Fluorescence-Based Soil Survival Analysis of the Xenobiotic- and Metal-Detoxifying Streptomyces sp. MC1

<i>Streptomyces</i> sp. MC1, a bacterium isolated from an environment contaminated with organic and inorganic pollutants, can reduce chromium and degrade lindane, making it a promising candidate for bioremediation. However, a major challenge in bioremediation trials is monitoring bacteria survival in soil. To assess the survival of <i>Streptomyces</i> sp. MC1 during bioremediation, we introduced fluorescence tagging and a selectable marker into this strain by intergeneric conjugation from <i>Escherichia coli</i>. Conjugation assays were performed using two <i>E. coli</i> strains (ET12567/pUZ8002 or S17-1) and <i>Streptomyces</i> sp. MC1 (spores or mycelium). The integrative plasmid pSC001, carrying a gene encoding the monomeric green fluorescent protein (mGFP), was used. Various donor and recipient concentrations were tested and the presence of MgCl₂ or CaCl₂ during conjugation was also evaluated. Optimal conditions included low concentrations of both <i>Streptomyces</i> sp. MC1 spores and <i>E. coli</i> S17-1, with MgCl₂ in the medium. Exconjugants were analyzed, confirming plasmid site-specific integration and mGFP expression. In bioremediation assays with soils co-contaminated with Cr(VI) and lindane, fluorescence-tagged <i>Streptomyces</i> sp. MC1 successfully demonstrated survival over 28 days. Our results, combined with the availability of the <i>Streptomyces</i> sp. MC1 genome sequence, will facilitate further characterization of this strain's features and accelerate its development for bioremediation applications.