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Chapter 6 Marine Microbes Karleskint Turner Small Key Concepts • Microbial life in the sea is extremely diverse, including members of all three domains of life as well as viruses. Key Concepts • Photosynthetic and chemosynthetic bacteria are important primary producers in marine ecosystems. • Heterotrophic bacteria, and fungi play essential roles in recycling nutrients in the marine environment. Key Concepts • Some Marine microbes contribute significantly to the accumulation of deepsea sediments. • Populations of several kinds of photosynthetic marine microbes may form harmful blooms that affect other marine and maritime organisms directly and indirectly. Marine Viruses • Virology—the study of viruses • Viruses are diverse and are more abundant than any other organism in the sea • Have significance for marine food webs, population biology and diseases of marine organisms Ecology of Marine Viruses • Viruses kill host cells, and thus control populations of bacteria and other microbes in plankton communities • Viruses also responsible for chronic infection and mass mortality of populations of marine animals Marine Bacteria • General characteristics – simple, prokaryotic organization: no nuclei or membrane-bound organelles, few genes – reproduce asexually by binary fission – many shapes and sizes • bacillus—rod shape • coccus—spherical shape Nutritional Types • Cyanobacteria (blue-green bacteria) – photosynthetic bacteria which are found in environments high in dissolved oxygen, and produce free oxygen – primary photosynthetic pigments are chlorophyll a and chlorophyll b Nutritional Types • Chemosynthetic bacteria – use energy derived from chemical reactions that involve substances such as ammonium ion, sulfides and elemental sulfur, nitrites, hydrogen, and ferrous ion – chemosynthesis is less efficient than photosynthesis, so rates of cell growth and division are slower – found around hydrothermal vents and some shallower habitats where needed materials are available in abundance Chemosynthetic bacteria (in animal tissues, in water, and on rocks) Carbon dioxide (CO2) Produce Water (H2O) Carbohydrates Hydrogen sulfide (H2S) Animal community Carbon dioxide (CO2) Hydrogen sulfide (H2S) Elemental sulfur (S) Carbon dioxide (CO2) Stepped Art Magma (molten rock) Fig. 6-10, p. 134 Nutritional Types • Heterotrophic bacteria – decomposers that obtain energy and materials from organic matter in their surroundings – return many chemicals to the marine environment through respiration and fermentation Nutritional Types (Heterotrophic Bacteria) • Heterotrophic bacteria – marine snow: large, cobweb-like drifting structures formed by mucus secreted by many kinds of plankton, where particles may accumulate Symbiotic Bacteria • Many bacteria have evolved symbiotic relationships with a variety of marine organisms • Chemosynthetic bacteria live within tube worms and clams • Some deep-sea or nocturnal animals host helpful bioluminescent bacteria – photophores – embedded in the ink sacs of squid Archaea • General characteristics – small (0.1 to 15 micrometers) – prokaryotic – adapted to extreme environmental conditions: high and low temperatures, high salinities, low pH, and high pressure – differences from bacteria • cell walls lack special sugar-amino acid compounds in bacterial cell walls • cell membranes contain different lipids, which help stabilize them under extreme conditions Archaea • Nutritional Types – photosynthesizers, chemosynthesizers and heterotrophs – most are methanogens: anaerobic organisms that metabolize organic matter for energy, producing methane as a waste product – halobacteria thrive at high salinities Archaea • Hyperthermophiles – organisms that can survive at temperatures exceeding 100o C, such as near deep-sea vents – Potential for biomedical and industrial application Eukarya • Eukarya includes all organisms with eukaryotic cells • Examples: – plants – animals – fungi – algae – single-celled animal-like protozoa Fungi • important in marine ecosystems as decomposers, prey, pathogens and symbionts Fungi • General features of fungi – heterotrohic decomposers that recycle organic material • can digest lignin (major component of wood) Fungi • Ecology and physiology of marine fungi – salinity is toxic to fungi, so they must devote energy to removing sodium – most marine fungi live on wood from land – some live on grass in salt marshes – others live on algae, mangroves or sand Maritime Lichens • Lichens: mutualistic associations between a fungus and an alga – algae are usually green or blue-green bacteria • The fungus provides attachment, general structure, minerals, moisture • The alga produces organic matter through photosynthesis Diatoms • Diatom structure – 2 basic diatom shapes: • radially symmetrical valves (generally planktonic) • bilaterally symmetrical valves (generally benthic) Diatoms • Diatomaceous sediments – frustules of dead diatoms sink and collect on the seafloor to form siliceous oozes – accumulations form sedimentary rock – these deposits, called diatomaceous earth, are mined for use as filtering material, a mild abrasive, and for soundproofing and insulation products – nutrient reserves, stored as lipids, accumulate in siliceous oozes accounting for most of the worlds petroleum reserves Alveolates • Dinoflagellates – globular, unicellular (sometimes colonial) with 2 flagella – Most are planktonic, some are benthic and others parasitic, also can be bioluminescent – Bioluminescent Bay, Puerto Rico Alveolates (Dinoflagellates) • Dinoflagellate structure – simple flagellum encircles the cell in the horizontal groove and produces a spinning motion – longer flagellum with hair-like filaments trails down the longitudinal groove and imparts most of the forward motion to the cell – number, size and shapes of plates are used to identify different species Alveolates (Dinoflagellates) • Ecological roles of dinoflagellates – major component of phytoplankton – some are parasites of copepods (crustaceans) – zooxanthellae: species lacking flagella which are symbionts of jellyfish, corals and molluscs – photosynthetic zooxanthellae provide food for hosts – hosts provide carbon dioxide, other nutrients, and shelter Alveolates (Dinoflagellates) • Harmful Algal Blooms (HABs) – occur when photosynthetic dinoflagellates undergo a population explosion – colors the water red, orange or brown – dinoflagellates that cause HABs produce toxins • paralytic shellfish poisoning (PSP) occurs in humans who consume shellfish contaminated with these toxins • toxins cannot be destroyed by cooking – oxygen content of the water may be reduced to deadly levels as bacteria decompose animals killed by dinoflagellate toxins