Plant growth promoting endophytic bacteria have been identified as potential growth regulators of crops. Endophytic bacterium, Sphingomonas sp. LK11, was isolated from the leaves of Tephrosia apollinea. The pure culture of Sphingomonas sp. LK11 was subjected to advance chromatographic and spectroscopic techniques to extract and isolate gibberellins (GAs). Deuterated standards of [17, 17-²H₂]-GA₄, [17, 17-²H₂]-GA₉ and [17, 17-²H₂]-GA₂₀ were used to quantify the bacterial GAs. The analysis of the culture broth of Sphingomonas sp. LK11 revealed the existence of physiologically active gibberellins (GA₄: 2.97 ± 0.11 ng/ml) and inactive GA₉ (0.98 ± 0.15 ng/ml) and GA₂₀ (2.41 ± 0.23). The endophyte also produced indole acetic acid (11.23 ± 0.93 μM/ml). Tomato plants inoculated with endophytic Sphingomonas sp. LK11 showed significantly increased growth attributes (shoot length, chlorophyll contents, shoot, and root dry weights) compared to the control. This indicated that such phyto-hormones-producing strains could help in increasing crop growth.

The Photorhabdus temperata M1021 secretes toxic compounds that kill their insect hosts by arresting immune responses. Present study was aimed to purify the insecticidal and antimicrobial compound(s) from the culture extract of P. temperata M1021 through bioassay guided fractionation. An ethyl acetate (EtOAc) extract of the P. temperata M1021 exhibited 100% mortality in Galleria mellonella larvae within 72 h. In addition, EtOAc extract and bioactive compound 1 purified form the extract through to column chromatography, showed phenol oxidase inhibition up to 60% and 80% respectively. The analysis of ¹H and ¹³C NMR spectra revealed the identity of pure compound as “benzaldehyde”. The benzaldehyde showed insecticidal activity against G. mellonella in a dose-dependent manner and 100% insect mortality was observed at 108 h after injection of 8 mM benzaldehyde. In a PO inhibition assay, 4, 6, and 8 mM concentrations of benzaldehyde were found to inhibit PO activity about 15%, 42%, and 80% respectively. In addition, nodule formation was significantly (P < 0.05) inhibited by 4, 6, and 8 mM of benzaldehyde as compare to control. Moreover, benzaldehyde was found to have great antioxidant activity and maximum antioxidant activity was 52.9% at 8 mM benzaldehyde as compare to control. Antimicrobial activity was assessed by MIC values ranged from 6 mM 10 mM for bacterial strains and 8 mM to 10 mM for fungal strains. The results suggest that benzaldehyde could be applicable for developing novel insecticide for agriculture use.