Exploration of novel ecological niches for pigmented bacteria with dye bioremediation potential

This study explores the comparative bioremediation potential of pigmented bacteria isolated from diverse ecological niches. Three distinct isolates were identified: Shewanella xiamenensis (U2f, from goldfish gills), Paracoccus sp. (THN1, a rose thorn endophyte), and Kocuria sp. (YC, an incidental laboratory isolate).

The isolated bacterial pigments were characterized using FTIR spectroscopy. The isolates and a developed bacterial consortium were evaluated for their ability to tolerate, decolorize, and degrade various synthetic dyes (Congo red, malachite green, bromophenol blue, methylene blue, and crystal violet). The resulting decolorization and biodegradation processes were validated using UV-Vis spectroscopic analysis, FTIR spectroscopy, and HPLC.

FTIR analysis indicated that the tan pigment from S. xiamenensis (U2f) was similar to melanin, the bright orange pigment from Paracoccus sp. (THN1) to astaxanthin, and the yellow pigment from Kocuria sp. (YC) to carotenoids. For bioremediation, S. xiamenensis (U2f) successfully decolorized the azo dye Congo red up to 200 mg/mL (70% efficiency) and tolerated levels up to 400 mg/mL. Conversely, Paracoccus sp. (THN1) and Kocuria sp. (YC) decolorized the triphenylmethane dye malachite green up to 200 mg/mL with 80-91% efficiency, tolerating concentrations up to 500 mg/mL. Notably, a consortium of Paracoccus sp. and Kocuria sp. achieved 100% degradation efficiency of malachite green (200 mg/mL) within 16 hours under shaking conditions.

These findings highlight the unique, niche-specific bioremediation capabilities of pigmented bacteria. The results demonstrate that targeted single isolates or designed consortia exhibit distinct and highly efficient degradation pathways against specific classes of toxic synthetic dyes, offering a promising tool for targeted environmental cleanup.