The Microbial World: Viruses and Prokaryotes
E N D
Presentation Transcript
Chapter 5 The Microbial World
Viruses • Non-cellular infectious agents that have two basic characteristics: • Not capable of reproduction without a host cell • Structure: • Nucleic acid core- can be ____ or ____ • 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. Many glycoprotein spikes extend from coat-these spikes mutate so frequently that our immune system cannot keep up.
Viruses • Notable Types of Viruses: • Retroviruses- store genetic information in the form of nucleic acid known as RNA • Bacteriophages – viruses that infect bacteria • Bacteriophages are either lytic or lysogenic • Viruses in eukaryotes can similarly be active or latent
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: • ____- no nucleus • Single chromosome (normally circular)- some also with plasmids • Most with cell wall • Great metabolic diversity • microscopic
Prokaryotes • Archea – • 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 • Can be found in many areas including near hydrothermal vents and salt flats (two very extreme environments)
Prokaryotes • Special Features of Bacteria: • A variety of shapes including ____, ____, and ____ • Cell wall structure is semi-rigid, but permeable; Made of polysaccharide called peptidoglycan • Wide variety of metabolic types • Very abundant worldwide
Prokaryotes • Special Features of Bacteria: • One of the most important functions 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 that are extremely important in food chains producing glucose and fixing nitrogen • Stromatolites, massive calcareous mounds formed by cyanobacteria, have been found that are over a 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
Diatoms • Diatoms: • Photosynthetic • Yellow-brown color in life is a result of photosynthetic pigments- chlorophyll (A and C) and carotenoids • Cell wall of silica called a frustule forms a complete cover called theca • When die, frustules accumulate forming diatomaceous earth used as abrasive, for filtering and as pesticide • Most important primary producer on Earth • Mostly unicellular but some form colonies
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 frustule 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 = Biomagnification or bioaccumulation
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 of epi- or hypotheca) • 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
Dinoflagellates • Dinoflagellates • Most species live in marine environment • Mostly photosynthetic, some can ingest particles • Each species has unique shape reinforced by plates of a polysaccharide called cellulose to form theca • Two flagella in grooves on body that produce motion • Also reproduce by cellular division • Some are ____ (Have you ever noticed the greenish glow as you wade in the Gulf?)
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)
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
Dinoflagellates • Dinoflagellates • A few species lack chloroplasts and live as parasites in marine organisms • Some species can reproduce in larger numbers and produce a “Red Tide” • 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
Protozoa • Foraminiferans (forams) • Exclusively found in marine community • Found on sandy or rocky bottoms • Tests (shell) of calcium carbonate • Can be important contributors of calcareous material on coral reefs or sandy beaches • ____ (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 • test 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 • ____ present for locomotion • Most live as solitary cells • Some build tests made of organic debris • May live on hard substrate • Some are planktonic
Fungi • Eukaryotic and mostly multicellular • Heterotrophic with unique cell walls made of polysaccharide called chitin • Most of the 1500 species of marine fungi are microscopic
Fungi • Like bacteria, many fungi break down dead organic matter into detritus • Some fungi 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
