Trichocoleus desertorum isolated from Negev desert petroglyphs: Characterization, adaptation and bioerosion potential

Abstract

The Negev petroglyphs are considered valuable cultural heritage sites, but unfortunately, they are exposed to deterioration processes caused by anthropogenic and natural forces. Despite the many studies that have already pointed to the role of cyanobacteria in biogenic rock weathering, the knowledge involved in the process is still lacking. In this study, a cyanobacterial strain was isolated from the Negev Desert petroglyphs aiming to reveal its involvement in geochemical cycles and in the weathering processes of the rock substrate. The strain was characterized using morphological, molecular, and microscopic studies. The morphological research revealed a green-bluish, bundle-forming filamentous strain characterized by trichomes embedded in a common sheath. A combination of Nanopore and Illumina sequencing technologies facilitated the assembly of a near-complete genome containing 5,458,034 base pairs. A total of 5027 coding sequences were revealed by implementing PROKKA software. Annotation of five replicas of the 16S ribosomal RNA genes revealed that the Negev cyanobacteria isolate is closely (99.73 %) related to Trichocoleus desertorum LSB90_MW403957 isolated from the Sahara Desert, Algeria. The local strain was thus named Trichocoleus desertorum NBK24 CP116619. Several gene sequences that code for possible environmental adaptation mechanisms were found. Our study also identified genes for membrane transporters involved in the exchange of chemical elements, suggesting a possible interaction with rock minerals. Microscopic observations of T. desertorum NBK24 CP116619 infected onto calcareous stone slabs under laboratory conditions demonstrated the effect of the isolated cyanobacteria on stone surface degradation. In conclusion, the findings of this study further our understanding of terrestrial cyanobacterial genomes and functions and highlight the role of T. desertorum NBK24 CP116619 in stone weathering processes. This information may contribute to the creation of efficient restoration strategies for stone monuments affected by cyanobacteria.