Calcite moonmilk of microbial origin in the Etruscan Tomba degli Scudi in Tarquinia, Italy

Angela Cirigliano,Rodolfo Negri,Maria Donatella Gentili,Maria Cristina Tomassetti,Barbara Cardazzo,Chiara Arrighi,Teresa Rinaldi,Francesco Mura,Marta Di Pietro,Cristina Mazzoni,Maria Lorella Maneschi

doi:10.1038/s41598-018-34134-y

Abstract

A white deposit covering the walls in the Stanza degli Scudi of the Tomba degli Scudi, Tarquinia, Italy, has been investigated. In this chamber, which is still preserved from any kind of intervention such as cleaning and sanitization, ancient Etruscans painted shields to celebrate the military power of the Velcha family. Scanning electron microscopy analysis has revealed the presence of characteristic nanostructures corresponding to a calcite secondary mineral deposit called moonmilk. Analysis of the microbial community identified Proteobacteria, Acidobacteria and Actinobacteria as the most common phyla in strong association with the moonmilk needle fibre calcite and nanofibers of calcium carbonate. Employing classical microbiological analysis, we isolated from moonmilk a Streptomyces strain able to deposit gypsum and calcium carbonate on plates, supporting the hypothesis of an essential contribution of microorganisms to the formation of moonmilk.

Highlights

The Tomba degli Scudi, dated to the late classical period[1], has been designated a UNESCO site since 2004 and is located in the Monterozzi necropolis of Tarquinia
We investigated the microbial activity in the burial chamber called Stanza degli Scudi, which was preserved from any intervention, such as cleaning or sanitization, during the restoration project of 2016 to 2017, and we describe for the first time the presence of a secondary calcite deposit, called moonmilk[5]
We found that the patina in the Stanza degli Scudi was distinct from the patina that was removed from the atrium chamber frescoes[4]; this difference prompted the decision to investigate samples from the burial chamber with scanning electron microscopy (SEM)

Summary

Introduction

The Tomba degli Scudi, dated to the late classical period (mid-IVth century B.C.)[1], has been designated a UNESCO site since 2004 and is located in the Monterozzi necropolis of Tarquinia This tomb is considered one of the largest tombs in Tarquinia, and its structure simulates an Etruscan house with a central atrium into which three chambers open[2,3] (Fig. 1a). We investigated the microbial activity in the burial chamber called Stanza degli Scudi, which was preserved from any intervention, such as cleaning or sanitization, during the restoration project of 2016 to 2017, and we describe for the first time the presence of a secondary calcite deposit, called moonmilk[5]. The analysis of the moonmilk sampled in the not-yet-restored burial chamber in the Tomba degli Scudi revealed that the deposit is intimately connected with a complex microbial community, containing, in particular, Actinobacteria species, supporting the hypothesis of a determinant biological contribution to this characteristic calcite formation[7,8,12,13,14,15,16,17]

Methods

Results

Conclusion