Profiling the bacterial diversity in historic limestone from Anazarbos archaeological site by advanced molecular and spectroscopic techniques

Abstract

The architectural remains as well as sculptures, mosaics, and other artifacts in the archaeological sites are mostly made of stone and susceptible to biodeterioration by microorganisms. Bacterial communities are known to have the most effective role in biological deterioration in stones. The ancient city of Anazarbos (Anavarza), chosen as the study area, is the 1st Degree Archaeological Site in the vicinity of Dilekkaya Village, Kozan District, about 70 km north of Adana. The microbiological, chemical, mineralogical, and microstructural properties of stone samples taken from different places were studied in this research. Samples were taken from i) where no deterioration occurred, ii) where different forms of deterioration were observed, iii) archaeological deposits, iii) archaeological deposits that came from deteriorated stone samples area. Spectroscopic, thermal, and microscopic techniques applied included: X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy-Energy Dispersive System (SEM-EDS), Thermogravimetric Analysis/Differential Thermal Analysis (TG/DTA). The bacterial biodiversity was analyzed by the application of Illumina-based next-generation sequencing methods. Results show intense biological colonisations with clay minerals on limestone surfaces. A patina of clay minerals was observed on newly excavated stone surfaces, while biological colonisations have not yet intensified. The metabarcoding analysis showed 15 bacterial phyla. The Proteobacteria and Actinobacteria were the most abundant phyla in both stones and archaeological deposits samples. Human activity (intensive agriculture, animal husbandry), accumulation of rainwater in excavated areas adversely affects stones, which leads to acceleration of biological deterioration in stones. Thus, all features of the site require multi-faceted studies prior to unearthing of archaeological remains.