Marine Microbes: Viruses, Bacteria, and Biochemistry

1. Marine BiologyChapter 6 Marine Microbes

2. Microbes • Any living thing that is microscopic • Can be one of the following: • Viruses • Prokaryotes (Bacteria) • Unicellular Protists • Unicellular Fungi • Even very tiny animals

3. 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

4. Viral Characteristics • Are they “alive”? Most say no • 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

5. Viral Characteristics • Viral structure • virus particle is called a virion when outside the host cell • Can’t do anything until it enters into a host cell • virion composed of a nucleic acid core surrounded by a coat of protein called a capsid • may have a protective envelope, a membrane derived from the host’s nuclear or cell membrane

7. Biodiversity and Distribution of Marine Viruses • 10 times more abundant than marine prokaryotes (bacteria) • may reach 1010 virons per liter of seawater, 1013 per kilogram of sediment • Bacteriophages – viruses that infect bacteria

8. Ecology of Marine Viruses • Viruses kill host cells, and thus control populations of bacteria and other microbes in plankton communities in the marine environment • Viruses also responsible for chronic infection and mass mortality of populations of marine animals • Examples: • Problems with shrimp aquaculture • Papillomivirus and morbillivirus in marine mammal populations

9. Now we will talk about bacteria

10. 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

11. Marine bacteria play many different roles based on species • Some photosynthesize • Some are important in the nitrogen cycle • Some cause disease • Some decompose • Some have symbiotic relationships with other organisms

12. Nutritional Types of bacteria • Cyanobacteria (blue-green bacteria) • photosynthetic bacteria which are found in environments high in dissolved oxygen, and produce free oxygen

13. Photosynthesis

14. Cyanobacteria • 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

15. Nutritional Types of Bacteria • 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

16. Nutritional Types (Heterotrophic Bacteria) • Heterotrophic bacteria • marine snow: large, cobweb-like drifting structures formed by mucus secreted by many kinds of plankton and bacteria, where particles may accumulate • Feces, dead material accumulate as marine snow • Drops through the water column feeding other species that are deeper

17. Nitrogen Fixation and Nitrification • Nitrogen cycle – nitrogen fixation and nitrification • Why do we need nitrogen? • Nitrogen is needed to make DNA and amino acids to make proteins • There is lots of nitrogen gas in the atmosphere, but most species are not able to use it in that form • Therefore, there are some bacteria that can convert the atomospheric nitrogen into nitrogen they can use to make their DNA and proteins • That nitrogen then makes it’s way up the food chain • There are bacteria that during the decomposition process can convert the nitrogen back into nitrogen gas, therefore continuing the nitrogen cycle

18. 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

19. Archaea Bacteria • Archaeans are bacteria that include the “extremophile” bacteria • Example: Hyperthermophiles • organisms that can survive at temperatures exceeding 100o C, such as near deep-sea vents • Potential for biomedical and industrial application

20. Nutritional Types of Bacteria • 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

23. Now we will talk about Eukaryotes

24. Eukarya • Eukarya includes all organisms with eukaryotic cells • Examples: • plants • animals • fungi • algae • single-celled animal-like protozoa

25. For this chapter, we are only going to talk about Eukaryotes that are microscopic • Within Eukarya, we will now talk about the Fungi

26. 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)

27. Fungi • 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

28. 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

29. 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”

30. Diatoms • Extremely diverse and distinct members of marine phytoplankton • Diatom structure • frustule—a two-part, box-shaped organic cell wall impregnated with silica

32. 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

33. Diatoms

34. Coccolithophores • Photosynthetic organisms with 2 simple flagella both used for locomotion • Most are coccolithophores with a surface coating of disc-shaped scales (coliths) of calcium carbonate • remains form calcereous oozes

35. Alveolates • Examples: • dinoflagellates • ciliates • apicomplexans (strictly parasitic)

36. 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

37. 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

38. Red Tides

40. 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

41. Paramecium – a ciliate

42. 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?

43. Choanoflagellate Sponge

44. 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

45. Amoeboid Protozoans • foraminiferans • radiolarians

46. 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

47. Amoeboid Protozoans • Radiolarians • named for long, needle-like pseudopods • 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

48. 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 (Phytoplankton) • Protozoans – ciliates, choanoflagellates, amoeboids (foraminiferans, radiolarians)