Carbazole Degradation and Genetic Analyses of Sphingobium sp. Strain BS19 Isolated from Antarctic Soil

Abstract

The Antarctic region is facing a higher risk of hydrocarbon pollution due to increased human activities. Compounds such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic compounds available in fuel are highly stable and can reside in the environment for prolonged periods if left untreated. The isolation of native strains is needed to develop bioremediation applications suitable for Antarctica. Strain BS19 was isolated as heterocyclic compound carbazole-degrading bacterium from Antarctic soil through culture enrichment. The 16S rRNA gene sequences identified strain BS19 as a member of the Sphingonium genus. Strain BS19 could remove 75% of carbazole after 15 days of culture at 15 °C. Whole genome sequencing resulted in incomplete genomes of 4.77 Mb in 96 contigs with the lowest GC content among Sphingobium sp. strains. The analyses revealed car gene cluster and ant genes and cat gene cluster required for the complete metabolism of carbazole as a source of carbon and energy. The comparison of the car gene cluster showed a similarity to the car gene cluster of Novosphingobium KA1. The expression of the car gene cluster was confirmed with an RT-PCR analysis indicating the involvement of the predicted genes in carbazole degradation. The findings from this study could provide more insight into developing bioremediation applications and approaches for Antarctica and other cold environments.