## 2 Bioconsolidation Techniques
### Microbial Cells in Bioconsolidation Treatments
The latter implies they are not accessible to other research groups for reproducibility or to undertake new studies. This is important for further research and also in terms of intellectual property rights. Access to microbial strains possessing desired properties such as biocalcifying activity can be exploited by patented biotechnological processes. [PERSON] [55] suggested that the most studied bacterium for MICP over the years was _Sporosarcina pasteurii_. [PERSON] et al. [56] found that this genus was the most abundant biocalcifying organism isolated from limestone cave samples, but many other species have been isolated, both by these authors and others (for example, [57]); since microorganisms with this ability are common, it is clear that there is a wide range of species available from which to choose the most appropriate for the particular stone and environment. The stone environment is often considered oligotrophic and thus isolation strategies of lithic-dwelling microorganisms should consider the design and use of low nutrient media [58; 59]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Organisms** & **Isolation Source/ Habitat** & **Testing Method** & **Reference** \\ \hline \multirow{3}{*}{_Pencilillium chrysogenum_ CS1 (Cement Sludge)} & Isolated from Cement sludge & \multirow{3}{*}{Comentation in sand column to form sandstone; compressive strength} & \multirow{3}{*}{[53]} \\  & Isolated during the course of the study & & \\ \hline \multirow{3}{*}{_Colletotrichum acutatum_} & Diseased fruit crops & & \\  & Isolated during the course of the study & & XRD \\ \hline \multirow{3}{*}{_Pencilomyces inflatus,_ _Plectosphaerella cuicumerina._} & Slalcite growing from a concrete ceiling & \multirow{3}{*}{SEM and XRD of carbonate crystals associated with hyphal growth in broth} & \multirow{3}{*}{[55]} \\  & Isolated during the course of the study & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \hline \hline \end{tabular} Abbreviations: FTIR: Fourier transform infra-red spectroscopy; XRD: X-ray diffraction analysis; SEM: scanning electron microscopy; EDS: energy dispersive X-ray spectroscopy.  
\end{table} 
Table 1: Cont. Not only is the type of culture medium an important factor in the design of strategies aiming to retrieve a large number of relevant bacteria from environmental samples, but it is also necessary to use a range of isolation methods, including plating, enrichment and micromanipulation or extinction-culturing, either alone or in combination [60]. This combined approach is imperative to obtain more pure cultures of potentially dominant microorganisms derived from the stone environment, allowing a significant advance in the study of the physiology of carbonatogenic microorganisms and the environmental determinants of their activity and abundance. Pure physiologically characterized novel bacterial isolates are a prerequisite for biotechnological development across economic sectors and markets, ranging from those traditional ones already used in the food or pharmaceutical industries to emerging sectors such as cultural heritage protection. The relatively new techniques of metagenomics and metabolomics could also play a role in selecting suitable organisms. [PERSON] et al. [61], using next generation sequencing (NGS), identified the presence of known carbonatogenic bacteria like _Arthobacter_ in the populations colonizing the medieval church of San Leonardo di Siponto in Italy. 16S rRNA and functional gene analyses could show the carbonatogenic potential of metabolic pathways linked to the appropriate biogeochemical cycles. For metabolomics to be successfully applied to the discovery of new potentially useful organisms, however, it is necessary to better understand the biochemical processes involved in carbonatogenesis. Earlier genetic studies have, for example, used mutants impaired in CaCO\({}_{3}\) precipitation to indicate a link between biomineralization, fatty acid metabolism, altered phospholipid membrane composition and surface properties [8; 62; 63; 64; 31].