Final answer:
Comma-shaped bacteria requiring 2-4% NaCl for growth and displaying non-lactose fermentation on MacConkey agar belong to the genus Vibrio.
Step-by-step explanation:
The bacteria in question, which are comma-shaped and require 2-4% NaCl for growth, belong to the genus Vibrio. This genus includes organisms such as Vibrio cholerae, which are known for causing cholera. The information about the bacteria being oxidase positive and showing non-lactose fermentation on MacConkey agar supports the identification of Vibrio since Vibrio species do not ferment lactose, unlike the normal gut microbiota which generally does.
Additionally, Vibrio can be cultured on thiosulfate citrate bile salts sucrose (TCBS) agar producing yellow colonies, which is distinctive for this genus. Considering these facts, it is clear that the correct answer is e. Vibrio.