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