Potential for plant growth promotion by a consortium of stress‐tolerant 2,4‐dinitrotoluene‐degrading bacteria: isolation and characterization of a military soil

• Published in: Microbial biotechnology 2014-07, Vol.7 (4), p.294-306
• Main Authors: Thijs, Sofie, Weyens, Nele, Sillen, Wouter, Gkorezis, Panagiotis, Carleer, Robert, Vangronsveld, Jaco
• Format: Article
• Language: English
• Subjects: Arabidopsis; Bacillus; Bacteria - growth & development; Bacteria - isolation & purification; Bacteria - metabolism; Biotransformation; Burkholderia; Dinitrobenzenes - metabolism; Microbial Consortia; Military Personnel; Plant Development; Plant Roots - growth & development; Plant Roots - microbiology; Pseudomonas; Ralstonia; Soil Microbiology; Soil Pollutants - metabolism; Stress, Physiological; Variovorax
• ISSN: 1751-7915; 1751-7915
• DOI: 10.1111/1751-7915.12111

Summary The presence of explosives in soils and the interaction with drought stress and nutrient limitation are among the environmental factors that severely affect plant growth on military soils. In this study, we seek to isolate and identify the cultivable bacteria of a 2,4‐dinitrotoluene (DNT) contaminated soil (DS) and an adjacent grassland soil (GS) of a military training area aiming to isolate new plant growth‐promoting (PGP) and 2,4‐DNT‐degrading strains. Metabolic profiling revealed disturbances in Ecocarbon use in the bare DS; isolation of cultivable strains revealed a lower colony‐forming‐unit count and a less diverse community associated with DS in comparison with GS. New 2,4‐DNT‐tolerant strains were identified by selective enrichments, which were further characterized by auxanography for 2,4‐DNT use, resistance to drought stress, cold, nutrient starvation and PGP features. By selecting multiple beneficial PGP and abiotic stress‐resistant strains, efficient 2,4‐DNT‐degrading consortia were composed. After inoculation, consortium UHasselt Sofie 3 with seven members belonging to Burkholderia, Variovorax, Bacillus, Pseudomonas and Ralstonia species was capable to successfully enhance root length of Arabidopsis under 2,4‐DNT stress. After 9 days, doubling of main root length was observed. Our results indicate that beneficial bacteria inhabiting a disturbed environment have the potential to improve plant growth and alleviate 2,4‐DNT stress. Cultivable bacteria obtained from a 2,4‐DNT contaminated shooting range were compared them to those obtained from a nearby non‐contaminated site and investigated for their capacity to metabolize Eco‐carbon sources, total cfu‐counts on non selective media and their diversity. 2,4‐DNT clearly had a negative impact. New 2,4‐DNT tolerant strains were identified by selective enrichments which were further characterized by auxanography for 2,4‐DNT use, resistance to drought stress, cold, nutrient‐starvation and PGP‐features. Some of these strains were studied for their capacity for chemotaxis, transformation of 2,4‐DNT and their ability to reduce phytotoxicity and improve growth of Arabidopsis plants exposed to this contaminant.