• WordNet 3.6
    • n bacterium (microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered to be plants
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Webster's Revised Unabridged Dictionary
    • n Bacterium băk*tē"rĭ*ŭm (Biol) A microscopic single-celled organism having no distinguishable nucleus, belonging to the kingdom Monera. Bacteria have varying shapes, usually taking the form of a jointed rodlike filament, or a small sphere, but also in certain cases having a branched form. Bacteria are destitute of chlorophyll, but in those members of the phylum Cyanophytathe blue-green algae) other light-absorbing pigments are present. They are the smallest of microscopic organisms which have their own metabolic processes carried on within cell membranes, viruses being smaller but not capable of living freely. The bacteria are very widely diffused in nature, and multiply with marvelous rapidity, both by fission and by spores. Bacteria may require oxygen for their energy-producing metabolism, and these are called aerobes; or may multiply in the absence of oxygen, these forms being anaerobes. Certain species are active agents in fermentation, while others appear to be the cause of certain infectious diseases. The branch of science with studies bacteria is bacteriology, being a division of microbiology. See Bacillus.
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Century Dictionary and Cyclopedia
    • n bacterium One of the micro-organisms which are concerned in the putrefactive processes, and are known as Schizomycetes, or fission fungi, in distinction from Saccharomycetes, or budding fungi, which produce alcoholic fermentation. Their true character was long in doubt, but they are now generally regarded as the lowest forms of vegetable life, and are known to multiply, in some species at least, by the formation of spores and even of true sporangia. They consist of exceedingly minute spherical, oblong, or cylindrical cells, without chlorophyl, multiply by transverse division, and may be found anywhere. Their origin and the part they take in putrefaction, fermentation, and disease have been the subject in recent years of much study and discussion. Very much remains in doubt, but there is no question of the importance of these investigations from a sanitary point of view. It also appears to have been demonstrated that the bacteria which exist in the soil are active in changing otherwise inert substances into matter suitable for the food of plants, converting the nitrogenous matter of organic origin into soluble nitrates. The genera and species have been variously defined, and are necessarily based on slight characters. The groups and principal genera usually recognized are Micrococcus, with spherical cells, concerned in certain fermentations and found in connection with special contagious diseases; the rod-bacteria, Bacterium; the straight filiform bacteria, Bacillus, etc.; and the spiral filiform bacteria, Vibrio, Spirillum, etc. Of the genus Micrococcus, M. diphtheriticus is considered to be the special cause of diphtheria, and M. vaccinæ of smallpox. See Bacteriaceæ, and cut under bacillus.
    • n bacterium A genus of microscopic fungi, consisting of a single short cylindrical or elliptical cell, or of two such cells united end to end, and capable of spontaneous movement. The best-known species, B. termo, is the prime cause of putrefaction, occurring early in all infusions of animal and vegetable substances and multiplying with great rapidity. The individuals of this species are about one ten-thousandth of an inch in length.
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Chambers's Twentieth Century Dictionary
    • n Bacterium bak-tē′ri-um Schizomycetes, extremely small, single-celled, fungoid plants, single or grouped, reproducing rapidly by cross division or by the formation of spores, almost always associated with the decomposition of albuminoid substances, and regarded as the germs or active cause of many diseases
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Webster's Revised Unabridged Dictionary
NL., fr. Gr. bakth`rion ba`ktron, a staff: cf. F. bactérie,
Chambers's Twentieth Century Dictionary
Gr. baktērion, dim. of baktron, stick, staff.


In literature:

Davaine's bacterium develops exclusively in the blood, and is never found at any depth in the tissues.
"Scientific American Supplement, No. 447, July 26, 1884" by Various
He then proceeded to describe the characters of this bacterium.
"Scientific American Supplement, No. 458, October 11, 1884" by Various
On the stage of the instrument, the Bacterium with its flagellum in distinct focus is placed.
"Scientific American Supplement, Vol. XIX, No. 470, Jan. 3, 1885" by Various
The peculiar bacterium that thrives on congenial alfalfa soil is essential to the highest development of the plant.
"The Fat of the Land" by John Williams Streeter
The former is in every way like a bacterium in its mode of self-division.
"Scientific American Supplement, No. 643, April 28, 1888" by Various
Imagine a normal bacterium trying to bore into flesh as hard as concrete.
"Highways in Hiding" by George Oliver Smith
I'd no sooner kill a bacterium than a song-bird.
"The Tyranny of the Dark" by Hamlin Garland
At the end of three days there is not a bacterium to be found in it.
"Fragments of science, V. 1-2" by John Tyndall
The microscope magnifies the distance traversed as well as the organism, and although a bacterium which covers 9-10 cm.
"Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 2" by Various
The morphology of the same bacterium may vary greatly under different conditions.
"The Elements of Bacteriological Technique" by John William Henry Eyre
Pasteur's researches on the Silkworm disease led him to the discovery of Bacterium anthracis, the cause of splenic fever.
"The Beauties of Nature" by Sir John Lubbock
The bacterium elongates and then divides in the middle to form 2 daughter cells.
"Special Report on Diseases of Cattle" by U.S. Department of Agriculture
LEHMANN, K. B.: 1889, Studien ueber Bacterium phosphorescens, Fischer.
"The Nature of Animal Light" by E. Newton Harvey
Bruce in 1887 isolated the bacterium that causes it.
"Essays In Pastoral Medicine" by Austin ÓMalley
But probably each colony arose from a single bacterium which got into the dish when it was exposed to the air.
"A Civic Biology" by George William Hunter
This propionic bacterium cannot, however, account for all the carbon dioxide produced.
"The Book of Cheese" by Charles Thom and Walter Warner Fisk

In news:

A new study from Stanford's Department of Chemistry reveals that the cell wall structure of Staphylococcus aureus, a bacterium responsible for a broad range of diseases, depends on growth stage and nutrient availability.
And there, on that alga, sits a tiny bacterium .
Down each bacterium run deep channels, which are aligned continuously as the bacteria join into one long filament.
But a new study reveals how a particular bacterium-and- fungus pair may be cooperating.
Enterococcus faecalis is a bacterium species that lives in the human gut.
This bacterium, Anaplasma phagocytophilum (Ap), secretes a protein that can start this process.
In 1977, he started testing infertile couples for a little-studied bacterium called mycoplasma that had been linked to infertility .
Listeria monocytogenes is a bacterium that is pathogenic — meaning that it is infectious to humans, causing the illness listeriosis .
Klebsiella pneumoniae, a Gram-negative bacterium that is known to harbor resistance to most antibiotics.
An infectious oral bacterium may be a sign for pancreatic cancer.
An infectious oral bacterium may be a sign for pancreatic cancer .
Understanding the Interaction between an Obligate Hyperparasitic Bacterium, Pasteuria penetrans and its Obligate Plant Parasitic Nematode Host, Meloidogyne spp.
Soybean cyst nematodes (SCN), which cause staggering losses for American soybean growers, could ultimately get eaten alive by a bacterium.
The bacterium that sickened more than 400 across the US and killed three is resistant to many sterilization techniques.
This bacterium causes increased breakouts and inflammation around the time of women's periods .

In science:

Metabolic network: a graph of interactions forming a part of the energy generation and small building block synthesis metabolism of the bacterium E.
Random graphs as models of networks
Recently, in the case of the transcription network of the bacterium E. coli, network motifs were shown theoretically and experimentally to function as elementary building blocks of the network, each performing specific information-processing tasks [15, 18, 19].
Topological Generalizations of network motifs
When rotated clockwise they fly apart and the bacterium “tumbles” without significant translocation.
An equation-free computational approach for extracting population-level behavior from individual-based models of biological dispersal
Hence, a bacterium runs at a constant velocity for a random length of time, then tumbles for a random length of time, chooses a new direction at random, and repeats the process.
An equation-free computational approach for extracting population-level behavior from individual-based models of biological dispersal
In order to find food or avoid noxious substances, a bacterium increases its runs in favorable directions and decreases them when going in an unfavorable direction.
An equation-free computational approach for extracting population-level behavior from individual-based models of biological dispersal
Since the tumbling time is small compared to the typical running time, we can decribe the motion of E. coli as a velocity jump process , which means that a bacterium runs in some direction and, at random instants of time changes its velocity according to a Poisson process with mean turning rate γ .
An equation-free computational approach for extracting population-level behavior from individual-based models of biological dispersal
Bennett compares this process with “rapid growth of bacteria following introduction of a seed bacterium” into a sterile nutrient solution.
Defining Complexity: A Commentary to a paper by Charles H. Bennett
For instance, a bacterium might have several metabolic modes depending on the environment it finds itself in and the density of other bacteria present.
A Mathematical Framework for Agent Based Models of Complex Biological Networks
However, with lactose present, the tunnelling can cause a mutation that will allow the bacterium to grow (with lactose present).
Comment on Book Review of `Quantum Evolution' (Johnjoe McFadden) by Mathew J. Donald
When the operon is “on”, the bacterium produces the enzymes necessary to import and digest lactose.
A First Exposure to Statistical Mechanics for Life Scientists
The motor of the bacterium Rhodobacter sphaeroides turns in only one direction but stops from time to time .
The hydrodynamics of swimming microorganisms
For a non-motile E. coli bacterium at room temperature, we have [D] ∼ 0.1 µm2 /s in water; while the time scale for thermal reorientation of the cell axis, [DR ]−1 , is a few minutes.
The hydrodynamics of swimming microorganisms
For a swimming bacterium such as E. coli, this argument leads to d ≈ 0.1 nm .
The hydrodynamics of swimming microorganisms
The bacterium Spiroplasma has an internal helical ribbon that is though to undergo contractions that in turn cause the body to change shape.
The hydrodynamics of swimming microorganisms
Since a swimming bacterium is in fact torque-free, the cell cannot swim straight but instead rotates at a rate such that the viscous torque from that rotation exactly balances the wall-induced torque, and therefore swims along circles on the surface (Fig. 12b, black dashed arrow).
The hydrodynamics of swimming microorganisms