The distribution of active ß-glucosidase-producing microbial communities in composting.

The composting ecosystem is a suitable source for the discovery of novel microorganisms and secondary metabolites. Cellulose degradation is an important part of the global carbon cycle, and ß-glucosidases complete the final step of cellulose hydrolysis by converting cellobiose to glucose. This work analyzes the succession of ß-glucosidase-producing microbial communities that persist throughout cattle manure - rice straw composting, and evaluates their metabolic activities and community advantage during the various phases of composting. Fungal and bacterial ß-glucosidase genes belonging to glycoside hydrolase families 1 and 3 (GH1 and GH3) amplified from DNA were classified and gene abundance levels were analyzed. The major reservoirs of ß-glucosidase genes were the fungal phylum Ascomycota and the bacterial phyla Firmicutes, Actinobacteria, Proteobacteria, and Deinococcus-Thermus. This indicates that a diverse microbial community utilizes cellobiose. The succession of dominant bacteria was also detected during composting. Firmicutes was the dominant bacteria in the thermophilic phase of composting; there was a shift to Actinomycetes in the maturing stage. Proteobacteria accounted for the highest proportions during the heating and thermophilic phases of composting. By contrast, the fungal phylum Ascomycota was a minor microbial community constituent in thermophilic phase of composting. Combined with the analysis of the temperature, cellulose degradation rate and the carboxymethyl cellulase and ß-glucosidase activities showed that the bacterial GH1 family ß-glucosidase genes make greater contribution in cellulose degradation at the later thermophilic stage of composting. In summary, even GH1 bacteria families ß-glucosidase genes showing low abundance in DNA may be functionally important in the later thermophilic phase of composting. The results indicate that a complex community of bacteria and fungi expresses ß-glucosidases in compost. Several ß-glucosidase-producing bacteria and fungi identified in this study may represent potential indicators of composting in cellulose degradation.

Compound transfer efficiency from polystyrene surfaces: application to microarrayed compound screening.

In microarrayed compound screening (microARCS), compounds are spotted and dried onto a polystyrene sheet (ChemCard)ata high density and introduced into the assay by contacting with agarose gels that contain reagents for the assay. The authors have conducted studies to characterize the compound transfer process using 59 compounds of diverse properties. The amount of compounds remaining on the ChemCard was determined by liquid chromatography/mass spectrometry after incubation with agarose gels for predetermined time periods. The results showed good correlation with kinetics of compound transfer to phosphate-buffered saline (PBS) buffer, but only moderate correlation with equilibrium solubility of compounds in PBS buffer. These observations indicate that the major factor determining compound transfer efficiency is the kinetics of dissolution of compounds, rather than equilibrium solubility and diffusion of compounds in the gel. Compounds of lower ClogP showed a higher rate of transfer to agarose gels and vice versa. Other compound properties such as molecular weight, size, acid-base, and H-bonding properties did not significantly affect compound transfer. Importantly, the majority of the compounds studied show greater than 20% transfer after a 10-min incubation with agarose gels, providing sufficient amounts of compounds for screening purposes.