Bacteria Ecology

Topics: Bacteria, Bacterial cell structure, Cell wall Pages: 2 (744 words) Published: October 12, 2010

This lab experiment serves as a model for community succession using bacterial colonies as the model. A bacterial colony grows from a single bacterium and is composed of millions of cells. Each colony has distinctive colony morphology: size, shape, color, consistency, and color. Community succession is a phenomenon observed in the organizational hierarchy of all living organisms. Community succession is not limited to bacterial colonies, but spans the entire community of life. As the community grows, it changes the environment it inhabits, and the resulting community is different than at the start. As community succession occurs in bacterial colonies pH, odor, color, and consistency changes take place. In this experiment, four different milk age samples, fresh, 24 hour old, 4 day old, and 8 day old milk, will be prepared on different sets of agar plates that will be diluted to different levels for optimum bacterial growth and measurement.

To identify the resulting colonies a procedure called gram stain is used in the identification of bacteria. Bacteria can be gram-positive, gram-negative, or gram-variable. Most bacteria however, are usually gram-positive or gram-negative. Gram-positive and gram-negative bacteria react differently to staining because of the differences in their cell walls. Bacterial cell walls contain a polymer called peptidoglycan. Gram-positive bacteria have more of this polymer than gram-negative bacteria. They are also less complex than gram-negative cell walls, missing different polysaccharides, lipids, and proteins that are found in gram-negative bacteria. Three different stain types are used in the identification process: safranin (pink/red), crystal violet (purple), and Gram iodine. Along with being either gram-positive or gram-negative, most bacterial cells can be classified according to three shapes: bacilli (rods), cocci (spheres), and spirilla (spirals, or corkscrews).

The hypothesis for this...
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