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Background: Compounds derived from hydrocarbons are essential for industry and our daily life; however, accidents such as spills or leaks occur regularly, causing severe environmental impact. Therefore, bacteria isolated from an oil well were characterized to assess their potential in the degradation of hydrocarbons under individual and consortium treatments. Soil samples, from a well contaminated with hydrocarbons in Tabasco, Mexico, were collected. The biosurfactant, emulsifying capacity, hemolytic activity, ionic charge, and biofilm formation were analyzed. Results: Most of the isolated strains belong to the genus Pseudomonas according to 16S rDNA sequencing. In general, emulsification percentages greater than 60% in the different substrates evaluated were observed. In addition, these strains can form biofilms, and those selected to integrate the microbial consortia present anionic surfactants. Three strains were selected to evaluate the degradation potential of soil contaminated with hydrocarbons from the same site where the bacteria were isolated in a microcosm. The microbial consortia degraded the contaminated soil more efficiently than the strains were evaluated alone, mainly the three bacteria consortia, with percentages greater than 80%. Conclusions: This study shows that, despite belonging to the same species, bacterial strains' metabolic capacity for the expression of surfactant compounds, emulsifiers, and the formation of biofilms are different. Furthermore, the more structured a community is, the greater the biodegradation process that occurs when bacteria act individually on the substrate. Therefore, this study demonstrates that strains of the same species integrated microbial consortia improve the bioremediation processes of hydrocarbons in contaminated soils. [ABSTRACT FROM AUTHOR]

BACKGROUND: Deterioration by microbial activity is common in the built cultural heritage, where phototrophic microorganisms are primary colonizers that form complex communities associated with heterotrophic microorganisms. Therefore, this article analyses the antiphototrophic effect of ZnO and CaZn2(OH)6·2H2O (CZ) nanoparticles (NPs) on three limestone lithotype coupons (Xcambo, red limestone and shellstone). The nanomaterials were obtained via sol–gel (SG), hydrothermal (HT) and mechanochemical (MS) routes and characterized using powder X‐ray diffraction and scanning electron microscopy. Two concentrations of NPs (5000 and 10 000 μg mL−1) were applied to the coupons; afterwards, phototrophic microorganisms isolated from Chichén‐Itzá, Yucatan were inoculated. The percentage of protection was calculated with ImageJ software, and chromatic parameters were measured to identify visible changes in the stones. RESULTS: The results show differences in the protective effect and color variations depending on the nanomaterials and phototrophic microorganisms applied in the limestone coupons. CZ and ZnO protect more than 72% on the surface of shellstone and Xcambo except for ZnO‐SG in shellstone. The growth of Gloeocapsa sp. in red limestone with ZnO‐SG and CZ‐SG was equal to or greater than that of the control without NPs. In general, the NPs protect the limestone surface against phototrophic microorganisms up to 10% more than commercial algaecide. The coupons treated with ZnO‐HT and CZ‐HT have greater protection against biofilm formation than other coatings. CONCLUSIONS: In general, the coatings show a higher antiphototrophic protection than the controls, mainly the CZ‐HT coatings, with better results at lower concentration. Therefore, these nanomaterials could be used to inhibit the formation of biofilms on built cultural heritage. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Halotolerant bacteria with biosurfactant (BS) and bioemulsifiers (BE) activity can coexist in Karstic sinkholes with marine influence. Two sinkholes in the Yucatan peninsula were selected to isolate bacteria with BE and BS activity stable in NaCl. The optimal time, the effect of nitrogen and carbon source in the medium, and the conditions (agitation, pH and salinity) for the production of BS and BE compounds in planktonic and sessile (stimulate the formation of biofilms in cell roller) culture were determined. Eighty strains showed the highest emulsification activity (EI24 ≥ 50%) and drop-collapse ≥ 4 mm. 87% of the strains are moderately halotolerant, and 21% bordered the limit of extreme halotolerance. Twenty-four strains maintained or improved their BS and BE activity under salinity conditions at 5% and 10%, being the most active genera Bacillus, Paenibacillus and Lysinibacillus, identified by sequencing of the 16S rRNA gene. The results show that the nitrogen source positively affects the BS and BE activity, regardless of the type of culture. The sessile culture markedly stimulated BS activity with significant differences. However, we did not find a greater influence on the culture conditions. The results suggest that halotolerant bacteria from sinkholes could be implemented in bioremediation and other biotechnological applications. [ABSTRACT FROM AUTHOR]

The assembly of fungal communities on stone materials is mainly influenced by the differential bioreceptivity of such materials and environmental conditions. However, little is known about the role of fungal interactions in the colonization and establishment of fungal species. We analyzed the effects of intra- and interspecific interactions between 11 species of fungi in oligotrophic and copiotrophic media and on limestone coupons. In a previous study, these species were the most frequently isolated in the epilithic biofilms of limestone walls exposed to a subtropical climate. In the culture media, we found a greater frequency of intra- and interspecific inhibitory effects in the oligotrophic medium than in the copiotrophic medium. On the limestone coupons, all fungi were able to establish; however, the colonization success rate varied significantly. Cladosporium cladosporioides had a less extensive colonization in isolation (control) than in dual interactions (coexistence) with other species. Phoma eupyrena exhibited the highest colonization success rate and competitive dominance among all tested species. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses revealed that Pestalotiopsis maculans and Paraconiothyrium sp. produced calcium oxalate crystals during their growth on coupon surfaces, both in isolation and in dual interactions. Our results demonstrate that interactions between abundant fungal species influence the fungal colonization on substrates, the biomineralization and the fungal community assemblage growing in limestone biofilms. [ABSTRACT FROM AUTHOR]

Abstract: Little is known about the dynamics of succession of fungi on limestone exposed in subtropical environments. In this study, the colonization of experimental blocks of compact and porous limestone by a fungal community derived from natural biofilms occurring on Structure X from the archaeological site of Becán (México), was studied using a cultivation-dependent approach after short-term (9 m) exposure in order to provide a preliminary insight of the colonization process under seminatural conditions. Microbial growth seen as the change of colour of stone surfaces to black/dark green was more abundant on the porous limestone. There was a fairly clear difference in microbial colonization between the onset of the experiment and the 6th month for both limestone types, but no significant increase in the colonization of coupons occurred between months 6 and 9. This could be related to the low rainfall expected for this period, corresponding to the dry season. A total of 977 isolates were obtained. From these, 138 sterile fungi were unidentified, 380 could only be assigned to the order Sphaeropsidales; the remaining isolates (459) were grouped into 27 genera and 99 different species. Nearly all detected fungal species belonged to the Ascomycota (90 %). Rare taxa (species represented by one to three isolates) included the recently described genus Elasticomyces, several species of genera Hyalodendron, Monodyctis, Papulospora, Curvularia, and Septoria. Other taxa were Minimedusa and Gliomastix luzulae, which have not been previously described for stone environments. Abundant fungi included several species of the common genera Cladosporium, Alternaria, and Taeniolella typical for a range of habitats. Succession of populations was observed for certain taxa, this shift in the composition of fungal communities was more evident in porous limestone. After 6 m of exposure, species of the genera Scolecobasidium, Hyalodendron, and Taeniolella were predominant, while after 9 m, the predominant species belonged to the genera Curvularia and Alternaria, particularly on porous stone. These results suggest that Curvularia and Alternaria replaced other fungi, due to a higher tolerance towards low levels of available water during the dry season. Higher levels of water within the porous stone, keep longer periods of microbial activity, minimizing the impact of desiccation. This study contributes to understand the diversity of fungal communities in stone surfaces in subtropical settings and the dynamics of colonization on limestone. [Copyright &y& Elsevier]