Transcript Chapter 6
Chapter 6 Marine Microbes Karleskint Turner Small 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 Viral Characteristics • Most authorities do not consider them to be alive • Remember you have to be made of at least one cell to be alive, viruses are not cells • Viruses consist of bits of DNA or RNA surrounded by protein • Have no metabolism, and rely entirely on host organism for energy, material and organelles to reproduce themselves • Viral replication must occur within a host cell • Viruses infect all groups of living organisms, but may be specialized • Infect specific species • Infect specific tissues of that species – Influenza infects respiratory cells – Hepatitis infects liver cells Viral Characteristics • Viral structure – virus particle is called a virion when outside the host cell – virion composed of a nucleic acid core surrounded by a coat of protein called a capsid (together called a nucleocapsid) – may have a protective envelope, a membrane derived from the host’s nuclear or cell membrane Biodiversity and Distribution of Marine Viruses • 10 times more abundant than marine prokaryotes, may reach 1010 virons per liter of seawater, 1013 per kilogram of sediment • Bacteriophages – viruses that infect bacteria 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 – For example – problems with shrimp aquaculture • Bacterial lysis can alter biogeochemical cycles and planktonic food webs Virus infecting a Bacterium • https://www.youtube.com/watch?v=41aqxc xsX2w • Now we will talk about bacteria Marine Bacteria • General characteristics – simple, prokaryotic organization: no nuclei or membrane-bound organelles, few genes, nonliving cell wall – reproduce asexually by binary fission – many shapes and sizes • bacillus—rod shape • coccus—spherical shape Nutritional Types of bacteria • Cyanobacteria (blue-green bacteria) – photosynthetic bacteria which are found in environments high in dissolved oxygen, and produce free oxygen Photosynthesis Nutritional Types (Cyanobacteria) • Cyanobacteria (con’t) – may exist as single cells or form dense mats held together by mucilage • form associates called stromatolites—a coral-like mound of microbes that trap sediment and precipitate minerals in shallow tropical seas Nutritional Types • Other photosynthetic bacteria – sulfur bacteria are obligate anaerobes (tolerating no oxygen) – non-sulfur bacteria are facultative anaerobes (respiring when in low oxygen or in the dark and photosynthesizing anaerobically when in the presence of light) Nutritional Types • Chemosynthetic bacteria – Chemosynthesize instead of photosynthesize • Use sulfides and elemental sulfur, nitrites, hydrogen, and ferrous ion that are coming up from hydrothermal vents – 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 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 – populate the surface of organic particles suspended in the water by secreting mucilage (glue-like substance) Nutritional Types (Heterotrophic Bacteria) • Heterotrophic bacteria – association of heterotrophic bacteria with particles in the water column aids with: • consolidation: adjacent particles adhere • lithification: formation of mineral cement between particles • sedimentation: settling of particles – marine snow: large, cobweb-like drifting structures formed by mucus secreted by many kinds of plankton, where particles may accumulate Nitrogen Fixation and Nitrification • Nitrogen cycle – nitrogen fixation and nitrification • Nitrogen fixation: process that converts molecular nitrogen dissolved in seawater to ammonium ion – major process that adds new usable nitrogen to the sea – only some cyanobacteria and a few archaeons with nitrogenase (enzyme) are capable of fixing nitrogen Nitrogen Fixation and Nitrification • Nitrification: process of bacterial conversion of ammonium (NH4+) to nitrite (NO2-) and nitrate (NO3-) ions – bacterial nitrification converts ammonium into a form of nitrogen usable by other primary producers (autotrophs) Symbiotic Bacteria • • • • Many bacteria have evolved symbiotic relationships with a variety of marine organisms Endosymbiotic theory – mitochondria, plastids & hydrogenosomes evolved as symbionts within other cells 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 • Hyperthermophiles – organisms that can survive at temperatures exceeding 100o C, such as near deep-sea vents – Potential for biomedical and industrial application • Now we will talk about Eukaryotes Eukarya • Eukarya includes all organisms with eukaryotic cells • Examples: – plants – animals – fungi – algae – single-celled animal-like protozoa • Within Eukarya, we will now talk about the Fungi Fungi • General features of fungi – eukaryotes with cell walls of chitin – many are unicellular yeasts – filamentous fungi grow into long, multi-cellular filaments called hyphae that can branch to produce a tangled mass called a mycelium – heterotrohic decomposers that recycle organic material • can digest lignin (major component of wood) Fungi • General features of fungi (con’t) – kingdom Fungi is divided into 4 phyla: • • • • Chytridiomycota (motile cells) Zygomycota (e.g. black bread mold) Basidiomycota (club fungi, e.g. mushrooms) Ascomycota (sac fungi) – in the sea, ascomycotes are the most diverse and abundant fungi Fungi • Ecology and physiology of marine fungi – can be either obligately marine, requiring ocean or brakish water or facultatively marine (primarily of terrestrial or fresh water origin) – 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 – fungi decompose the chitinous remains of dead crustaceans in open sea plankton communities • Now we will talk about the protists • Here we will talk mainly about the unicellular protists » Unicellular algae – Phytoplankton » Unicellular heterotrophs - protozoans • Later, we will talk about multicellular protists » Algae - “seaweed” Stramenophiles • A diverse group of eukaryotic organisms unified by the nature of their cells’ 2 flagella – includes diatoms and brown algae Diatoms • Extremely diverse and distinct members of marine phytoplankton • Diatom structure – frustule—a two-part, box-shaped organic cell wall impregnated with silica – 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 – Ancient diatoms sank to the bottom of the ocean, were covered by sediment before they decomposed, were subjected to pressure and heat and turned into petroleum Diatoms Other Ochrophytes • Silicoflagellates – abundant in cold marine waters – basket-shaped external skeletons of silica which the cell wraps around – cell wraps around skeleton which appears internal Coccolithophores • Photosynthetic organisms with 2 simple flagella both used for locomotion • Have haptonema: a unique structure arising from the cell surface between the 2 flagella, captures food • Most are coccolithophores with a surface coating of disc-shaped scales (coliths) of calcium carbonate – remains form calcereous oozes Alveolates • Recent re-grouping of several kinds of marine microbes • Examples: – dinoflagellates – ciliates – apicomplexans (strictly parasitic) • 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 – https://www.youtube.com/watch?v=eFY7rbEO H-8 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 – 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 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 Red Tides • Ciliates – protozoans that bear cilia for locomotion and for gathering food • membranelles—tufts or long rows of fused adjacent cilia • cytostome—an organelle serving as a permanent site for phagocytosis of food – planktonic and benthic – major links in marine food chains – form symbiotic and parasitic relationships Paramecium – a ciliate Choanoflagellates • Phylum of marine and freshwater flagellated cells that are more closely related to animals than any other group of one-celled microbes • Unicellular or colonial – colonies may be stalked or embedded in a gelatinous mass • Highly efficient consumers of bacteria • Ancestors to the animals? Amoeboid Protozoans • All have an organelle called a pseudopod—an extension of the cell surface that can change shape and is used for locomotion (benthic species) and food capture (benthic and pelagic) • Are hererotrophs consuming bacteria and other small organisms Amoeboid Protozoans • Two major phyla: – foraminiferans (abundant, diverse) – actinopods, which include: • radiolarians (predominant type) • acantharians • heliozoans Amoeboid Protozoans • Foraminiferans (forams) – have branched pseudopods that form reticulopods (elaborate, net-like structures) used to: • snare prey • crawl (benthic) • reduce sinking rate (pelagic) – consume bacteria and diatoms – some harbor symbiotic green and red algae and zooxanthellae Amoeboid Protozoans (Foraminiferans) • Foraminiferan test – elaborate, multi-chambered tests of calcium carbonate – globigerina ooze: sediments of dead planktonic forams, largely Globigerina Amoeboid Protozoans • Radiolarians – named for long, needle-like pseudopods • central nuclear region is surrounded by a capsule— an external organic membrane • pseudopods pass through pores in the capsule and form a region called the calymma • pseudopods capture food and slow sinking – radiolarian oozes form from the internal siliceous skeleton of dead radiolarians – live in the photic zone and capture phyto- and zooplankton, sometimes copepods – larger radiolarians prey on copepods and other planktonic crustaceans • So far, we have talked about: – Viruses – Infect bacteria, protists, plants and animals in the marine environment – Domain Archaea – prokaryotes, extremophiles – Domain Bacteria – Cyanobacteria – photosynthetic bacteria – Heterotrophic bacteria – can be nitrogen fixers, can have symbiotic relationship with other organisms, can infect other organisms, can help with decay – Domain Eukarya – Fungi – Protists » Unicellular algae – diatoms, dinoflagellates, coccolithophores » Protozoans – ciliates, choanoflagellates, amoeboids (foraminiferans, radiolarians)