To solve this problem, we need to identify which enzyme's activity is inhibited by Melonate, thereby inhibiting the growth of pathogenic bacteria.$\newline$Let's analyze each option:$\newline \bullet$Option 1: Succinic dehydrogenase$\newline$ - Succinic dehydrogenase is an enzyme that is part of the citric acid cycle (Krebs cycle).$\newline$ - It catalyzes the oxidation of succinate to fumarate, with the reduction of FAD to FADH$_2$.$\newline$ - Melonate is known to be a competitive inhibitor of succinic dehydrogenase.$\newline$ - By inhibiting this enzyme, Melonate disrupts the citric acid cycle, which is crucial for energy production in bacteria.$\newline \bullet$Option 2: Amylase$\newline$ - Amylase is an enzyme that breaks down starch into sugars.$\newline$ - It is not directly involved in the citric acid cycle or energy production in bacteria.$\newline \bullet$Option 3: Lipase$\newline$ - Lipase is an enzyme that breaks down fats into fatty acids and glycerol.$\newline$ - It is not directly involved in the citric acid cycle or energy production in bacteria.$\newline \bullet$Option 4: Dinitrogenase$\newline$ - Dinitrogenase is an enzyme involved in nitrogen fixation, not in the citric acid cycle.$\newline$ - It is not related to the inhibition caused by Melonate.$\newline$Based on the analysis, Melonate inhibits the activity of Succinic dehydrogenase, which is crucial for the citric acid cycle and energy production in bacteria.$\newline$Therefore, the correct option is Option 1: Succinic dehydrogenase.