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Chapter 5
Marine Microbes
Intro to Microbes
 Australian Institute for Marine Science Video
 Viruses
 Prokaryotes
 Bacteria and Archaea
 Eukaryotes
 Unicellular algae/plant-like protists – diatoms,
dinoflagellates, silicoflagellates, coccolithophorids
 Protozoans/animal-like protists – forams, radiolarians,
and ciliates
 Fungi
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)
Nature.com
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)
Prokaryotes
 Archea and Bacteria
 Characteristics of Archean and Bacterial Cells:
– Prokaryotic- no nucleus
– Single chromosome (normally circular)- some also
with plasmids
– Most with cell wall
– Great metabolic diversity
Prokaryotes
 Archea –
 Ancient organisms – fossils found that date back 3.8
billion years
 Extremophiles – Found in extreme environments like
hydrothermal vents and salt flats (two 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)
Bacteria
 Domain Bacteria
 Prokaryotes
 Many shapes – spheres, spirals, rods, rings
 Cell walls
 Ensure the recycling of nutrients in detritis (VERY
important!)
 Most abundant form of life on earth!
Prokaryotes
 Metabolic diversity:
 Photosynthetic – derive energy from light
 Chemosynthetic – derive energy from chemical
compounds
 Heterotrophic – derive energy from organic matter by
respiration
Cyanobacteria
 Chlorophyll-a, phycocyanin (bluish pigment),
phycoerythrin (redish pigment) – color depends on the
amount of pigment of each color
 Epiphytes (on seagrasses and seaweeds) and
Endophytes (in algae)
 Stromatolites – calcareous mounds formed by
cyanobacteria
Cyanobacteria
 Red tides – planktonic species
multiply rapidly and contain red
pigment. Can be devistating to
ecosystems.
www.wikipedia.com
 Endolithic species burrow into rocks
and coral or form thick, dark crusts on
wave-splashed rocky coasts
 Prochlorococcus – most abundant
marine organism!
http://www.whoi.edu/redtide/
Diatoms
 Photosynthetic
 Yellow-brown from photosynthetic pigments,
chlorophyll-a and chl-c and carotenoids
 Shell of silica called a frustule
 Most important primary producer on Earth
 Mostly solitary and unicellular, but some colonial
Diatoms
– Around half of the 12,000 known species are marine
– Most 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
Diatoms
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 for motion
 Also reproduce by cellular division
 Some are bioluminescent (read “Bay of Fire” on pg. 96)
Dinoflagellates
 Symbiodinium sp.
 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)
Noaa.gov
Auburn.cedu
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
Noaa.gov
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 pg. 338)
 Pfiesteria 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
Whoi.edu
Other 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
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
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
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
Fungi
 Eukaryotic and mostly multicellular
 Heterotrophic
 Most of the 1500 species of marine fungi are
microscopic
Biotec.or.th
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