In the food chain above bacteria are best classified as which of the following. Grass-gazelle - lion-bacteria

Your wording is a bit confusing, but I will do my best.

In the energy pyramid/food chain, there are around seven trophic levels; Apex predators, teritiary consumers, secondary consumers, primary consumers, producers, and decomposers in a separate bottom level. In your case, you only need the apex predator, primary consumer, producer, and decomposer.

Lion - Apex predator

Gazelle - Primary consumer

Grass - Producer

Bacteria - Decomposer