Estimation by PLFA of Microbial Community Structure Associated with the Rhizosphere of Lygeum spartum and Piptatherum miliaceum Growing in Semiarid Mine Tailings

The objective of this study was to compare the microbial community composition and biomass associated with the rhizosphere of a perennial gramineous species (Lygeum spartum L.) with that of an annual (Piptatherum miliaceum L.), both growing in semiarid mine tailings. We also established their relationship with the contents of potentially toxic metals as well as with indicators of soil quality. The total phospholipid fatty acid (PLFA) amount was significantly higher in the rhizosphere soil of the annual species than in the rhizosphere soil of the perennial species. The fungal/bacterial PLFA ratio was significantly greater in the perennial species compared to the annual species. The fatty acid 16:1ω5c, the fungal/bacterial PLFA ratio and monounsaturated/saturated PLFA ratio were correlated negatively with the soluble contents of toxic metals. The cyc/prec (cy17:0 + cy19:0/16:1ω7 + 18:1ω7) ratio was correlated positively with the soluble contents of Pb, Zn, Al, Ni, Cd, and Cu. The results of the PLFA analysis for profiling microbial communities and their stress status of both the plant species indicate that perennial and annual gramineous species appear equally suitable for use in programmes of revegetation of semiarid mine tailings.