A comparative metagenomic and spectroscopic analysis of soils from an international point of entry between the US and Mexico.

The Paso del Norte region is characterized by its dynamic industries and active agriculture. Throughout the years, urban and agricultural soils from this region have been exposed to xenobiotics, heavy metals, and excess of hydrocarbons. In this study, samples of urban [domestic workshops (DW)] and agricultural-intended (AI) soils from different sites of Ciudad Juárez, Mexico were evaluated for their fertility, element content, and microbial diversity. Chemical analyses showed that nitrites, nitrates, P, K, Mg, and Mn were predominantly higher in AI soils, compared to DW soils (p ≤ 0.05). The composition of soil microbial communities showed that Proteobacteria phylum was the most abundant in both soils (67%, p ≤ 0.05). In AI soils, Paracoccus denitrificans was reduced (p ≤ 0.05), concurring with an increment in nitrates, while the content of nitrogen was negatively correlated with the rhizobium group (r = -0.65, p ≤ 0.05). In DW soils, the Firmicutes phylum represented up to ~25%, and the relative abundance of Proteobacteria strongly correlated with a higher Cu content (r = 0.99, p ≤ 0.0001). The monotypic genus Sulfuricurvum was found only in oil-contaminated soil samples. Finally, all samples showed the presence of the recently created phylum Candidatus saccharibacteria. These results describe the productivity parameters of AI soils and its correlation to the microbial diversity, which are very important to understand and potentiate the productivity of soils. The data also suggest that soils impacted with hydrocarbons and metal(oid)s allow the reproduction of microorganisms with the potential to alleviate contaminated sites.