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

## TL;DR

This study develops a method to track the survival of a pollution-eating bacterium in soil using fluorescence tagging, aiding its use in bioremediation.

## Contribution

A novel fluorescence tagging method for monitoring Streptomyces sp. MC1 survival in contaminated soils during bioremediation.

## Key findings

- Fluorescence tagging via intergeneric conjugation was successfully applied to Streptomyces sp. MC1.
- Optimal conjugation conditions included low spore and donor concentrations with MgCl2.
- Tagged bacteria survived for 28 days in co-contaminated soil, demonstrating viability for bioremediation.

## Abstract

Streptomyces 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 Streptomyces sp. MC1 during bioremediation, we introduced fluorescence tagging and a selectable marker into this strain by intergeneric conjugation from Escherichia coli. Conjugation assays were performed using two E. coli strains (ET12567/pUZ8002 or S17-1) and Streptomyces 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 Streptomyces sp. MC1 spores and E. coli 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 Streptomyces sp. MC1 successfully demonstrated survival over 28 days. Our results, combined with the availability of the Streptomyces sp. MC1 genome sequence, will facilitate further characterization of this strain’s features and accelerate its development for bioremediation applications.