In our previous study, we reported that the transport of monochloramine is affected by the extracellular polymeric substance (EPS) composition, which in turn affects the cell viability of both biofilm and detached clusters.11 However, although the transport and reaction of monochloramine in biofilm could be observed, the specific biomolecules reacting with the disinfectant and the mechanism of disinfection remains elusive. In this study, the impact of EPS composition on bacteria disinfection by monochloramine was qualitatively determined using both wild-type and isogenic mutant Pseudomonas strains with different EPS-secretion capacity and composition. To evaluate their EPS reactivity and contribution to susceptibility to monochloramine, we investigated the bacteria disinfection process using Fourier transform infrared spectroscopy (FTIR) and matrix-assisted laser desorption-ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). Canonical correlation analysis and partial least-squares regression modeling were employed to explore the changes that EPS underwent during the monochloramine disinfection process. The analyses results suggested significant reactions of the monochloramine with peptide fragments of proteins that are associated with carbohydrate utilization. Selected enzymes also showed different levels of inhibition by monochloramine when tested.
S-adenosyl-l-methionine (AdoMet) is an essential metabolite, playing a wide variety of metabolic roles. The enzyme that produces AdoMet from l-methionine and ATP (methionine adenosyltransferase, MAT) is thus an attractive target for anti-cancer and antimicrobial agents. It would be very useful to have a system that allows rapid identification of species-specific inhibitors of this essential enzyme. A previously generated E. coli strain, lacking MAT (∆metK) but containing a heterologous AdoMet transporter, was successfully complemented with heterologous metK genes from several bacterial pathogens, as well as with MAT genes from a fungal pathogen and Homo sapiens. The nine tested genes, which vary in both sequence and kinetic properties, all complemented strain MOB1490 well in rich medium. When these strains were grown in glucose minimal medium, growth delays or defects were observed with some specific metK genes, defects that were dramatically reduced if l-methionine was added to the medium.
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