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Chapter 6 Marine Microbes
Viruses
Virology- the study of viruses. Had a late start in marine
sciences.
•First reported case in mid 1900’s
•Reliable counts of marine viruses were first made in 1980’s.
Characteristics
• Protein case (capsid)
•DNA/RNA inside
•Have no true metabolism
•Rely on host for everything (energy, replication, etc..)
Question – are viruses alive?
Virus Life Cycles
• Lytic cycle – Destroy the host DNA and reprogram the
cell to make more viruses.
• Lysogenic cycle – The DNA combines with the host DNA
and everytime the cell reproduces it makes more
viruses.
• Viral replication – ONLY takes place in a host cell
Ecological Roles
• Viruses…
– Play a key role in population control
– Help alter ecological cycles (biogeochemical and food
webs)
– May be a medium of global climate change
– Are themselves controlled by biotic and abiotic factors
Marine Bacteria
Bacteria• Belong to kingdom Monera
• Prokaryotic,
• possess a cell wall composed of polysaccharides
• reproduce by binary fission.
Marine Bacteria
• Very important organisms on the ancient Earth
– Helped to make Earth “habitable” for life to evolve
• Marine bacteria are important
– Producers, decomposers, food sources, symbionts,
pathogens, modifiers of sediments.
Bacteria reproduce mainly by asexual reproduction
Bacteria have three main shapes: Bacillus, Coccus, and Spirillia
Some are heterotrophs, some autotrophs
Types of Bacteria
• Photosynthetic Bacteria – use sunlight and
pigments to produce food
– Cyanobacteria (domain Eubacteria)
• Chemosynthetic bacteria – use
inorganic molecules like sulfur or
nitrogen to produce food
– Bacteria found near hydrothermal vents
• Heterotrophic Bacteria – common decomposers;
breakdown the bodies of dead organisms releasing
nutrients like carbon, nitrogen, and sulfur into the
environment.
Kingdom Protista
• Eukaryotic organisms – organisms with a true nucleus
• Both unicellular & multicellular
• Both autotrophic & heterotrophic
Protists are either plant-like, animal-like, or fungus-like.
Plant-like protists are autotrophs(phytoplankton) – they
contain chloroplasts and make their own food.
Animal like (zooplankton) and fungus like protists are
heterotrophs.
• Plant-like protists are algae.
• Algae are eukaryotic autotrophs.
• They, along with other eukaryotic autotrophs, form the
foundation for many of Earth’s food chains.
• They produce much of Earth’s oxygen.
Simple marine food web
Phytoplankton
Diatoms- composed of two parts (larger and smaller) called
frustules made of silica.
• Bacteria can’t decompose silica, and when they die their
frustules accumulate on the seafloor and produce
diatomaceous earth.
Small size and small pores make an excellent filtering material.
DIATOMS
Coccolithophores- covered by calcareous plates called
coccoliths, found mostly in the tropics.
Silicoflagellates- found in extremely cold water, internal shells
Made of silica, and one or two silica rods that extend from their
shell.
Phytoplankton
Dinoflagellates- are single celled, cell walls made of cellulose,
two flagella , most are photosynthetic, and some are
bioluminescent.
Zooxanthellae- symbionts of jellyfish and corals give them their
coloration.
Plankton is captured with standard sized nets are called net
plankton.
•Microplankton- cyanoplankton, dinoflagellates, and diatoms.
• Nanoplankton- coccolithophores, and silicophores.
Some dinoflagellate species are responsible for the
phenomenon known as algal blooms.
Algal blooms occur when the dinoflagellate undergoes a
population explosion which results the number of organisms
being so great that the water color will be red, brown, or orange.
Ultimately the toxins will kill fish and other marine organisms.
P. piscicata
Zooplankton
Protozoans- animal like protists, rely on phytoplankton for their
food.
•Foraminiferans- shelled amoebas, produce elaborate
multi-chambered shells made of calcium carbonate.
•Radiolarians- primarily members of zooplankton, intricate silica
shells. Important source of silica in some areas of the world.
•Tintinnids- ciliated protists, cilia function in locomotion and
sometimes in feeding.