Columbia Encyclopedia

Search results

500 results found

lincomycin

(Encyclopedia)lincomycin lĭngˌkōmīˈsĭn [key], antibiotic isolated from bacteria of the genus Streptomyces. Similar in activity to erythromycin, it is effective against most gram-positive organisms including s...

isotope

(Encyclopedia)CE5 Isotopes of hydrogen isotope īˈsətōp [key], in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of ...

ampicillin

(Encyclopedia)ampicillin ămˌpĭsĭlˈĭn [key], a penicillin-type antibiotic that is effective against both gram-negative microorganisms and gram-positive microorganisms such as Escherichia coli. It is often used...

bacitracin

(Encyclopedia)bacitracin băsˌĭtrāˈsĭn [key], antibiotic produced by a strain of the bacterial species Bacillus subtilis. It is widely used for topical therapy such as for skin and eye infections; it is effect...

streptomycin

(Encyclopedia)streptomycin strĕpˌtōmīˈsĭn [key], antibiotic produced by soil bacteria of the genus Streptomyces and active against both gram-positive and gram-negative bacteria (see Gram's stain), including s...

nucleus, in physics

(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...

antibiotic

(Encyclopedia)antibiotic, any of a variety of substances, usually obtained from microorganisms, that inhibit the growth of or destroy certain other microorganisms. Although for centuries preparations derived from ...

gramicidin

(Encyclopedia)gramicidin grămˌĭsīdˈən [key], antibiotic obtained from the bacterial species Bacillus brevis, which is found in soil. Gramicidin is particularly effective against gram-positive bacteria (see Gr...

ozone

(Encyclopedia)ozone ōˈzōn [key], an allotropic form of the chemical element oxygen (see allotropy). Pure ozone is an unstable, faintly bluish gas with a characteristic fresh, penetrating odor. The gas has a dens...

cgs system

(Encyclopedia)cgs system, system of units of measurement based on the metric system and having the centimeter of length, the gram of mass, and the second of time as its fundamental units. Other cgs units are the dy...