Chapter 5
The Microbial World
Microbial World
• Primary producers
• Very important in the ocean’s ecosystems!
Prokaryotes
• Oldest forms of life
• cell wall, cell membrane,
no nucleus, ribosomes
are different
• Divided into 2 Domains
– Bacteria and Archaea
– As different from each
other as they are from
humans
Domain Bacteria
• Branched early
– Evolved great range
of abilities
• Variation based on
–
–
–
–
Shape
Cell wall
Movement
Nutrition
Role of Bacteria
Positive
• Decay Bacteria
– Live in detritus
• Dead organic matter
– Break down waste and
release nutrients into
environment
• Food for animals
• Degrading pollutants
– Oil and other toxins
Negative
• Spoil fish and
shellfish catches
• Disease in
animals and
humans
• Pelagibacter ubique
• High numbers in open
waters
• Found in sediment 300m
under the sea floor
Cyanobacteria
• Widely spread
• First Photosynthetic
bacteria
– Chlorophyll a
– Phycocyanin (bluish)
– Phycoerythrin (reddish)
– Polar bear hair
• Endolithic: burrow into
calcareous rocks and coral
skeletons
– Form thick crusts along coasts
– Exploit oxygen-poor sediments
• Planktonic: surface
• Produced oxygen as a
– Rapidly multiply
waste product
– Cause a Red tide
• Stromatolites: mounds • Epiphytes: live on algae or
plants
formed by cyano
• Endophytes: live inside algae
Domain Archaea
• Look very similar to oldest fossils
• First found in extreme environments
– Extremophiles
• Not all archaea are extremophiles
– Common in marine environments
Prokaryote Metabolism
Photoautotrophic
• Chlorophyll : perform
photosynthesis on folded
membranes
• Different chlorophyll:
produces sulfur instead of
oxygen
• Proteorhodopsin or
bacteriorhodopsin:
capture light energy and
store as ATP
– Does not make organic
compounds
Chemoautotrophic
• Derive energy from
chemical compounds
– Hydrogen sulfide
• Methanogens
– Produce methane
Metabolism
Heterotrophic
• Obtain energy from
organic matter by cellular
respiration
• Many are decomposers
• Aerobic: uses oxygen
• Anaerobic: does not
require oxygen
– Oxygen can be poisonous
– Anoxic: sediments that do
not have oxygen
Nitrogen Fixation
• Convert gaseous nitrogen
into ammonium
• Nitrogen can then be
used by plants or algae
Unicellular Algae
Kingdom Protista
Algae
• Photosynthesis takes place in
chloroplasts
• Lack flowers, true leaves, stems, and
roots
– Simple cells and reproduction
• Some have flagella
• Some are multicelluar, like seaweeds
Diatoms
• Unicellular with glass-like cell
wall
– Contains silica; same mineral that
makes up glass
– Variety of shapes
• Contain chlorophyll and other
pigments
• Store food as oil; float to
surface for photosynthesis
• When they die, glass walls
accumulate and fossilize
– Sediments called diatomaceous
earth
– Used as filter material, grinding
and polishing, toothpaste
Dinoflagellates
•
dinoflagellates: unicellular,
mostly photosyn., cell walls of
cellulose, 2 flagella
– Both fresh and salt
• Reproduce by simple cell
division
• plankton: communities of
organisms that drift near the
surface
Red Tide
• Large number of dinoflagellates
that turn coastal marine waters
pinkish-orange
– Produce toxins that kill fish
– Can be deadly to humans that eat the
shellfish
Bioluminescence
• Ability to produce light
Other Algae
• Silicoflagellates:
– Star-shaped
internal skeleton
and 2 flagella
• Coccolithophorids
– Flagellated,
spherical cells with
button-like
strcutures
• Cryptophytes
– 2 flagella and lack a
skeleton
Protozoans
Kingdom Protista
Protozoans
• Protozoans; animal-like
• Eat bacteria, other protists,
non-living organic matter
• Lack cell wall
• Live in most aquatic
environments & some in
body fluids
• Classified by movement
Foraminiferans •
forams: marine
protozoans with
porous shells made
of organic material
and calcium
carbonate
– Extends
pseudopodia through
pores
• Forms limestone by
build up of shells in
sediment
Radiolarians
• Planktonic protozoans that have shells of
silica
• Shells are usually spherical with radiating
spines
• Use pseudopodia
• Remains create radiolarian ooze
Ciliates
• Ciliates: diverse group of protists
named for the hair-like projections
called cilia to move and feed
• Cilia are shorter and more
numerous than flagella and are
arranged in rows or clusters
• Paramecium - free-living pond
water organism
• Tintinnids: drift in water and build
vase-like cases
– Loricas: loose fitting shells that drift
Kingdom Fungi
•
•
•
•
Cannot perform photosynthesis
500 known marine species
Mostly microscopic
Decomposers
– Mangrove leaves
• Some are parasites
• Lichen