1. Chapter 5 Lecture Slides
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2. Chapter 5
The Microbial World

3. Viruses
Non-cellular infectious agents that have two basic characteristics:
Not capable of reproduction without a host cell
Structure:
Nucleic acid core- can be DNA or RNA
Capsid (Protein coat)-
consists of numerous protein subunits organized into rod-like or many sided shape.
Protein coat also contains specific proteins that bind with receptors on host cells (great at mimicry!!)
Many glycoprotein spikes extend from coat-these spikes mutate so frequently that our immune system cannot keep up.

4. Viruses Notable Types of Viruses:
Retroviruses- store genetic information in the form of nucleic acid known as RNA
Lysogenic viruses – reproduce by inserting their DNA into the DNA of the host cell
Bacteriophages – viruses that infect bacteria

5. Viruses Viruses in the Marine Community:
They are common in marine waters
They can infect bacteria, plankton, fish, sea turtles and marine mammals
Lysis (bursting) of viral infected cells spills contents and releases large amounts of organic matter that can be utilized by other organisms (dissolved organic matter or DOM)

6. Prokaryotes Archaea and Bacteria
Characteristics of Archaean and Bacterial Cells:
Prokaryotic- no nucleus
Single chromosome (normally circular)- some also with plasmids
Most with cell wall
Great metabolic diversity

7. Prokaryotes
Archaea –
“Ancient organisms” – fossils found that date back “3.8 billion years”
Some live in very extreme environments
Variety of metabolic types
Widely distributed in the marine community
They can tolerate wide ranges in temperature, salinity and even desiccation (drying out)
Can be found in many areas including near hydrothermal vents and salt flats (two very extreme environments)

8. Prokaryotes Special Features of Bacteria:
A variety of shapes including spirals, spheres, rods and rings
Cell wall structure is semi-rigid, but permeable; most with cell wall
Size is normally microscopic, but a few are large
Wide variety of metabolic types
Very abundant worldwide

9. Prokaryotes Special Features of Bacteria:
One of the most important jobs of bacteria in the marine community is to break down dead organic matter – this forms detritus, which are minute particles of organic matter now available as nutrition for other organisms
Cyanobacteria are a group of photosynthetic bacteria
Stromalites, massive calcareous mounds formed by cyanobacteria, have been found that are billion years old

10. Prokaryotes Metabolic diversity:
Photosynthesis – derive energy from light
Chemosynthetic – derive energy from chemical compounds
Heterotrophs – derive energy from organic matter by respiration

11. Diatoms Diatoms: Photosynthetic
Yellow-brown color in life is a result of photosynthetic pigments, chlorophyll A and C and carotenoids
Shell of silica called a frustule
Most important primary producer on Earth
Mostly solitary and unicellular
Some can form colonies

13. Diatoms Diatoms Around half of the 12, 000 known species are marine
Most are planktonic
Store excess energy as an oil which also aids in buoyancy
Tiny pores in shell used for gas/nutrient exchange
Some produce a toxin, known as domoic acid, that can accumulate in the tissues or organisms that eat diatoms such as shellfish and small fish
Larger organisms that eat these shellfish or small fish can become ill or die from this accumulated toxin

14. Diatoms
Diatoms
Mainly reproduce by cellular division (a form of asexual reproduction)
In this type of reproduction, the cell divides and each result cell gets one-half of the frustule.
This cell now must secrete the other half of the frustule (smaller piece)
Due to this, diatoms get smaller each time they reproduce
To restore normal size, they must either sexual reproduce or cast off the frustule and secrete an entire new frustule

16. Dinoflagellates Dinoflagellates
Most species live in marine environment
Mostly photosynthetic, some can ingest particles
Each species has unique shape reinforced by plates of cellulose
Two flagella in grooves on body that produce motion
Also reproduce by cellular division
Some are bioluminescent (read “Bay of Fire” on pg. 96)

17. Dinoflagellates Dinoflagellates
Zooxanthellae are important dinoflagellates that live in a symbiotic relationship with corals, sea anemones and other organisms (many of these host organisms have little or no growth without their symbiotic partner)

18. Algal Blooms
Diatoms and dinoflagellates can go through periods of rapid growth known as “blooms”
This is a result of high levels of nutrients in the water
These blooms can be harmful to marine organisms and even people at times

19. Protists Dinoflagellates
A few species lack chloroplasts and live as parasites in marine organisms
Some species can reproduce in larger numbers and produce “Red Tide” (read “Red Tides and Harmful Algal Blooms, pg. 338)
Pfiesteria is a dinoflagellate that produces very serious toxins that can cause massive fish kills, harm shellfish and impair the nervous system in humans.
Pfiesteria was discovered near the Outer Banks in North Carolina

20. Protists A few more species of phytosynthetic plankton:
Silicoflagellates
Star-shaped internal skeleton of silica
Two flagella of varying lengths
Coccolithophores
Ornate shells of calcium carbonate

21. Protozoa Foraminiferans (forams) Exclusively found in marine community
Found on sandy or rocky bottoms
Shells of calcium carbonate
Can be important contributors of calcareous material on coral reefs or sandy beaches
Pseudopods (false feet) extend through pores in the shell where they are used to capture minute food particles such as phytoplankton

23. Protozoa Radiolarians
Planktonic, mostly microscopic, although a few can reach large sizes
Shell of silica
Like forams, they use pseudopods that extend through pores in the shell where they are used to capture minute food particles such as phytoplankton

25. Protozoa Ciliates Cilia present for locomotion
Most live as solitary cells
Some build shells made of organic debris
May live on hard substrate
Some are planktonic

27. Fungi Eukaryotic and mostly multicellular Heterotrophic
Most of the 1500 species of marine fungi are microscopic

28. Fungi
Like bacteria, many fungus break down dead organic matter into detritus
Some fungus live in symbiosis with cyanobacteria, these are known as lichens
Marine lichens often live in wave-splashed areas of rocky shorelines and other hard substrate

29. Most Important Characteristics of Marine Microbes