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Previously, two municipal solid waste commercial composts (MSW1 and MSW2) were characterized. Although sharing the same type of raw material, most of their physicochemical, stability and maturity properties differed. The present study aimed to characterize them at a microbiological level, and to infer on possible relationships between the composts properties and the structure of their bacterial communities. Both the 16S rRNA gene-based PCR-DGGE profiling and 454-pyrosequencing technology showed that the structure of the bacterial communities of these composts was distinct. The bacterial community of MSW1 was more diverse than that of MSW2. Multivariate analyses revealed that the high electrical conductivity, Cu content as well as the low phytotoxity of compost MSW1, when compared to MSW2, contributed most to shape its bacterial community structure. Indeed, high abundance of halophilic ( Halomonadaceae and Brevibacteriaceae ) and metal resistant organisms ( Brevibacteriaceae and Bacillaceae ) were found in MSW1. In addition, Pseudonocardiaceae , Streptomycetaceae , Bacillaceae , and Brevibacteriaceae may have contributed to the high humic-like acids content and low phytotoxicity of MSW1. In contrast, the high organic matter content and the high density of the cultivable fungi population were the parameters most correlated with the structure of the bacterial community of compost MSW2, dominated by Corynebacteriaceae and mainly Aerococcaceae , taxonomic groups not commonly found in composts. [ABSTRACT FROM AUTHOR]

Crop rotation is a practice harmonized with the sustainable rice production. Nevertheless, the implications of this empirical practice are not well characterized, mainly in relation to the bacterial community composition and structure. In this study, the bacterial communities of two adjacent paddy fields in the 3rd and 4th year of the crop rotation cycle and of a nonseeded subplot were characterized before rice seeding and after harvesting, using 454-pyrosequencing of the 16 S r RNA gene. Although the phyla Acidobacteria, Proteobacteria, Chloroflexi, Actinobacteria and Bacteroidetes predominated in all the samples, there were variations in relative abundance of these groups. Samples from the 3rd and 4th years of the crop rotation differed on the higher abundance of groups of presumable aerobic bacteria and of presumable anaerobic and acidobacterial groups, respectively. Members of the phylum Nitrospira were more abundant after rice harvest than in the previously sampled period. Rice cropping was positively correlated with the abundance of members of the orders Acidobacteriales and ' Solibacterales' and negatively with lineages such as Chloroflexi ' Ellin6529'. Studies like this contribute to understand variations occurring in the microbial communities in soils under sustainable rice production, based on real-world data. [ABSTRACT FROM AUTHOR]

The main purpose of this work was to assess the (i) short-term effect of the main nitrification and denitrification variables on the nitrogen’s biological removal via nitrite from highstrength leachates, and (ii) the effect of the presence/absence of nitrites/nitrates in a downstream photo-oxidation process. The biological reaction rates were evaluated as a function of several parameters: (i) temperature, dissolved oxygen (DO) concentration and pH, on the nitrification; and (ii) pH, temperature and the addition of phosphate ions, on the denitrification. At the beginning of most nitrification assays, it was verified that the ammonia stripping occurred simultaneously to the nitrification, reaching up to 31% removal of total dissolved nitrogen. The maximum nitrification rate obtained was 37 ± 2 mg NH 4 + -N/(h⋅g VSS) (25 °C, 1.02.0 mg O 2 /L, pH not controlled), consuming 5.3 ± 0.4 mg CaCO 3 /mg NH 4 + -N. The highest denitrification rate achieved was 27 ± 1 mg NO 2 − -N/(h⋅g VSS) (pH between 7.5 and 8.0, 30 °C, adding 30 mg PO 4 3− /L), with a C/N consumption ratio of 1.6 ± 0.1 mg CH 3 OH/mg NO 2 − -N and an overall alkalinity production of 3.2 ± 0.1 mg CaCO 3 /mg NO 2 − -N. The denitrification process showed to be sensitive to all studied parameters, while the nitrification reaction did not suffered significant change when DO content was changed. The two most abundant bacterial groups in the nitrification and denitrification processes, as indicated by the 454-pyrosequencing analysis of the 16S rRNA gene, were affiliated to Saprospiraceae / Nitrosomonadaceae and Hyphomicrobiaceae / Saprospiraceae , respectively. The abundance of Nitrosomonadaceae and Hyphomicrobiaceae (in particular, Hyphomicrobium ) in the nitrification and denitrification process, respectively, is in agreement with the nitrifying and denitrifying activity of these bacterial members. The photo-Fenton reaction rate was assessed considering the presence of nitrites and nitrates and the absence of both in a leachate after biological oxidation and coagulation/sedimentation steps. The results showed that for a pre-treated leachate without nitrogen, the DOC degradation rate decreased 28%, while for a bio-treated leachate containing nitrites, the H 2 O 2 consumption was 2.4 times higher. [ABSTRACT FROM AUTHOR]