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...
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 »
FungiLast Updated on 2014-10-12 17:18:45The 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 (500 spp.) 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 absorb the... 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 »
Composting tipsLast Updated on 2014-06-29 18:07:28
Composting turns household wastes into valuable fertilizer and soil organic matter.
All organic matter eventually decomposes. Composting speeds the process by providing an ideal environment for bacteria and other decomposing microorganisms. The final product, humus or compost, looks and feels like fertile garden soil. This dark, crumbly, earthy-smelling stuff works wonders on all kinds of soil and provides vital nutrients to help plants grow and look better.
Decomposing organisms consist of bacteria, fungi, and larger organisms such as worms, sow bugs, nematodes, and numerous others. Decomposing organisms need four key elements to thrive: nitrogen, carbon, moisture, and oxygen. For best results, mix materials high in nitrogen (such as clover, fresh grass clippings, and livestock manure) and those high in carbon (such as dried leaves and twigs). If there is not a good supply of... More »
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