MB303 Midterm 1 Exam Questions and Correct Answers.

Simple stain - Answer Stain used to contrast between the specimen and its background Basic/cationic dye - Answer Color in the positive ion of the dye (eg methylene blue) Acidic/anionic dye - Answer Color in the negatively charged ion How are dyes used? - Answer The difference in the charge produced affinity between the dye and the bacterial cell Cocci - Answer Sphere-shaped bacteria Diplococci - Answer Pairs of cocci stuck together Streptococci - Answer Chains of four or more organisms Staphylococci - Answer Regular groups of microorganisms resembling grape clusters Tetrads - Answer Packets of four cells Bacilli (sing. Bacillus) - Answer Rod shaped bacteria (not as constant as cocci and should not be considered a characteristic) Filamentous bacilli - Answer Long changes of bacilli Spiral - Answer Various spiral-shaped forms, as rods with one or more curves (ALL MOTILE) Spirochetes - Answer Hard to see with bright-field microscope, flexible rods with several curves Spirilla - Answer Rigid rods with several curves Vibrios - Answer Short, curved bacteria (rods with a single curve)