Microbial diversity and mineral composition of weathered serpentine rock of the Khalilovsky massif

Abstract

Endolithic microbial communities survive nutrient and energy deficient conditions while contributing to the weathering of their mineral substrate. This study examined the mineral composition and microbial communities of fully serpentinized weathered rock from 0.1 to 6.5 m depth at a site within the Khalilovsky massif, Orenburg Region, Southern Ural Mountains, Russia. The mineral composition includes a major content of serpentinite family (mostly consisting of lizardite and chrysotile), magnesium hydrocarbonates (hydromagnesite with lesser amounts of hydrotalcite and pyroaurite) concentrated in the upper layers, and clay minerals. We found that the deep-seated weathered serpentinites are chrysotile-type minerals, while the middle and surface serpentinites mostly consist of lizardite and chrysotile types. Microbial community analysis, based on 16S rRNA gene sequencing, showed a similar diversity of phyla throughout the depth profile. The dominant bacterial phyla were the Actinobacteria (of which unclassified genera in the orders Acidimicrobiales and Actinomycetales were most numerous), Chloroflexi (dominated by an uncultured P2-11E order) and the Proteobacteria (predominantly class Betaproteobacteria). Densities of several groups of bacteria were negatively correlated with depth. Occurrence of the orders Actinomycetales, Gaiellales, Solirubrobacterales, Rhizobiales and Burkholderiales were positively correlated with depth. Our findings show that endolithic microbial communities of the Khalilovsky massif have similar diversity to those of serpentine soils and rocks, but are substantially different from those of the aqueous environments of actively serpentinizing systems.

Distinct Microbial Communities in Adjacent Rock and Soil Substrates on a High Arctic Polar Desert

“…The relative abundances of Actinobacteria, FBP, and Deinococcus-Thermus were also higher in the lithic communities. The order Solirubrobacterales in Actinobacteria were the most abundant group observed in lithic niches, consistent with previous studies that have been observed in rocks ( Esposito et al, 2015 ; Khilyas et al, 2019 ). The 16S rRNA sequence of candidate division FBP was first reported from a lichen-dominated lithic habitat in Antarctica ( de la Torre et al, 2003 ), and Deinococcus-Thermus was also dominant in cryptoendolithic environments ( Cary et al, 2010 ).…”

The activity and functions of soil microbial communities in the Finnish sub-Arctic vary across vegetation types

“…Another active actinobacterial group abundant in these soils, order Solirubrobacterales, is not well characterized. These are mesophilic heterotrophs and based on 16S rRNA gene analysis, Solirubrobacterales have been encountered in diverse environments, such as weathered serpentine rock (Khilyas et al ., 2019), Antarctic soil (Chong et al ., 2012), agroecosystem soils (Shange et al ., 2012), Sphagnum peat bog (Ivanova et al ., 2016), and shrub-associated desert soil (Saul-Tcherkas & Steinberger, 2011). This wide range of habitats suggests that this order includes mixotrophic bacteria with the ability to survive in environments with fluctuating conditions, including temperature, nutrients, and UV radiation.…”

Balanced stochastic versus deterministic assembly processes benefit diverse yet uneven ecosystem functions in representative agroecosystems

“…For instance, Anaerolineaceae (the keystone taxa in one module uncorrelated with the measured enzymes) have been found to participate into methanogenesis (Liu et al ., 2020a). Also, Solirubrobacterales were largely detected in weathered serpentine rock, which implied a potential mineral cycling capacity (Khilyas et al ., 2019). Regardless, distributed ecosystem functions across soil microorganisms can increase the stability and sustainability of arable soils (Rolland et al ., 2012; Bhatt et al ., 2016), which is supported by the high stability of the community in the paddy agroecosystem (Table 5).…”