Marine Microbiology - Evolution of marine microorganisms...

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Unformatted text preview: Evolution of marine microorganisms Fossil bacteria have been found that are approximately 3.8 billion years old The first marine organisms were prokaryotes (lacking a cell nucleus and mitochondria) Eukaryotic cells evolved about 1 billion years later These cells had a nucleus, mitochondria and were able to respire using oxygen (mitochondria were probably, originally, symbiotic bacteria) Chloroplasts (the site of photosynthesis) were probably also symbiotic bacteria Some tunicates and other marine species contain symbiotic photosynthetic bacteria ( Prochloron ) very similar to choroplasts a missing link Prokaryote cell Eukaryote cell (animal) Eukaryote cell (plant) Photosynthesis At present most biologists split organisms into 3 domains -2 of which contain single-celled (or colonial) prokaryote organisms- 1 Contains single-celled, colonial or multi eukaryote celled organisms Marine Microorganisms Marine microorganisms have a very important role in the ecology of the oceans Microorganisms are the most important PRIMARY PRODUCERS-they directly or indirectly feed all marine organisms Either they synthesize organic matter from carbon dioxide (usually by photosynthesis) Or they are DECOMPOSERS breaking down dead and dying organisms, releasing organic matter and nutrients into the marine ecosystem Other marine microorganisms swim and ingest other organisms (CONSUMERS) acting in a way similar to animals, but also playing an important role in the marine ecosystem Marine prokaryotes - Bacteria Prokaryotes are spilt into two kingdoms: Bacteria and Archaea Bacteria are abundant in all parts of the ocean on every surface and in the water column-They come in many shapes spheres, spirals, rods and rings Although typically many orders of magnitude smaller than eukaryote cells (e.g. 0.001mm); a marine filamentous bacteria was found of SW Africa which was 0.75 mm wide (observable with the naked eye) Another giant bacterium (0.5mm long) is found in the intestines of some coral reef fish Marine bacteria The most abundant organism on the planet is a open water marine bacterium SAR11 Many marine bacteria are found in benthic sediments where they decompose DETRITUS (decaying organic matter) However due to cold temperatures and high pressures, decomposition can be 1000 times slower than in shallow water Bacteria have been found in sediments up to 300m below the bottom of the Pacific Ocean These deep sea bacteria produce organic material (e.g. sugars) using energy produced by chemical reactions = CHEMOSYNTHESIS Cyanobacteria Once called blue-green algae- They were one of the first organisms to produce organic molecules (e.g. sugars) using energy from sunlight (=PHOTOSYNTHESIS) They have existed for more than 3 billion years and the oxygen they produced is largely responsible for the oxygen rich atmosphere of today....
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Marine Microbiology - Evolution of marine microorganisms...

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