Ilya N. Zubkov , Anatoly P. Nepomnyshchiy , Vadim D. Kondratyev , Pavel N. Sorokoumov , Konstantin V. Sivak , Edward S. Ramsay , Sergey M. Shishlyannikov
J. Microbiol. 2021;59(12):1104-1111. Published online October 26, 2021
An essential part of designing any biotechnological process is
examination of the physiological state of producer cells in
different phases of cultivation. The main marker of a bacterial
cell’s state is its fatty acid (FA) profile, reflecting membrane
lipid composition. Consideration of FA composition
enables assessment of bacterial responses to cultivation conditions
and helps biotechnologists understand the most significant
factors impacting cellular metabolism. In this work,
soil SDS-degrading Pseudomonas helmanticensis was studied
at the fatty acid profile level, including analysis of rearrangement
between planktonic and aggregated forms. The set of
substrates included fat hydrolysates, SDS, and their mixtures
with glucose. Such media are useful in bioplastic production
since they can help incrementally lower overall costs. Conventional
gas chromatography-mass spectrometry was used
for FA analysis. Acridine orange-stained aggregates were observed
by epifluorescence microscopy. The bacterium was
shown to change fatty acid composition in the presence of
hydrolyzed fats or SDS. These changes seem to be driven by
the depletion of metabolizable substrates in the culture medium.
Cell aggregation has also been found to be a defense
strategy, particularly with anionic surfactant (SDS) exposure.
It was shown that simple fluidity indices (such as saturated/
unsaturated FA ratios) do not always sufficiently characterize
a cell's physiological state, and morphological examination
is essential in cases where complex carbon sources are used.