Question

You are examining two tubes of nutrient broth that are not labeled with the names of the bacteria they contain. One tube contains E.coli; the other tube contains S. marcescens. Based only on your observation of the two tubes, how would you know which tube contains S. marcescens?

Answer 1

Answer-

According to the given question-

• Escherichia coli and Serratia marcescens both are rod shaped, facultative anaerobic, belongs to the group of gram negative bacteria.
• E.coli are present in the lower part of intestine of endothermin organisms, and they are responsible for producing  vitamin K₂ and also inhibit the growth of other harmfull, pathogenic bacteria.  
• Serratia marcescens is responsible for the infection in wound , infections in urinary tract, as well as hospital-acquired infections and generally present in the respiratory tracts as well as urinary tracts of adult.  
• S. marcescens have the capability to produce a pigment known as prodigiosin which is of reddish-orange color,  due to which they are appeared as red and easily can be distinguished from the other microorganisms.

So If we are examining two tubes of nutrient broth that contains the E.coli and other tube contains S. marcescens. Based only on your physical observation of the two tubes, we can easily predict from the color of tube that have S. marcescens because at room temperature the S. marcescens form a orange red color pigment prodigiosin due to which they appeared as red.