Are there any non-pathogenic gram-positive bacteria in human gut? I wish to know if there are any non-pathogenic (not even opportunistic pathogen) gram-positive bacteria in the human gut? Is there any reference that shows there exists a non-pathogenic gram-positive bacterium in the human gut? I searched the internet but was unable to find anything conclusive.

A recent _Nature_ article, entitled _A new genomic blueprint of the human gut microbiota_, contains the following Figure:

![Phylogeny of reference and uncultured human gut bacterial genomes](

[Fig. 3 Phylogeny of reference and uncultured human gut bacterial genomes]

I don’t know much about bacteria, but, according to their entries in Wikipedia, _Actinobacteria_ , and most _Firmicutes_ are gram-positive and, as these appear to be present in abundance in the human gut of healthy individuals, one assumes that they are not pathogenic to humans.