Algae, Protozoa, and Slime Molds

• Algae


  Familiar as large brown kelp, green scum, green stains on soil/rocks. Some are responsible for food poisonings. Can be unicellular, form chains of cells, or have thalli.
• Phycology


  Branch of microbiology that deals with the study of algae
• Algae


  Not a taxonomic group, but a way to describe photoautotrophs that lack the roots and stems of plants. Historically considered plants but lack the embryos of true plants. Currently grouped into super clades.
• Habitats of algae


  • Mostly aquatic, some in soil or on trees, unusual habitats include hair of sloth and polar bear. Water is necessary for physical support, reproduction, and diffusion of nutrients. Generally found in cool temperate waters. Large floating mats of brown alga Sargassum in subtropical Sargasso Sea. Some brown algae grow in Antarctic waters.
• General features of algae

  • Relatively simple eukaryotic phototrophs lacking tissues of plants. Identification of unicellular and filamentous algae requires microscopic examination. Most algae are found in the ocean. Their locations depend on availability of appropriate nutrients, wavelengths of light, and surfaces on which they can grow.
• Thallus


  The body of a multicellular alga
• Vegetative structures of algae

  • Thalli of larger multicellular algae (seaweeds) consist of branched holdfasts, stemlike and often hollow stipes, and leaflike blades. Cells covering the thallus can carry out photosynthesis. Thallus lacks conductive tissue (xylem and phloem) of vascular plants. Algae absorb nutrients from water over entire surface. Stipe is not lignified or woody, not offering support. Surrounding water supports the algal thallus. Some algae have floating, gas-filled bladder called pneumatocyst.
• Life cycle of algae

  All algae can reproduce asexually. Multicellular and filamentous algae can fragment, each piece forming a new thallus or filament. Unicellular algae divide, with nucleus dividing (mitosis) and two nuclei moving to opposite parts of the cell, then cell dividing into two (cytokinesis). Algae can also reproduce sexually, with some species alternating between asexual and sexual reproduction.
• Nutrition of algae


  Most algae are photosynthetic, with chlorophyll a and accessory pigments responsible for their distinctive colors. Some, like oomycotes, are chemoheterotrophs. Photosynthetic algae found throughout photic (light) zone of water bodies. Algae classified based on rRNA sequences, structures, pigments, and other qualities.
• Phylum Phaeophyta (brown algae or kelp)


  • Macroscopic, some reaching 50m in length. Mostly found in coastal waters, with phenomenal growth rates up to 20cm/day. Cell walls contain algin, used as thickener in foods and other products. Laminaria japonica used to induce vaginal dilation.
• Phylum Rhodophyta (red algae)


  • Members have delicately branched thalli, can live at greater ocean depths than other algae, some form crustlike coatings. Red pigments enable absorption of blue light. Used to extract agar and carrageenan, used as thickening agents.
• Phylum Chlorophyta (green algae)


  • Members have cellulosic cell walls, contain chlorophyll a and b, and store starch. Believed to have given rise to terrestrial plants. Most are microscopic, but some form grass-green scum in ponds.
• Kingdom Stramenopila: Diatoms


  • Unicellular or filamentous algae with complex cell walls of pectin and silica. Symmetrical, with distinctive wall patterns useful for identification. Store energy as oil. Some produce toxins like domoic acid, causing neurological disease.
• Kingdom Stramenopila: Dinoflagellates


  • Collectively called phytoplanktons, these unicellular algae are free-floating. Have rigid structure due to cellulose in plasma membrane. Worldwide increase in toxic marine algae has killed millions of fish, hundreds of marine mammals, and some humans. Produce neurotoxins, saxitoxins, and ciguatoxins causing various poisonings.
• Kingdom Stramenopila: Oomycota (water molds)


  • Decomposers that form cottony masses on dead algae and animals, usually in freshwater. Asexually resemble zygomycete fungi, producing spores in sporangia. Have cellulosic cell walls, close relations to diatoms and dinoflagellates. Many are plant parasites, causing diseases like potato blight, soybean, cocoa, and sudden oak tree.
• Roles of algae in nature

  Primary producers, converting CO2 to O2 through photosynthesis. Planktonic algae produce about 80% of Earth's O2. Algal blooms indicate pollution. Much of world's petroleum formed from ancient diatoms and other planktonic organisms. Some algae have symbiotic relationships with marine animals like giant clams.
• Protozoa


  Also called protists. Unicellular eukaryotic organisms with many variations in cell structure. Inhabit water and soil. Feeding and growing stage called trophozoite, feeding on bacteria and small particulate nutrients.
• Diversity of protozoa


  • Some are part of normal microbiota of animals. Researchers studying protozoan that reduces egg production in fire ants. Of nearly 20,000 species, relatively few cause human disease. Protozoology is the branch of microbiology that deals with the study of protozoa.
• Characteristics of protozoa


  • The term "protozoa" means "first animals", describing their animal-like nutrition. Quite different from animals - some are photosynthetic, many have complex life cycles to move between hosts. Classified in same super clades as algae based on DNA analyses.
• Life cycle of protozoa

  Reproduce asexually by fission, budding, or schizogony (multiple fission). Sexual reproduction observed in some, like conjugation in ciliates. Some produce gametes (gametocytes).
• Protozoology


  The branch of microbiology that deals with the study of protozoa
• Protozoa


  • Animal-like nutrition
  • Many have complex life cycles enabling them to get from one host to the next
  • Classified in the same super clades as algae, based on DNA analyses
• Protozoa reproduction


  1. Asexual by fission, budding, or schizogony

  2. Sexual reproduction observed in some protozoa
• Schizogony


  Multiple fission; the nucleus undergoes multiple divisions before the cell divides
• Conjugation


  Sexual reproduction in ciliates like paramecium, very different from the bacterial process
• Gametes (gametocytes)


  Haploid sex cells, two gametes fuse to form a diploid zygote
• Cyst


  A protective capsule produced by some protozoa under certain adverse conditions
• Oocyst


  Cyst formed by members of the Phylum Apicomplexa, a reproductive structure in which new cells are produced asexually
• Nutrition


  Protozoa are mostly aerobic heterotrophs, many intestinal protozoa are capable of anaerobic growth, some have chlorophyll and are photosynthetic
• Protozoa


  • All live in areas with a large supply of water, some transport food across the plasma membrane, some have a protective covering called pellicle
• Cytostome


  Mouth-like opening in ciliates where cilia wave to take in food
• Pseudopods


  Blunt lobe-like projections of the cytoplasm in amebae used to engulf food by phagocytosis
• Vacuoles


  Membrane-enclosed structures where food digestion takes place in protozoa
• Superkingdom Excavata


  Single-celled eukaryotes with a feeding groove in the cytoskeleton, most are spindle-shaped and possess flagella
• Giardia intestinalis


  Parasite without mitochondria, causative agent of giardiasis, found in the small intestine of humans and other mammals
• Trichomonas vaginalis


  Human parasite that lacks mitochondria, causative agent of trichomoniasis, a sexually transmitted disease, has an undulating membrane
• Euglenozoa


  Includes euglenoids and hemoflagellates, have disk-shaped mitochondria and lack sexual reproduction
• Euglenoids


  Photoautotrophic flagellates with semirigid plasma membrane called pellicle, some are facultative chemoheterotrophs
• Hemoflagellates


  Blood parasites transmitted by the bites of blood-feeding insects, found in the circulatory system of the bitten host
• Amebae


  Move by extending blunt lobe-like projections of the cytoplasm called pseudopods