Microbiology Lab Quiz 1 with Complete Solutions

Microbiology Lab Quiz 1 with Complete Solutions ocular lens demagnifies the image formed by the objective lens body tube transmits the image from the objective lens to the ocular lens objective lenses primary lenses that magnify the specimen mechanical stage holds the microscope slide condenser focuses light through specimen diaphragm controls the amount of light entering the condenser illuminator light source fine focusing knob used for focusing the specimen; turning the know changes the distance between the objective lens and the specimen microscope Nutrient Broth When agar is added it becomes a solid medium Agar extract from marine red algae, has some unique properties that make it useful in culture media, few microbes can degrade it and it remains solid Steam sterilization/autoclaving common method of sterilization which uses steam under pressure Petri Plates containing solid media provide a large surface area for examination of colonies inoculated intentionally introduced onto nutrient agar and into nutrient broth Colony forming unit same microbes attach to one another total magnification ocular lens magnification x objective lens magnification field of vision area seen through a microscope focal point where the image is formed spherical aberration multiple focal points that results in fuzzy image bacillus rod coccus sphere spiral spiral chromatic aberration prism like effect of the lens as various wavelengths of white light pass through the lens to different focal points resulting in a multitude of colors in the field of vision data collection from microscopes size relationships, spatial relationships, sequence of events numerical aperture characteristic of the lens system, denoted on the objective lenses resolution (resolving power) the ability of lenses to reveal fine detail or two points distinctly separated complex media media for which the exact chemical composition varies slightly from batch to batch contamination presence of unwanted organisms streak plate technique loop used to streak the mixed sample many times over the surface the surface of a solid culture medium in a petri plate spread plate technique small amount of a previously diluted specimen is spread over the surface of a solid medium using a spreading rod Colony-forming units per ml number of colonies/Dilution X Amount plated Gram Stain differential stain that allows you to classify bacteria as either gram positive or gram negative, discovered by Hans Christian Gram in 1884 Primary Stain (crystal violet) all bacteria stained purple Mordant (iodine) combines with crystal violet in the cell to form a crystal violet iodine complex Decolorizing Agent (ethanol, Acetone) primary stain is washed out of some bacteria (decolorized) whereas others are unaffected Secondary Stain or counterstain (Safranin) basic dye stains the decolorized bacteria red nutrient broth liquid complex media inoculate microbes intentionally introduced onto nutrient agar and into nutrient broth colony a population of cells that arises from a single bacterial cell after an incubation period flocculent clumps of microbial cells pellicle membrane on the surface sediment microbial cells settled on the bottom colony forming unit a colony that arises from a group of the same microbes attached to one another agar extract from marine red algae, liquifies at 100 degrees, solidifies at 40 degrees, few microbes can degrade agar, solid during microbial growth gram negative pink- a classification of bacteria that decolorizes easily gram positive purple- classification of bacteria that decolorize slowly and retain the primary stain peptidoglycans a complex lattice structure of the bacterial cell wall. gram - have thin layer; while gram + have thick layer nutrient agar complex media used to assess bacterial morphology that is solidified with the addition of agar pure culture consisting of only one species of microorganism Gram stain 1. primary stain (crystal violet) 2. mordant (Gram's iodine) 3. decolorizing agent (ethanol) 4. secondary stain (safranin) common gram stain errors 1. loop was too hot 2. excessive heat during heat fixing 3. decolorizing agent (ethanol) was left on smear too long 4. culture was too old 5. smear too thick simple stains one reagent is used and all bacteria are usually stained similarly differential stains multiple reagents are used and bacteria to react to the reagents