Linked from
The 36 pages that link to Gram-negative bacteria, each with the reason it gives.
CephalosporinRelated: Later cephalosporins often have expanded activity against these bacteria.
SalmonellaRelated: Salmonella has the cell-envelope structure characteristic of this group.
SafraninRelated: They typically appear pink or red after safranin counterstaining in Gram staining.
PilusRelated: Many well-studied pili cross this two-membrane envelope during assembly.