1. Phototrophy: This involves using light as an energy source. These bacteria are called phototrophs.

* Photoautotrophs use light energy to convert carbon dioxide into organic compounds (like sugars) through photosynthesis. They are often found in environments like ponds and lakes. Examples include cyanobacteria.

* Photoheterotrophs use light energy but cannot fix carbon dioxide. Instead, they get their carbon from organic compounds produced by other organisms. These bacteria are often found in marine environments.

2. Chemotrophy: This involves using chemical compounds as an energy source. These bacteria are called chemotrophs.

* Chemoautotrophs obtain energy from the oxidation of inorganic compounds, such as hydrogen sulfide, ammonia, or iron. They can then use this energy to fix carbon dioxide and make their own organic compounds. These bacteria are often found in extreme environments like hot springs or hydrothermal vents.

* Chemoheterotrophs obtain energy by breaking down organic compounds produced by other organisms. They are the most common type of bacteria and can be found in a wide range of environments, including our bodies.

3. Organotrophy: This is a subcategory of chemotrophy where the organic compounds used as energy sources are derived from other living organisms. Organotrophs include:

* Saprophytes: These bacteria break down dead organic matter, such as fallen leaves or animal carcasses.

* Parasites: These bacteria obtain energy from living organisms, often causing harm to their hosts.

It's important to note that these are broad categories, and there is significant diversity within each. For example, some bacteria can use both light and chemical compounds for energy.