The Microbial World

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The Microbial World
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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

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Electron micrograph showing Cyclobacteriaum
marinus, A ring forming marine bacterium.
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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.

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Thiomargarita namibiensis, largest bacterium! Can
be .03 inches wide. Round grains are sulfur
granules.
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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

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B. 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

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C. 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.

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D. 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 bact 109 years!
• Many species of cyanobacteria can withstand wide
  ranges of salinity and temperature.

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Stromatolites, calcareous mounds deposited by
cyanobacteria, are often found as fossils.
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Planktonic species may reproduce quickly and
change the water color (red tide). Some cause
rashes on swimmers.
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• Some endolithic cyanobacteria burrow
• into rocks and coral skeletons

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Endophytes are cyanobacteria that live inside
algae. Some cyanobacteria lose their ability to
photosynthesize and are heterotrophs. Many carry
out nitrogen fixation.
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Epiphytes are photosynthetic cyanobacteria that
live on other plants
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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.)
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II. Archaea

• 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.

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Methanogens methane makers, are Important
decomposers. Some are N2 Fixers. Some break
down material in Sewage plants.
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A. 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.

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III. Unicellular AlgaeKingdom Protista

• 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

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Some unicellular organisms that are claimed by
both botanists and zoologists are classified as
Protista.
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A. Diatoms

• 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.

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• 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.

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Diatom Cell
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• 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

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B. Dinoflagellates

• 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

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Dinoflagellate showing the theca (cell wall)
made of cellulose plates. The theca is marked by
grooves for flagella.
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Dinoflagellate, Gonyaulax polyedra is
bioluminescent and causes red tides!
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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.
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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.

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ii. Pfiesteria (phantom dinoflagellate)

• Parasitic with life cycles that include
  free-swimming 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

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Other Unicellular Algae
Dictyocha speculum, a silicoflagellate
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Other Unicellular Algae
Umbilicosphaera sibogae, covered with calcium
carbonate button called a coccolith (hence name
Coccolithophorids)
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IV. ProtozoansKingdom 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!

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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

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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)

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Foraminiferans with calcareous shells. Long
strands are pseudopodia that capture food. On
right, Homotrema Rubrum is responsible for
Bermudas pink sand.
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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.

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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.

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Radiolarian cell made of a dense central portion
surrounded by a less dense zone that is involved
in capturing food and buoyancy.
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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.

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Tintinnids, (ciliates) form a lorica, a loosely
fitting shell made of sand grains. Cilia are
used in feeding.
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Fungi

• 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.

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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.
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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.