Kingdom Eubacteria are "true bacteria", meaning they are prokaryotes. Depending on how they get nutrients, they can either be photoautotrophs, chemoautotrophs, photoheterotrophs, or chemoheterotrophs. They need to get energy and carbon to live and they do so in different ways.

Photoautotrophs: Use light as an energy source and carbon dioxide as a carbon source.
Photoheterotrophs: use light as an energy source and organic compounds as a carbon source.

Chemoautotrophs: use inorganic chemicals as an energy source and carbon dioxide as a carbon source.
Chemoheterotrophs: use organic chemicals as an energy source and organic compounds as a carbon source.

As you can see "photo" refers to light as an energy source, "autotroph" is carbon dioxide as a carbon source, and "heterotroph" refers to organic compounds as a carbon source. Autotrophs soak up light and don't use metabolism, whereas heterotrophs obtain their food.

Can you guess what animals are? If you guessed heterotrophs, you're right! Animals, including humans, are heterotrophic because they obtain their own food and metabolize it for energy.

Eubacteria can obtain foods in a bunch of different ways. The earliest bacteria were likely lithotrophs which use inorganic compounds (compounds that don’t have carbon) along with CO₂ to make food. There are also photosynthetic bacteria which use the sun’s light to use CO₂ from the environment to make food. For these two groups of bacteria, the idea is that they use sunlight or inorganic compounds to turn CO₂ into something useful for the bacterium. There are also bacteria which eat organic compounds for food that they find in their environment because they can’t turn CO₂ into useful compounds. Another class of bacteria is predatory in that they eat other bacteria. The bacteria that are most dangerous are parasitic bacteria which eat food taken in by the host organism which in some cases is a human. These bacteria “steal” food from the host organism and release waste products and toxins which can be dangerous for the host.