| aerobe |
A
microorganism that lives and grows in the presence of free gaseous oxygen (O2). |
| anaerobe |
A microorganism that
grows best, or exclusively, in the absence of oxygen. |
| binary fission |
The
formation of two new cells of approximately equal size as the result of parent cell
division |
| commensalism |
An unequal relationship
in which one species derives benefit without harming the other |
| diffusion |
The
dispersal of molecules, ions, or microscopic particles propelled down a concentration
gradient by spontaneous random motion to achieve a uniform distribution. |
| essential nutrient |
Any ingredient such as
a certain amino acid, fatty acid, vitamin, or mineral that cannot be formed by an organism
and must be supplied in the diet. A growth factor. |
| heterotroph |
An
organism that relies upon organic compounds for its carbon and energy needs. |
| lag phase |
The early phase of
population growth during which no signs of growth occur |
| niche |
In
ecology, an organism’s biological role in or contribution to its community |
| normal microbial flora |
The native microbial
forms that an individual harbors |
| nutrients |
Any
chemical substance that must be provided to a cell for normal metabolism and growth.
Macronutrients are required in large amounts, and micronutrients in small amounts. |
| obligate |
Without alternative;
restricted to a particular characteristic. Example: An obligate parasite survives and
grows only in a host; an obligate aerobe must have oxygen to grow; an obligate anaerobe is
destroyed by oxygen |
| opportunistic |
In
infection, ordinarily nonpathogenic or weakly pathogenic microbes that cause disease
primarily in an immunologically compromised host |
| parasite |
An organism that lives
on or within another organism (the host), from which it obtains nutrients and enjoys
protection. The parasite produces some degree of harm in the host. |
| pathogens |
Any
agent, usually a virus, bacterium, fungus, protozoan, or helminth, that causes disease. |
| photoautotroph |
An organism that
utilizes light for its energy and carbon dioxide chiefly for its carbon needs. |
| saprobes |
A
microbe that decomposes organic remains from dead organisms. Also known as a saprophyte or
saprotroph. |
| symbiosis |
An intimate association
between individuals from two species; used as a synonym for mutualism. |
