Marine Viruses and Prokaryotes

Marine Viruses

• Non-cellular infectious agents that cannot reproduce without a host cell
• Core of nucleic acid, either DNA or RNA
• Capsid is a protein coat consisting of numerous protein subunits organized into rod-like or many-sided shapes

Types of Viruses

• Retroviruses store genetic information as RNA
• Lysogenic viruses reproduce by inserting DNA into the host cell's DNA
• Bacteriophages infect bacteria

Marine Viruses

• Common in the marine environment and infect bacteria, plankton, seaweeds, plants, and animals
• Lysis is the bursting of cells infected with viruses spills contents and releases large amounts of organic matter

Prokaryotes

• Archaea and Bacteria are prokaryotes
• Prokaryotic organisms lack a nucleus with a single, circular chromosome
• Most have a cell wall and exhibit great metabolic diversity
• Archaea are ancient organisms dating back 3.8 billion years, with a variety of metabolic types
• Archaea are widely distributed at sea and tolerate wide ranges in temperature, salinity, and desiccation that can be found near hydrothermal vents and salt flats

Marine Bacteria

• Possess a variety of shapes, including spirals, spheres, rods, and rings
• Cell wall structure is semi-rigid and permeable
• Most are microscopic, exhibit a wide variety of metabolic types, and are very abundant

Marine Bacteria

• Breaks down dead organic matter into detritus, which other organisms utilize as nutrition
• Cyanobacteria are photosynthetic bacteria and important in the marine environment
• Stromatolites are massive calcareous mounds formed by cyanobacteria

Prokaryotes Metabolic Diversity

• Photosynthesis enables them to derive energy from light
• Chemosynthesis enables them to derive energy from chemical compounds
• Heterotrophs derives energy from organic matter by means of respiration

Marine Diatoms

• Photosynthetic organisms that are yellow-brown in color, and have photosynthetic pigments containing chlorophyll A & C, and carotenoids
• Consists of a shell of silica called a frustule and is the most important primary producer on Earth
• They are mostly solitary and unicellular, but some can form colonies
• Around half of the 12,000 known species are marine
• Most are planktonic, store excess energy as an oil for buoyancy, and use tiny pores in their shells for gas/nutrient exchange
• Some produce domoic acid, a toxin that can accumulate in the tissues of organisms

Marine Diatoms Reproduction

• Reproduce by cellular division (asexual reproduction) through cell-division
• Each resulting cell gets one-half of the frustule, so each cell must secrete the other half to cause diatoms to get smaller each time they reproduce
• To restore normal size, they must either reproduce sexually or cast off the frustule and secrete an entire new frustule

Marine Dinoflagellates

• Mostly marine while some can ingest particles
• Each species has a particular shape, reinforced by plates of cellulose
• They have two flagella in grooves for motion, and some are bioluminescent
• Zooxanthellae are dinoflagellates that live in a symbiotic relationship with reef corals, some sea anemones, and other organisms

Algal Blooms

• Diatoms and dinoflagellates can go through periods of rapid growth
• Caused by high levels of nutrients in the water can be harmful to marine organisms and even humans

Red Tides and Pfiesteria

• Some species lack chloroplasts and live as parasites in other marine organisms
• Some species can reproduce in larger numbers and produce red tides
• Pfiesteria is a dinoflagellate, produces very serious toxins that can cause massive fish kills, harm shellfish, and impair the nervous system in humans

Other Marine Protists

• Silicoflagellates: Star-shaped internal skeleton of silica, with two flagella of varying lengths
• Coccolithophorids: Ornate shells of calcium carbonate plates

Marine Protozoans

• Foraminifera: Exclusively marine, non-photosynthetic heterotrophs, also animal-like
• Shells of calcium carbonate are important contributors of calcareous material on coral reefs or sandy beaches
• Pseudopods (false feet) extend through pores in the shell to capture minute food particles like phytoplankton
• Radiolarians: Planktonic and microscopic, with a shell of silica that they use to capture minute food particles such as phytoplankton

Ciliates

• Contains hair-like cilia for locomotion
• Most live as solitary cells, and some build shells made of organic debris and live on hard substrates; while some are planktonic
• Tintinnids are ciliates who make shells known as loricas

Marine Fungi

• Eukaryotic and mostly multicellular heterotrophs
• The majority of at least 1,500 species are microscopic
• Parengyodontium album can break down plastic
• Fungi break down dead organic matter into detritus
• Some fungi live in symbiosis with cyanobacteria to form lichens
• Marine lichens often live in wave-splashed areas of rocky shores and other hard substrates