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The colonisation of stone by different organisms often leaves biodeterioration patterns (BPs) on the surfaces even if their presence is no longer detectable. Peculiar weathering patterns on monuments and rocks, such as pitting phenomena, were recognised as a source of information on past colonisers and environmental conditions. The evident inhibition areas for new bio-patinas observed on the marble blocks of the Caestia Pyramid in Rome, recognisable as tracks of previous colonisations, seem a source for developing new natural products suitable for restoration activities. To hypothesise past occurring communities and species, which gave rise to such BPs, we carried out both in situ observations and analyses of the rich historical available iconography (mainly photographs). Moreover, we analysed literature on the lichen species colonising carbonate stones used in Roman sites. Considering morphology, biochemical properties and historical data on 90 lichen species already reported in Latium archaeological sites, we suppose lichen species belonging to the genus Circinaria (Aspicilia s.l.) to be the main aetiological agent of such peculiar BPs. These results seem relevant to highlight the long-lasting allelopathic properties of some lichen substances potentially applicable as a natural product to control colonisation, improving the environmental and economical sustainability of stone restoration.

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The balance between lichen biodeterioration and bioprotection processes on stone surfaces depends on many variables and is crucial to understanding the role of lichens in biogeomorphology and their threat to stone heritage conservation. However, stones colonized by lichens have still been mostly examined in terms of affected volumes and physico-chemical modes of interactions, overlooking the overall effects on properties related to surface durability. In this study, the impact of lichen colonization patterns on Cortemilia sandstone was examined beneath thalli of three lichen species. Rock hardness, a proxy for rock durability, was measured at different depths from the surface using an Equotip hardness tester and compared to that of freshly cut surfaces and exposed surfaces uncolonized by lichens. Mineralogical analyses were performed by X-ray powder diffraction on rock beneath lichen colonization, in comparison with unweathered rock. Equotip analyses quantified a differential, species-specific decrease in stone hardness. This variability was related to differences in hyphal penetration patterns and, possibly, calcite (re-)precipitation. In particular, in the case of the species most impacting rock hardness, X-ray diffraction patterns of calcite showed a remarkable stability of crystallographic plane (01-12), known to be enhanced in the presence of organic chelants. These results confirm that decisions on lichen removal from stone surfaces should consider species-specific behaviour. Moreover, the innovative approach of measuring stone hardness variation in association with the analysis of biomineralization processes contributes to unveil the extension of the sphere of lichen interaction within the stone substrate beyond the limit of the hyphal penetration.

Il microbiota ambientale si sovrappone e stimola quello umano, contribuendo alla sua diversità. L'abbondanza e la varietà di microrganismi negli ambienti urbani è in continua diminuzione e negli ultimi anni l'ipotesi che la perdita di biodiversità porti ad una disregolazione immunitaria ed a conseguenti patologie croniche è sempre più evidente, visto che ambiente, microbiota umano e sistema immunitario sono sistemi che interagiscono costantemente. Mentre in Occidente gli studiosi si concentrano soprattutto su allergie e patologie respiratorie, i giapponesi indagano anche l'impatto sistemico del verde urbano e del paesaggio arboreo, dimostrandone l'indiscutibile effetto positivo sull'essere umano. Non è ancora chiaro però quale sia la funzione che, la variabilità della specie all'interno delle aree verdi, svolge sulla salute. L'ipotesi più interessante è legata al ruolo che i segnali microbici possono avere sul neurosviluppo fisiologico e sull'influenzare, a livello cerebrale, la programmazione dei comportamenti sociali. È di primaria importanza sensibilizzare ad una salute globale, partendo da un'educazione sistemica, che curi la plant blindness, evidenziando il valore della diversità biologica intesa come biblioteca della vita, capitale umano fondamentale per permettere l'adattamento ai cambiamenti e l'allenamento del sistema immunitario nella difesa da malattie esistenti e del progresso.