Persulphide-responsive transcriptional regulation and metabolism in bacteria

Hydrogen sulphide (H2S) impacts on bacterial growth both positively and negatively; it is utilized as an electron donor for photosynthesis and respiration, and it inactivates terminal oxidases and iron-sulphur clusters. Therefore, bacteria have evolved H2S-responsive detoxification mechanisms for survival. Sulphur assimilation in bacteria has been well studied, and sulphide:quinone oxidoreductase, persulphide dioxygenase, rhodanese and sulphite oxidase were reported as major sulphide-oxidizing enzymes of sulphide assimilation and detoxification pathways. However, how bacteria sense sulphide availability to control H2S and sulphide metabolism remains largely unknown. Recent studies have identified several bacterial (per)sulphide-sensitive transcription factors that change DNA-binding affinity through persulphidation of specific cysteine residues in response to highly reactive sulphur-containing chemicals and reactive sulphur species (RSS). This review focuses on current understanding of the persulphide-responsive transcription factors and RSS metabolism regulated by RSS sensory proteins.

Crop adaptation to air pollution ii. tolerance to so2 stress is regulated by oxidative and antioxidative characteristics and sulphur assimilation

Sulphur dioxide (SO2) and particulate matter (PM) are one of the major air pollutants emerging out of the industrial development and human activities. Plants exhibit differential sensitivity to SO2 pollution and its effects on plant growth can be both direct and/or indirect. We have earlier reported that a high SO2 stress contributes toward the S-nutrition of crops. The SO2 enriched environment significantly improved the activity of serine transacetylase (SAT) in all the experimental crops, however, the activity of O-acetylserine (thiol) lyase (OAS-TL) was enhanced chiefly in wheat but not in chickpea and barley. Further, the relative tolerance of crops to the particulate and gaseous pollutants was related to a lower level of superoxide and H2O2 radicals and lipid peroxidation and a higher level of antioxidants such as ascorbic acid and peroxidase activity. Relative tolerance of crops to the particulate and gaseous pollutants was related to a lower oxidative stress and a higher anti-oxidative defence that elevated SO2 contributes to S-nutrition of crops however, the threshold value of phyto-toxicity need to be determined across the crops.