You can't distinguish between *Escherichia* and *Proteus* based solely on Gram reaction. Both are Gram-negative bacteria.

Here's why:

* Gram staining is a technique that differentiates bacteria based on the structure of their cell wall.

* Gram-negative bacteria have a thin peptidoglycan layer in their cell wall, which makes them appear pink after Gram staining.

* Both *Escherichia* (like *E. coli*) and *Proteus* (like *P. mirabilis*) have this thin peptidoglycan layer and will both stain pink.

To differentiate between these genera, you would need to consider other characteristics, such as:

* Shape: *Escherichia* are typically rod-shaped (bacilli), while *Proteus* are also rod-shaped but can exhibit swarming motility, leading to distinctive colony patterns.

* Biochemical tests: Each genus has specific metabolic and enzymatic characteristics that can be used to differentiate them in a lab setting.

Let me know if you'd like to know more about these characteristics!