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Composting is a process of stabilizing organic wastes through the degradation of biodegradable components by microbial communities under controlled conditions. In the present study, genera and species diversities, amylohydrolysis, protein and cellulose degradation abilities of culturable bacteria in the thermophilic phase of composting of cattle manure with plant ash and rice bran were investigated. The number of culturable thermophilic bacteria and actinomyces decreased with the increasing temperature. At the initiation and end of the thermophilic phase, genera and specie diversities and number of bacteria possessing degradation abilities were higher than during the middle phase. During the thermophilic composting phase, Bacillus, Geobacillus and Ureibacillus were the dominant genera, and Geobacillus thermodenitrificans was the dominant species. In later thermophilic phases, Geobacillus toebii and Ureibacillus terrenus were dominant. Bacillus, at the initiation, and Ureibacillus and Geobacillus, at the later phase, contributed the multiple degradation abilities. These data will facilitate the control of composting in the future.

Soil physicochemical properties, soil microbial biomass and bacterial community structures in a rice-wheat cropping system subjected to different fertilizer regimes were investigated in two seasons (June and October). All fertilizer regimes increased the soil microbial biomass carbon and nitrogen. Both fertilizer regime and time had a significant effect on soil physicochemical properties and bacterial community structure. The combined application of inorganic fertilizer and manure organic-inorganic fertilizer significantly enhanced the bacterial diversity in both seasons. The bacterial communities across all samples were dominated by Proteobacteria, Acidobacteria and Chloroflexi at the phylum level. Permutational multivariate analysis confirmed that both fertilizer treatment and season were significant factors in the variation of the composition of the bacterial community. Hierarchical cluster analysis based on Bray-Curtis distances further revealed that bacterial communities were separated primarily by season. The effect of fertilizer treatment is significant (P = 0.005) and accounts for 7.43% of the total variation in bacterial community. Soil nutrients (e.g., available K, total N, total P and organic matter) rather than pH showed significant correlation with the majority of abundant taxa. In conclusion, both fertilizer treatment and seasonal changes affect soil properties, microbial biomass and bacterial community structure. The application of NPK plus manure organic-inorganic fertilizer may be a sound fertilizer practice for sustainable food production.

An unbiased DNA extraction protocol is necessary for analysis of genetic diversity, particularly, of genes in complex environmental samples by nucleic acid techniques. In the present study, three manual extraction methods and two commonly used commercial kits, which were accompanied by two DNA purification strategies, were compared based on cell lysis efficiency, DNA and humic acid yields, PCR amplification and denaturing gradient gel electrophoresis (DGGE) analysis. The results show that in spite of higher cell lysis efficiencies of the two commercial kits, the purified DNA yields were only one-third of that obtained by the two manual methods of FTSP (Freeze-thaw-SDS-Protein K) and FTSPP (Freeze-thaw-SDS-Protein K-Polyvinylpolypyrrolidone). The purified DNA from all five methods was pure enough for successful PCR and real-time PCR amplifications in the presence of 1 μg μL(-1) BSA. However, the FTSPP extraction method with DNA purification by a Wizard(®) kit yielded the largest number of 16S rRNA gene copies and ribotypes or bands in DGGE profiles, which indicated a superiority over the other four methods. The development of this optimized DNA extraction and purification method may provide a valuable tool for further molecular analysis of compost.

Fusaricidins produced by Paenibacillus polymyxa are lipopeptide antibiotics with outstanding antifungal activity. In this study, the whole gene cluster responsible for fusaricidin biosynthesis ( fusA) was isolated and identified from the cDNA library of one biocontrol agent P. polymyxa SQR-21 (SQR-21). MALDI-TOF MS analysis confirmed that SQR-21 could produce four kinds of fusaricidins: A, B, C, and D. A central promoter that drove the transcription of fusGFEDCBA was revealed by mapping of the fus promoter region by 5′ deletions. The disruption of fusA in SQR-21 led to the abolishment of fusaricidin production and antifungal activity. The direct interaction between a potential regulator, AbrB, and the promoter region of fus gene cluster was confirmed by electrophoretic mobility shift assays. One abrB disruption mutant showed significantly higher antifungal activity compared with the wild type. These results revealed a pathway for the transcriptional regulation of the fus gene cluster in P. polymyxa. [ABSTRACT FROM AUTHOR]

Bacterium djl-6, capable of degrading carbendazim, was isolated by continuous enrichment culture originating from carbendazim-treated soil. The isolate was identified as Rhodococcus sp. according to its phenotypic features, physiologic and biochemical characteristics, and phylogenetic analysis. The strain could use carbendazim as sole carbon or nitrogen source. It showed a high average degradation rate of 55.56 mg · L−1 · d−1 in M9 medium amended with carbendazim. High-pressure liquid chromatography–mass spectrometry (HPLC-MS) analysis showed the presence of 2-aminobenzimidazole, benzimidazole, and an unknown metabolite with molecular ions (M+) of m/z 104.8 and 118.5. The degradation in the isolate djl-6 seems to be initiated with the cleavage of the methyl carbemate side chain, resulting in the formation of 2-aminobenzimidazole and benzimidazole. This is the first report of the intermediates benzimidazole and 2-aminobenzimidazole found together in the culture filtrate of pure bacterium. [ABSTRACT FROM AUTHOR]

• An ionically and chemically crosslinked PHEAA/CS DN hydrogels with tunable mechanical properties was successfully prepared. • The hybrid DN hydrogels have high tensile strength (3.8 MPa), fast self-recovery ability and excellent fatigue resistance. • The destruction and reconstruction of the networks in DN hydrogel was proved and theorized. • The hybrid DN hydrogels have excellent antifouling and antibacterial properties called "repelling and killing" effect. Hydrogels with good mechanical properties are promising for various applications. In this work, a simple yet effective method for preparing a novel double-network hydrogel was reported. First, nonfouling polymer, poly(N- (2-hydroxyethyl)acrylamide) (PHEAA), was crosslinked through covalent bonds. Antibacterial polysaccharide, chitosan (CS), was then crosslinked by chelation between the N- glucosamine units on the CS and citrate or sulfate ions. The poly(N- (2-hydroxyethyl)acrylamide)/chitosan double-network hydrogels (PHEAA/CS DN hydrogels) exhibited high tensile strength (3.8 MPa), strong elastic modulus (0.6 MPa). And the dynamic ionic crosslinking in CS network provided the DN gels with fast self-recovery ability as well as excellent fatigue resistance. Furthermore, the mechanical properties of the DN gels were enhanced after stretching and relaxing because of the molecular orientation and reconstruction of chitosan network. More importantly, the hydrogels have excellent antifouling and antibacterial properties, which is called "repelling and killing", making them competitive candidates for applications in the biomedical field. [ABSTRACT FROM AUTHOR]

Soil microorganisms play an essential role in the redistribution of soil aggregate sizes due to the microenvironmental changes. Yet, little is known regarding how individual microbial taxa within different-sized aggregates respond to agronomic practice. This study integrated physical, chemical, and molecular techniques (i.e., high-throughput DNA sequencing and qPCR) to assess the influence of corn-tobacco rotation on the soil microbial community at the soil microenvironment scale, i.e., within mega- (>2 mm), macro- (0.25–2 mm) and micro-aggregate (<0.25 mm) fractions. The soil samples (0–20 cm) analyzed in this study originated from corn and tobacco, which were cultivated under three different fertilization regimes. The results demonstrate that corn-tobacco rotation substantially impacted the distribution of aggregate sizes, and the shift in soil microbial communities associated with soil aggregates was related to changes in soil total carbon (TC), the C/N ratio and pH. The indicator microbial taxa (i.e., those were sensitive to crop rotation) varied with aggregate size. When compared with tobacco soil, the corn soil showed higher relative abundances of probably more copiotrophic taxa across large-sized aggregates, also with more bacteria in mega-aggregates and more fungi in macro-aggregates. Changes in total microbial communities associated with mega- and macro-aggregates in response to crop rotation were driven mainly by alterations in bacterial and fungal communities, respectively. Overall, the results of this study demonstrate that soil aggregate size strongly affected the microbial community composition on agricultural fields, promoting the differential responses between bacteria and fungi to crop rotation in specific size of aggregates. [ABSTRACT FROM AUTHOR]