Bacteriaassociated with arbuscular mycorrhizal fungi within roots of plants growing in a soil highly contaminated with aliphatic and aromatic petroleum hydrocarbons

Abstract

Arbuscular mycorrhizal fungi (AMF) belong to phylum Glomeromycota, an early divergent fungal lineage forming symbiosis with plant roots. Many reports have documented that bacteria are intimately associated with AMF mycelia in the soil. However, the role of these bacteria remains unclear and their diversity within intraradical AMF structures has yet to be explored. We aim to assess the bacterial communities associated within intraradical propagules (vesicles and intraradical spores) harvested from roots of plant growing in the sediments of an extremely petroleum hydrocarbon-polluted basin. Solidago rugosa roots were sampled, surface-sterilized, and microdissected. Eleven propagules were randomly collected and individually subjected to whole-genome amplification, followed by PCRs, cloning, and sequencing targeting fungal and bacterial rDNA. Ribotyping of the 11 propagules showed that at least five different AMF OTUs could be present in S. rugosa roots, while 16S rRNA ribotyping of six of the 11 different propagules showed a surprisingly high bacterial richness associated with the AMF within plant roots. Most dominant bacterial OTUs belonged to Sphingomonas sp., Pseudomonas sp., Massilia sp., and Methylobacterium sp. This study provides the first evidence of the bacterial diversity associated with AMF propagules within the roots of plants growing in extremely petroleum hydrocarbon-polluted conditions.

Petroleum hydrocarbon contamination, plant identity and arbuscular mycorrhizal fungal (AMF) community determine assemblages of the AMF spore‐associated microbes

“…Recently, Iffis et al . () identified fungi belonging to Chytridiomycota , as well as bacteria belonging mainly to the genera Sphingomonas , Pseudomonas , Massilia , and Methylobacterium from vesicles and intraradical spores of AMF collected within Solidago rugosa roots growing in the extremely petroleum hydrocarbon‐polluted basin on the same site used in our study. However, the roles of the microorganisms associated with AMF and the mechanisms that govern their interactions remain poorly explored particularly in highly stressful conditions such as polluted environments.…”

“…The observed AMF-associated microbial communities are in line with what was observed previously by other authors both in in vitro conditions and in agricultural soils (Hijri et al, 2002;Mirabal Alonso et al, 2008;Scheublin et al, 2010;Lecomte et al, 2011;Lace et al, 2015;Battini et al, 2016), although much larger bacterial and fungal communities were found here owing to the use of high throughput sequencing. Recently, Iffis et al (2014) identified fungi belonging to Chytridiomycota, as well as bacteria belonging mainly to the genera Sphingomonas, Pseudomonas, Massilia, and Methylobacterium from vesicles and intraradical spores of AMF collected within Solidago rugosa roots growing in the extremely petroleum hydrocarbon-polluted basin on the same site used in our study. However, the roles of the microorganisms associated with AMF and the mechanisms that govern their interactions remain poorly explored particularly in highly stressful conditions such as polluted environments.…”

“…An additional 50 spores sample was harvested from each plant and they were subjected to electron scanning microscopy using a Quanta 200 3D SEM (FEI, Burlington, MA), as described in Iffis et al (2014).…”

“…As fungi that extend their hypha into the rhizosphere and the surrounding soil, AMF not only interact with plants, but also with a myriad of soil microbes. Several in vivo and in vitro studies have demonstrated that a large range of bacterial species are living on the surface and/or inside mycelia, spores and intraradical propagules of AMF (Bianciotto et al, 1996;Scheublin et al, 2010;Lecomte et al, 2011;Cruz and Ishii, 2012;Iffis et al, 2014;Agnolucci et al, 2015). Some fungal taxa belonging to Ascomycota and Chytridiomycota have also been reported to be associated with AMF mycelia (Paulitz and Menge, 1984;Hijri et al, 2002;Iffis et al, 2014).…”

The Arbuscular Mycorrhizal Fungus Funneliformis mosseae Alters Bacterial Communities in Subtropical Forest Soils during Litter Decomposition

“…In addition, Welc et al (2010) reported that AMF mycelium could suppress the soil bacterial community. Furthermore, many specific bacterial taxa are highly associated with AMF as they colonize and live on the surface of the hyphae (Cruz and Ishii, 2011; Iffis et al, 2014). For example, certain Proteobacteria and Firmicutes taxa have been documented as co-existing with AMF (Bonfante and Anca, 2009; Scheublin et al, 2010; Lecomte et al, 2011).…”