Proteobacteria
Proteobacteria is a large and varied phylum that includes many everyday gut residents as well as familiar names like Escherichia. In a typical gut it usually forms a relatively small share of the community.
Researchers watch Proteobacteria because a persistently expanded share of this group has been discussed as a possible signal of an unsettled or imbalanced gut environment. It is one of the more talked-about phyla when it comes to gut balance.
A higher Proteobacteria share means this group takes up a larger part of your sample than usual, which some studies associate with a less settled gut environment. Because this is relative and compositional, a higher share is a signal to interpret in context, not a diagnosis of any condition.
A lower or modest Proteobacteria share is common and typically unremarkable, simply meaning this group forms a small portion of your sample.
Rather than a target number, general framing is that a modest Proteobacteria share is usual and a persistently high one is worth discussing. This science is still developing, so review a notably elevated share, especially with gut symptoms, together with a clinician.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.