Vocabulary Experiment 1 02 26 2015 Culture medium contains nutrients such as carbon and nitrogen required for cells to grow Used to grow microorganisms in the laboratory Complex medium composed of digests of chemically undefined substances such as yeast and meat extracts Defined medium one for which a precise chemical composition is known Broth a culture medium prepared as a liquid Solid medium contains a solidifying agent usually agar o Agar extracted from Rhodophyta red algae o Nutrient Agar and Trypticase Soy Agar are general purpose media for variety or microorganisms o Sabouraud Dextrose Agar used when cultivating fungi or yeasts Plates solid media in Petri dishes Deeps test tubes containing solid medium which has been allowed to solidify in an upright position and are usually used 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 Sterilization the killing or removal of all living organisms and their viruses from a growth medium o Autoclave a sealed device that allows the entrance of steam under pressure Kills all microorganisms including bacterial endospores Heated to 121C at 15 psi for at least 15 minutes Used to sterilize liquid media and other items that are heat resistant o Dry heat sterilization kills by oxidation effects Direct flaming used for inoculating loops Hot air sterilization items to be sterilized are placed in an oven and heated to 170C for 2 hours Useful for glassware o Filtration used to sterilize heat sensitive liquids or gasses Physical removal of bacteria or other contaminates o Gaseous chemosterilizers used for heat sensitive objects such as plastic Petri dishes Ethylene oxide toxic and explosive Released into a tightly sealed chamber where it circulates for up to 4 hours Can also sterilize paper leather wood metal and rubber products Cold sterilization uses no heat o Electromagnetic radiation microwaves UV radiation X rays gamma rays and electrons UV radiation causes damage to the DNA thymine dimers leading to the death of exposed organisms 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 Food industry and medical supplies Experiment 2 Experiment 3 Pathogenic disease causing for humans The minority of microorganisms o Majority are nonpathogenic Nosocomial hospital acquired infections o Even nonpathogenic bacteria have potential to cause disease if someone is sick or injured Infectious dose the number of microorganisms or viruses sufficient to establish an infection Normal or resident microbiota flora establish themselves on or in the body but do not produce disease under normal conditions o May become pathogenic if the opportunity arises harmless on skin but harmful if introduced to bloodstream o Can survive and multiply on skin o Outer layer of skin usually dry so normal flora usually associated with apocrine and sebaceous glands provide moisture and nutrients o Washing hands sloughs off dead outer layer and may expose normal flora Transient microbiota flora may be present on the body temporarily but do not become firmly entrenched pH of skin is usually acidic 4 6 ubiquity of microorganisms found everywhere Experiment 4 colony morphology colony a single cell replicates and gives rise to a colony microorganisms growing on a solid culture medium will form colonies colony morphology characteristics of the colony such as the shaper the form of the colony margin and elevations and pigmentation visible to the naked eye o Dependent on the medium on which the microorganism is growing Type and amount of nutrients present in medium will influence size shape and color of a colony Contaminant and unwanted organism which has been accidentally introduced into the culture Can be seen by there being more than one type of colony present on a plate Experiment 5 aseptic technique Incoculating loop must e sterilized before being used to transfer bacterial cultures and after culture transfer If culture tube is glass neck of culture tube must be passed briefly through loop Utilize proper technique at all times Experiment 6 pure culture Pure culture one containing a single kind of organism Streak plate the bacteria in a mixed culture will be diluted in order to separate the organisms and isolate each in pure culture Experiment 7 smear preparation Oil immersion objective must be used to observe microorganisms and the total magnification achieved is 1000x Staining makes cells more visible Often hard to see because cells consist of mostly water Heat fixation kills the cells destroying autolytic enzymes and causes the cells to adhere to the slide Adhesion is essential or the cells will be washed from the slide during staining Experiment 8 simple stain Contrast provided by staining cells Morphology cell morphology or shape can be determined by staining Cocci round o Diplococci remain in pairs o Stroptococci remain in chains o Tetrads groups of four cocci o Staphylococci grapelike clusters Bacilli rod shaped cells that divide only across the short axis o Diplobacilli in pairs o Streptobacilli in chains o Coccobacilli short oval calls that resemble cocci Spiral one or more twists o Vibrios look like curved rods o Spirilla helical shape that is rigid o Spirochetes helical and flexible and resemble a corkscrew Prosthecate cells produce prosthecae cellular appendages that increase cell surface area and hence help transport of nutrients into the cell o Caulobacter crescentus and Hyphomonas neptunium Filamentous growth some actiomycete bacteria Streptomyces coelicolor produce filamets or hyphae that form a mycelium network of hyhae Hyphae later differentiate and fragment to produce spores Simple stain an aqueous or alcohol solution of a single basic dye Primary purpose is to highlight the entire microorganism so that cellular shapes and basic structures are visible o Methylene blue safranin crystal violet Experiment 9 use of the microscope Bright field microscope used in this class to observe microorganisms objective lenses lens Compound microscope consists of a series of ocular and the Binocular for each eye there is an ocular containing a magnifying Total magnification the product of the magnification of the ocular lens and the magnification of the objective lens Resolving power