1. Marine Biology Chapter 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

6. Figure 6-2 STRUCTURE OF MARINE VIRUSES.

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. Figure 6-8 (a) BACTERIAL 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)
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

21. Figure 6-10 CHEMOSYNTHESIS.

22. Figure 6-8 (b) BACTERIAL PHOTOSYNTHESIS.

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

31. Pls note: I do not see this figure in text
Pls note: I do not see this figure in text. Has it been preplaced by Figure 6-18 DIATOMS ?

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

39. Figure 6-25 DINOFLAGELLATES.

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
Figure 6-27 (a) CHOANOFLAGELLATES.
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)