SELECTIVE INHIBITION OF THE MAIN STRUCTURAL COMPONENT OF ESCHERICHIA COLI BIOFILMS BY A BACTERIAL SECONDARY METABOLITE

LEIVA, PABLO; SERRA, DIEGO; CORDISCO, ESTEFANÍA

Congreso; Congreso conjunto SAIB-SAMIGE 2021; 2021

SAIB (Sociedad Argentina de Investigación Bioquímica y Biología Molecular) Y SAMIGE ( Asociación civíl de Microbiología General)

Biofilms are surface-associated multicellular communities that bacteria build by embedding themselves in an extracellular matrix (ECM) composed of polymeric fibers. Due to their high antibiotic tolerance, bacterial biofilms are involved in more than 50% of all chronic infections. An example of that are the urinary tract infections (UTI) caused by Escherichia coli, which frequently associate with the formation of biofilms on catheters and the bladder. Recognizing the need for solutions to combat biofilm-based infections in general, and of E. coli in particular, we focused on the search for compounds that can interfere with the production of curli, which are amyloid protein fibers that constitute the major structural component of E. coli biofilms. To do so, we explored interactions of E. coli with distinct microorganisms in agar-grown macrocolonies biofilms as a platform for the search of curli inhibitors. We found that B. subtilis NCIB 3610 is able to inhibit the production of curli amyloid fibers in macrocolonies of E. coli strains that produce them as the main ECM element. Curli inhibition was detected by the loss of staining with amyloid-specific dyes and by the absence of curli-dependent morphology of E. coli macrocolonies when they grew in close proximity to B. subtilis NCIB 3610 or in the presence of extracts derived from cell-free culture supernatants (CFCS) of this strain. This inhibitory action on curli is mediated by a metabolite whose synthesis in B. subtilis requires activation by the 4'-phosphopantetheinyl transferase (PPTase) associated with secondary metabolism, as a PPTase deficient mutant of B. subtilis NCIB 3610 and its CFCS showed no inhibitory effect on curli production. Analyses of expression of the csgBAC operon, which encodes the curli structural subunits (CsgB and CsgA), and of key regulators of curli biogenesis in E. coli cells grown in the presence or absence of the effector metabolite, indicate that the inhibitory effect occurs at post-transcriptional level, affecting either translation of csgBAC mRNA or the assembly of CsgB and CsgA into amyloid fibres. In sum, this work provides molecular insights into the mode of action of a microbial compound that targets the major structural component of E. coli biofilms.