Biod Exp 2 & 3

EXPERIMENT 2: EUBACTERIA Eubacteria Eubacteria are prokaryotes that include most bacteria and cyanobacteria. Autotroph Autotroph is an organism that is capable of synthesizing its own organic substances from inorganic compounds, i.e., carbon dioxide. Organisms that use light energy to synthesize organic compounds are called photoautotrophs, i.e., cyanobacteria. Heterotroph Heterotroph is an organism that requires organic substrates, such as glucose, as energy source for growth and development. All animals are heterotrophic. Fungi and many bacteria that lack chloroplast are also heterotrophic. Cyanobacteria Cyanobacteria, or blue-green algae, are one of the largest and most important eubacteria. They are aquatic and photosynthetic, serving as primary producers in many areas of the ocean. For example, Oscillatoria sp., which is a filamentous cynobacteria, can be found in a diverse range of conditions, in stagnant water, damp soil, freshwater, and sea. The Shapes of Bacteria Coccus 1. Cocci are microorganisms with spherical shapes. 2. They occur in several basic forms: (i) coccus (single) (iii) Streptococcus (bead-like chain) (ii) Diplococcus (pair) (iv) Staphlylococcus (grape-like cluster) 3. An example is Staphlylococcus aureus, which causes a wide range of diseases from minor skin infections to pneumonia. Bacillus 1. Bacilli are rod-shaped bacteria. 2. An example is Bacillus subtilis, which is a model organism. 3. A model organism is a species that has been studied extensively and often its entire genome has been sequenced. Spirillum 1. Spiral-shaped bacteria of the family Spirillaceae are classified under the genus Spirillum. 2. An example is Spirillum minus, which causes rat-bite fever in human. 3. Rat-bite fever is caused by bacteria that pass from rodent to human via the rodent's urine or mucous secretions. Its symptoms include inflammation of the site of bite, recurring fever, headache, and muscle ache. It is often treated with antibiotic penicillin or tetracyclines. Gram Staining The Gram staining technique is used to group bacteria on the basis of their forms, sizes, and Gram reactions. Gram staining permits the separation of all bacteria into two large groups: Gram-positive and Gram-negative. Gram-positive bacteria (e.g., Streptococcusspp.) have a thick peptidoglygan wall outside the cell membrane and retain the primary dye, that is, crystal violet, in the staining procedure. This is because decolorizing the cell with alcohol causes the thick peptidoglycan wall to dehydrate and to shrink, hence closing the pores in the cell wall and preventing the primary stain from exiting the cell. In contrast, Gram-negative bacteria

(e.g., Escherichia spp.) have peptidoglygan wall that is sandwiched between outer and inner cell membrane and take up the color of the counter-stain dye. Gram staining procedure 1. Soak the entire slide with crystal violet (basic primary dye) 2. Soak the slide with the iodine solution (mordant- facilitates further interactions between the primary dye and the cell wall) 3. Wash with ethanol (decolorizing agent) 4. Add safranin or carbol-fuchsin (counter-stain dyes) EXPERIMENT 3: PROTISTA / PROTOCTISTA Protista Protista consists of single-celled organisms that are eukaryotes but unable to be classified as animal, plant or fungi. It has been traditionally lumped into three groups: (i) animal-like protists (e.g., protozoa) (ii) plant-like protists (e.g., protophyta) (iii) fungus-like protests (e.g., slime molds) Amoeba Amoeba belongs to the family Amoeboid and is a unicellular organism. It moves by cytoplasmic streaming and pseudopods. Pseudodops, or ‘false feet’, are temporary projections of eukaryotic cells which allow reversible cytoplasmic extensions of the cells. Paramecium Paramecium spp. are a group of unicellular ciliated protozoa. Cilia allow the organism to move. They are alveolates, with only tiny membrane-bound sacs called alveoli (singular: alveolus) underneath their outer membranes. The sacs may stabilize the cell surface. Because Paramecium has an internal solute concentration higher than its surrounding, osmoregulation is therefore needed. Osmoregulation is carried out by a pair of contractile vacuoles, which actively expel water absorbed by osmosis from their surroundings. Euglena Euglena spp. are unicellular flagellated protozoa. They can make their own food through photosynthesis (autotroph) or absorb food from the surrounding environment (heterotroph). Euglena spp. move by flagellum (flagella-plural) at the anterior (front end). The stigma is a light-sensitive structure which detects light for photosynthesis. Due to osmosis, Euglena will take in excess water and need to expel by contractile vacuole.

Figure 1: The Amoeba.

Figure 2: The structures of Euglena.