Microbiology Lab - Exam 2 Questions and Answers 100% Pass

Microbiology Lab - Exam 2 Questions and Answers 100% Pass medium - a mixture of nutritional substances on or in which microorganisms grow autotroph - nutritionally deficient mutants that have lost the ability to synthesize a particular enzyme many microorganisms in this group: - can carry out photosynthesis - usually do not cause disease - synthesize organic compounds to obtain energy heterotroph - an organism that uses compounds to produce biomolecules autoclave - an instrument for sterilization by means of moist heat under pressure Autoclaving combines ____ and ____ to destroy high resistant bacteria. - high temp and high pressure What are six basic nutritional requirements of every living thing? - Water, carbon, nitrogen, metallic elements, energy and growth factors such as vitamins general purpose media - Designed to grow a broad spectrum of microbes that do not have special growth requirements enriched media - medium that contains special additives that could promote certain metabolic activities. (ex. trypticase soy agar, blood agar, yeast extract broth) 2 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE - especially used for fastidious bacteria selective media - is a nutrient that inhibits the growth of a certain type of microorganisms (ex. Gram + bacteria) while permitting the growth of a different type (in this example, Gram - ) differential media - medium which will differentiate between bacteria based on how they change the medium or their appearance on the medium EMB and HE are both ____ and ____. - selective and differential EMB and HE are selective for ____ and differential for ____. - selective for gram-negative bacteria and differential for lactose fermenters. What do lactose fermenters and nonfermenters look like on each media? - - Organisms which quickly ferment lactose will give dark-green to black colonies on this medium; these colonies have a metallic sheen (Ecoli) - Organisms that are slow fermenters of lactose will give pink to maroon colonies on this medium. Those organisms that cannot ferment lactose at all give white (colorless) colonies on EMB agar (since nonfermenters of lactose are often high pathogenic, this is a useful way to identify potential pathogens) What is Shigella associated with? - a genus associated with bacillary dysentery HE and EMB are useful for distinguishing between _____. - Enterobacteriaceae What are Enterobacteriaceae? - a group of short, Gram-negative, facultative anaerobic rods that are found in the intestinal tract of various mammals, including humans PEA and MS agar are _____ for ____. - selective for gram-positive bacteria MS is _____ and _____ for _____. - selective and differential for mannitol fermenters 3 | P a g e Created by Katelyn Whitman © 2025, All Rights Reserved. 100% PASS GUARANTEE What bacterial genus is Mannitol Salt (MS) agar used to distinguish? - Staphylococcus -- high levels of salt in medium are tolerated by its cells What do fermenters and non-fermenters look like on Mannitol Salt (MS) agar? - - fermentation of mannitol causes the medium to turn deep yellow in the area of bacterial growth - if mannitol not fermented, the color of the medium will remain pink PEA agar is ONLY ____, NOT ____. - is ONLY selective, NOT differential catalyst - a molecule or compound that greatly accelerates the rate of a chemical reaction, without being changed by the reaction. enzyme - the catalyst of biochemical reactions that occur in the living cell endoenzyme - (cytoplasmic enxymes) function inside the cell exoenzyme - (exocellular enzymes or secreted enzymes) released to the outside of the cell, where they perform theft work catabolism - most act in the breakdown of foodstuffs What is the major protein in milk? - casein What enzyme breaks down the protein found in milk? - caseinase What media is used to test for this enzyme? - Milk Agar What does a positive and negative reaction look like for this enzyme? - action of caseinase causes the medium to lose its opacity, turning clear around bacterial growth