The catE gene of Bacillus licheniformis M2-7 is essential for growth in benzopyrene, and its expression is regulated by the Csr system

Abstract

Benzopyrene is a high molecular weight polycyclic aromatic hydrocarbon with highly recalcitrant and develops carcinogenic effects. CsrA is a conserved regulatory protein, which controls the translation and stability of its target transcripts, having negative or positive effects depending on the target mRNAs. It is known that Bacillus licheniformis M2-7 has the ability to grow and survive in concentrations of hydrocarbons as benzopyrene, which prompted in part by CsrA, as it occurs in the presence of gasoline.However, there are a few studies that reveal the genes involved in that process. In order to know the involved genes in the Bacillus licheniformis M2-7 degradation pathway, the plasmid pCAT-sp containing a mutation in the catEgen was constructed and used to transform B. licheniformis M2-7 and generate the CAT1 strain. We determined the capacity of the mutant B. licheniformis(CAT1) to grow in the presence of glucose and benzopyrene as a carbon source. We observed that CAT1 strain presented an increase in growth in the presence of glucose, but a statistically considerable decrease in the presence of benzopyrene with respect to the wild strain M2-7. Also we demonstrated that the Csr system regulates its expression positively since it was observed that the expression of the gene in the mutant strain LYA12 (M2-7 csrA:: Sp, SpR) decreased considerably with respect to the wild strain. This allowed to characterize the metabolic pathway that Bacillus licheniformis M2-7 implements in the presence of benzopyrene.