Chapter 21
The Nature of Microorganisms
Domains
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The three domains:
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Eubacteria
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Archaea
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Eucarya
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Kingdom Protista
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia
Bacteria
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Differences in Eubacteria and Archaea
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Eubacteria has the compound peptidoglycan in their
cell wall, Archaea does not
Different kind of lipids in their plasma membrane
The DNA of Archaea is largely unique from other
living organisms
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Eubacteria and Eukaryotes are more similar in genetic
make-up, than Eubacteria and Archaea
Eubacteria “True Bacteria”
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There are 2,000 species of Eubacteria which
have been named
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Mostly spherical, rod-shaped, or spiral shaped
Many kinds of bacteria are heterotrophs that must
break down organic matter to provide themselves
with energy, so they are known as decomposers
Can be aerobic or anaerobic
The decomposition process is important in the
recycling of carbon, nitrogen, and phosphorus
Some bacteria can be used to metabolize oil and be
used to clean up oil spills
Different Types of Eubacteria
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Commensal Bacteria is bacteria that have a
commensal relationship (cause no harm, but
don't perform any valuable function)
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Most organisms are lined and covered by
populations of bacteria
Escherichia coli is common in the intestinal tract of
humans
Different Types of Eubacteria
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Photosynthetic Bacteria carry on a form of photosynthesis
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Cyanobacteria carries out a form of photosynthesis that is
essentially same as plants
Cyanobacteria are thought to have been the first oxygenreleasing organisms, leading to aerobic respiration
Cyanobacteria are common in fresh and marine waters
Purple and green bacteria carry on different forms of
photosynthesis which release sulfur instead of oxygen
Different Types of Eubacteria
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Mutualistic Bacteria occur between bacteria and
other organisms
Mutualism is an interrelationship in which two
species live in close association with one
another and both benefit
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Some intestinal bacteria produces antibiotics for
humans to inhibit disease-causing bacteria
When people travel, they consume local bacteria
and have problems establishing a new symbiotic
relationship with these foreign bacteria
Disease-Causing Bacteria
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Pathogens are organisms that cause disease
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Only a small minority of bacteria fall into this
category
Streptococcus pneumoniae grows in the throats of
healthy people, but when their numbers increase, it
can cause illness
After a viral flu, person's resistance is lowered, and
can invade lungs
Goes from commensalistic to parasitic
Some bacteria can invade healthy tissue of host by
releasing enzymes to break down tissue
Other bacteria can produce toxins or poisons
Biological Warfare
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Bacteria and other microbes can spread
through a population quickly and cause disease
Biological agents can reproduce, spread
through populations and cause epidemics, even
after a war has ended
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More recent example in 2001, letters containing
anthrax where mailed from New Jersey. Five
people died, and 22 were infected
Other human bacterial diseases: Botulism, plague,
TB, typhoid fever
Domain Archaea
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Archaea is a diverse group of organisms that
generally live in extreme environments, so they
are known as extremophiles
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Methanogens are strict anaerobes, and release
methane as a waste product
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Live in mud at bottom of lakes and swamps; intestinal
tracts of animals, including humans
Extreme Halophiles (salt lovers) live in only extremely
acidic environments, such as the Great Salt Lake; they
grow best at solutions which are 20% salt
Thermophiles (heat lovers) live in extremely hot
environments; hot springs at Yellowstone National Park,
hydrothermal vents on the ocean floor
Domain Eucarya
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Kingdom Protista are a broad category of
simple eukaryotic organisms; not necessarily
closely related to one another
There are more than 100,000 species
The species are divided into three general
groups
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Autotrophic Unicellular Organisms (Algae)
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Heterotrophic Unicellular Organisms (Protozoa)
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Funguslike Protists (Slime & Water molds)
Kingdom Protista - Algae
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Algae are protists which contain chlorophyll in
their chloroplasts so they undergo
photosynthesis
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Many are single-celled, many are multicellular
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Live in bodies of freshwater, and other moist places
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Plankton is a collection of small, floating or weakly
swimming organisms
Phytoplankton consists of photosynthetic plankton,
which algae is a major component
Algae
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Single-Celled Algae
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Three common forms:
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Euglenids
Dinoflagellates
Diatoms
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Euglenids are single-celled algae moved by
flagella, most are found in freshwater
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Dinoflagellates (two flagellas) are important food
producers
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Some have a symbiotic relationship with coral reefs by
providing nutrients for the reef
Diatoms are a major component of phytoplankton
and a major food source for filter-feeders
Algae
• Multicellular algae
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Can grow to be quite large with some specialized
cells and body parts
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Commonly known as seaweed
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Red Algae live in warm oceans and attach to the
ocean floor
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Brown Algae is found in cooler marine
environments and can grown into over 100 m of
length
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Used as jellying agent or thickener
Protozoa
• Protozoa are eukaryotic, heterotrophic, singlecell organisms that lack cell walls
• Flagellates
• Amoeboid Protozoans
• Apicomplexa
• Ciliates
Protozoa
• Flagellates
• Very diverse group that have a flagella and lack cell
walls and chloroplasts
• Termites have flagellated protozoa that digest the
cellulose found in wood
• Amoeboid Protozoans
• Have extensions of their cell surface called
pseudopods (false foot)
• Amoebas use the pseudopod for movement and to
engulf food
Protozoa
• Apicomplexa
• Nonmotile parasites
• Plasmodium vivax causes malaria
• Ciliates
• Complex cellular structure and numerous short,
flexible extensions from the cell called cilia
• Paramecium have 15,000 cilia per cell and move at
1 mm/ssec
Funguslike Protists
• Funguslike Protists are often confused with
fungi. However, funguslike protists have
cellulose in their cell wall, while fungus cell walls
have chitin.
• Slime molds are amoeba-like organisms that crawl
and digest dead organic matter
• Water molds
• A water mold was responsible for the Irish potato blight
Kingdom Fungi
• Members of Kingdom Fungi are nonphotosynthetic,
eukaryotic organisms with rigid cell walls containing
chitin
• Fungus usually consists of a filaments composed of many
cells, each individual filament is known as a hypha. Several
hyphae form a network known as a mycelium.
Kingdom Fungi
• Even though fungi are nonmotile, they are easily
dispersed through huge numbers of spores. A spore is
a cell with a tough, protective cell wall that can resist
extreme conditions.
• A good-sized puffball can have as many as 8 trillion
spores
• Fungi are heterotrophs that secrete enzymes that
digest large molecules into smaller ones.
• Can be free-living and absorb nutrients from
decomposing dead organisms. Also can be parasitic
that are responsible for athlete’s foot, and ringworm.
Kingdom Fungi
• Phylum Ascomycota, the ascomycetes is the
largest group (75% of all fungi)
• Develop by sexual means; ascospores are formed
inside a sac called an ascus
• Includes yeasts, morels and truffles
• Phylum Zygomycetes
• Includes black bread mold and makes up 1% of
named fungi
Kingdom Fungi
• Basidiomycetes include mushrooms, toadstools,
puff balls and shelf fungi
• Some may be used as food, while others are deadly
poisons
• Form a club shaped reproductive structure called a
basidium
Kingdom Fungi
• Yeasts are single-celled fungi
• Include Saccharomyces cerevisiae, bakers yeast
• Imperfect Fungi
• Seem to have lost their ability to reproduce sexually
• Penicillium
Kingdom Fungi
• Mycorrhizae is the relationship between fungi
and the roots of plants
• Help absorb 10x more minerals than roots alone
• Lichens is the relationship between fungi and
algae or cyanobacteria
• Cyanobacteria/algae provide food through
photosynthesis
• Fungi help produce a damp environment needed for
algae to