Interactions of bacteria and viruses with membranes and nanoparticles: Characterization of extracellular polymeric substances and photoinactivation of bacteriophages by fullerol nanoparticles

The extracellular polymeric substances produced by suspended cultures of Escherichia coli, Serratia marcescens, and Brevundimonas diminuta in the presence and absence of bismuth thiols and by activated sludge microorganisms in the presence of glucose were characterized in detail using colorimetric, spectroscopic, and microscopic techniques. 2:1 molar ratio preparations of three lipophilic bismuth thiols (BisBAL, BisEDT, and BisPYR) were investigated and BisBAL was found to be most effective for EPS suppression. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, carbohydrates and nucleic acids varying predominantly only in total amounts expressed. Fourier transform infrared spectroscopy (FTIR) suggested that a possible mechanism of biofilm disruption by BisBAL is the inhibition of carbohydrate O-acetylation and changes in protein secondary structures. Results suggest that antifouling properties of bismuth thiols originate in their ability to suppress O-acetylation, protein secondary structure formation, and free and bound EPS secretion. Bioflocculation appears to be inhibited through electrostatic repulsions when EPS content was low but was enhanced via polymeric interactions at high EPS concentrations. More specifically, microorganisms appeared to aggregate by producing protein secondary structures including aggregated strands, beta-sheets, alpha- and 3-turn helical structures, O-acetylated carbohydrates, as well as overall C--(0,N) and O=C--OH + O=C--OR functionalities.;Production of reactive oxygen species through photosensitization of polyhydroxylated fullerene (fullerol) is shown to enhance viral inactivation rates. The first-order MS2 bacteriophage inactivation rate nearly doubled due to the presence of 102, and increased by 125% due to 102 and superoxide when compared with UV-A illumination alone. When fullerol and NADH were present in solution, dark inactivation of viruses occurred at nearly the same rate as that produced by UV-A illumination without nanoparticles. Mechanisms of loss of virus infectivity were also probed using dsDNA bacteriophages with capsids of different composition (T7 and PRD1). The first order inactivation rate of phages in the presence of UV-A illuminated fullerol suspensions varied as MS2 > T7 > PRDI indicating the role of capsid composition in the susceptibility of viruses to singlet oxygen. Damage to T7 and PRD1 capsid proteins was identified using FTIR and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). SDS-PAGE analysis revealed the 1O2 induced alterations in capsid proteins such as oxidative cross-linking.