ABSTRACT
The
influence of the carbon source on cell wall properties was analyzed in
an efficient alkane-degrading strain of Rhodococcus
erythropolis (strain E1), with particular focus on the mycolic
acid content. A clear correlation was observed between the carbon
source and the mycolic acid profiles as estimated by high-performance
liquid chromatography and mass spectrometry. Two types of mycolic acid
patterns were observed after growth either on saturated linear alkanes
or on short-chain alkanoates. One type of pattern was characterized by
the lack of odd-numbered carbon chains and resulted from growth on
linear alkanes with even numbers of carbon atoms. The second type of
pattern was characterized by mycolic acids with both even- and
odd-numbered carbon chains and resulted from growth on compounds with
odd-numbered carbon chains, on branched alkanes, or on mixtures of
different compounds. Cellular short-chain fatty acids were twice as
abundant during growth on a branched alkane (pristane) as during growth
on acetate, while equal amounts of mycolic acids were found under both
conditions. More hydrocarbon-like compounds and less polysaccharide
were exposed at the cell wall surface during growth on alkanes.
Whatever the substrate, the cells had the same affinity for
aqueous-nonaqueous solvent interfaces. By contrast, bacteria displayed
completely opposite susceptibilities to hydrophilic and hydrophobic
antibiotics and were found to be strongly stained by hydrophobic dyes
after growth on pristane but not after growth on acetate. Taken
together, these data show that the cell wall composition of R.
erythropolis E1 is influenced by the nutritional regimen and that
the most marked effect is a radical change in cell wall
permeability.
A Mycobacterial Cyclic AMP Phosphodiesterase That Moonlights as a Modifier of Cell Wall Permeability
