MICRO Lab Exam 2 Questions With Complete Solutions

Organisms that require specialized environments due to complex nutritional requirements are known as...? correct answer: fastidious organisms The blood agar plate (BAP) is an enrichment medium that tests for fastidious organisms such as? correct answer: Streptococcus spp. (species) The blood agar permits demonstration of what property of microbes, such as streptococci...? correct answer: hemolytic properties The blood agar test can show what three possible hemolytic results...? correct answer: Gamma, Alpha, & Beta hemolysis What does gamma hemolysis of a BAP look like...? correct answer: no significant change to medium surrounding colonies What causes the lack of change around bacterial colonies in gamma hemolysis of a BAP...? correct answer: no lysis of RBCs What does alpha hemolysis look like on a blood agar plate...? correct answer: greenish halo around bacterial growth What causes the greenish halo around bacterial growth in alpha hemolysis of BAP test...? correct answer: incomplete lysis of RBCs & reduction of hemoglobin to methemoglobin (met-hemoglobin) What does beta hemolysis look like on a BAP test...? correct answer: clear zone surround colonies What causes the clear zones surrounding bacterial colonies in beta hemolysis of a BAP...? correct answer: complete utilization and destruction of hemoglobin by organism What does MSA stand for...? correct answer: mannitol salt agar What color is the MSA plate...? correct answer: red What does growth on the MSA plate indicate...? correct answer: Staphylococci, which were able to grow in the high salt (NaCl)