692 MICROBIOLOGY
algae) and Zoomastigophorea or animal-like fl agellates which
are divided into nine orders.1) Choanoflagellida have a single anterior flagellum
surrounded posteriorly by a collar. Some forms
are attached to substrates. They are solitary or
colonial and are all free-living.
2) Bicosoecida have 2 flagella (one free, the other
attached to the posterior of the organism). They
are free-living.
3) Rhizomastigida have pseudopodia and 1–4 or
more flagella. Most species are free-living.
4) Kinetoplastida have 1–4 flagella and all have a
kinetoplast (specialized mitochondrion). Many
important pathogens (e.g. trypanosomes) and
some free-living genera are included.
5) Retortamonadida have 2–4 flagella. The cytostome
is fibril-bordered. All are parasitic.
6) Diplomonadida have 2 karyomastigonts, each with
4 flagella and sets of accessory organelles. Most
species are parasitic.
7) Oxymonadida have one or more karyomastigonts,
each with 4 flagella. All species are parasitic.
8) Trichomonadida have mastigont systems with
4–6 flagella. Some have undulated membranes.
Many important pathogens (e.g. Trichomonas )
are included.
9) Hypermastigida have mastigont systems with
numerous flagella and multiple parabasal apparatus.
All are parasitic. Some forms reproduce sexually.B. Opalinata Are an intermediary group related to both
ciliates and fl agellates and are entirely parasitic. Opalinics
have many cilia-like organelles arranged in oblique rows over
their entire body surface. They lack cytosomes (oral open-
ings). They have multiple nuclei (ranging from 2 to many)
which divide acentrically. The whole organism divides by
binary fi ssion. Life cycles are complex.
C. Sarcodina Or ameboid organisms have Pseudopodia
which are typically present but fl agella may be present
during certain restricted developmental stages. Some forms
have external or internal tests or skeletons which vary widely
in type and chemical composition. All reproduce asexually
by fi ssion but some also reproduce asexually. Most species
are free-living (in both aquatic and terrestrial habitats) but
some are important pathogens; for example, Entameba his-
tolytica , which causes amebic dysentary. The sarcodinids are
further divided into three classes.1) Rhizopodae, a free-living, mostly particle-eating
(phagotrophic) group which includes both naked
and shelled species. The specialized pseudopodia
are called lobopodia, filopodia, or reticulopodia.
2) Piroplasmea. These parasitic small, piriform,
round, rod-shaped or ameboid organisms do not
form spores, flagella or cilia. Locomotion is by
body-flexing or gliding. They reproduce by binary
fission or schizogony.3) Actinopodea are free-living, spherical, typically
floating forms with typically delicate and radiose
pseudopodia. Forms may be naked or have mem-
braneous, clutenoid, or silicated tests. Both asex-
ual and sexual reproduction occurs. Gametes are
usually flagellated.II. Sporozoa typically form spores without polar fi laments
and lack fl agella or cilia. Both asexual and sexual reproduc-
tion takes place. All species are parasitic. Some have rather
complicated life cycles.
The Sporozoa are divided into three classes:A. Telesporea Can reproduce sexually or asexually, have
spores, move by body fl exion or gliding and generally do not
have pseudopodia.
B. Toxoplasmea Reproduce asexually, lack spores, pseudo-
podia or fl agella, and move by body fl exion or gliding.
C. Haplosporea Reproduce asexually and lack fl agella. They
have spores and may have pseudopodia.III. Cnidospora have spores with one or more polar fi laments
and one or more sporoplasms. All species are parasitic. There
are two classes.
IV. Ciliophora have simple cilia or compound ciliary organ-
elles in at least one stage of their life cycle. They usually
have two types of nucleus. Reproduction is asexually by
fi ssion or sexually by various means. Most species are free-
living but parasitic forms are known.ENERGY AND CARBON METABOLISMAll cells require a source of chemical energy and of carbon
for building protoplasm. Regardless of whether the cell type
is prokaryote or eukaryote or whether it is more plant-like
or more animal-like, this basic requirement is the same. The
most basic division relates to the source of carbon used to
build protoplasm. Organisms which can manufacture all their
carbon-containing compounds from originally ingested inor-
ganic carbon (CO 2 ) are called autotrophs while those which
require ingestion of one or several organic compounds for use
in the manufacture of cellular carbon compounds are called
heterotrophs. Some organisms are nutritionally versatile and
may operate either as autotrophs or heterotrophs and are
therefore referred to as facultative-autotrophs or facultative-
heterotrophs (depending upon which mode of nutrition usu-
ally predominates).
Autotrophs are further divided according to the manner
in which they obtain energy. Chemoautotrophs (also called
chemotrophs or chemolithotrophs oxidize various inorganic
compounds to obtain energy while photoautotrophs (also called
phototrophs or photolithotrophs ) convert light to chemical
energy via the absorption of light energy by special pig-
ments (chlorophylls and carotenoids). In both cases, chemical
energy is stored in the form of chemical bond energy in the
compound adenosine triphosphate (ATP).C013_004_r03.indd 692C013_004_r03.indd 692 11/18/2005 10:41:59 AM11/18/2005 10:41:59 AM