Bacterial diversity and composition in major fresh produce growing soils affected by physiochemical properties and geographic locations

Abstract

Azo dyes and their intermediate degradation products are common contaminants of soil and groundwater in developing countries where textile and leather dye products are produced. The toxicity of azo dyes is primarily associated with their molecular structure, substitution groups and reactivity. To avoid contamination of natural resources and to minimize risk to human health, this wastewater requires treatment in an environmentally safe manner. This manuscript critically reviews biological treatment systems and the role of bacterial reductive and oxidative enzymes/processes in the bioremediation of dye-polluted wastewaters. Many studies have shown that a variety of culturable bacteria have efficient enzymatic systems that can carry out complete mineralization of dye chemicals and their metabolites (aromatic compounds) over a wide range of environmental conditions. Complete mineralization of azo dyes generally involves a two-step process requiring initial anaerobic treatment for decolorization, followed by an oxidative process that results in degradation of the toxic intermediates that are formed during the first step. Molecular studies have revealed that the first reductive process can be carried out by two classes of enzymes involving flavin-dependent and flavin-free azoreductases under anaerobic or low oxygen conditions. The second step that is carried out by oxidative enzymes that primarily involves broad specificity peroxidases, laccases and tyrosinases. This review focuses, in particular, on the characterization of these enzymes with respect to their enzyme kinetics and the environmental conditions that are necessary for bioreactor systems to treat azo dyes contained in wastewater.

Do composition and diversity of bacterial communities and abiotic conditions of spring water reflect characteristics of groundwater ecosystems exposed to different agricultural activities?

“…Differences between sampling sites regarding bacterial diversity and relative taxonomic abundance are furthermore confirmed by analysis of principal coordinates of bacterial OTU composition at the family level. We found a significant effect of sampling site on OTU composition ( R 2 = 0.311; p = 0.031; PERMANOVA), a result that was previously reported by others (Kaiser et al., ; Ma, Ibekwe, Yang, & Crowley, ; Tardy et al., ). However, the effect of sampling site on OTU composition was low (31%) in comparison to findings reported by Ma et al.…”

“…We found a significant effect of sampling site on OTU composition (R 2 = 0.311; p = 0.031; PERMANOVA), a result that was previously reported by others (Kaiser et al, 2016;Ma, Ibekwe, Yang, & Crowley, 2016;Tardy et al, 2015). However, the effect of sampling site on OTU composition was low (31%) in comparison to findings reported by Ma et al (2016) (50.9%), and is only apparent for samples collected at sampling site BB3 ( Figure 5). Hence, variation in community composition must be partly accounted for by variables other than sampling site.…”

“…However, the effect of sampling site on OTU composition was low (31%) in comparison to findings reported by Ma et al. () (50.9%), and is only apparent for samples collected at sampling site BB3 (Figure ). Hence, variation in community composition must be partly accounted for by variables other than sampling site.…”

Below‐ground connections underlying above‐ground food production: a framework for optimising ecological connections in the rhizosphere

“…However, it is important to acknowledge that soil organismal networks and their connections with plants are likely to depend on edaphic soil characteristics, such as soil texture and cation exchange capacity (Ma et al . ,b). The design of novel management approaches to promote networks will have to take into account context‐specificity and be tailored for different crops, soil types and climatic conditions.…”

High abundance of Ralstonia solanacearum changed tomato rhizosphere microbiome and metabolome

“…Soil microbial community is causally affected by abiotic factors such as physiochemical soil properties, pH, temperature, and soil moisture [13,25]. Whereas, little attention is given to the effects of soil metabolome on soil microbiota, such as sugars, organic acids, and other low molecular weight compounds, which can serve as available nutrients for soil microbes and can be responsible for the interactions of plants with rhizosphere microbes [26].…”