BackgroundTemperature is an important factor determining the performance and stability of the anaerobic digestion process. However, the microorganism-regulated mechanisms of temperature effects on the performance of anaerobic digestion systems remain further elusive. To address this issue, we investigated the changes in composition, diversity and activities of microbial communities under temperature gradient from 25 to 55 °C using 16S rRNA gene amplicon sequencing approach based on genomic DNA (refer to as “16S rDNA”) and total RNA (refer to as “16S rRNA”).ResultsMicrobial community structure and activities changed dramatically along the temperature gradient, which corresponded to the variations in digestion performance (e.g., daily CH4 production, total biogas production and volatile fatty acids concentration). The ratios of 16S rRNA to 16S rDNA of microbial taxa, as an indicator of the potentially relative activities in situ, and whole activities of microbial community assessed by the similarity between microbial community based on 16S rDNA and rRNA, varied strongly along the temperature gradient, reflecting different metabolic activities. The daily CH4 production increased with temperature from 25 to 50 °C and declined at 55 °C. Among all the examined microbial properties, the whole activities of microbial community and alpha-diversity indices of both microbial communities and potentially relative activities showed highest correlations to the performance.ConclusionsThe whole activities of microbial community and alpha-diversity indices of both microbial communities and potentially relative activities were sensitive indicators for the performance of anaerobic digestion systems under temperature gradient, while beta-diversity could predict functional differences. Microorganism-regulated mechanisms of temperature effects on anaerobic digestion performance were likely realized through increasing alpha-diversity of both microbial communities and potentially relative activities to supply more functional pathways and activities for metabolic network, and increasing the whole activities of microbial community, especially methanogenesis, to improve the strength and efficiency in anaerobic digestion process.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0491-x) contains supplementary material, which is available to authorized users.

No abstract

Methanosarcina barkeri (DSM 800) is a metabolically versatile methanogen and shows distinct metabolic status under different substrate regimes. However, the mechanisms underlying distinct transcriptional profiles under different substrate regimes remain elusive. In this study, based on transcriptional analysis, the growth performances and gene expressions of M. barkeri fed on acetate, H + CO, and methanol, respectively, were investigated. M. barkeri showed higher growth performances under methanol, followed by H + CO and acetate, which corresponded well with the variations of gene expressions. The α diversity (evenness) of gene expressions was highest under the acetate regime, followed by H + CO and methanol, and significantly and negatively correlated with growth performances. The gene co-expression analysis showed that "Energy production and conversion," "Coenzyme transport and metabolism," and "Translation, ribosomal structure, and biogenesis" showed deterministic cooperation patterns of intra- and inter-functional classes. However, "Posttranslational modification, protein turnover, chaperones" showed exclusion with other functional classes. The gene expressions and especially the relationships among them potentially drove the shifts of metabolic status under different substrate regimes. Consequently, this study revealed the diversity-related ecological strategies that a high α diversity probably provided more fitness and tolerance under natural environments and oppositely a low α diversity strengthened some specific physiological functions, as well as the co-responses of gene expressions to different substrate regimes.

No abstract

In this study, we evaluated the phylogenetic diversity of the cecal microbiota of 3-week-old ducklings fed three diets differing in metabolizable energy. The contents of the ceca were collected from ducklings of different groups. The ceca bacterial DNA was isolated and the V3 to V4 regions of 16S rRNA genes were amplified. The amplicons were subjected to high-throughput sequencing to analyze the bacterial diversity of different groups. The predominant bacterial phyla were Bacteroidetes (~65.67%), Firmicutes (~17.46%), and Proteobacteria (~10.73%). The abundance of Bacteroidetes increased and that of Firmicutes decreased with increasing dietary energy level. The diversity decreased (Simpson diversity index and Shannon diversity index) with the increase in dietary energy level, but the richness remained constant. Notably, Brachyspira bacteria were detected with a very high relative abundance (4.91%) in ceca of ducks fed a diet with 11.30 MJ/kg metabolizable energy, suggesting that low energy content may affect their colonization in cecum.

No abstract

No abstract