Halophilic microbial communities in deteriorated buildings

Abstract

Halophilic microorganisms were traditionally isolated from an aquatic environment. There has been little research conducted into halophiles inhabiting the terrestrial environment in which historic monuments deteriorate. Salt efflorescence deposited on the walls is an observed phenomenon on the surface of historic buildings, and would favour the growth of halophiles. However, some conditions have to be fulfilled in order for efflorescence to occur: (1) the presence of salts, (2) porosity, (3) a source of water. Salt crystallization influences the material structure (cracking, detachment, material loss), but active growth of halophilic microorganisms may be a serious threat to historic materials as well, leading to aesthetical changes such as coloured biofilms, orange to pink or even violet stains. This is why it is important to investigate halophilic microorganisms, taking into consideration both the environmental conditions they need to grow in, material characteristics they inhabit, the mechanisms they possess to cope with osmotic stress, and the methods that should be applied for their identification.

Factors Determining the Biodiversity of Halophilic Microorganisms on Historic Masonry Buildings

“…Only 8 out of the 50 tested samples had a pH of more than 8.5 (8.7–11.7). Environments with neutral pH enable the growth and proliferation of halophilic microorganisms (2), which suggests that the materials studied are suitable for their development. It is important to note that the pH of mortar is typically markedly higher, exceeding 11.…”

“…However, it is important to note that Halobacillus spp. are generally detected using culture-dependent methods, while the vast majority of halophilic bacteria may be detected using only molecular-based techniques (2, 30). The culture-independent analysis on brick samples (B1), with low salinity levels, not only identified members of the phylum Firmicutes , but also Proteobacteria and Actinobacteria members dominating the bacterial community.…”

“…The microorganisms identified were described as “halophiles” based on established knowledge and up-to-date literature (2, 11, 16, 19, 26, 31, 46). …”

Untargeted Metabolomics Approach in Halophiles: Understanding the Biodeterioration Process of Building Materials

“…Among them, salt crystallization, which forms as a result of salt migration with capillary water and subsequent drying out and precipitation, poses a serious threat to the materials' structure (Stryszewska, 2014 ). Moreover, salt-attacked monuments constitute a suitable habitat for halophilic microorganisms (Piñar et al, 2014 ; Adamiak et al, 2015 ; Otlewska et al, 2017 ) as these can easily adapt to salty micro-niches available on a building's surface, thus contributing to its structural destabilization (Saiz-Jimenez and Laiz, 2000 ; Piñar et al, 2009 ; Adamiak et al, 2015 , 2016 ).…”

Identification of Carotenoids and Isoprenoid Quinones from Asaia lannensis and Asaia bogorensis

“…On the other hand, in the heterotrophic microorganisms, biosynthesis of these compounds is relatively rare, and considered as a phenomenon associated with adaptability to the environment [ 2 ]. Occurrence of carotenoids have been reported in thermophilic ( Thermus thermophilus ), psychrotrophic ( Arthrobacter agilis ), radioresistant ( Rubrobacter radiotolerans ), halophilic ( Salinibacter ruber , Rubrobacter bracarensis , Halobacillus litoralis ), and other microorganisms [ 3 , 4 , 5 , 6 , 7 ]. These compounds are characterized by many biological activities.…”