Amicrobiology instructor prepares cultures for a gram-staining laboratory by inoculating growth medium with a gram-positive coccus (non motile) and a gram-negative rod (motile). the goal is to demonstrate staining of a mixed culture of gram negative and gram positive cells. the flask in incubated at 35 c for 24 hours without aeration or shaking. a sample is stained and reveals only gram-negative rods. both cultures are known facultative anaerobes. give a likely reason for success of the gram-negative rod. assume that the cultures have comparable intrinsic growth rates.