A sulfide-sensor and a sulfane sulfur-sensor collectively regulate sulfur-oxidation for feather degradation by Bacillus licheniformis

Abstract

Bacillus licheniformis MW3 degrades bird feathers. Feather keratin is rich in cysteine, which is metabolized to produce hazardous sulfide and sulfane sulfur. A challenge to B. licheniformis MW3 growing on feathers is to detoxify them. Here we identified a gene cluster in B. licheniformis MW3 to deal with these toxicity. The cluster contains 11 genes: the first gene yrkD encodes a repressor, the 8th and 9th genes nreB and nreC encode a two-component regulatory system, and the 10th and 11th genes encode sulfide: quinone reductase (SQR) and persulfide oxygenase (PDO). SQR and PDO collectively oxidize sulfide and sulfane sulfur to sulfite. YrkD sensed sulfane sulfur to derepress the 11 genes. The NreBC system sensed sulfide and further amplified the transcription of sqr and pdo. The two regulatory systems synergistically controlled the expression of the gene cluster, which was required for the bacterium to grow on feather. The findings highlight the necessity of removing sulfide and sulfane sulfur during feather degradation and may help with bioremediation of feather waste and sulfide pollution.

In the Alphaproteobacterium Hyphomicrobium denitrificans SoxR Serves a Sulfane Sulfur-Responsive Repressor of Sulfur Oxidation

“…The physiological processes involving the various sulfane sulfur-responsive regulators characterized so far [ 34 , 35 , 69 , 70 , 71 , 72 ] differ fundamentally from those controlled by SoxR. The former mainly regulate stress responses, sense intracellular and extracellular reactive sulfur species, and ensure upregulation of H 2 S oxidation genes for the purpose of detoxification, i.e., they control the removal of excess sulfide and sulfane sulfur, thus contributing to cell survival in the presence of external reactive sulfur species.…”

“…Clearly, this difference inspires future research that should also include a detailed inspection of the conformational changes triggered by the formation of a sulfur bridge and resulting in the detachment of SoxR from its target DNA (Figure 10). The physiological processes involving the various sulfane sulfur-responsive regulators characterized so far [34,35,[69][70][71][72] differ fundamentally from those controlled by SoxR. The former mainly regulate stress responses, sense intracellular and extracellular reactive sulfur species, and ensure upregulation of H2S oxidation genes for the purpose of detoxification, i.e., they control the removal of excess sulfide and sulfane sulfur, thus contributing to cell survival in the presence of external reactive sulfur species.…”