4a-methyl-dodecahydro-1H-pyrrolo[3,4-b]quinoline-6-one produced by Endophytic Fungi Aspergillus niger E12 obtained from Dodonaea viscosa Plant Leaves as a Novel Antibacterial Compound.

Endophytic fungi were isolated from forty plant leaf samples from Gudiyam forest. The potent antibacterial strain Aspergillus niger E12 isolated from the plant Dodonaea viscosa showed maximal antibacterial activity against all the test organisms, viz., Staphylococcus aureus, Bacillus coagulans, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The production of the antibacterial compound was optimized using the yeast extract sucrose medium (2% YES) using response surface methodology (RSM). For the production, the optimal parameters were carbon/nitrogen (C:N) ratio, 9:1; temperature, 25 °C; pH, 5.7; incubation time, 240 h; and rpm, 30. A zone of inhibition of 19.33 mm was observed as maximal bioactivity against Pseudomonas aeruginosa. The antibacterial compound was purified by extraction with ethyl acetate, activity-guided fractionation, and preparative high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) studies showed that the Aspergillus niger E12 bioactive substance is 4a-methyl-dodecahydro-1H-pyrrolo [3,4-b] quinoline-6-one.

A novel colorimetric technique for estimating iron in magnetosomes of magnetotactic bacteria based on linear regression.

Magnetotactic bacteria (MTB) use iron from their habitat to create magnetosomes, a unique organelle required for magnetotaxis. Due to a lack of cost-effective assay methods for estimating iron in magnetosomes, research on MTB and iron-rich magnetosomes is limited. A systemized assay was established in this study to quantify iron in MTB using ferric citrate colorimetric estimation. With a statistically significant R2 value of 0.9935, the iron concentration range and wavelength for iron estimation were optimized using linear regression. This colorimetric approach and the inductively coupled plasma optical emission spectrometry (ICP-OES) exhibited an excellent correlation R2 value of 0.961 in the validatory correlative study of the iron concentration in the isolated magnetotactic bacterial strains. In large-scale screening studies, this less-expensive strategy could be advantageous.