6 -MICROBIAL DIVERSITY - 5

Algae

are photosynthetic, eucaryotic organisms that, together with protozoa, are classified in the second kingdom (Protista) of the Five- Kingdom System of Classification.

Algae and protozoa

are referred to as protists because they are in the kingdom Protista.

phycology or algology

study of algae

phycologist or algologist

person who studies algae

All algal cells

consist of cytoplasm, a cell wall (usually), a cell membrane, a nucleus, plastids, ribosomes, mitochondria, and Golgi bodies. In addition, some algal cells have a pellicle (a thickened cell membrane), a stigma (a light-sensing organelle, also known as an eyespot), and flagella.

pellicle

(a thickened cell membrane),

Algae

are more plantlike than protozoa

moist or wet environment

contains cellulose

produce their energy by photosynthesis, using energy from the sun, carbon dioxide, water, and inorganic nutri- ents from the soil to build cellular material.

cellulose

a polysaccharide not found in the cell walls of any other microorganisms.

green, golden (or golden brown), brown, or red.

pigments of algae

diatoms

are tiny, usually unicellular algae that live in both freshwater and seawater.

important members of the phytoplankton.

have silicon dioxide in their cell walls; thus, they have cell walls made of glass.

Dinoflagellates

are microscopic, unicellular, flagellated, often photosynthetic algae. Like diatoms, they are important members of the phytoplankton, producing much of the oxygen in our atmosphere and serving as important links in food chains

responsible for red tides

green algae

include desmids, Spirogyra, Chlamydo- monas, Volvox, and Euglena, all of which can be found in pond water

desmids

are unicellular algae, some of which resemble a microscopic banana.

Spirogyra

is an example of a filamentous alga, often producing long green strands in pond water.

Chlamydomonas

is a unicellular, bi-flagellated alga, containing one chloroplast and a stigma.

Volvox

is a multicellular alga (sometimes referred to as a colonial alga or colony), consisting of as many as 60,000 interconnected, bi-flagellated cells, arranged to form a hollow sphere.

Euglena

is a rather interesting alga, in that it possesses features possessed by both algae and protozoa.

contains chloroplasts, is photosyn- thetic, and stores energy in the form of starch.

photosynthetic protists

are considered to be algae, and non-photosynthetic protists are considered to be protozoa.

Algae

are an important source of food, iodine and other minerals, fertilizers, emulsifiers for pudding, and stabilizers for ice cream and salad dressings; they are also used as a gelling agent for jams and nutrient media for bacterial growth. Because algae are nearly 50% oil, scientists are studying them as a source of biofuels.

agar

used as a solidifying agent in laboratory culture media is a complex polysaccharide derived from a red marine alga.

Prototheca

a very rare cause of human infections

lives in soil and can enter wounds,

Protothecosis

is an example of a human algal infection.especially those located on the feet.

phycotoxins

substance that are poisonous to humans, fish, and other animals.

Protozoa

are eucaryotic organisms that, together with algae, are classified in the second kingdom (Protista) of the Five-Kingdom System of Classification. As previously stated, not all taxonomists agree that algae and protozoa should be combined in the same kingdom.

protozoology,

study of protozoa

protozoologist

person who studies protozoa

trophozoite stage and cysts stage

2 stages of protozoa

pellicle

serves the same purpose as a cell wall—protection.

contractile vacuole,

which pumps water out of the cell.

trophozoite

is the motile, feeding, dividing stage in a protozoan’s life cycle

cyst

is the nonmotile, dormant, survival stage.

are like bac- terial spores.

mutualistic symbiotic relationship

a relationship in which both organisms benefit.

Protozoa

are classified taxonomically by their mode of locomotion. Some move by pseudopodia, others by flagella, others by cilia, and some are nonmotile.

Amebae

move by means of cytoplasmic extensions called pseudopodia

“false feet”

Ciliates

move about by means of large numbers of hairlike cilia on their surfaces. Cilia exhibit an oarlike motion.

are the most complex of all protozoa.

Balantidium coli

is the only ciliated protozoan that causes disease in humans.

FUNGI

are in a kingdom all by themselves—the Kingdom Fungi.

Some are harmful, whereas others are beneficial.

diverse group of eucaryotic organisms that include yeasts, moulds, and mushrooms.

are the “garbage disposers” of nature—the “vultures” of the microbial world.

they are not photosynthetic

mycology

study of fungi

mycologist

a person who studies fungi

saprophytes

their main source of food is dead and decaying organic matter.

fungal cell walls

do not contain cellulose but contain chitin which is not found in the cell walls of any other microorganisms.

hyphae

filaments which intertwine to form a mass called a mycelium

septate hyphae

the cytoplasm within the hypha is divided into cells by cross-walls or septa

aseptate hyphae

the cytoplasm within the hypha is not divided into cells; no septa

fungal cells

can reproduce by budding, hyphal ex- tension, or the formation of spores.

sexual spores and asexual spores

2 general categories of fungal spores

sexual spores

are produced by the fusion of two gametes

asexual spores

also called conidia

are formed in many different ways, but not by the fusion of gametes

Fungal spores

are very resistant structures that are carried great distances by wind. They are resistant to heat, cold, acids, bases, and other chemicals. Many people are allergic to fungal spores.

blastospores

individual yeast cell

Saccharomyces cerevisiae

yeast for baking

Candida albicans

vaginal yeast

penicillium

fungi that is used for penicillin

Zygomycotina and Chytridiomycotina

two phyla known as “lower fungi”

Zygomycotina

include the common bread moulds and other fungi that cause food spoilage.

Chytridiomycotina,

which are not considered to be true fungi by some taxonomists, live in water (“water moulds”) and soil.

Ascomycotina and Basidiomycotina

two phyla known as “higher fungi”

Ascomycotina

include certain yeasts and some fungi that cause plant diseases

Basidiomycotina

include some yeasts, some fungi that cause plant diseases, and the large “fleshy fungi” that live in the woods

Deuteromycotina

Fungi Imperfecti

fifth phylum, contains fungi having no mode of sexual reproduction, or in which the mode of sexual repro- duction is not known.

Yeasts

are eucaryotic single- celled (unicellular) organisms that lack mycelia. Individual yeast cells, sometimes referred to as blastospores or blastoconidia, can only be observed using a microscope.

are found in soil and water and on the skins of many fruits and vegetables. Wine, beer, and alcoholic beverages

are also a good source of nutrients for humans because they produce many vitamins and proteins.

are usually larger than bacteria (ranging from 3 to 8 m in diameter) and are usu- ally oval-shaped; some may be observed in the process of budding

pseudohypha

string of elongated buds

It resembles a hypha, but it is not a hypha

Moulds

are the fungi often seen in water and soil and on food. They grow in the form of cytoplasmic filaments or hy- phae that make up the mycelium of the mould.

aerial hyphae

hyphae) extend above the surface of whatever the mould is growing on

vegetative hyphae

are beneath the surface

Mould reproduction

is by spore formation, either sexually or asexually, on the aerial hyphae; for this reason, aerial hyphae are sometimes referred to as reproductive hyphae.

fleshy fungi

The large fungi that are en- countered in forests, such as mushrooms, toadstools, puff- balls, and bracket fungi,

mushroom

are a class of true fungi that consist of a network of filaments or strands (the mycelium) that grow in the soil or in a rotting log, and a fruiting body (the mushroom that rises above the ground) that forms and releases spores.

mycotoxins

toxins that cause disease in humans and animals

mycoses

variety of infectious diseases of humans and animals

superficial, cutaneous, subcutaneous, or systemic mycoses.

3 categories of mycoses

Superficial mycoses

are fungal infections of the outermost areas of the human body: hair, fingernails, toenails, and the dead, outermost layers of the skin (the epidermis).

Cutaneous mycoses

are fungal infections of the living layers of skin (the dermis). A group of moulds, collectively referred to as dermatophytes, cause tinea infections, which are often referred to as “ringworm” infections.

Subcutaneous mycoses

are fungal infections of the dermis and underlying tissues. These conditions can be quite grotesque in appearance. An example is Madura foot (a type of eucaryotic mycetoma), in which the patient’s foot becomes covered with large, un- sightly, fungus-containing bumps.

Systemic or generalized mycoses

are fungal infections of internal organs of the body, sometimes affecting two or more different organ systems simultaneously (e.g., si- multaneous infection of the respiratory system and the bloodstream, or simultaneous infection of the respiratory tract and the central nervous system).

Microscopic examination

of the mould reveals the types of structures on which or within which spores are produced (Fig. 5-6); the method of spore production varies from one species of mould to another.

dimorphism

can live either as yeasts or as moulds, depending on growth conditions.

dimorphic fungi

organisms that can live either as yeasts or as moulds, depending on growth conditions.

lichens

is actually a combination of two organisms—an alga (or a cyanobacterium) and a fungus—living together in such a close relationship that they appear to be one organism.

classified as protist

found on soil and rotting logs

Slime moulds

which are found in soil and on rotting logs, have both fungal and protozoal characteristics and very interesting life cycles.

When they run out of food, they fuse together to form a motile, multicellular form known as a slug, which is only about 0.5 mm long.

Cellular slime moulds

represent cell differentiation at the lowest level, and scientists are studying them in an attempt to deter- mine how some of the cells in the slug know that they are to become part of the stalk,