Phytoremediation is an attractive alternative to excavating and chemically treating contaminated soils. Certain plants can directly bioremediate by sequestering and/or transforming pollutants, but plants may also enhance bioremediation by promoting contaminant-degrading microorganisms in soils. In this study, we used high-throughput sequencing of bacterial 16S rRNA genes and the fungal internal transcribed spacer (ITS) region to compare the community composition of 66 soil samples from the rhizosphere of planted willows (Salix spp.) and six unplanted control samples at the site of a former petrochemical plant. The Bray-Curtis distance between bacterial communities across willow cultivars was significantly correlated with the distance between fungal communities in uncontaminated and moderately contaminated soils but not in highly contaminated (HC) soils (>2000 mg kg(-1) hydrocarbons). The mean dissimilarity between fungal, but not bacterial, communities from the rhizosphere of different cultivars increased substantially in the HC blocks. This divergence was partly related to high fungal sensitivity to hydrocarbon contaminants, as demonstrated by reduced Shannon diversity, but also to a stronger influence of willows on fungal communities. Abundance of the fungal class Pezizomycetes in HC soils was directly related to willow phylogeny, with Pezizomycetes dominating the rhizosphere of a monophyletic cluster of cultivars, while remaining in low relative abundance in other soils. This has implications for plant selection in phytoremediation, as fungal associations may affect the health of introduced plants and the success of co-inoculated microbial strains. An integrated understanding of the relationships between fungi, bacteria and plants will enable the design of treatments that specifically promote effective bioremediating communities.

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Fungal endophytes associated with medicinal plants have potential role to promote plant growth through different mechanisms. However, the biological and ecological roles of fungal endophytes still totally unexplored. In this study, three different fungal endophytes were isolated from the medicinal plant of Asclepias sinaica and identified as Penicillium chrysogenum Pc_25, Alternaria alternata Aa_27 and the third fungal strain was described as sterile hyphae Sh_26. It was recorded that, these endophytes had various ability to produce several extracellular enzymes including amylase, pectinase, cellulase, gelatinase, xylanase and tyrosinase. Their antimicrobial activities against different specific test organisms were investigated as well. In addition, both endophyte isolates i.e. Sh_26 and Aa_27 were found to promote root growth higher than Pc_25 and control treatments. These fungal isolates had a considerable impact on plant growth parameters including root elongation as a result of ammonia and IAA production. ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University.

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We assessed the indigenous arbuscular mycorrhizal fungi (AMF) community structure from the roots and associated soil of Plantago major (plantain) plants growing on sites polluted with trace metals (TM) and on unpolluted sites. Uncontaminated and TM-contaminated sites containing As, Cd, Cu, Pb, Sn and Zn were selected based on a survey of the TM concentration in soils of community gardens in the City of Montréal. Total genomic DNA was extracted directly from these samples. PCR followed by denaturing gradient gel electrophoresis (PCR-DGGE), augmented by cloning and sequencing, as well as direct sequencing techniques, was all used to investigate AMF community structure. We found a decreased diversity of native AMF (assessed by the number of AMF ribotypes) in soils and plant roots harvested from TM-polluted soils compared with unpolluted soils. We also found that community structure was modified by TM contamination. Various species of Glomus, Scutellospora aurigloba and S. calospora were the most abundant ribotypes detected in unpolluted soil; ribotypes of G. etunicatum, G. irregulare/G. intraradices and G. viscosum were found in both polluted and unpolluted soils, while ribotypes of G. mosseae and Glomus spp. (B9 and B13) were dominant in TM-polluted soils. The predominance of G. mosseae in metal-polluted sites suggests the tolerance of this species to TM stress, as well as its potential use for phytoremediation. These data are relevant for our understanding of how AMF microbial communities respond to natural environments that contain a broad variety of toxic inorganic compounds and will substantially expand our knowledge of AMF ecology and biodiversity.

Desert plants are able to survive under harsh environmental stresses inherent to arid and semiarid regions due to their association with bacterial endophytes. However, the identity, functions, and the factors that influence the association of bacterial endophytes with desert plants are poorly known. These bacterial endophytes can be used as an untapped resource to favor plant growth and development in agro-ecosystems of arid regions. The present study is therefore focused on the isolation and identification of bacterial endophytes from two native medicinal plants (Fagonia mollis Delile and Achillea fragrantissima (Forssk) Sch. Bip.) growing spontaneously in the arid region of the South Sinai (Egypt), and characterization of their plant growth promoting (PGP) traits. Thirteen putative bacterial endophytes were isolated from the leaves of both plant species and characterized for their plant growth promoting abilities using molecular and biochemical approaches, as well as greenhouse trials. Selected endophytic bacterial strains were applied to maize plants (Zea mays L. var. Single cross Pioneer 30K08) to further evaluate their PGP abilities under greenhouse conditions. Isolated bacterial strains have variable plant growth promoting activities. Among these activities, isolated bacterial endophytes have the efficacy of phosphate solubilizing with clear zones ranging from 7.6 ± 0.3 to 9.6 ± 0.3 mm. Additionally, the obtained bacterial endophytes increased the productivity of indole acetic acid (IAA) in broth media from 10 to 60 µg·mL−1 with increasing tryptophan concentration from 1 to 5 mg·mL−1. Bacillus and Brevibacillus strains were frequently isolated from the leaves of both plant species, and had significant positive effects on plant growth and shoot phosphorus (P) and nitrogen (N) contents. Results suggest that these endophytes are good candidates as plant growth promoting inoculants to help reduce chemical input in conventional agricultural practices and increase nutrient uptake and stress resilience in plant species.