EpsD

EpsD is a gene symbol used in several bacteria to denote different proteins that participate in secretion or exopolysaccharide production. In many Gram-negative bacteria, epsD encodes a member of the secretin family that forms part of the Type II secretion system (T2SS). In this context, EpsD serves as an outer membrane channel that enables the export of folded proteins from the periplasm to the extracellular space or cell surface. The EpsD secretin works with other T2SS components, and proper assembly of the secretin pore is essential for secretion of various enzymes and virulence factors in many organisms. Mutations that reduce EpsD function commonly impair secretion efficiency and can influence pathogenicity or environmental adaptation.

In some Gram-positive bacteria, such as Bacillus species, epsD is part of the eps operon involved in exopolysaccharide (EPS) synthesis. Here, the exact enzymatic role of epsD can vary between species, and in some cases it is linked to regulation or coordination of the EPS biosynthetic machinery rather than a single catalytic step. The epsD-dependent pathways affect extracellular polysaccharide production, which in turn influences biofilm formation, colony morphology, and surface properties. Because epsD is used in multiple, distinct genetic contexts, its precise function should be interpreted in a species- and operon-specific framework.