MARINE BIOLOGY

Chapter 5: The Microbial World

  1. DEFINITION/EXPLANATION
  1. Etymology: Gr. “pro = before,” “karyon = nut, kernel” (therefore before nucleus)
  2. They are the smallest, structurally simplest and the oldest forms of life on earth
  3. They are unicellular
  4. Cell wall, plasma/cell membrane
  5. They make up the two main domains: Bacteria & Archaea
  6. Different than eukaryotes
  1. circular shape of DNA
  2. ribosome size
  3. number of other ways
  1. BACTERIA
  1. Etymology: Gr. “bakterion = small staff” (first ones discovered were rod-shaped)
  2. Domain Bacteria
  3. Come in many shapes: spheres, spirals, rods
  4. Decay bacteria break down waste products and dead organic matter, releasing nutrients into the water column
  5. They themselves are food for some organisms (found in detritus as well)
  6. They help to degrade toxic pollutants
  7. They can cause diseases for marine organisms
  8. They’re everywhere!!
  9. PelagibacterUbique is pretty abundant (perhaps most abundant), and plays a major role in the carbon cycle
  10. Cyanobactera(dba blue-green algae) are photosynthetic
  1. Why is incorrect to call them algae??
  2. They contain chlorophyll a (etymology: “chloro = green,” “phylon = leaf”)
  3. C55H72O5N4Mg is the chemical composition of chlorophyll a (as opposed to chlorophyll b, c1, c2, d and f, all based on structure differences)
  4. Most contain a bluish pigment, phycocyanin (etymology: “phyco = seaweed/algae,” “cyan =blue”)
  5. Some also contain a reddish pigment, phycoerythrin (etymology: “phyco = seaweed/algae,” “erycro = red”)
  6. Important role in the accumulation of oxygen in the atmosphere
  7. Stromatolites
  8. Cyanobacteria create a mucus sheet on the outside of the cell (numerous reasons, e.g. as a defense mechanism to make them “taste bad”; swim easier;nitrogen limitation increases mucus)
  9. This mucus is sticky and sediments get caught in the mucus, which can “glue” sediments together
  10. Cyanobacteria continue to grow around the sediment, toward the sun
  11. Sediment continues to accumulate, and cyanobacteria continue to move toward sun
  12. Calcium carbonate (from the water column)cements the sediments together, with the cyanobacteria
  13. Tada! A structure is formed that grows at a rate of about 5 cm/100 years
  14. Stromatolite-creating cyanobacteria are usually found in areas where there is reduced grazing and borrowing by other organism, and a reduced occurrence of macro-algae and plants
  15. These areas usually include hypersaline conditions, but also include habitats of increased alkalinity, low nutrient levels, elevated or decreased temperatures, precipitation of mineral material during growth, and strong wave or current actions
  16. Modern stromatolites were first discovered in Shark Bay, Australia in 1956 (Hamelin pool), and throughout western Australia in both marine and non-marine environments
  17. Stromatolites continued to be discovered in places, such as the thermal springs of Yellowstone National Park, USA, lakes in Antarctica, marine environments off the Bahamas, and in land-locked pools supersaturated with calcite on Aldabra, in the western Indian Ocean
  18. Some cyanobacteria are endolithic, (etymology: “endo = within,” “lith = rock”), which means they live inside rocks (burrow into calcareous rocks and coral skeletons)
  19. HAB happen because of cyanobacteria
  20. Photosynthetic organisms that live on algae or plants are called epiphytes (etymology: “epi=upon,” “phyte=plant”), which means they love on plants
  21. Those that live on the inside of plants are called endophytes
  1. ARCHAEA
  1. Etymology: “of the earliest geological age” – “arkhaios = ancient”
  2. These are simple and primitive forms of live
  3. Come in many shapes: spheres, spirals or rods
  4. Extremophiles - They exist in all types of environments: hydrothermal vents bio communities, hypersaline areas, etc.
  5. Differ from bacteria because of cell wall structure & composition, and RNA
  6. But they can exist in temperate areas as well
  7. We detect their presence by looking at particular nucleic acid sequences
  1. PROKARYOTE METABOLISM
  1. Autotrophs
  2. Photosynthesis occurs on folded cell membranes within the cell wall, rather than in chloroplasts, like in plants and algae
  3. Photosynthetic bacteria account for most of the primary production in the ocean
  4. Table 5.1 p.99
  5. Some contain proteorhodopsin to capture light energy and store it in ATP, while some bacteria contain bacteriorhodopsin (in absence of chlorophyll) that converts light energy into ATP
  6. Methanogens are any of a diverse group of widely distributed archaea that occur in anaerobic environments, as the intestinal tracts of animals, freshwater and marine sediments, and sewage, and are capable of producing methane from a limited number of substrates, including carbon dioxideand hydrogen
  1. Methanopyrus is one such example
  1. Heterotrophs
  2. Most marine bacteria get their energy from respiration
  3. In fact, many are decomposers
  4. Nitrogen Fixation
  1. Many bottom-dwelling and planktonic cyanobacteria carry out nitrogen fixation, converting gaseous nitrogen (N2) into ammonium (NH4+)
  1. DEFINITION/EXPLANATION
  2. Algae are a diverse group of simple, mostly aquatic, mostly photosynthetic organisms
  3. They are eukaryotic and they are protists
  4. Photosynthesis takes place in chloroplasts (green, brown or red)
  5. Algae lack flowers, true leaves, roots and stems
  6. DIATOMS
  7. Etymology (Gr. “diatomos = to cut in two”)
  8. Phylum Heterokontophyta, class Bacillariophyta
  9. Though unicellular, many species aggregate unto chains or star-like groups
  10. They have cell walls of silica
  11. The glassy shell, or frustule (epithecahypotheca)
  12. The frustule allows light to pass through, while the minute perforations allow dissolved gases to enter and exit
  13. They contain a brown carotenoid as well as chlorophyll a and c (p.108, Table 6.1)
  14. Some diatoms have a stalk-like structure that allows them to hold onto rocks (brownish scum in mudflats are millions of diatoms)
  15. Diatoms reproduce sexually and asexually
  1. The smaller frustule becomes the parent half of an even smaller one, the daughter half
  2. This keeps getting smaller, but some are resistant – the auxospores
  3. The auxospores sexually reproduce to create bigger, similar diatoms
  4. Diatoms die, shells sink, creating diatomaceous ooze, a type of siliceous ooze
  1. DINOFLAGELLATES
  2. Phylum Pyrrophyta or Dinoflagellata
  3. They are mixotrophic (both autotrophic & heterotrophic)
  4. Two flagella: one wrapped around itself, and one trailing off
  5. Most have plates of cellulose
  6. The armored plates are called theca and can have pores, spines, or other ornaments and is made up of cellulose ((C6H10O5)n)
  7. Almost all are marine and can become HAB
  8. Some are bioluminescent (
  9. Some round, golden-brown dinoflagellates are the famous zooxanthellae
  10. Some highly highly specialized dinoflagellates are parasites and have life cycles that include free-swimming stages
  11. Pfiesteria
  1. “phantom dinoflagellate”
  2. It spends most of its life as a harmless resting stage, or cyst, in the sediments
  3. Coastal pollution can cause blooms
  4. They cause deadly open sores on fishes
  5. OTHER UNICELLULAR ALGAE (Smaller than diatom or dinoflagellate)
  6. Silicoflagellates
  1. Phylum Heterokontophyta, Class Chrysophyta
  2. Star-shaped internal skeleton made of silica
  3. Two flagella of different lengths
  4. Fossil silicoflagellates are common in sediment and can be used to date them
  5. Coccolothophorids
  1. AKA Coccolithophores
  2. Phylum Heterokontphyta, Class Haptophyta
  3. Spherical cells, with plates of calcium carbonate called coccoliths
  4. Can be found in sediments as fossils
  5. Cryptophytes
  1. Phylum Cryptophyta, Class Cryptophyceae
  2. Most have plastids (with chlorophyll a and c)
  3. Have two flagella and lack a skeleton
  4. Have a coil inside that is released for propulsion if necessary
  1. DEFINITION/EXPLANATION
  1. They are simple and very diverse
  2. Etmology: “proto = first,” “zo = animal”
  3. Comprise several groups of unrelated origins
  4. They are unicellular, but it could be considered a “super cell”
  5. Foraminiferans
  1. Phylum Granuloreticulosa
  2. Often called forams
  3. Have a test comprised of calcium carbonate, possible with several chambers
  4. They have pseudopodia (extensions of the cytoplasm), which protrude through pores in the shell and trap diatoms
  5. Foraminiferan ooze (a type of calcareous ooze) is created by dead forams
  6. Limestone and chalk beds are a result of this, just like white cliffs of Dover in England
  7. Some are kleptoplastic
  1. Radiolarians
  1. Phylum Polycystina
  2. Secrete elaborate and delicate shells of silica (glass)
  3. Shells are generally spherical with radiating spines
  4. Thin, needle-like pseudopodia capture food, similar to forams
  5. Radiolarian ooze (a type of siliceous ooze) is created by dead radiolarians
  6. This ooze is more extensive cause silica is more resistant to dissolution under pressure than those of forams
  1. Ciliates
  1. Phylum Ciliophora
  2. Hair-like cilia that are used in locomotion and feeding
  3. Paramecium is one of the most famous
  4. Tintinnids are common ciliates that build vase-like cases called loricas (loosely fitting shells, like body armor)

Scientists suspect that the green sea slug (Elysiachlorotica) is guilty of kleptoplasty—the stealing of genetic material from another organism. For some time, experts have known that the green sea slug acquires chloroplasts from the algae it eats. The sea slug stores those chloroplasts in cells that line its gut. There, they act as miniature powerhouses, converting sunlight into sugar. Yet scientists have been puzzled as to how the chloroplasts continue to function on their own. The DNA inside the stolen chloroplasts encodes only about one tenth of the proteins needed to keep it running. So chloroplasts alone do not give the sea slug the ability to photosynthesize.

Research by green sea slug expert Mary Rumpho of the University of Maine may point to the missing piece of the puzzle. Rumpho's observations suggest that the green sea slug may also be stealing nuclear DNA from the algae (in addition to chloroplasts). The sea slug then may be incorporating the algae's DNA it into its own genetic material so it can synthesize the proteins the stolen chloroplasts need to function.