Cyanobacterial Mats in Calcite-Precipitating Serpentinite-Hosted Alkaline Springs of the Voltri Massif, Italy

Abstract

(1) Background: Microbial communities in terrestrial, calcifying high-alkaline springs are not well understood. In this study, we investigate the structure and composition of microbial mats in ultrabasic (pH 10–12) serpentinite springs of the Voltri Massif (Italy). (2) Methods: Along with analysis of chemical and mineralogical parameters, environmental DNA was extracted and subjected to analysis of microbial communities based upon next-generation sequencing. (3) Results: Mineral precipitation and microbialite formation occurred, along with mat formation. Analysis of the serpentinite spring microbial community, based on Illumina sequencing of 16S rRNA amplicons, point to the relevance of alkaliphilic cyanobacteria, colonizing carbonate buildups. Cyanobacterial groups accounted for up to 45% of all retrieved sequences; 3–4 taxa were dominant, belonging to the filamentous groups of Leptolyngbyaceae, Oscillatoriales, and Pseudanabaenaceae. The cyanobacterial community found at these sites is clearly distinct from creek water sediment, highlighting their specific adaptation to these environments.

Local and global chemical shaping of bacterial communities by redox potential

“…The Alkaline Spring datasets represent water samples from serpentinizing systems associated with weathering of ultramafic peridotites. Positive correlations between Eh7 and Z C are exhibited by samples from the Voltri Massif, Italy (Kamran et al, 2021), which include two spring sites with different ranges of redox potential and a more oxidizing creek sample, samples from wells with different borehole depths in the Coast Range Ophiolite Microbial Observatory (CROMO), California, USA (Sabuda et al, 2020) and the Samail Ophiolite, Oman (Rempfert et al, 2017) (Fig. 4), and depth-resolved water samples from the Samail Ophiolite collected using a packer system (Nothaft et al, 2021).…”

The influence of microbial mats on travertine precipitation in active hydrothermal systems (Central Italy)

“…Samples were collected as described in Kamran et al (2021); they were refrigerated and kept frozen until further processing. Samples were processed for extraction of environmental DNA, amplification of 16S and 18S marker genes for Bacteria and Eukaryotes, Illumina next generation sequencing and sequencing data processing as described by von Hoyningen‐Huene et al (2019), Schulz et al (2019) and Kamran et al (2021). Raw reads were processed as described in Hoyningen‐Huene et al (2019) and, as a result, amplicon sequence variants (ASVs), which could be assigned to a taxon, were generated (Callahan et al, 2017).…”

“…Images were recorded with a Colour view III camera (Motic GmbH). Samples were collected as described in Kamran et al (2021); they were refrigerated and kept frozen until further processing. Samples were processed for extraction of environmental DNA, amplification of 16S and 18S marker genes for Bacteria and Eukaryotes, Illumina next generation sequencing and sequencing data processing as described by von Hoyningen‐Huene et al (2019), Schulz et al (2019) and Kamran et al (2021).…”

Comparative Metagenomics Highlight a Widespread Pathway Involved in Catabolism of Phosphonates in Marine and Terrestrial Serpentinizing Ecosystems

“…In most marine ecosystems, phosphonate could be synthesized by some phylotypes of Cyanobacteria and Thaumarchaeota ( 80 ), two groups also usually found in serpentinizing ecosystems. Nonetheless, their ecological importance was not discussed here due to their low abundance, despite their potential strong adaptation to this extreme environment ( 81 ). Therefore, we could not identify any microbial phosphonate producer in these metagenomes and, thus, a biological source of phosphonates.…”