Biomedical Engineering Reference
In-Depth Information
which has killed millions of people throughout history, is a Group IV hepatitis virus
(Chapter 42). Here is a list of the named hepatitis viruses:
Hepatitis A virus is a member of Class Picornaviridae (Group IV, Chapter 42).
Hepatitis B virus is a member of Class Hepadnaviridae (Group VII, Chapter 45).
Hepatitis C virus is a member of Class Flaviviridae (Group IV, Chapter 42), the same
class that contains yellow fever virus, which also produces hepatitis.
Hepatitis D is a member of an unassigned class in Group V (Chapter 43).
Hepatitis E virus is a member of class Hepeviridae (Group IV, Chapter 42).
Hepatitis F virus is a hypothetical organism, supposedly responsible for some cases of
hepatitis that cannot be diagnosed under any of the non-imaginary taxa.
Hepatitis G virus is now thought to be the same virus as GB virus C, a virus not
known to produce any human disease.
Heterotrophic An organism is heterotrophic if it must acquire organic compounds from
the environment as its energy source. All animals and all fungi (both of Class
Opisthokonta) are heterotrophs. In contrast, members of Class Plantae, and other
chloroplast-containing members of Class Eukaryota, are phototropic autotrophs; pro-
ducing organic compounds from light, water, and carbon dioxide.
Infectious disease A disease caused by an organism that enters the human body. The term
“infectious disease” is sometimes used in a way that excludes diseases caused by para-
sites. In this topic, the parasitic diseases of humans are included among the infectious
diseases.
Intermediate host Same as secondary host. A eukaryotic organism that contains a para-
sitic eukaryotic organism for a period of time during which the parasite matures in its
life cycle, but in which maturation does not continue to the adult or sexual phase.
Maturation to the adult or sexual phase occurs in the primary, or definitive host. A par-
asitic eukaryotic organism may have more than one intermediate host. The survival
advantages offered to the parasite by the intermediate host stage may include the fol-
lowing: to provide conditions in which the particular stages of the parasite can
develop, that are not available within the primary host; to disseminate the parasite
(e.g. via water or air) to distant sites; to protect the immature forms from being eaten
by the adult forms; to protect the parasite from harsh conditions that prevail in the pri-
mary host; to protect the parasite from external environmental conditions that prevail
when the parasite leaves the primary host. See Primary host.
Kleptoplast Secondary chloroplast, wherein a host cell captures a chloroplast from another
organism and uses the captured chloroplast as a temporary source of energy, until the
chloroplast eventually ceases to function. Kleptoplasts typically capture chloroplasts
throughout their lives, continuously replenishing exhausted organelles [73]. The only
animal known to practice kleptoplasty is a type of sea slug (Class Mollusca), that
ingests chloroplast-rich marine organisms.
Largest species For some time, the largest known bacterium was
Epulopiscium fishelsoni
,
which grows to about 600 microns by 80 microns, much larger than the typical animal
epithelial cell (about 35 microns in diameter) [159]. This record has since been
exceeded by
Thiomargarita namibiensis
, a proteobacterium. This ocean-dwelling non-
pathogen can reach a size of 0.75 millimeter, visible to the unaided eye. The largest
single-celled organisms are deep-sea protists of Class Xenophyophorea, a subclass of
