Adaptive response of Rhodococcus opacus PWD4 to salt and phenolic stress on the level of mycolic acids.

Carla C C R De Carvalho,Birgit Würz,Sandra Kirsten,Martin A Fischer,Hermann J Heipieper,Lukas Y Wick

doi:10.1186/s13568-016-0241-9

Abstract

Mycolata form a group of Gram-positive bacteria with unique cell envelope structures that are known for their high tolerance against antibiotics and both aromatic and aliphatic hydrocarbons. An important part of the unique surface structure of the mycolata is the presence of long chain α-alkyl-β-hydroxy fatty acids, the mycolic acids. In order to investigate the adaptive changes in the mycolic acid composition, we investigated the composition of mycolic acids during the response both to osmotic stress caused by NaCl and to 4-chlorophenol in Rhodococcus opacus PWD4. This bacterium was chosen as it is known to adapt to different kinds of stresses. In addition, it is a potential biocatalyst in bioremediation as well as for biotechnological applications. In the present study, cells of R. opacus PWD4, grown in liquid cultures, responded to toxic concentrations of NaCl by increasing the ratio between mycolic acids and membrane phospholipid fatty acids (MA/PLFA-ratio). Cells reacted to both NaCl and 4-chlorophenol by decreasing both the average chain length and the unsaturation index of their mycolic acids. These changes in mycolic acid composition correlated with increases in cell surface hydrophobicity and saturation of membrane fatty acids, demonstrating the relation between mycolic acid and phospholipid synthesis and their contribution to cell surface properties of R. opacus PWD4.

Highlights

The Rhodococcus cell envelope is characterized by the presence of long chain α-alkyl-β-hydroxy fatty acids, the mycolic acids (MA) (Asselineau and Lederer 1950)
The FAS-II system of the mycolata is more similar to the fatty acid synthase system found in bacteria and consists of various dissociable subunits fulfilling the necessary reactions for chain elongation of the meromycolate chain (Asselineau and Lederer 1950; Barry et al 1998; Nishiuchi et al 2000; Takayama et al 2005)
Effect of NaCl on growth and membrane fatty acid composition Cells of R. opacus were cultivated in mineral medium and NaCl was added in different concentrations during the early exponential growth phase

Summary

Introduction

The Rhodococcus cell envelope is characterized by the presence of long chain α-alkyl-β-hydroxy fatty acids, the mycolic acids (MA) (Asselineau and Lederer 1950). These mycolic acids, which are linked to an arabinogalactan complex or attached to a trehalose disaccharide, form an outer lipid layer. This layer is characteristic for the taxon mycolata and is found in eight other genera: Corynebacteria, Dietzia, Gordonia, Mycobacteria, Nocardia, Rhodococcus, Skermania and Tsukamurella (Sutcliffe 1998). The FAS-II system of the mycolata is more similar to the fatty acid synthase system found in bacteria and consists of various dissociable subunits fulfilling the necessary reactions for chain elongation of the meromycolate chain (Asselineau and Lederer 1950; Barry et al 1998; Nishiuchi et al 2000; Takayama et al 2005)

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Conclusion