Forms pores that allow passive diffusion of small molecules across the outer membrane (By similarity). Plays a role in resistance to carbapenems; this carbapenem-resistant, noncarbapenemase-producing clinical isolate has a deletion in ompF and a mutated marR gene that does not induce expression of this protein. However if this gene is overexpressed, or if wild-type marR is introduced, this leads to decreased resistance to the carbapenem antibiotics ertapenem, imipenem and meropenem (PubMed:23318808). Expression induced by marR. Belongs to the Gram-negative porin family.