The current study investigated the effects of Pseudomonas putida strain KT2440 on the drought tolerance of tomato plants during fruit maturation. Plants at the ripening stage of the mature-green were not watered for 20 days to promote drought stress. Concentrations of photosynthetic pigments were determined. Bacteria-soaked tomato plants (BSS) had higher levels of chlorophyll and carotenoids than non-soaked plants (DWS) under stress conditions. Compared to the DWS, stomatal conductance, lipid peroxidation, and hydrogen peroxide content in the BSS plants decreased under drought stress. The ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD) activities increased in BSS plants compared to DWS under drought stress. Furthermore, the number and weight of fruits in both DWS and BSS plants was reduced by the stress, but the reduction in BSS plants was lower than in DWS plants. These results showed that bacteria treatment conferred tolerance to drought stress in tomato plants by reducing the peroxidation extent of polar lipids (PLs), increasing photosynthetic pigment content, and activities of the antioxidant enzymes in the leaves. Therefore, P. putida KT2440 has supported high fruit yield under drought stress as a biotic tolerance elicitor for this plant stress.

A novel protease producing strain Bacillus sp. MK12 was isolated from the gut waste of Salmo trutta. After being enhanced production through optimization, extracellular alkaline protease of this strain (BMK12) was purified and partially characterized. Molecular weight was determined as 28 kDa by SDS-PAGE. The optimum temperature of the enzyme was 50°C, retained 98% of its activity at 60°C, and it was stable for 24 h at 40°C. BMK12 showed the maximal proteolytic activity at pH 8.0, and it was still highly active from pH 7.0 to 10.0. The inhibition of the activity with EDTA (1 mM) emphasized that BMK12 was a member of the metalloprotease family. The presence of oxidizing agent H₂O₂ (1%) strongly increased the activity of BMK12 and the enzyme also showed stability towards non-ionic surfactants and commercial detergents. The pH and thermal stability, the stability towards non-ionic surfactants and commercial detergents, and the removal of blood stains from cotton clothes with BMK12 would allow to use this enzyme in industrial applications.