The research was carried out in collaboration with the company AFEPASA and involved the collection of soil samples from various locations with different pH and sulphur concentration characteristics. The samples were brought to the laboratory to isolate the bacterium and culture it on different media. Changes in the colour of the culture medium showed whether the microorganisms isolated from the soil samples had the ability to oxidise sulphur. Once the sulphur-oxidising ones had been selected, laboratory tests were carried out to determine which of them had the greatest capacity for plant growth enhancement. Then, in the next phase, greenhouse trials were conducted to determine their actual effect on plants, given that when the microorganisms are introduced to real crops, the results can differ from those obtained in the laboratory.<\/p>\n The research began with the intention of finding bacteria capable of oxidising sulphur or solubilising phosphorus, leading to the discovery of Variovorax palleresanus<\/em>, which oxidises sulphur. Furthermore, “it also presents associated bio-stimulant activities, such as the production of auxins \u2013 substances that regulate plant growth \u2013 and the synthesis of organic molecules that have a high affinity for iron (siderophores) and which activate the crop’s metabolism or act as antioxidants,” notes Cristina Comas, a researcher in the Nutrigenomics Research Group of the URV\u2019s Department of Biochemistry and Biotechnology, who is undertaking an industrial doctoral thesis jointly supervised by the URV and the company AFEPASA.<\/p>\n Field studies show that this bacterium improves plant metabolism and transforms soil sulphur into assimilable sulphates, and that its application increases crop yield by up to 30%, a very high figure for a bio-stimulant.<\/p>\n![\"\"](\"https:\/\/diaridigital.urv.cat\/wp-content\/uploads\/2026\/04\/IMG_3229-1024x768.jpg\")
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