Molecular Techniques to Study Microbial Wastewater Communities

Abstract wastewater treatment (WT) is of major importance on modern cities, removing wastewater pollutants resultant from anthropogenic activities. The unique abilities of microbes to degrade organic matter, remove nutrients and transform toxic compounds into harmless products make them essential players in waste treatment. The microbial diversity determines the metabolic pathways that may occur in WT and quality of treated wastewater. Therefore, understanding WT microbial community structure, distribution, and metabolic functioning is essential for development and optimization of efficient microbial engineering systems. Since cultivation methods can only detect a small fraction of the microbial diversity, the use of culture-independent molecular methods has circumvented this issue, allowing unprecedented access to genes and genomes used for microbial composition and function evaluation. Traditional approaches like RAPD, DGGE, ARDRA, RISA, SSCP, T-RFLP, and FISH and modern approaches like microarray, qPCR, and metagenomics are essential techniques for identifying and depicting the total microbial community structure and their interaction with environmental and biotic factors. Thus, this review describes traditional and state of the art molecular techniques which provide insights into phylogenetic and functional activities of microbial assemblages in a WT system.

Multiple Effect of Different Plant Growth Promoting Microorganisms on Beans (Phaseolus vulgaris L. ) Crop

Abstract We evaluated the effect of combined Rhizobium tropici, Trichoderma asperellum and plant growth-promoting rhizobacteria (PGPR) in beans crop. The hypothesis that strains of T. asperullum, R. tropici and PGPR combined could improve growth, biomass accumulation and beans yield was tested under greenhouse and field conditions. The treatments consisted of control, mineral nitrogen application and inoculation, isolated and associated with the following microorganisms: Rhizobium tropici, Bacillus subtilis, Trichoderma asperellum and Burkholderia sp. 10N6. Results were evaluated by shoot dry weight (SDW) and root dry weight (RDW), number of nodules and yield components. In greenhouse environment all the microorganisms behaved similarly, and the treatments inoculated with Burkholderia sp. 10N6 (IBu) and R. tropici (IR) stood out regarding the production components. In field conditions the treatments IR and IRTBa presented the highest values of SDW and RDW. Our results suggest that inoculation with R. tropici, T. asperellum and PGPR may promote beans growth and bring benefits to shoot and root accumulation, increase the number of nodules as well as improve yield components, contributing to a sustainable agriculture.

Liming and Nitrogen Fertilization Effects on Soil Microbial Community in Long Term No-till

Abstract Soil management influences organic matter decomposition rates as well soil microbial community functional behavior. No-till (NT) is the most used management system by farmers due to its conservation practices and high productivity. The main objective of this study was to evaluate the impact of surface-applied lime, nitrogen (N) application, and black oat residues on soil microbial community of a Typic Hapludox under continuous NT. Therefore, soil chemical attributes, microbial biomass carbon, basal respiration, metabolic quotient, most probable number of diazotrophs, as well as bacterial functional analysis were performed. The effect of liming and N fertilization amendments inputs were saw in soil respiration and metabolic quotient measurements, showing them to be good indicators of soil quality. Further studies should be carried out in order to molecularly identify microbial communities present in soils with different liming and N fertilization management to evaluate the behavior of specific bacterial taxa under such conditions.