Abundance and Activity of 16S rRNA,AmoAandNifHBacterial Genes During Assisted Phytostabilization of Mine Tailings

Abstract

Mine tailings in semiarid regions are highly susceptible to erosion and are sources of dust pollution and potential avenues of human exposure to toxic metals. One constraint to revegetation of tailings by phytostabilization is the absence of microbial communities critical for biogeochemical cycling of plant nutrients. The objective of this study was to evaluate specific genes as in situ indicators of biological soil response during phytoremediation. The abundance and activity of 16S rRNA, nifH, and amoA were monitored during a nine month phytostabilization study using buffalo grass and quailbush grown in compost-amended, metalliferous tailings. The compost amendment provided a greater than 5-log increase in bacterial abundance, and survival of this compost-inoculum was more stable in planted treatments. Despite increased abundance, the activity of the introduced community was low, and significant increases were not detected until six and nine months in quailbush, and unplanted compost and buffalo grass treatments, respectively. In addition, increased abundances of nitrogen-fixation (nifH) and ammonia-oxidizing (amoA) genes were observed in rhizospheres of buffalo grass and quailbush, respectively. Thus, plant establishment facilitated the short term stabilization of introduced bacterial biomass and supported the growth of two key nitrogen-cycling populations in compost-amended tailings.

Bacterial Rhizoplane Colonization Patterns of Buchloe dactyloides Growing in Metalliferous Mine Tailings Reflect Plant Status and Biogeochemical Conditions

“…Pore water chemistry and plant establishment were monitored during the course of the experiment as explained previously [7,34]. Here we examine bacterial rhizoplane colonization of plants harvested at 3, 6, and 9 months during acidification of metalliferous pyritic tailings.…”

“…The tailings are characterized by low organic carbon content (0.14 g kg −1 ), hypersalinity (EC 6.5–9.0 ds m −1 ), poor substrate structure [6,7], and the complete absence of vegetation. Both a controlled 1-year greenhouse mesocosm study [7,34] and a 7-year field trial [31] have been conducted to develop phytostabilization strategies for heavy metal containment at this site. This study examines plant-microbe relationships for buffalo grass plants grown in IKMHHS tailings from both the mesocosm study and field trial, as described below.…”

“…Buffalo grass plants were harvested to assess bacterial rhizoplane colonization patterns from a previously established controlled, greenhouse mesocosm experiment [7,34]. The mesocosm experiment was designed to evaluate phytostabilization of IKHMSS mine tailings in a controlled system undergoing defined acidification.…”

“…Pore water subsamples collected at 0, 3, 6, and 9 months were analyzed for pH, dissolved organic carbon (DOC), dissolved nitrogen (DN), and electrical conductively (EC) as described previously [7,34]. …”

Plant-Mediated Changes in Soil N-Cycling Genes during Revegetation of Copper Mine Tailings

“…To rehabilitate soil biogeochemical functions in mine tailings using the revegetation strategy, it is necessary to concert changes in physical, mineralogical, geochemical, and biological properties to support sustainable plant communities (Huang et al, 2012;Zornoza et al, 2015). Therein, the development of Ncycling microbial communities and their functions is one of the most important aspects of the ecological development of mine tailings (Nelson et al, 2015). However, research on this subject is greatly lacking.…”