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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
• First Photosynthetic bacteria– Chlorophyll a– Phycocyanin (bluish)– Phycoerythrin (reddish)
• Produced oxygen as a waste product
• Stromatolites: mounds formed by cyano
• Widely spread– Polar bear hair
• Endolithic: burrow into calcareous rocks and coral skeletons– Form thick crusts along coasts– Exploit oxygen-poor
sediments
• Planktonic: surface– Rapidly multiply– Cause a Red tide
• Epiphytes: live on algae or plants
• 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
• 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
Foraminiferans
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