Sulfide removal and elemental sulfur recycling from a sulfide-polluted medium by Allochromatium vinosum strain 21D / Eliminación de sulfuro y reciclado de azufre elemental de un medio contaminado con sulfuro por Allochromatium vinosum cepa 21D

Phototrophic purple sulfur bacteria oxidize sulfide to elemental sulfur, which is stored as intracellular sulfur globules. The mutant Allochromatium vinosum strain 21D, containing an inactivated dsrB gene, is unable to further oxidize intracellularly stored sulfur to sulfate. This mutant was used as a biocatalyst in a biotechnological process to eliminate sulfide from synthetic wastewater and to recycle elemental sulfur as a raw material. For this purpose, the mutant was grown in an illuminated 5-liter bioreactor (30 microE/m2/s PAR) at 30 degrees C for 61 days in anoxic phototrophic medium. The process of sulfide removal was semi-continuous and consisted of three consecutive fed-batch sections. Sulfide was repeatedly added into the bioreactor and oxidized by the cells to sulfur. In the presence of the mutant, no unwanted sulfate was produced during sulfide removal. A maximum sulfide removal rate of 49.3 microM/h, a maximum sulfide removal efficiency of 98.7%, and 60.4% sulfur recycling were achieved (AU)

Las bacterias fotótrofas rojas del azufre oxidan sulfuro a azufre elemental, que se almacena en el interior de la célula en forma de glóbulos de azufre. Debido a una inactivación del gen drsB, el mutante Allochromatium vinosum 21D es incapaz de continuar la oxidación del azufre almacenado intracelularmente y formar sulfato. Este mutante se utilizó como biocatalizador en un proceso biotecnológico para eliminar sulfuro de agua residual sintética y para reciclar azufre elemental como materia prima. Con esta finalidad, se cultivó dicho mutante en un biorreactor iluminado de 5 litros (30 μE/m2/s PAR), durante 61 días a 30°C en un medio fototrófico anóxico. El proceso de eliminación de sulfuro era semicontinuo y consistía en tres secciones consecutivas de cultivo con alimentación (fed-batch). El sulfuro se añadía continuamente al biorreactor y las células lo oxidaban hasta azufre. En presencia del mutante, durante la eliminación de sulfuro no había producción del sulfato no deseado. Se obtuvo una velocidad máxima de eliminación de sulfuro de 49,3 μM/h, con una eficacia máxima de 98,7% y un reciclado del 60,4% de azufre (AU)

Sulfate-reducing bacteria in relation with other potential periodontal pathogens.

BACKGROUND, AIMS: Oral sulfate-reducing bacteria are involved in several clinical categories of periodontitis. The aim of this cross-sectional study was to compare the presence of sulfate-reducing bacteria (SRB) with other putative pathogens including spirochetes, Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Porphyromonas gingivalis, and Treponema denticola in periodontal lesions. METHOD: Periodontal SRB were detected by enrichment culture and compared with a microscopic spirochete count (n=168). Species-specific oligonucleotide probes directed against the 16S rRNA were employed to determine the presence of A. actinomycetemcomitans, P. gingivalis, B. forsythus, and T. denticola (n=55). RESULTS: A significant positive correlation was observed between the presence of SRB and the proportions of spirochetes in subgingival plaque, although the 2 bacterial groups also occurred separately. SRB tended to be negatively correlated with the presence of A. actinomycetemcomitans. In contrast, all pockets with SRB harbored either T. denticola, or both T. denticola and B. forsythus (12/14) before therapy. Interestingly, the combination of SRB with P. gingivalis occurred in 32% of the periodontal pockets before treatment. After initial periodontal therapy, the prevalence of this combination was reduced to 2% of the sites, and to 25% of the sites in recall patients. CONCLUSION: The presence of SRB was positively correlated with T. denticola, B. forsythus, and P. gingivalis in periodontal lesions. These suspected pathogens form a complex strongly associated with destructive periodontitis.

Sulfate-reducing bacteria in association with human periodontitis.

BACKGROUND, AIMS: Sulfate-reducing bacteria (SRB) may be etiologically involved in destructive periodontal diseases. These strictly anaerobic bacteria utilize fermentation products for energy conservation by reduction of sulfate to sulfide. This toxic product can accumulate in periodontal pockets in concentrations causing cellular destruction. SRB depend on an actively degrading microbiota to produce a reduced environment, fermentation products and sulfate. The detection frequency of these bacteria is strongly increased in periodontitis compared with healthy sites in the oral cavity. METHOD: In this study, the presence of SRB was determined in relation to clinical features of the patients and to site-specific clinical parameters of periodontitis, such as pocket depth, bleeding and attachment level. Patients with clinical characteristics of severe periodontitis (n=87) were included in the study, 78 were untreated patients and 9 patients were in maintenance care after treatment. Samples were taken (n=261) from the deepest periodontal pockets, and presence of SRB was determined by enrichment culture in an anoxic chamber. RESULTS: In 64% of the patients, SRB were present in at least 1 pocket. They occurred among patients from 23 to 57 years old, and tended to prevail among patients older than 30 years. There was a tendency to increased SRB occurrence among patients with more than 50% of bleeding sites, or with several angular bony defects or furcations. In 44% of the periodontal pockets SRB were present. They tended to prevail in pockets showing bleeding on probing, furcations, angular bony defects, or an endodontal complication. Presence of SRB was positively correlated with increased pocket depth (p<0.05). SRB were found to be associated with various clinical categories of periodontitis, including early onset periodontitis, rapidly progressive periodontitis, adult periodontitis, and refractory periodontitis. Although SRB predominated among patients with an adult form of periodontitis, i.e., with an occurrence of 72%, there was no significant correlation with age of the patient. Among treated patients under maintenance care, SRB prevalence was significantly reduced in comparison with untreated patients (p<0.02). Occurrence of SRB in periodontal pockets showed an odds ratio of 11.2 in comparison with healthy oral sites. CONCLUSION: Periodontal sulfate-reducing bacteria are associated with several clinical categories of periodontitis and with periodontal sites of increased pocket depth.

Ashkenazi Jews, sulfur gases, and ulcerative colitis.

Fecal pathogens have been suspected to cause ulcerative colitis, yet none have been identified. Meanwhile, the 400 species comprising normal colonic flora have received little attention as potential pathogens. Sulfate-reducing bacteria (SRB), a frequent colonic commensal, have been identified in greater numbers in people with ulcerative colitis. The bacteria produce hydrogen sulfide, a toxic compound with the potential to cause colonic injury and possibly ulcerative colitis. If these bacteria are pathogenic, high-risk populations may harbor greater numbers of these organisms in their colons. We compared a group with a high incidence of ulcerative colitis, Ashkenazi Jews, to a control population to assess carriage rates for SRB. Breath samples were collected to indirectly determine colonic conditions. No difference was found between the two groups studied.