BIOL 1122 Lecture Notes - Lecture 1: Methylene Blue, Trypticase Soy Agar, Eosin
2 May 2017
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Selective medium: contains components that inhibit growth of undesirable organisms and favors growth of desirable ones. Differential medium: shows marked differences between various organisms - makes it easy to distinguish between colonies. Favors growth of staphylococci (gram positive and salt tolerant) over gram negative. S. aureus is capable of growing in this media. E. coli cannot due to high salt concentration. Mannitol and phenol red - acid/base indicator. Staphylococci produce alkaline amines as by-products of protein degradation. Moderately inhibiory of some gram positive bacteria. Gram negative bacilli are differentiated by ability to ferment lactose. Appear to have black center as result of acid precipitating two yes. Enriched with sheep blood - addded to tryptic soy agar base. Based on ability of some species to lyse red blood cells. S. aureus - produces hemolysins that fully rupture rbcs.
