Insights into microbial involvement in desert varnish formation retrieved from metagenomic analysis

Naama Lang-Yona, Stefanie Maier, Dorothea S. Macholdt, Isabell Müller-Germann, Petya Yordanova, Emilio Rodriguez-Caballero, Klaus P. Jochum, Abdullah Al-Amri, Meinrat O. Andreae, Janine Fröhlich-Nowoisky, Bettina Weber, Isabell Mueller-Germann

Research output: Contribution to journalArticlepeer-review


Desert varnishes are dark rock coatings observed in arid environments and might resemble Mn-rich coatings found on Martian rocks. Their formation mechanism is not fully understood and the possible microbial involvement is under debate. In this study, we applied DNA metagenomic Shotgun sequencing of varnish and surrounding soil to evaluate the composition of the microbial community and its potential metabolic function. We found that the α diversity was lower in varnish compared to soil samples (p value < 0.05), suggesting distinct populations with significantly higher abundance of Actinobacteria, Proteobacteria and Cyanobacteria within the varnish. Additionally, we observed increased levels of transition metal metabolic processes in varnish compared to soil samples. Nevertheless, potentially relevant enzymes for varnish formation were detected at low to insignificant levels in both niches, indicating no current direct microbial involvement in Mn oxidation. This finding is supported by quantitative genomic analysis, elemental analysis, fluorescence imaging and scanning transmission X-ray microscopy. We thus conclude that the distinct microbial communities detected in desert varnish originate from settled Aeolian microbes, which colonized this nutrient-enriched niche, and discuss possible indirect contributions of microorganisms to the formation of desert varnish.

Original languageEnglish
Pages (from-to)264-271
Number of pages8
JournalEnvironmental Microbiology Reports
Issue number3
StatePublished - Jun 2018

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Agricultural and Biological Sciences (miscellaneous)


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