Viruses Chapter 5 The Microbial World Non-cellular infectious agents that have two basic characteristics: Not capable of reproduction without a host cell Structure: Nucleic acid core- can be DNA or RNA Capsid (Protein coat)- consists of numerous protein subunits organized into rod-like or many sided shape. Protein coat also contains specific proteins that bind with receptors on host cells (great at mimicry!!) Many glycoprotein spikes extend from coat-these these spikes mutate so frequently that our immune system cannot keep up. Viruses Viruses in the Marine Community: They are common in marine waters They can infect bacteria, plankton, fish, sea turtles and marine mammals Lysis (bursting) of viral infected cells spills contents and releases large amounts of organic matter that can be utilized by other organisms (dissolved organic matter or DOM) Archea and Bacteria Characteristics of Archean and Bacterial Cells: Prokaryotic- no nucleus Single chromosome (normally circular)- some also with plasmids Most with cell wall Great metabolic diversity Archea Ancient organisms fossils found that date back 3.8 billion years Some live in very extreme environments Variety of metabolic types Widely distributed in the marine community They can tolerate wide ranges in temperature, salinity and even desiccation (drying out) Can be found in many areas including near hydrothermal vents and salt flats (two very extreme environments) Special Features of Bacteria: A variety of shapes including spirals, spheres, rods and rings Cell wall structure is semi-rigid, but permeable; most with cell wall Size is normally microscopic, but a few are large Wide variety of metabolic types Very abundant worldwide
Aerobic respiration Metabolic diversity: Photosynthesis derive energy from light Chemosynthetic derive energy from chemical compounds Heterotrophs derive energy from organic matter by respiration Prokaryote metabolic diversity Heterotrophic microbial metabolism Fermentation Special metabolic properties Methylotrophy Syntrophy Anaerobic respiration Denitrification - nitrate as electron acceptor Sulfate reduction - sulfate as electron acceptor Electron donors Energy for reduction Acetogenesis - carbon dioxide as electron acceptor Other inorganic electron acceptors Organic terminal electron acceptors Chemolithotrophy Hydrogen oxidation Sulfur oxidation Ferrous iron (Fe2+) oxidation Nitrification Anammox Phototrophy Dissolved organic carbon in the ocean Forms polymers and particles (snow) that are the habitat for many prokaryotes in the water column Carbon in the ocean (gigatons) organisms 3 dissolved organic 700 surface ocean 1020 deep ocean sediment 38100 150 39973
Transparent exopolymers Recall that there are 700 gigatons of dissolved organic compounds in the ocean Transparent exopolysaccharides(tep) Marine snow Phytoplankton Unicellular algae and cyanobacterial component of the plankton 50% of global photosynthesis Some major algal groups Diatoms Dinoflagellates coccolithophores Global primary production Diatoms Diatoms: Photosynthetic Yellow-brown color in life is a result of photosynthetic pigments, chlorophyll A and C and carotenoids Shell of silica called a frustule Most important primary producer on Earth Mostly solitary and unicellular Some can form colonies
Diatoms Diatoms Around half of the 12, 000 known species are marine Most are planktonic Store excess energy as an oil which also aids in buoyancy Tiny pores in shell used for gas/nutrient exchange Dinoflagellates Dinoflagellates Most species live in marine environment Mostly photosynthetic, some can ingest particles Each species has unique shape reinforced by plates of polysaccharide (like cellulose) Two flagella in grooves on body that produce motion Some are bioluminescent (read Bay of Fire Fire on pg. 96) Ceratium-dinoflagellates Dinoflagellates occur in enormous numbers in the ocean, particularly in tropical waters and display a huge diversity of form. The large protrusions seen on this Ceratium-dinoflagellate are used for protection against predators.
Dinoflagellates Dinoflagellates Zooxanthellae are important dinoflagellates that live in a symbiotic relationship with corals, sea anemones and other organisms (many of these host organisms have little or no growth without their symbiotic partner) Algal Blooms Diatoms and dinoflagellates can go through periods of rapid growth known as blooms This is a result of high levels of nutrients in the water These blooms can be harmful to marine organisms and even people at times Algal bloom southern England Coccolithophore bloom Bering Sea Red tides - dinoflagellates Dinoflagellates A few species lack chloroplasts and live as parasites in marine organisms Some species can reproduce in larger numbers and produce Red Tide (read Red Tides and Harmful Algal Blooms, pg. 338) Pfiesteria is a dinoflagellate that produces very serious toxins that can cause massive fish kills, harm shellfish and impair the nervous system in humans. Pfiesteria was discovered near the Outer Banks in North Carolina
Coccolithophores Ornate shells of calcium carbonate Protozoa Foraminiferans (forams) Exclusively found in marine community Found on sandy or rocky bottoms Shells of calcium carbonate Can be important contributors of calcareous material on coral reefs or sandy beaches Pseudopods (false feet) extend through pores in the shell where they are used to capture minute food particles such as phytoplankton Protozoa Radiolarians Planktonic, mostly microscopic, although a few can reach large sizes Shell of silica Like forams, they use pseudopods that extend through pores in the shell where they are used to capture minute food particles such as phytoplankton
Protozoa Ciliates Cilia present for locomotion Most live as solitary cells Some build shells made of organic debris May live on hard substrate Some are planktonic Fungi Eukaryotic and mostly multicellular Heterotrophic Most of the 1500 species of marine fungi are microscopic Fungi Like bacteria, many fungus break down dead organic matter into detritus Some fungus live in symbiosis with cyanobacteria, these are known as lichens Marine lichens often live in wave-splashed areas of rocky shorelines and other hard substrate