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Chrome File Edit View History Bookmarks People Window Help u Home l Roxbury Community C-Course Invitation: Microbiolog X -Blackboar c Secure https/www.coursesites.com/webapps/assessmenthake/launch.jsp? D 7-FULL Reading Th. Digital Learning and-R Lightings-TV Produ. BPS EDFS s Remaining Time: 55 minutes, 33 seconds. Question Completion Status: A reducing medium contains O sugars that can be fermented. extra oxygen. hemoglobin, vitamins, or other growth factors. O substances that remove oxygen O inhibiting agents. QUESTION 17 At the end of the Gram stain, gram-positive bacteria will be seen as purple cells True FalseExplanation / Answer
Q) Reducing medium contains
Ans) Substances that remove oxygen
The anaerobic bacteria are grown in environments with little or no oxygen. To culture, the anaerobes and obligate anaerobes reducing media are used. Reducing media has several substances (eg. thioglycolate) which remove the molecular oxygen that is dissolved in it favor the growth of anaerobic bacteria. thioglycolate broth is one of the example for reducing media and it is a differential media.
Q) At the end of gram stain gram-positive bacteria will be seen as purple cells
Ans) true
Gram staining was discovered by the Hans Christian Gram in 1884. Gram staining classifies the bacteria into Gram +ve and Gram-ve based on cell wall composition.
A fresh bacterial smear is taken on a clear slide and the primary stain is crystal violet is added then it is dried and iodine is added to slide which acts as mordant that increases the interaction between the primary stain and bacteria. Next decolorizing agent alcohol (ethanol or acetone) is added to slide & dried. Now counter stain Safranin added to the slide. Excess of stain will be washed with water. When slide is observed in light microscope, the Gram +ve bacteria appear in purple color due to the presence of thick peptidoglycan layer in cell wall which is porous and hydrophilic structure in which primary stain crystal violet trapped and resist to decolorize with alcohol & do not take the counterstain safranin but Gram –ve take counterstain safranin appear in pink.