Degradation of nitrocellulose-based paint by Desulfovibrio desulfuricans ATCC 13541.

Nitrocellulose is one of the most commonly used compounds in ammunition and paint industries and its recalcitrance to degradation has a negative impact on human health and the environment. In this study the capability of Desulfovibrio desulfuricans ATCC 13541 to degrade nitrocellulose as binder in paint was assayed for the first time. Nitrocellulose-based paint degradation was followed by monitoring the variation in nitrate, nitrite and ammonium content in the culture medium using Ultraviolet-Visible spectroscopy. At the same time cell counts and ATP assay were performed to estimate bacterial density and activity in all samples. Infrared spectroscopy and colorimetric measurements of paint samples were performed to assess chemical and colour changes due to the microbial action. Microscope observations of nitrocellulose-based paint samples demonstrated the capability of the bacterium to adhere to the paint surface and change the paint adhesive characteristics. Finally, preliminary studies of nitrocellulose degradation pathway were conducted by assaying nitrate- and nitrite reductases activity in D. desulfuricans grown in presence or in absence of paint. We found that D. desulfuricans ATCC 13541 is able to transform nitrocellulose as paint binder and we hypothesised ammonification as degradation pathway. The results suggest that D. desulfuricans ATCC 13541 is a good candidate as a nitrocellulose-degrading bacterium.

Macromolecular crowding tunes folding landscape of parallel α/ß protein, apoflavodoxin.

Proteins normally fold in crowded cellular environments. Here we use a set of Desulfovibrio desulfuricans apoflavodoxin variants to assess--with residue-specific resolution--how apoflavodoxin's folding landscape is tuned by macromolecular crowding. We find that, under crowded conditions, initial topological frustration is reduced, subsequent folding requires less ordering in the transition state, and ß-strand 1 becomes more important in guiding the process. We propose that conditions more closely mimicking the cellular environment make the ensemble of unfolded conformations less expanded, resulting in a folding funnel that is smoother and narrower.

Antibacterial inorganic-organic hybrid coatings on stainless steel via consecutive surface-initiated atom transfer radical polymerization for biocorrosion prevention.

To enhance the corrosion resistance of stainless steel (SS) and to impart its surface with antibacterial functionality for inhibiting biofilm formation and biocorrosion, well-defined inorganic-organic hybrid coatings, consisting of a polysilsesquioxane inner layer and quaternized poly(2-(dimethyamino)ethyl methacrylate) (P(DMAEMA)) outer blocks, were prepared via successive surface-initiated atom transfer radical polymerization (ATRP) of 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The cross-linked P(TMASPMA), or polysilsesquioxane, inner layer provided a durable and resistant coating to electrolytes. The pendant tertiary amino groups of the P(DMAEMA) outer block were quaternized with alkyl halide to produce a high concentration of quaternary ammonium groups with biocidal functionality. The so-synthesized inorganic-organic hybrid coatings on the SS substrates exhibited good anticorrosion and antibacterial effects and inhibited biocorrosion induced by sulfate-reducing bacteria (SRB) in seawater media, as revealed by antibacterial assay and electrochemical analyses, and they are potentially useful to steel-based equipment under harsh industrial and marine environments.

Versatility of a new bioinorganic catalyst: palladized cells of Desulfovibrio desulfuricans and application to dehalogenation of flame retardant materials.

The versatility and reaction specificity of a novel bioinorganic catalyst is demonstrated in various reactions. Palladized cells (bioPd) of the sulphate-reducing bacterium Desulfovibrio desulfuricans showed an increased product selectivity and a catalytic activity comparable to a commercial Pd catalyst in several industrially relevant hydrogenations and hydrogenolyses (reductive dehalogenations). The ability of palladized cells to promote the reductive debromination of a polybrominated diphenyl ether (PBDE #47) is demonstrated, although chemically reduced Pd(II) and commercial Pd(0) were more effective debromination agents. Polybrominated diphenyl ethers are being supplanted as flame retardants by other compounds, e.g. tris(chloroisopropyl)phosphate (TCPP), the concentration of which was seen to increase approximately 10-fold in groundwater samples between 2000 and 2004. BioPd dechlorinated TCPP in groundwater samples with >90% recovery of free chloride ion, and was five times more effective than using commercial Pd(0) catalyst. Examination of the spent groundwater using 31P NMR showed a phosphorus species novel to the bioPd-treated solution, which was not evident in a commercial reference sample of TCPP.

Susceptibility of Desulfovibrio desulfuricans intestinal strains to sulfasalazine and its biotransformation products.

BACKGROUND: Desulfovibrio desulfuricans intestinal bacteria may contribute to toxic hydrogen sulfide production in the human gut. Our objective was to examine whether the D. desulfuricans strains isolated from the human body are susceptible to sulfasalazine (SAS) and the products of its biotransformation, i.e. 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), in order to determine the relationship between the strains' susceptibility to SAS and their ability to reduce the azo bond within this drug. MATERIAL/METHODS: Six wild strains of D. desulfuricans (isolated from feces and biopsy specimens from patients with colitis ulcerosa, Crohn's disease, irritable bowel syndrome, colonic diverticula, primary biliary cirrhosis, or tubular adenomas of the colon) were cultured in the presence of SAS, 5-ASA, and SP. Growth inhibition coefficients were compared with coefficients of inhibition of the azo-bond reduction in SAS. RESULTS: The D. desulfuricans strains present in the human digestive tract were susceptible to a small degree to SAS and to 5-ASA and SP. CONCLUSIONS: The intestinal D. desulfuricans strains differed in their susceptibility to SAS and its biotransformation products. The strains showing higher susceptibility to SAS lost the ability to reduce the azo bond in this drug, which may be attributed to the lower metabolic activity of the bacteria. The presence of D. desulfuricans in the large intestines of patients with ulcerative colitis and the confirmed diversity of the biological activity of the isolated strains demonstrate the need for clinical examination of the role of these bacteria in the development of some inflammatory disorders.