Fig. 2

Nile red fluorescence microscopy. Broth samples with cells in the growth phase (a), cells in the oil production phase (b), cells in oil production phase with in situ OCA (c) and those contacted to ex situ OCA, post-oil production (d), were stained by Nile red dye and observed under a fluorescence microscope. Fluorescence at 593 nm shows extracellular oil in the sample (− 1); Phase contrast mode shows intracellular oil accumulation (white) inside the cells (− 2) and an overlay (− 3) shows the distribution of microbial oil in the samples