Bacterial adhesion on glyco-hydrogels: impact of glycan and hydrogel stiffness

Bacterial adhesion on substrate surface is governed by multiple factors, with ligand-bacteria interactions and substrate stiffness among the most important. Using Mycobacterium smegmatis (M. smegmatis) and trehalose as a model system, we synthesized trehalose-functionalized polyacrylamide (Tre-PAAm) of varying stiffness and investigated how trehalose content and substrate stiffness affect the adhesion of M. smegmatis on Tre-PAAm hydrogels. Results show that glycan-bacteria interactions play a more dominant role than substrate stiffness. At 30 % trehalose monomer loading, M. smegmatis adhered more strongly to soft than to hard Tre-PAAm hydrogels. However, this stiffness-dependent effect was reduced at lower trehalose monomer loading, and minimal adhesion was observed on PAAm hydrogels without trehalose. Furthermore, non-complementary glycan-bacterium combinations, e.g., E. coli on Tre-PAAm and M. smegmatis on mannose-functionalized polyacrylamide (Man-PAAm) hydrogels, showed almost no bacterial adhesion regardless of hydrogel stiffnesses. Taken together, these findings demonstrate that specific glycan-bacteria interactions play a dominant role over substrate stiffness in governing bacterial adhesion.