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

stromatolites

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 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

Dinoflagellates often cause red tides

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

Foraminiferans thin pointed pseudopods in ___ tests.

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

Radiolarian

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

Ciliate

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

Marine lichens

Most Important Characteristics of Marine Microbes