The
Microbial
World
Taxonomy of Chapter 5: The
Microbial World
Monera (Prokaryotes)
Bacteria
• Heterotrophic bacteria
• Autotrophic bacteria
• Cyanobacteria
• Archaea
Taxonomy of Chapter 5: The
Microbial World
Protista
Unicellular Algae – Plant like protists
• Diatoms
• Dinoflagellates
• Zooxanthellae
• Pfiesteria
• Other Unicellular Algae
Taxonomy of Chapter 5: The
Microbial World
Protista Cont.
Protozoans – Animal Like Protists
• Foriminiferans
• Radiolarians
• Ciliates
Fungi
Microorganisms
• Include the smallest and simplest organisms on
earth
• Represent all three biological domains
• Are the most important primary producers in
many marine environments
• Directly or indirectly feed most marine animals
Electron micrograph showing Cyclobacteriaum marinus,
A ring forming marine bacterium.
I. Prokaryotes
• Simplest and smallest and oldest life forms
• Carry out most all chemical processes of more
complex organisms
• Differ from eukaryotes in the circular DNA that
encodes genetic information and size of
ribosomes
• All are enclosed by a cell wall in which lies a
plasma or cell membrane
• All lack membrane-bound organelles.
Thiomargarita namibiensis, largest bacterium!
Can be .03 inches wide.
Round grains are sulfur granules.
A. Bacteria
• Structurally simple but have a great range of
metabolic abilities and chemical features
• Have many shapes: spheres, coils, rods, rings
• Much smaller than single-celled eukaryotes
• Have rigid, strong cell walls
• Often covered by gelatinous material
• Sometimes visible as pink or iridescent patches
in stagnant pools
i. Heterotrophic Bacteria
• Most are decomposers (decay bacteria) and
ensure the recycling of nutrients
• Found throughout the water column
• Feed many benthic animals
• Some can degrade oil and toxic pollutants
• Some spoil fish and shellfish catches
ii. Autotrophic Bacteria
• Are primary producers, only some are
photosynthetic
• Account for much of primary production in sea
• Some bacteria produce sulfur instead of oxygen!
• Chemosynthetic (chemoautotrophic) bacteria
derive energy from H2, or H2S or NH3.
iii. Cyanobacteria
• “Blue-green” algae
• Contain chlorophyll and phycocyanin and often
phycoerythrin.
• Photosynthesis occurs on folded membranes in
the cell, not in chloroplasts.
• Probably among the first photosynthetic
organisms on earth.
• Stromatolites may date back 109 years!
• Many species of cyanobacteria can withstand
wide ranges of salinity and temperature.
Stromatolites, calcareous mounds deposited
by cyanobacteria, are often found as fossils.
Planktonic species may reproduce
quickly and change the water color (red
tide). Some cause rashes on swimmers.
•Some endolithic cyanobacteria burrow
into rocks and coral skeletons
.
Endophytes are cyanobacteria that live inside algae.
Some cyanobacteria lose their ability to photosynthesize
and are heterotrophs.
Many carry out nitrogen fixation.
Epiphytes are photosynthetic
cyanobacteria that live on other plants
Japanese Pufferfish store a deadly toxin, tetrodotoxin
produced by a symbiotic bacteria. The fish is prepared
by special chefs and many deaths occur each year in
Japan (as well as suicides by disgraced chefs.)
iv. Archaea
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Simplest, most primitive forms of life
3.8 x 109 years old!!
Small, spherical, spiral or rod-shaped cells
Used to be classified with bacteria, now thought
to be more closely related to eukaryotes.
• May be heterotrophs or autotrophs.
Methanogens: methane makers, are
Important decomposers. Some are
N2 Fixers. Some break down material
in Sewage plants.
Archaea: Extremophiles
• Some archaea have been found in sulfur springs,
saline lakes and highly acid or alkaline
environments.
• Some are found in hydrothermal vents.
• Some can exist at temperatures up to 235 degres
Fahrenheit!
• They do not depend upon extreme environments,
contrary to popular opinion.
II. Unicellular Algae
Kingdom Protista
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Are mostly aquatic, mostly photosynthetic
Are eukaryotic (cells contain organelles)
Photosynthesis takes place in chloroplasts.
Lack flowers, have simple reproductive
structures.
• Lack true leaves, stems and roots
Some unicellular organisms
that are claimed by both botanists
and zoologists are classified as
Protista.
A. Diatoms
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Phylum Bacillariophyta
Unicellular, may form chains or stars
Enclosed by cell walls made of SiO2 (sillica)
Frustule, glassy shell, is made of two halves
with intricate perforations (holes) and
ornaments.
• Frustule allows passage of light for
photosynthesis, as well as gases.
• Diatoms’ color is due to carotenoid pigments
and chlorophyll a and c.
• Efficient photosynthetic factories
• Account for major share of C and O produced
on earth.
• Half of all species are marine, most planktonic,
but some attach.
• Brown scum of mudflats or aquaria is made of
diatoms.
Diatom Cell
• Reproduce asexually or sexually.
• Fertilization results in auxospores
• Blooms are periods of rapid reproduction
- diatoms get smaller because they use up the
silica in sea water
Frustules of dead diatoms falls to the sea bed and
forms siliceous material called diatomaceous
ooze.
- mined and used as filters in pools, for clarifying
beer, as insulators and in toothpaste
B. Dinoflagellates
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Phylum Dinoflagellata
Large group of planktonic, unicellular organisms
Possess two flagella that direct movement
Cell wall is armored with cellulose plates
Most can photosynthesize
Some have a light sensitive crude eye
Most are marine
Dinoflagellate showing the theca (cell wall)
made of cellulose plates.
The theca is marked by grooves for flagella.
Dinoflagellate, Gonyaulax polyedra
is bioluminescent and causes red tides!
The Bay of Fire in Puerto Rico is filled with bioluminescence
from Phrodinium bahamense, a photosynthetic dinoflagellate.
They have a symbiotic relationship with mangrove trees that
border the bay.
i. Zooxanthellae
• Golden brown photosynthetic cells that are
dinoflagellates that live with an animal host.
• Host may be a sponge, anemone or clam.
• They fix CO2 and release organic matter used by
coral to help build the coral skeleton.
ii. Pfiesteria (phantom
dinoflagellate)
• Parasitic with life cycles that include freeswimming stages
• Spends most of its life as a cyst in sediments
• Blooms are triggered by coastal pollution
• Pfiesteria releases powerful poisons that stun
fish
• Harmful to shellfish and humans
– Memory loss and gastrointestinal side effects
Other Unicellular Algae
Dictyocha speculum, a silicoflagellate
Other Unicellular Algae
Umbilicosphaera sibogae, covered with
calcium carbonate button called a coccolith
(hence name Coccolithophorids)
III. Protozoans
Kingdom Protista and ??
• Structurally simple, diverse organisms that are
animal like
• Ingest food and are eukaryotic
• Some contain chlorophyll
• Most are single celled and microscopic
• Placed in Protista with unicellular algae and
seaweeds
• Only common characteristic is their single cell!
Protozoans
• The single cell is considered a “super cell” which
performs many of the functions carried out by
cells in more complex organisms.
• They live in fresh and marine environments and
inside other organisms
A. Foraminiferans
• Marine protozoans with a shell of CaCO3.
• Pseudopodia, extensions of cytoplasm, are used
to trap diatoms and other food
• Most live on the bottom
• Shells contribute to calcareous material on coral
reefs and beaches.
• Shells of the few planktonic forams sink and
form foraminiferan ooze (limestone and chalk
beds – white cliffs of Dover)
Foraminiferans with calcareous shells. Long strands
are pseudopodia that capture food. On right,
Homotrema Rubrum is responsible for Bermuda’s
pink sand.
Climate, Oil and Forams
• Because the shells of warm water species are
larger and more porous than cold water species,
they are used to estimate ocean temperatures.
• The distribution also helps determine the age of
sediments and aids in finding oil.
B. Radiolarians
• Planktonic protozoans that secrete beautiful
shells made of silica and other minerals.
• Pseudopodia capture food as in forams.
• Some form 3 meter long sausage shaped
colonies!
• Shell remains for radiolarian ooze on the sea
bed.
• Shells are more resistant to pressure and thus
more common than forams.
Radiolarian cell made of a dense central
portion surrounded by a less dense zone that
is involved in capturing food and buoyancy.
C. Ciliates
• Protozoans with hair like cilia used in
locomotion and feeding.
• Most common freshwater ciliate is the
Paramecium.
• Marine ciliates creep over seaweeds and bottom
sediments.
• Some live inside clams or other organisms.
Tintinnids, (ciliates) form a lorica, a loosely
fitting shell made of sand grains. Cilia are used
in feeding.
Fungi
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Eukaryotic , mostly multicellular
Heterotrophs lacking chloroplasts
500 marine species, mostly microscopic
Decomposers of dead organic matter
Important in mangrove ecosystem
Some are parasites that cause diseases
Some live with algae to form lichens
Marine lichens are seen as dark brown or black
patches on rocky shores in the North Atlantic.
Verruculina enalia, a marine Ascomycotina consists
of black and carbonaceous fruiting bodies on branches
and twigs at both low and high water marks. It is one of
the most dominant marine fungi to colonise woody
mangrove substrata.
This is the black tar lichen.
Tar lichens get their common name from
the fact that they form great swathes of dark
smudges on rocks, giving the rock an impression
of being covered in crude oil from an oil spill.