BIOL 2051 Lab Midterm Study Guide Terms to be familiar with Binomial name Latin name for each individual species that contains a genus name and a species name The genus is capitalized the species is not Strains organisms that have not been officially named yet Phylogenetic tree family trees that show us how one organism is related to another Medium contains nutrients such as carbon and nitrogen that are required for cells to grow Complex medium composed of digests of chemically undefined substances such as yeast and meat extracts Defined medium A precise chemical composition is known Deeps test tubes containing solid medium that have been allowed to solidify in an upright Broth liquid culture medium Solid medium contains a solidifying agent usually agar Plates solid media in Petri dishes position These are usually for anaerobic growth Slants Test tubes containing solid medium that has been allowed to solidify at an angle and the surface of the agar is used for the maintenance of stock cultures of microorganisms Used for anaerobic and aerobic bacteria Sterilization the killing or removal of all living organisms and their viruses from a growth medium Autoclave a sealed device that allows the entrance of steam under pressure The moist heat facilitates the killing of all microorganisms including bacterial endospores Dry heat sterilization kills by oxidation effects Flaming one of the simplest methods of dry heat sterilization used when inoculating loops are flamed Hot air sterilization items to be sterilized are placed in an oven and heated to 170o C for 2 hours This method is useful for glassware Filtration Heat sensitive liquids or gases can be sterilized by being filtrated through a filter with pores that are too small for microorganisms to pass through This is a physical removal of bacteria or other contaminants Chemosterilizers Used on heat sensitive objects such as plastic Petri dishes a toxic gas is placed in a chamber with the items to be sterilized Ethylene oxide toxic and explosive is released into a tightly sealed chamber where it circulates for up to 4 hours with the objects being sterilized Cold sterilization no heat is used in the process of sterilization Electromagnetic radiation includes microwaves ultraviolet radiation X rays gamma rays and electrons also used for sterilization UV radiation causes damage to DNA leading to the death of exposed organisms Cannot penetrate solid opaque light absorbing surfaces and is useful only to sterilize exposed surfaces Ionizing radiation causes ions and other reactive molecules to be produced and these reactive molecules can degrade or alter biopolymers such as DNA and proteins Pathogenic disease causing for humans majority of microorganisms Nosocomial hospital acquired infections Infectious dose the number of microorganisms or viruses sufficient to establish an infection Resident microflora establish themselves on or in the body but do not produce disease under normal conditions Normal flora survives and multiplies in its area of the body Can become pathogenic under the right conditions Transient microflora may be present on the body temporarily but do not become firmly entrenched Transient microbiota come into contact with skin constantly but most organisms are unable to multiply there and will die Acidic pH of the skin ranges from 4 6 Colony a single cell replication Colony morphology Properties of a colony such as shape form elevation and pigmentation that are visible to the naked eye Provide useful information for description of an organism Genetically different organisms however can share similar colony morphologies Contaminant an unwanted organism which has accidentally been introduced into the culture Colony Morphologies Category Whole colony shape Description Illustration Round Irregular Rhizoid Lobate Filamentous Flat Opaque Translucent Dull Shiny Color Margin Shape Smooth entire Elevation Convex Umbonate button like Optical properties Surface characteristics Pigmentation Can NOT see through it Can see through it Aseptic technique essential for preventing contamination of bacterial cultures and the environment Pure culture a culture containing a single kind of organism Streak plate using this technique the bacteria in a mixed culture will be diluted in order to separate the organisms and isolate each in pure culture Oil immersion objective must be used to observe microorganisms and the total magnification achieved is 1000x Staining makes cells more visible using color Smear made from cultures in liquid or on solid medium first step in staining cells Heat fixation kills the cells destroying autolytic enzymes and causes the cells to adhere to the slide Contrast What staining cells allows for Cellular Morphologies Shape Spherical Coccus Arrangement Diplococcus pairs Staphylococcus random or grapelike clusters Streptococcus chains Micrococcus tetrad or cubical packets Rod shaped Bacillus Chain of rods Streptobacillus Spiral Spirillium Spiral with an axial rod Spirochete Incomplete spiral vibrio Irregular or variable shape pleomorphic Simple stain an aqueous or alcohol solution of a single basic dye Its primary purpose is to highlight the entire microorganism so that cellular shapes and basic structures are visible Compound microscope consists of a series of ocular and the objective lenses Bright field microscope uses specific lenses to magnify the image of a cell such that the details of its structure are apparent Binocular for each eye there is an ocular containing a magnifying lense Total magnification the product of the magnification of the ocular lens and the magnification of the objective lens Immersion oil reduces the amount of light lost and increases resolution Lens paper use to clean the microscope Differential stain utilize a combination of dyes to demonstrate a chemical or structural component of a cell Peptidoglycan consists of repeating disaccharides attached by a polypeptide to form a lattice which surrounds and protects the cell Gram positive have many layers of peptidoglycan which makes the structure rigid Gram negative consist of a few layers of peptidoglycan surrounded by an outer membrane Crystal violet primary stain in Gram staining Iodine the mordant in gram staining Mordant sets the primary stain Decolorizing agent removes excess color that did not stain the cell walls as necessary Safranin counterstain of Gram staining Counterstain contrasts color of the original stain so gram positive cells will be