most fungi live on the substrate upon which they feed. Numerous hyphae penetrate the wood, cheese, soil, or flesh in which they are growing. The hyphae secrete digestive enzymes that break down the substrate, enabling the fungus to... More »
Gut reaction: environmental effects on the human microbiotaLast Updated on 2014-11-29 21:03:07This article, written by Melissa Lee Phillips, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences.
The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth.
Living with each of us—on our skin, in our mucosa, and in our gastrointestinal (GI) tract—are microorganisms whose numbers dwarf the number of our own cells and genes. Although some of these microbes are pathogens, most are harmless or even beneficial. The body’s assortment of microorganisms, collectively called the microbiota, is similar to an organ in that it performs functions essential for our survival. Some microbes produce... More »
BacteriaLast Updated on 2014-10-12 18:54:28
Bacteria are any of a very large group of single-celled microorganisms that display a wide range of metabolic types, geometric shapes and environmental habitats—and niches—of occurrence. Normally only several micrometers in length, bacteria assume the form of spheres, rods, spirals and other shapes. Bacteria are found in a very broad gamut of habitats; for example, bacterial extremophiles that thrive in such places as hot springs, arctic environments, radioactive waste, deep sea oil seeps, deep Earth crustal environments, hypersaline ponds and within other living organisms. There are approximately 50 million bacterial organisms in a single gram of typical surface soil. The worldwide bacterial biomass exceeds that of all plants and animals on Earth. However, the majority of bacteria have not yet been characterised,
Bacteria are members of the prokaryote... More »
CellsLast Updated on 2014-06-30 14:15:10
Cells are the smallest component of the body that can perform all of the basic life functions. Each cell performs specialized functions and plays a role in the maintenance of homeostasis. While each cell is an independent entity, it is highly affected by damage to neighboring cells. These various cell types combine to form tissues, which are basically collections of specialized cells that perform a relatively limited number of functions specific to that type of tissue. The human body is made up of several trillion cells; these cells are of various types, which can differ greatly in size, appearance and function.
While there are approximately 200 types of cells, they all have similar features: cell membrane, cytoplasm, organelles, and nucleus. The only exception is that the mature red blood cell does not contain a nucleus. In general, toxins can injure any of the components of... More »
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