Pseudomonas is a genus of gammaproteobacteria. They are in the family of pseudomonads. Pseudomonas bacteria can be found in many different environments, such as soil, water, and plant and animal tissue.
There are many Pseudomonas species. Some are parasitic and invade animal tissues. In humans, pathogenic Pseudomonas thrive, especially after antibiotic treatment: once they are able to multiply rapidly they can be harmful.