Introduction, Lab Safety Quiz, And Environmental Plates Mic 224 Introduction, Lab Safety Quiz, And Environmental Plates

Microorganisms in the Environment Microbes are ubiquitous From the Antarctic to Hydrothermal vents Found in either 2 stages of development Active- water is available, organisms are dividing Dormant-spores

Tools of the Trade Petri Dishes-used to grow organisms of interest 3 parts: lid, bottom, media (located in bottom of dish) Organisms must be transferred directly to the media, NEVER TO THE LID

Petri Dish

Culture Media Contains nutrients organisms need to survive Proteins, carbohydrates, vitamins, minerals, water Media is available in two forms: broth or solid Broth-liquid, usually in a test tube Solid-deeps, slants, plates Solid media contains agar (the solidifying agent) Normal concentration is 1.5% agar

Culture Media May be chemically defined or complex Todays media: Defined: one in which the exact chemical composition is known Complex: exact composition is not known: contains products such as blood, etc Todays media: Nutrient agar: general purpose-supports the growth of a wide range of organisms Potato Dextrose Agar: selective media- selects for Fungi

Colony Morphology Colony- result of a single organism dividing into millions of organisms that become visible Colonial Morphology- consists of size-diameter of colony (mm); elevation-raised/lowered; margin (edge)-rough, variegated, etc; pigment-color; and texture-smooth, rough,etc

Colony Morphology Size of Colony:

Colony Morphology Shape refers to the overall appearance of the colonies. The descriptors here are punctiform, circular, irregular, filamentous (has individual thin projections), or rhizoid (has thin, branching projections).

Colony Morphology Height/Elevation The colony height, or elevation, is a description of how the colony grows vertically. To see the elevation of the colonies, it may be helpful to look through the side of the petri dish. The descriptors here are flat, raised, convex (sloping up from the edges), pulvinate (sloping steeply from the edges and very high in the center), and umbonate (has a raised center)

Colony Morphology Edge, or margin, describes the borders of the colony. The edge can be entire (smooth, with no projections), undulate (wavy), lobate (lobed), filamentous, or rhizoid.

Colony Morphology Color/Pigment Texture Some bacteria produce pigments, giving the colony a distinct color. Pigments can span the entire color spectrum. Recording the color is the first step. In addition to describing the color, this is also the time to identify if the colony is opaque (you can't see through it), translucent (you can see through it), dull, or shiny. Texture Texture refers to the characteristics of the colony surface. Colonies can be dry, mucoid (thick, stringy, and wet), moist, smooth, rough, rugose (wrinkled), or contain concentric rings.

Useful Terminology Normal Flora: microorganisms that are typically present in a particular environment Ex: Staphylococcus epidermidis is found on essentially every surface of the human body Contaminants: transients organisms that are often invaders in a particular environment