AVS 60th International Symposium and Exhibition
    Biomaterial Interfaces Monday Sessions
       Session BI+AI+BA+IS-MoA

Invited Paper BI+AI+BA+IS-MoA3
The Role of Bacterial Physiology in Biodeterioration of Polyurethane Coatings

Monday, October 28, 2013, 2:40 pm, Room 201 B

Session: Biofouling
Presenter: W.J. Crookes-Goodson, Air Force Research Laboratory
Authors: S. Zingarelli, Air Force Research Laboratory
D.E. Barlow, Naval Research Laboratory
J.C. Biffinger, Naval Research Laboratory
L.J. Nadeau, Air Force Research Laboratory
D. Babson, Naval Research Laboratory
B.W. Stamps, University of Oklahoma
R.K. Pirlo, Naval Research Laboratory
C.N. Drake, Air Force Research Laboratory
B.S. Stevenson, University of Oklahoma
J.N. Russell, Jr., Naval Research Laboratory
W.J. Crookes-Goodson, Air Force Research Laboratory
Correspondent: Click to Email
Microbial biofilms frequently contaminate surfaces and can cause degradation of polyurethane coatings that are intended to protect against environmental degradation. Historically, investigations of polyurethane biodeterioration have focused on identification and characterization of the organisms and ‘polyurethanase’ enzymes involved in the degradation process. However, many questions remain unanswered. For example, microbes capable of polymer degradation are ubiquitous in the environment, yet only affect polymers under some circumstances. What controls the production of polyurethanases? What is the role of planktonic vs. biofilm populations in the biodeterioration process? The goal of our research is to define the parameters and regulatory mechanisms that result in polyurethane biodeterioration by Pseudomonas protegens Pf-5, with a focus on environmental conditions (nutrients, pH, oxygen) and microbial ‘lifestyles’ (planktonic vs. biofilm populations). First, we screened a variety of carbon sources with a polyurethane agar plate-clearing assay using the polyester polyurethane Impranil DLN. Results showed that strain Pf-5 could grow on a variety of carbon sources but that degradation of polyurethane varied depending on the carbon source. We observed strong polyurethane degradation in the presence of M9-citrate medium but severely reduced clearing of polyurethane when glucose was provided as a carbon source. Subsequent studies with planktonic cultures of P. protegens Pf-5 verified the inhibitory effect of glucose on polyurethanase activity. Using proteomic tools, activity in citrate-grown planktonic culture supernatants was ascribed to two esterases, polyurethane esterases A and B. Currently the regulation of these enzymes is being investigated through a combination of genetic and transcriptomic approaches. Biofilms were grown on Impranil DLN in M9-citrate or -glucose to determine if these nutrients also regulated polyurethanase secretion in biofilms. Micro ATR-FTIR surface chemical analysis of the coatings after biofilm removal showed that degradation proceeds through preferential loss of the ester component. However, optical microscopy and profilometry clearly show that subsequent bulk coating loss can occur under certain conditions, resulting in complete loss of the original coating surface, and eventually complete loss of the coating. Transmission FTIR microscopy was also used to detect bulk coating degradation in a biofilm culture plate assay we developed to complement the Impranil clearing assay. This assay demonstrated significant Impranil coating degradation from citrate-grown biofilms versus minor degradation for glucose-grown biofilms.