Characteristics of rice straw and sewage sludge as composting materials in Valencia (Spain).

This work supports the idea that composting can be useful for minimizing the rice straw and sewage sludge environmental impact. Several physical, chemical and microbiological properties of these raw materials were analyzed. The characteristics of the rice straw were complementary to those of the sewage sludge for the application of composting. The C/N ratios suitable for a rapid increased in microbial activity were the lowest (17-24). A temperature of 62 degrees C during 48 h removed pathogenic microorganisms from rice straw and sewage sludge mixture. The results obtained in the present work suggested that these materials could be use in the composting process.

The SRD2 gene is involved in Saccharomyces cerevisiae morphogenesis.

Saccharomyces cerevisiaepresents two alternative vegetative forms of growth, switching between yeast forms to pseudohyphal forms depending on the specific environmental conditions. To identify genes involved in cell wall morphogenesis, a haploid S. cerevisiae monomorphic mutant, W27, which exhibits pseudohyphal growth in the absence of the normal external signals that induce the formation of filamentous forms, was characterized. S. cerevisiaeW27 did not demonstrate agar-invasive growth, a characteristic of most filamentous strains. The mutant wall had no obvious alterations with respect to mannan and glucan content, but had three times more chitin than the parental strain. This produced an increase in the amount of proteins linked covalently to chitin. The same protein species, however, were released from the cell walls of the mutant and the parental strain. The W27 mutation was complemented with a genomic library and the SRD2/ECM23 gene was identified as the complementing ORF. Transformation of S. cerevisiaeW27 with the Ycplac33 vector carrying the SRD2 gene produced the original phenotype. These results suggest that the SRD2gene acts as a negative regulator of pseudohyphal growth.