BIOL 3007W Lecture
by Gilbert Keith
Part 2: Lecture 15
ALgal motile cells. Basic type: cells with two falgella pointing forward.
Looking at cryptophytes, strameophiles, haptophyta, dinophyta, euglenophyta, chlorophyta.
Chloroplasts occur in 4 supergroups: archeplastida: primary endosymbiosis. others: secondary or tertiary or exotic flavours.
Review of primary/secondary symbiosis. Remember to look at membrane arrangement in chloroplasts.
Beginning with Euglenophyta (Euglenoids.) Green or colorless flagellates. Mostly freshwater. They really like pollution (excess nutrients, etc.) Ancestor s were non-photosynthetic, and phagocytosed things.
Chloroplasts arose by secondary endosymbiosis (have chlorophyll a, b) with an extra membrane. There is no sexual reproduction.
They are widely distributed in freshwater habitats, but oftentimes they are found at air-water or water-soil interfaces. They are highly tolerant of extreme environments. Look at soil on euglenoid diversity.
They don’t have true cell walls. Flagella are apical. long flagellum with tinsels emerges out, but the second one does not emerge. There are a set of protein plates beneath the plasma membrane (called the pellicle.) They have eyespots to orient them towards light.
They have pyrenoids, where photosynthetic carbon is metabolized. However, these pyrenoids are negative for iodine stains, since they do not have starch. They store a material called paramylon. Euglena have contractile vacuoles for water modulation. Lots of contractions and expansions to maintain water balance.
moving onto Chromalveolate group.
Chromalveolates’ origins from endosymbiosis of red algae. Typically they have three or four membranes. Interesting uptake of chloroplasts. THey are not very common. They tend to be in deeper and colder waters. Important components of freshwater and marine habitats/
They have two flagella at the apex, which are differently decorated compared to each others. They have chlorophylls a and c, and phycobilins (light harvesting complexes) and carotenoids. Some are photosynthetic, and some are colorless. Remember: phycobilins are only found in red algae, glaucophytes and cryptomonads.
Outer membrane of chloroplasts (4th) is continuous with host’s nuclear membrane. Review Gene transfer slide. (transfer from plastid to secondary host, plastid to nucleomorph, nucleomorph to nucleus, etc.
SIDE NOTE: the professor is pretty boring.
BACK TO SCHEDULED PROGRAMMING.
Haptophyta. Cells can be unicellular or colonial. Mainly marine. Cell structure is pretty unique. They have two whiplash flagella, with a funny thing coming out of the middle, called a haptonema. They have both chlorophyll a, c, and carotenoids (especially fucoxanthin, makes them look brown.) They store chrysolaminarin in vacuole.
They have scales, which are sometimes calcified (then called coccoliths.) They can take up dissolved nutrients or ______. Haptonema have a sticky tip which adheres to microbes or other food particles. Upon attachment to a food source, the haptonema brings the food closer to a membrane, which allows the haptophyta to engulf them.
Often called coccolithophores. Round, calcium bearing organisms. They can have multiple layers of scales. They come in a remarkable set of patterns. http://en.wikipedia.org/wiki/Coccolithophore
They have a big impact on carbon and sulfur cycles. A big CO2 sink, since the calcium carbonate captures it permanently. They drop down to the bottom of the surface. They also make Dimethyl sulfide, which rises up and provides nucleation sites. Less light on oceans. The sulfur comes back down, enhancing acidity.
Acidic oceans: will the coccoliths breakdown? will the organims be able to compensate? http://www.sciencemag.org/cgi/content/abstract/sci;320/5874/336 At higher concentrations, they are able to compensate by building bigger coccoliths. Evidence for increasing size of coccoliths since industrial revolution. They have big impacts worldwide.
Last group: dinoflagellates. Diverse set or chloroplasts. Some have green plastids, though most have green plastids. Dinos = whirling. When they swim, they spiral. One flagellum goes around the cell and the other flagellum goes back. The one that goes around is a tinsel flagellum, the other is a whiplash flagellum. Some have amoeboid stages, and some others have starch.
They have chromosomes which are condensed, but there are no histones. They always appear as though they are in division… i.e. always condensed. Possess chlorophylls a and c. They also have carotenoids, (predominantly perdinin.) They characteristically have plates, though some can be unarmored (only with vesicles.) They have a filament that emerges from the cell, an arm of cytoplasm comes down and engulfs the substrate. They are mixotrophic organisms.
They make elaborate cysts. They accumulate in sediments, and used in oil exploration (to date the sediments.)
Pigmented dinoflagellates may be symbionts in other protists or in invertibrates. Zooxanthellae: cells of dinoflagellates that get taken up from organisms. If they re-emerge from hosts, they will have the characteristic dinoflagellate shape. They synthesize many compounds used by the corals. In return, they get CO2 from corals.
Increase in temperatures may cause corals to expel zooxanthellae. Coral bleaching. Red tides. They produce toxins which are colorful, but also responsible for major fish kills. They are neurotoxins which accumulate in fish. Bioluminescence during night. Not known why they do it.