Different pioneer plant species select specific rhizosphere bacterial communities in a high mountain environment

Abstract

The rhizobacterial communities of 29 pioneer plants belonging to 12 species were investigated in an alpine ecosystem to assess if plants from different species could select for specific rhizobacterial communities. Rhizospheres and unvegetated soils were collected from a floristic pioneer stage plot at 2,400 m a.s.l. in the forefield of Weisskugel Glacier (Matsch Valley, South Tyrol, Italy), after 160 years of glacier retreat. To allow for a culture-independent perspective, total environmental DNA was extracted from both rhizosphere and bare soil samples and analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and Denaturing Gradient Gel Electrophoresis (DGGE). ARISA fingerprinting showed that rhizobacterial genetic structure was extremely different from bare soil bacterial communities while rhizobacterial communities clustered strictly together according to the plant species. Sequencing of DGGE bands showed that rhizobacterial communities were mainly composed of Acidobacteria and Proteobacteria whereas bare soil was colonized by Acidobacteria and Clostridia. UniFrac significance calculated on DGGE results confirmed the rhizosphere effect exerted by the 12 species and showed different bacterial communities (P < 0.05) associated with all the plant species. These results pointed out that specific rhizobacterial communities were selected by pioneer plants of different species in a high mountain ecosystem characterized by oligotrophic and harsh environmental conditions, during an early primary succession.

Microbial communities and primary succession in high altitude mountain environments

“…A first insight into the bacterial communities associated with different environmental matrices showed distinct variations among sites: Acidobacteria mostly found in mineral soil; Proteobacteria in sediments, biofilms, and lichens; Cyanobacteria on rock surfaces; and Firmicutes and Bacteroidetes in biofilms (Esposito et al 2013). Among the different environmental matrices of higher Matsch Valley, mineral soil showed the highest bacterial diversity in terms of taxa, even accounting for nitrogen fixing bacteria (Ciccazzo et al 2014b).…”

“…The study also highlighted a clear plant species effect on the associated rhizobacterial community. Different plant species selected specific rhizobacterial communities (Ciccazzo et al 2014b) mainly composed of Acidobacteria and Proteobacteria, while bare soils were characterized by a lower bacterial diversity with a predominance of Acidobacteria and Clostridia. Even the fungal communities of the rhizosphere of different alpine species were strictly related to the host identity for Taraxacum ceratophorum, Taraxacum officinale, and Polemonium viscosum (Becklin et al 2012).…”

Rhizosphere effect of three plant species of environment under periglacial conditions (Majella Massif, central Italy)

“…Indeed, in poorly developed soils of cold areas, the presence of vascular plants strongly modifies the soil properties and the structure and function of the soil microbial community (Yergeau et al, 2007). In this areas, rhizospheric processes resulting from soileplantemicrobes interactions may improve the ability of plants to overcome abiotic disturbances such as freezing, high soil daily and seasonal temperature excursions, freezeethaw and wetedry cycles, excessive drainage, and strongly oligotrophic conditions (e.g., Tscherko et al, 2004Tscherko et al, , 2005Edwards et al, 2006;Ciccazzo et al, 2014). The amount of energy supplied by the plants in form of exudates to rhizosphere heterotrophic microbial community is key for stimulating rhizospheric processes (Kuzyakov, 2002;Wookey et al, 2009;Ciccazzo et al, 2014;Jorquera et al, 2014).…”

Bacterial alkaline phosphomonoesterase in the rhizospheres of plants grown in Chilean extreme environments

“…Biogeography, plant species, and physicochemical soil properties can influence the composition of rhizosphere microbial communities (Edwards et al 2006;Fierer and Jackson 2006;Stegen et al 2009), including those of plants grown in hostile environments (Ciccazzo et al 2014;Massaccesi et al 2015). Differences in bacterial community composition were also observed in rhizosphere soils of plants from agroecosystems and extreme environments in Chile, such as Atacama Desert (Jorquera et al 2013(Jorquera et al , 2014Neilson et al 2012).…”