Characterization of medicinal plant-associated biocontrol Bacillus subtilis (SSL2) by liquid chromatography-mass spectrometry and evaluation of compounds by in silico and in vitro methods

Abstract

This study explores the antimicrobial properties of bioactive secondary metabolites extracted from the medicinal plant (Solanum surattense)-associated Bacillus subtilis strain SSL2. The secondary metabolites were extracted from B. subtilis (SSL2) using ethyl acetate, acetone, butanol, chloroform and methanol solvents. The crude extract was tested against two wilt causing pathogens: Ralstonia solanacearum and Fusarium oxysporum. The results revealed that the ethyl acetate extract has maximum inhibition against both the pathogens tested in this study. Furthermore, liquid chromatography-mass spectrometry (LC-MS) analysis of ethyl acetate extract identified 80 different compounds based on mass-to-charge ratio, database difference, resolution of mass spectrum and so on. Among the 80 compounds, citrulline (m/z?=?158.0917), chloramphenicol (m/z?=?195.075) and carnitine (m/z 162.11) were further selected based on m/z ratio for in silico and in vitro analyses. The in silico analysis revealed that citrulline, chloramphenicol and carnitine inhibited the virulent genes phcA (R. solanacearum) and ste12 (F. oxysporum). Further, under in vitro condition, citrulline and chloramphenicol were found to inhibit the growth of R. solanacearum and F. oxysporum. On the basis of the biocontrol activity of B. subtilis (SSL2) in in silico and in vitro conditions, the bacteria could be used as a biocontrol agent against both bacterial and fungal wilt-causing pathogens. However, this needs to be tested in pot studies or field conditions before being used as biocontrol agents.

Communicated by Ramaswamy H. Sarma     

Characterization of 2T engine oil degrading indigenous bacteria,isolated from high altitude (Mussoorie), India

The biodegradability of petroleum hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs) and n-branched alkanes etc. of 2T engine oil were studied in aqueous media using bacterial strain isolated from petroleum contaminated soil of high altitude. Out of five petroleum degrading bacterial strain one of the most growing bacteria was identified as Enterobacter strain by morphological, physiological, biochemical and partial sequencing of 16S rDNA. This strain was capable of degrading 75 ± 3% of n-alkanes, 32 ± 5% PAHs, and the abiotic loss was 24 ± 6% during 10 days incubation period. 85 ± 2% of n-alkanes and 51 ± 3% PAHs were biodegraded in 20 days. The abiotic loss during this period was 15 ± 3%. In 30 days of incubation period 98% ± 1% n-alkanes and 75 ± 3% PAHs were degraded. As expected abiotic losses were smaller with increasing long chain alkanes and PAH’s concentration. An increment in oil degradation was correlated to an increase in cell number indicating that the bacterial isolate was responsible for the oil degradation. The hydrocarbon contents were measured by Shimadzu QP-2000 Gas chromatography/mass spectrometry by ULBON HR-1 column.     

Inoculation of Cucumber (Cucumis sativus L.) Seedlings with Salt-Tolerant Plant Growth Promoting Bacteria Improves Nutrient Uptake,Plant Attributes and Physiological Profiles

Journal of Plant Growth Regulation - Salinity is one of the major abiotic stresses that cause retarded plant growth and crop production. It has been reported that harmful effects of salinity could...     

Thermo-optic measurements and their inter-dependencies for delineating cancerous breast biopsy tissue from adjacent normal

The histopathological diagnosis of cancer is the current gold standard to differentiate normal from cancerous tissues. We propose a portable platform prototype to characterize the tissue's thermal and optical properties, and their inter-dependencies to potentially aid the pathologist in making an informed decision. The measurements were performed on 10 samples from five subjects, where the cancerous and adjacent normal were extracted from the same patient. It was observed that thermal conductivity (k) and reduced-scattering-coefficient (μ'_s) for both the cancerous and normal tissues reduced with the rise in tissue temperature. Comparing cancerous and adjacent normal tissue, the difference in k and μ'_s (at 940 nm) were statistically significant (p = 7.94e-3), while combining k and μ'_s achieved the highest statistical significance (6.74e-4). These preliminary results promise and support testing on a large number of samples for rapidly differentiating cancerous from adjacent normal tissues.     

Modelling of microbial growth for sequential utilization in a multisubstrate environment

Microbial growth in multisubstrate environments is posed as a problem of multivariable constraint optimization. The optimization aims at maximizing the instantaneous growth rate of cells. The model developed for microbial growth using this hypothesis involves simple representation of complex cell structure as an optimization function which regulates the interplay of cellular machinery. The model parameters are estimated using single substrate growth data. Model simulation fits very well with earlier published experimental data of bacterial growth of Klensiella oxytoca on a variety of sugar mixtures involving glucose, fructose, lactose, and xylose. Moreover, the model is also able to predict the diauxic growth of Saccharomyces cerevisiae on glucose and galactose. One of the interesting outcomes of the above representation is the ability to prove analytically that the growth on the mixture of two sugars will be diauxic if one of the substrates has a very low K_s value and a high μ_m value.