Fusarium delphinoides (Ascomycota; Nectriaceae) is an indole-3-acetic acid (IAA) producing plant pathogen and a causal agent of wilt in chickpea. The IAA biosynthetic pathway in F. delphinoides strain GPK (FDG) was examined by analyzing metabolic intermediates and by feeding experiments. Gas chromatograph (GC) analysis of FDG culture filtrates showed the presence of metabolic intermediates of indole-3-pyruvic acid (IPyA), indole-3-acetamide (IAM), and tryptamine (TRA) pathways. The different IAA biosynthetic pathways were further confirmed by identifying the presence of different enzymes of these pathways. Substrate specificity study of aromatic amino acid aminotransferase revealed that the enzyme is highly specific for tryptophan (Trp) and α-ketoglutarate (α-kg) as amino group donor and acceptor, respectively. Furthermore, the concentration-dependent effect of exogenous IAA on fungal growth was established. Low concentration of exogenous IAA increases the fungal growth and at high concentration it decreases the growth of FDG.

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The present study describes the N,N-dimethylformamide (DMF)-induced oxidative stress in Paracoccus sp. SKG. The oxidative stress was evaluated by analysing membrane and periplasmic proteins and K+ efflux, as well as by monitoring the activities of antioxidant enzymes like catalase, superoxide dismutase (SOD) and glutathione S-transferase (GST). The exposure of bacterial cells to a higher concentration of DMF resulted in the modification of membrane fatty acid composition which is accompanied by K+ efflux. Further, this oxidative stress resulted in increased periplasmic protein which can be attributed to the induction of GST and methionine sulphoxide reductase (Msr) enzymes under solvent stress. Paracoccus sp. SKG is tolerant to high concentrations of DMF up to 6% (v/v) and its toxic effects. DMF concentration-dependent induction of GST and Msr activities advocates the significant role of these enzymes in the bacterial defence system. The present study provides information which helps us to understand the ROS scavenging machinery in bacteria. The high tolerance of Paracoccus sp. SKG to DMF can be efficiently explored for various bioremediation and biotransformation applications.