Genome sequence of the model sulfate reducer Desulfovibrio gigas: a comparative analysis within the Desulfovibrio genus.

Desulfovibrio gigas is a model organism of sulfate-reducing bacteria of which energy metabolism and stress response have been extensively studied. The complete genomic context of this organism was however, not yet available. The sequencing of the D. gigas genome provides insights into the integrated network of energy conserving complexes and structures present in this bacterium. Comparison with genomes of other Desulfovibrio spp. reveals the presence of two different CRISPR/Cas systems in D. gigas. Phylogenetic analysis using conserved protein sequences (encoded by rpoB and gyrB) indicates two main groups of Desulfovibrio spp, being D. gigas more closely related to D. vulgaris and D. desulfuricans strains. Gene duplications were found such as those encoding fumarate reductase, formate dehydrogenase, and superoxide dismutase. Complexes not yet described within Desulfovibrio genus were identified: Mnh complex, a v-type ATP-synthase as well as genes encoding the MinCDE system that could be responsible for the larger size of D. gigas when compared to other members of the genus. A low number of hydrogenases and the absence of the codh/acs and pfl genes, both present in D. vulgaris strains, indicate that intermediate cycling mechanisms may contribute substantially less to the energy gain in D. gigas compared to other Desulfovibrio spp. This might be compensated by the presence of other unique genomic arrangements of complexes such as the Rnf and the Hdr/Flox, or by the presence of NAD(P)H related complexes, like the Nuo, NfnAB or Mnh.

Physiological characterization of thermotolerant yeast for cellulosic ethanol production.

The conversion of lignocellulose into fermentable sugars is considered a promising alternative for increasing ethanol production. Higher fermentation yield has been achieved through the process of simultaneous saccharification and fermentation (SSF). In this study, a comparison was performed between the yeast species Saccharomyces cerevisiae and Kluyveromyces marxianus for their potential use in SSF process. Three strains of S. cerevisiae were evaluated: two are widely used in the Brazilian ethanol industry (CAT-1 and PE-2), and one has been isolated based on its capacity to grow and ferment at 42 °C (LBM-1). In addition, we used thermotolerant strains of K. marxianus. Two strains were obtained from biological collections, ATCC 8554 and CCT 4086, and one strain was isolated based on its fermentative capacity (UFV-3). SSF experiments revealed that S. cerevisiae industrial strains (CAT-1 and PE-2) have the potential to produce cellulosic ethanol once ethanol had presented yields similar to yields from thermotolerant strains. The industrial strains are more tolerant to ethanol and had already been adapted to industrial conditions. Moreover, the study shows that although the K. marxianus strains have fermentative capacities similar to strains of S. cerevisiae, they have low tolerance to ethanol. This characteristic is an important target for enhancing the performance of this yeast in ethanol production.

Production and characterization of ß-glucanase secreted by the yeast Kluyveromyces marxianus.

An extracellular ß-glucanase secreted by Kluyveromyces marxianus was identified for the first time. The optimal conditions for the production of this enzyme were evaluated by response surface methodology. The optimal conditions to produce ß-glucanase were a glucose concentration of 4% (w/v), a pH of 5.5, and an incubation temperature of 35 °C. Response surface methodology was also used to determine the pH and temperature required for the optimal enzymatic activity. The highest enzyme activity was obtained at a pH of 5.5 and a temperature of 55 °C. Furthermore, the enzyme was partially purified and sequenced, and its specificity for different substrates was evaluated. The results suggest that the enzyme is an endo-ß-1,3(4)-glucanase. After optimizing the conditions for ß-glucanase production, the culture supernatant was found to be effective in digesting the cell wall of the yeast Saccharomyces cerevisiae, showing the great potential of ß-glucanase in the biotechnological production of soluble ß-glucan.

Wade histoid leprosy: histological and immunohistochemical analysis.

Histoid leprosy is a rare multibacillary form that presents with disseminated papule-nodular cutaneous lesions. To study the inflammatory infiltrate of the histoid form and to compare it with other lepromatous forms, we performed histological and immunohistochemical analysis on skin biopsies. Fifteen patients were included for histopathological analysis (10 histoid and five lepromatous) via the haematoxylin-eosin and Ziehl-Neelsen-Faraco stains. Thus, immunohistochemical techniques using immunoperoxidase assay were performed for: anti-BCG, anti-M. leprae, anti-CD8, anti-CD3, anti-CD20, anti-S100, anti-CD1a, anti-CD68 and antivimentin. Spindle cells were present in all histoid patients. A pseudocapsule was observed in half of both studied forms. A comparison using the Ziehl-Neelsen-Faraco stain to evaluate anti-BCG and anti-M.leprae showed no major differences. The CD3+ cells were more pronounced in the histoid form than the lepromatous form. There was greater immunoreactivity toward CD8+ cells in the histoid form, as well as the CD20+ cell count. A similar count of S100+ cells in the epidermis of both leprosy forms was observed. There was a slight increase of dendritic cells in the histoid patients in the superficial and deep dermis. For CD1a marker, we observed expression in the epidermis and superficial dermis in both forms. A diffuse and intense infiltrate of CD68+ cells was also observed in the histoid and lepromatous forms. The high positivity for vimentin did not allow for a positive cell count. We concluded that the activation of both the cellular and humoral response is more pronounced in the histoid form because the T and B cells showed greater infiltration than those in the lepromatous form. The activation of dendritic and Langerhans cells is similar in both forms. The spindle cells likely belong to the macrophage population, thus maintaining phagocytic ability. The quantities of pseudocapsules and bacilli are similar and cannot serve as criteria for diagnosis.

The influence of presaccharification, fermentation temperature and yeast strain on ethanol production from sugarcane bagasse.

Ethanol can be produced from cellulosic biomass in a process known as simultaneous saccharification and fermentation (SSF). The presence of yeast together with the cellulolytic enzyme complex reduces the accumulation of sugars within the reactor, increasing the ethanol yield and saccharification rate. This paper reports the isolation of Saccharomyces cerevisiae LBM-1, a strain capable of growth at 42 °C. In addition, S. cerevisiae LBM-1 and Kluyveromyces marxianus UFV-3 were able to ferment sugar cane bagasse in SSF processes at 37 and 42 °C. Higher ethanol yields were observed when fermentation was initiated after presaccharification at 50°C than at 37 or 42° C. Furthermore, the volumetric productivity of fermentation increased with presaccharification time, from 0.43 g/L/h at 0 h to 1.79 g/L/h after 72 h of presaccharification. The results suggest that the use of thermotolerant yeasts and a presaccharification stage are key to increasing yields in this process.