Important
words and concepts from Chapter 11, Black, 1999 (3/28/2003):
by Stephen T. Abedon (abedon.1@osu.edu)
for Micro 509
at the Ohio State University
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Course-external links are
in brackets Click [index] to access site index Click here to access
text’s website Vocabulary
words
are found below |
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(1) Chapter title: Eukaryotic Microorganisms and Parasites
(a)
A
parasite is an organism that lives in or on another organism (the host), which
damages the host in some way plus fails to compensate for this damaging by also
failing to help the host to an appreciable extent
(b)
More
narrowly, the term parasite is often used to describe parasitic protozoa,
helminths
(worms), and arthropods
(c)
(in
addition to parasites of animals, there exist numerous parasites of plants as
well as parasites of members of the other various kingdoms)
(d)
Some
general external links: [Dave Gibson’s parasitological
URLs] [A
directory of academic links to Ectoparasites and Endoparasites, Medicine and
Veterinary Science] [ASM’s parasite division page] [index]
(a)
A
pathogen is a parasite that causes disease; yes, by and large pathogens are
parasites (in the broader sense of the word) and parasites (ditto) are
pathogens
(b)
From
here on out in this lecture I will be employing the term parasite is its
narrower sense, limiting it to describing protozoa, helminths
(worms), and arthropods
(c)
[pathogen definition,
definition pathogen
(Google Search)]
[index]
(a)
An
ectoparasite is a parasite that lives on the surface of a host
(b)
Ticks
and lice (which are arthropods) are examples of ectoparasites
(c)
[ectoparasite (Google Search)] [an ectoparasite is a parasite
that attaches to skin and body openings of host organism
(definition) (Agripedia)] [index]
(d)
[Question:
Are all ecoparasites arthropods? I don't think so. Yes, barnacles are indeed
arthropods, but there must be mollusks that act as ectoparasites. Any
additional phyla? Are there any worm ectoparasites? What about medusa?]
(a)
An
endoparasite is a parasite that lives within a host
(b)
These
include most parasitic protozoa and helminths
(c)
[endoparasite (Google Search)] [diagnostics of veterinary endoparasitic infections (still very much under construction but
still lots of cool stuff (University of Pennsylvania School of Veterinary Medicine)]
[parasites and parasitological
resources (a very cool site) images of parasites
(ditto) (Peter W. Pappas)] [index]
(a)
A
vector is a living organism that carries a disease-causing organism to new
hosts
(b)
See
arthropod vectors, below
(c)
Vectors
may be differentiated variously into:
(ii)
mechanical vectors
(d)
Organisms
that carry diseases include:
(i)
definitive
hosts
(ii)
intermediate hosts
(iii)
reservoir
hosts
(e)
(typically,
from our perspective, these would be animals that carry human diseases, or
humans themselves)
(f)
These
various hosts are either vectors themselves or what a vector carries a
parasite/pathogen to from another host
(g)
[parasite and vector
(Google Search)]
[index]
(a)
A
biological vector is a vector in which or upon which a parasite
goes through part of its life cycle (e.g., replicates)
(b)
See
also definitive host, intermediate host,
and reservoir host, below
(c)
[biological vector (Google Search)] [index]
(a)
A
mechanical vector is a vector in which or upon which a parasite
is transported but otherwise the parasite does not go through significant
aspects of its life cycle while in contact with this vector (e.g., does not
replicate)
(b)
[mechanical vector (Google Search)] [index]
(a)
Parasites
that go through their sexual stage associated with a given host, that host is
called the definitive host
(b)
For
example, the malaria parasite's definitive host is the
mosquito; this mosquito additionally (simultaneously) serves as the biological
vector for the malaria parasite
(c)
[definitive vector (Google Search)] [index]
(a)
The
intermediate host is one that harbors the parasite but associated
with which the parasite does not undergo sexual reproduction
(b)
For
example, the malaria parasite's intermediate host is humans
(though for anthropocentric reasons we don’t typically consider humans to be
vectors for the transmission of malaria to mosquitoes; besides, the malaria
parasite does not make the mosquito sick)
(c)
[intermediate vector
(Google Search)]
[index]
(a)
The
reservoir host is the host that a parasite normally resides in
(b)
Many
parasites predominately infect animals rather than humans, but humans can
become infected following contact with the animal reservoir (for example, Toxoplasma gondii)
(c)
[reservoir vector (Google Search)] [index]
(a)
Host
specificity is a description of the range of hosts which can serve as biological vectors, e.g., within which the parasite can mature
to produce infectious progeny
(b)
[parasite host specificity
(Google Search)]
[index]
KINGDOM PROTISTA
(a)
Members
of Kingdom Protista are always eukaryotic and mostly unicellular organisms
(b)
Some
protists are photoautotrophs (algae)
(c)
Most
protists are chemoheterotrophs
(d)
Kingdom
Protista represents an extremely diverse taxon including members that are
described as
(i)
Flagellates
(ii)
Ciliates
(iii)
Amoebas (many of which have shells)
(iv)
Sporozoans
(e)
Kingdom
Protista also includes a number of parasitic members
(f)
[protozoa (Google Search)] [the
origins of eukaryotic diversity (MicroDude)] [protist images
(lots and lots) (Protist Information Server)] [protist image data
(Molecular Evolution & Organelle Genomics)] [index]
(14) Parasitic protists (parasites)
(a)
A
few examples of many (and, yes, please learn these):
(b)
Trichomonas vaginalis
(i)
sexually
transmitted disease
(ii)
[graphic images of Trichomonas vaginalis (Parasites and Parasitological
Resources)] [Trichomonas vaginalis
(Google Search)]
(c)
Giardiasis
(i)
Giardia lamblia
(ii)
Infections
obtained upon drinking cyst-contaminated water
(iii)
The
reservoir host (probably) includes numerous mammals
(iv)
(infections
are also known as, for example, “beaver fever” and may be avoided by chemically
treating drinking water obtained from otherwise unknown sources, by filtering
the water, or by boiling the water)
(v)
[graphic images of Giardia lamblia (Parasites and Parasitological
Resources)] [Giardia lamblia
(Google Search)]
(d)
Toxoplasmosis
(i)
Toxoplasma spp.
(ii)
The
definitive host = cats = reservoir host
(iii)
Obtained
upon inhaling or ingesting eggs associated with cat litter, or by consuming
not-fully cooked meat that contains infectious cells (called bradiozoites)
(iv)
Typically
not highly pathogenic in humans but
·
Can
seriously harm fetuses when mother is infected during pregnancy
·
Can
lead to significant disease in immunocompromised individuals
(v)
[graphic images of Toxoplasma gondii (Parasites and Parasitological
Resources)] [Toxoplasma gondii
(Google Search)]
(e)
Malaria
(i)
Plasmodium spp.
(ii)
vector
= mosquitoes = definitive host
(iv)
(“There’s
no preventive vaccine for malaria, which kills about 2 million people a year,
and in the past 2 decades the organism has become resistant to other key
antimalarial drugs in addition to chloroquine.” Elizabeth Pennisi, 1999,
Malarial genome comes into view, Science,
286:1263-1265)
(v)
[graphic images of Plasmodium spp. (Parasites and Parasitological
Resources)]
(vi)
[Plasmodium (Google Search)]
(vii)
[Malaria Foundation International]
(f)
See Figure 11.4, The life
cycle of the malaria parasite Plasmodium
(g)
[parasite life cyles]
[parasitic protists
(Joe Camp)] [index]
KINGDOM FUNGI
(15) 
Fungi
(a)
Fungi
are eukaryotic organisms that are heterotrophic
(b)
Fungi
have cell walls, and those cell walls are composed of chitin (insect
exoskeletons are also composed of chitin)
(c)
Like
animals, fungi are extracellular digesters of their food plus are nutrient
absorbers
(d)
Typically
fungi reside within the food they are
consuming
(e)
Often
that food is plant material, but their food can be animal in origin as well
(f)
Most
fungi are multicellular and many are macroscopic
(g)
[fungi (Google Search)] [fungi (MicroDude)]
[index]
(a)
Saprophytes
are organisms that consume and digest dead organic matter and organic waste
(b)
Most
fungi are saprophytes
(c)
[saprophyte (Google Search)] [index]
(a)
The
study of fungi is called mycology
(b)
[mycology (Google Search)] [index]
(18) 
Fungal anatomy (chitin,
hyphae, mycelia, thallus)
(a)
The
"body" of a fungi is its thallus
(b)
The
thallus of most multicellular fungi consists of mycelia, which are branched
mycelia
(c)
Hyphae
are linear arrangements of cells, forming multicellular, or (minimally)
multinucleated threads
(d)
Fungi
live by growing mycelia into (or onto) substrate (e.g., a dead plant), secreting
exoenzymes from these cells, and then absorbing digested nutrient into the
mycelia
(e)
Mycelia
often are tangled masses of hyphae; this is an image of fungal mycelia à
(f)
[thallus fungus or fungi,
thalli fungus or fungi
(Google Search)]
[chitin, hyphae, mycelium (MicroDude)]
[index]
(a)
Hyphae
may be divided up into individual cells by crosswalls called septa
(b)
These
septa are typically incomplete barriers between cells
(c)
In
many cases, the septa are absent altogether, resulting in hyphae consisting of
long chains of multinucleated, unpartitioned cytoplasm
(d)
Movement
of nutrients, cytoplasm, and organelles (including the nucleus) along hyphae,
i.e., through septa, allows fungi to divert resources to new food supplies;
fungi can grow extremely rapidly at the growing ends of hyphae due to this
movement of cytoplasm along hyphae
(e)
[septa (MicroDude)] [index]
(a)
Fungi
tend to be able to do the same kinds of things bacteria do, especially
gram-positive bacteria, (that is, they are exoenzyme-employing
absorbers) but do so in dryer, more acidic, more highly osmotic environments
than most bacteria prefer
(b)
Some
fungi are parasitic, but most fungi are decomposers, especially of plant
material
(c)
"Fungi
are never obligate parasites because all fungi can obtain nutrients from dead
organisms. Even when fungi parasitize living organisms, they kill cells and
obtain nutrients as saprophytes."
(d)
Many
fungi produce antibiotics that they use to inhibit bacterial growth and thus
reduce competition for resources
(e)
"Saprophytic
fungi are beneficial as decomposers and as producers of antibiotics. The
digestive activities of such fungi provide nutrients not only for the fungi
themselves but for other organisms, too. The carbon and nitrogen compounds they
release from dead organisms contribute significantly to the recycling of
substances."
(f)
See Figure 11.7, One method
of sexual reproduction in fungi
(g)
[fungal ecology, fungi ecology, fungus ecology (Google Search)] [index]
(a)
A
fungi-caused disease is called a mycosis
(b)
Fungal
diseases can be superficial (on the skin), subcutaneous (under the skin), or systemic
(throughout various organs of the body)
(c)
Fungal
diseases tend to progress slowly but can be especially difficult to treat (the
latter is a consequence of the close similarities between human and fungal
metabolisms)
(d)
Examples
of mycoses include:
(i)
Disease-causing
fungi include Candida albicans (yeast
infections, etc.)
(ii) Histoplasmosis is a fungal disea