* Omnivores are organisms that eat both plants and animals. Bacteria are single-celled organisms and lack the complex digestive systems needed to break down large food sources like plants and animals.

* Bacteria are decomposers. They obtain nutrients by breaking down dead organic matter, such as decaying plants, animals, and waste products. This process is called decomposition.

* Bacteria can also be autotrophs, meaning they can produce their own food through processes like photosynthesis (using sunlight) or chemosynthesis (using chemical energy).

In short: Bacteria have unique ways of obtaining nutrients that don't fit the definition of "omnivore."