## 3 Results
### Characterization of Biological Colonization
In S6a isolate number 4, _Microobacterium flaves  
is Gram-positive, non-motile, soil aerobe bacterium, forming pale yellow colonies, and showing a tolerance to 5-10% of NaCl [57]. In S\({}_{6a}\) isolate number 5, _Arthobacter parietis_ cells are Gram-positive, short rods and cocci (diameter 0.8-1 \(\upmu\)m) occurring in pairs or clusters. They are non-motile and do not form endospores. Colonies are yellow-orange, round with entire margins, of low convexity, opaque, and smooth. The optimal temperature for growth is 22-30 \({}^{\circ}\)C. Growth occurs in a medium with 15% NaCl [54]. Finally, the closest relative of isolate number 6 is _Noviherbspirillum suwonense_. However, due to the low sequence identity (98.36%), the bacterium may belong to the genus _Noviherbspirillum_ but may represent a previously uncharacterized species. _N. suwonense_ is a Gram-negative bacterium, aerobic, motile, mesophilic, and forms rod-shaped cells. It was isolated from air samples collected in Suwon, Republic of Korea. The colonies on R2A agar were convex, circular, and pale orange with entire margins. Growth occurs at 2% NaCl [58]. The samples from S\({}_{11}\) showed a light green alteration phenotype, and the morphological analysis by optical microscope identified the presence of _Chlorella_ sp. Additionally, optical images of the fractured samples suggest an endolithic growth (Figure 4(d\({}_{1}\))), whereas epilithic growth is visible where the painting layer is detached. Moreover, although the cultural approach on BBM and BG-11 agar did not yield results, changing the culture conditions (by exposing the Petri dishes for 48 h in a dark condition) allowed a wide pink colonization to grow. Their molecular identification is ongoing. This result was further confirmed by SEM analysis (Figure 4(d\({}_{4}\))), in which the presence of bacterial cells was visible. The Raman analysis of cultures from the isolated colonies corresponding to S\({}_{6a}\) isolation numbers (3), (5) and S\({}_{11}\), characterized by a pink color, has revealed bands with features typical of carotenoids, with characteristic bands corresponding to C=C stretching around 1520 cm\({}^{-1}\), C\(-\)C stretching near 1150 cm\({}^{-1}\), and C=CH bending near 1000 cm\({}^{-1}\)[59]. Carotenoids, present both in prokaryotes and eukaryotes, represent a diverse group of compounds that are produced as metabolic by-products in various microorganisms and are distinguished by a polyene skeletal backbone [60]. Among these, \(\beta\)-carotene is frequently detected in many microbial species. The Raman bands (Figure 5A) obtained on isolated colonies S\({}_{6a}\) (3) and (5) show peaks at 1527, 1157, and 1104 cm\({}^{-1}\) associable to \(\beta\)-carotene, although the presence of a carotenoid mixture cannot be excluded [59]. No spectrum was detected in the measurements performed on the isolated colonies corresponding to S\({}_{6a}\) number (1). In the case of isolated cultures S\({}_{11}\) (found in the green sample as a potential satellite bacterium), a different carotenoid, associable with bacterioruberin, is shown by the Raman band (Figure 5A). Bacterioruberin is distinguished from \(\beta\)-carotene by the length of its conjugated chain. Specifically, the conjugated isoprenoid chain of bacterioruberin is composed of 13 C=C units (compared to 11 in \(\beta\)-carotene) [59; 61]. This difference is noted in the Raman spectrum, where the peak at 1506 cm\({}^{-1}\) is attributed to the C=C stretching band of bacterioruberin, and the bands at 1151 and 1003 cm\({}^{-1}\)are assigned to the C-C and C-CH stretches, respectively (Figure 5A). Bacterioruberin is a red-orange xanthophyll pigment responsible for the coloration observed in halophilic organisms and is considered a key carotenoid in halophilic archaea [59; 62].