Question

how did the colonies from the two treated conditions differ (shape, color, quantity, etc)?

Answer 1

Bacterial colonies in culture need to be identified morphologically. First, the bacterial culture is streaked back and forth using the inoculation loop and then incubated, later identified on the basis of shape, size, color, etc. The colonies by different bacteria look different as described below:

shape: they may be spherical, oval, filamentous, rhizoid, irregular

Quantity: The bacterial colonies when grow by binary fission can be seen as an increase in the number of cells as quantity. This can be observed at different times or can be counted using hemocytometer or using streak plate.

Color: they may appear as a visible patch in white or yellow. For example, pseudomonas aeruginosa colony gives green colored pigment.

They can be identified using simple stains like methylene blue. this basic stain bind with negative charge bacterial colonies( Gram-negative) and gives color.

Another method is using gram stain which separates bacteria into two groups.: Gram-negative and Gram-positive

in this process, crystal violet and mordant iodine react with the peptidoglycan layer of bacteria and form complex. Gram-positive bacteria have a thick peptidoglycan layer and hence forms the complex with these two more strongly than Gram-negative with thin peptidoglycan layer. Hence on washing with alcohol, Gram-negative loses its color while gram-positive retain its purple color. Gram-negative bacteria can be stained with counterstain safranin which imparts pink color to the bacteria.