Algae, Protozoa & Slime Molds

• Algae are familiar as the large brown kelp in coastal waters, the green scum in a puddle, and the green stains on soil or on rocks.
• A few algae are responsible for food poisonings.
• Some algae are unicellular; others form chains of cells (are filamentous); and a few have thalli.
• Phycology is the branch of microbiology that deals with the study of algae.
• Algae is not a taxonomic group; it is a way to describe photoautotrophs that lack the roots and stems of plants.
• Historically they were considered plants, but they lack the embryos of true plants.
• Algae are currently grouped into super clades.
• Algae are mostly aquatic, although some are found in soil or on trees when sufficient moisture is available there.
• Unusual algal habitats include the hair of both the sedentary South American sloth and the polar bear.
• Water is necessary for physical support, reproduction, and the diffusion of nutrients of algae.
• The large floating mats of the brown alga Sargassum are found in the subtropical Sargasso Sea.
• Some species of brown algae grow in antarctic waters.
• Algae are relatively simple eukaryotic phototrophs lacking tissues of plants.
• The identification of unicellular and filamentous algae requires microscopic examination.
• Most algae are found in the ocean.
• The body of a multicellular alga is called a thallus.
• Thalli of the larger multicellular algae, those commonly called seaweeds, consist of branched holdfasts (which anchor the alga to a rock), stemlike and often hollow stipes, and leaflike blades.
• The thallus lacks the conductive tissue (xylem and phloem) characteristic of vascular plants.
• Algae absorb nutrients from the water over their entire surface.
• The stipe is not lignified or woody, not offering support.
• Some algae are also buoyed by a floating, gas-filled bladder called a pneumatocyst
• This is Macrocysis, a brown alga.

  
• All algae can reproduce asexually; but can also reproduce asexually.
• Multicellular algae with thalli and filamentous forms can fragment; each piece can form a new thallus or filament.
• Other species alternate generations so that the offspring resulting from sexual reproduction reproduce asexually, and the next generation then reproduces sexually.
• This is the life cycle of Chlamydomonas spp., a unicellular green alga.

  
• Nutrition of Algae:

  • Algae is a common name that includes several phyla.  Most algae are photosynthetic.
  • Oomycotes, or fungal-like algae, are chemoheterotrophs.s.
  • Photosynthetic algae are found throughout the photic (light) zone of bodies of water.
  • Chlorophyll a (a light-trapping pigment) and accessory pigments involved in photosynthesis are responsible for the distinctive colors of many algae.
  • Algae are classified according to their rRNA sequences, structures, pigments, and other qualities.
• Phylum Phaeophyta is commonly known as brown algae or kelp; macroscopic with some reaching lengths of 50 m.
• Phylum Phaeophyta is mostly found in coastal waters with phenomenal growth rate with some exceeding 20 cm/day growth rate and therefore can be harvested regularly.
• Algin can be extracted from the cell walls of brown algae. Some of its uses are: 1. Thickener in many foods such as ice cream and cake decorations

  2. Production of rubber tires and hand lotions
• Laminaria japonica is used to induce vaginal dilation before surgical entry into the uterus through the vagina.
• Phylum Rhodophyta is commonly known as red algae in which members have delicately branched thalli.
• Phylum Rhodophyta can live at greater ocean depths than other algae; few have thalli that forms crustlike coatings on rocks and shells.
• The red pigments enable red algae to absorb the blue light that penetrates deepest into the ocean.
• Applications of red algae:

  1. The agar used in microbiological media is extracted from many red algae.
  2. Carrageenan comes from a species of red algae commonly called Irish moss.
  3. Both carrageenan and agar can be used as a thickening ingredient in evaporated milk, ice cream, and pharmaceutical agents.
  4. Species of genus Gracillaria are used by humans for foods but some members of this genus can produce a lethal toxin.
• Microcladia sp. & Gracillaria parvispora

  
• Phylum Chlorophyta is commonly known as green algae; members have cellulosic cell walls, contain chlorophyll a and b, and store starch.
• Phylum Chlorophyta:

  • Believed to have given rise to terrestrial plants.
  • Most are microscopic, although they may be either unicellular or multicellular.
  • Some filamentous kinds form grass-green scum in ponds.
• Diatoms are unicellular or filamentous algae with complex cell walls that consist of pectin and a layer of silica.
• Diatoms store energy captured through photosynthesis in the form of oil.