Is there any non-pathogenic gram negative bacteria? In the category of Gram-negative bacteria, is there any non-pathogenic species? Is such a list of non-pathogenic gram-negative bacteria's available? Can you give maximum 5 examples of such bacteria which has been proved to be non-pathogenic and is gram-negative?

As **Canadianer** already mentioned in the comments, the majority of bacteria (this includes gram-negative bacteria) are non-pathogenic.

I think a prime example is the human gut flora. You can find loads of bacterial species living in your gut without doing you any harm, if anything they are doing you a favour by breaking down food.

Here some examples of gram-negative genera:

* _Bacteroides_
* _Escherichia_



Most species within those genera are non-pathogenic, however, there are exceptions.