the microbial world shipley’s marine biology. non-cellular infectious agents that have two basic...
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The Microbial WorldThe Microbial World
Shipley’s Marine BiologyShipley’s Marine Biology
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.
Viruses
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
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)
Viruses
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
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)
Prokaryotes
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
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
Prokaryotes
Metabolic diversity: Photosynthesis – derive energy from light Chemosynthetic – derive energy from
chemical compounds Heterotrophs – derive energy from organic
matter by respiration
Prokaryotes
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
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
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
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 that produce motion
Also reproduce by cellular division
Some are bioluminescent (read “Bay of Fire” on pg. 96)
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)
Dinoflagellates
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
Algal Blooms
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
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
Protists
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
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
Protozoa
Eukaryotic and mostly multicellular Heterotrophic Most of the 1500 species of marine fungi are
microscopic
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
Fungi
Most Important Characteristics of Marine Microbes