Fate of Functional Bacterial and Eukaryotic Community Regulated by Earthworms during Vermicomposting of Dewatered Sludge, Studies Based on the 16S rDNA and 18S rDNA Sequencing of Active Cells

DNA sequencing of active cells involved in vermicomposting can clarify the roles of earthworms in regulating functional microorganisms. This study aimed to investigate the effect of earthworms on functional microbial communities in sludge by comparing biodegradation treatments with and without earthworms. PCR and high throughput sequencing based on pretreatment of propidium monoazide (PMA) were used to detect the changes in active bacterial 16S rDNA and eukaryotic 18S rDNA during vermicomposting. The results showed that the nitrate in sludge vermicomposting and control were significantly different from day 10, with a more stable product at day 30 of vermicomposting. Compared with the control, the Shannon indexes of active bacteria and eukaryotes decreased by 1.9% and 31.1%, respectively, in sludge vermicompost. Moreover, Proteobacteria (36.2%), Actinobacteria (25.6%), and eukaryotic Cryptomycota (80.3%) were activated in the sludge vermicompost. In contrast, the control had Proteobacteria (44.8%), Bacteroidetes (14.2%), Cryptomycota (50.00%), and Arthropoda (36.59%). Network analysis showed that environmental factors had different correlations between active bacterial and eukaryotic community structures. This study suggests that earthworms can decrease the diversity of bacterial and eukaryotic communities, forming a specific-functional microbial community and thus accelerating organic matter decomposition during vermicomposting of dewatered sludge.

COMPARATIVE PERFORMANCE OF CARBOXYMETHYL CELLULOSE AS SUBSTRATE FOR ELECTRICITY GENERATION IN MICROBIAL FUEL CELL: A REVIEW

Due to the global energy crisis in the world and no proper utilization of renewable and non-renewable resources, different experimental design approaches and substrates have been employed to produce bioelectricity in an MFC. The major substrate that has been tried to focus in this review paper is carboxymethyl cellulose (CMC). Carboxymethyl cellulose is an important factor in Microbial fuel cell with great importance in industry. No known enzyme is directly involved in the oxidation/reduction of CMC, however, carboxymethyl cellulases attack, specifically CMC. Moreover, our knowledge on electrochemically active bacteria is inadequate. Although, knowledge about electrochemically active bacteria is inadequate, distinct cellulose degrading bacteria have been isolated for their higher cellulase activity. Similarly, pure bacterial cultures and co-cultures have been extensively used in degrading CMC for power and electricity generation. CMC concentration and effect of different substitution factors also play an important role in voltage generation. Different ways to make enzymatic electrode for current production using CMC fed reactor were also discussed in this study. This review gives an overview about the current developments of CMC being used as substrate in MFCs and encourages to develop more efficient processes for improved bioelectricity production in MFCs.

Diet-Related Alterations of Gut Bile Salt Hydrolases Determined Using a Metagenomic Analysis of the Human Microbiome

The metabolism of bile acid by the gut microbiota is associated with host health. Bile salt hydrolases (BSHs) play a crucial role in controlling microbial bile acid metabolism. Herein, we conducted a comparative study to investigate the alterations in the abundance of BSHs using data from three human studies involving dietary interventions, which included a ketogenetic diet (KD) versus baseline diet (BD), overfeeding diet (OFD) versus underfeeding diet, and low-carbohydrate diet (LCD) versus BD. The KD increased BSH abundance compared to the BD, while the OFD and LCD did not change the total abundance of BSHs in the human gut. BSHs can be classified into seven clusters; Clusters 1 to 4 are relatively abundant in the gut. In the KD cohort, the levels of BSHs from Clusters 1, 3, and 4 increased significantly, whereas there was no notable change in the levels of BSHs from the clusters in the OFD and LCD cohorts. Taxonomic studies showed that members of the phyla Bacteroidetes, Firmicutes, and Actinobacteria predominantly produced BSHs. The KD altered the community structure of BSH-active bacteria, causing an increase in the abundance of Bacteroidetes and decrease in Actinobacteria. In contrast, the abundance of BSH-active Bacteroidetes decreased in the OFD cohort, and no significant change was observed in the LCD cohort. These results highlight that dietary patterns are associated with the abundance of BSHs and community structure of BSH-active bacteria and demonstrate the possibility of manipulating the composition of BSHs in the gut through dietary interventions to impact human health.

Viability study of ice nucleating active bacteria (Pseudomonas Syringae) in freezing cloud droplets

<p>The plant pathogenic bacteria<em> Pseudomonas syringae</em> are capable of inducing ice nucleation at low supercooling due to the presence of INA proteins on the outer cell membrane. Moreover, <em>P. Syringae</em> was shown to survive long-range transport in cold airmasses and redeposition to the earth’s surface with rain and snow. Thus, the life cycle of <em>P. syringae</em> is tightly coupled to the water cycle in the Earth's ecosystem. Understanding the survival mechanism of <em>P. Syringae</em> exposed to atmospheric cloud conditions is a prerequisite for characterization of bacteria as atmospheric ice nucleating particles, describing its dissemination paths and potential role in the spread of plant-pathogenic disease.</p><p>In this contribution we report on the viability study of ice nucleating active bacteria in freezing cloud droplets. To investigate the bacterial viability, water droplets containing several bacterial cells with low and high concentration of INA proteins are levitated in an electrodynamic balance (EDB) and cooled down to a temperature of -25°C. After freezing, the droplets are extracted from the EDB and the survival probability of the bacteria is determined by colony counting. A fluorescence stain and a high-speed video camera were used to visualize individual bacteria in the levitated droplets and to study their behavior during freezing.</p><p>The results have shown that the survival of bacteria depends on the freezing dynamics of bacteria-containing droplets (growth rate of ice in supercooled water). The <em>P. syringae</em> bacteria with high concentration of INA proteins are capable of inducing freezing at low supercooling and thus inhibit the growth rate of ice crystals, resulting in higher chance to survive the freezing. If high supercooling is achieved, the ice growth rate immediately after nucleation is very high and the survival probability is dramatically reduced.</p>