The ecological niche of many bacteria and fungi in an ecosystem is often referred to as decomposers.

Here's why:

* Decomposers break down dead organic matter. This includes plant and animal remains, waste products, and other organic materials.

* Bacteria and fungi are essential decomposers. They use enzymes to break down complex molecules into simpler ones, releasing nutrients back into the ecosystem.

* This process is crucial for nutrient cycling. The nutrients released by decomposers become available for other organisms to use, supporting the entire food web.

While "decomposers" is the most common term, other related terms you might see include:

* Saprotrophs: This term emphasizes the feeding strategy of these organisms, which is to obtain nutrients from dead organic matter.

* Reducers: This term highlights the role of these organisms in reducing complex organic molecules into simpler forms.

Let me know if you'd like more information on any of these topics!