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

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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.

No MeSH data available.


Effect of NaCl on the mycolic acid patterns
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Fig3: Effect of NaCl on the mycolic acid patterns

Mentions: The qualitative analysis of MA of cells grown in the absence of NaCl showed a typical profile of chain length between C31 and C38 of the MA (Fig. 3). No saturated MA could be detected, and the unsaturation varied between monounsaturated and triple unsaturated MA with 35:3 being the predominant MA. In the presence of NaCl, the MA profile showed significant modifications when compared to the control cells. These changes can be expressed as the average chain length (ACL) of the MA as well as the unsaturation index (UI) which is the average amount of double bonds present in fatty acid chains (Kaszycki et al. 2013). Thus, the higher the UI is, the more fluid the cell wall becomes due to a lower melting temperature of the corresponding MA. In the present study, both ACL and UI values decreased with increasing salt concentration up to 1.5 M NaCl but an increase was observed for higher salt concentrations (Fig. 4).Fig. 3


Adaptive response of Rhodococcus opacus PWD4 to salt and phenolic stress on the level of mycolic acids
Effect of NaCl on the mycolic acid patterns
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016484&req=5

Fig3: Effect of NaCl on the mycolic acid patterns
Mentions: The qualitative analysis of MA of cells grown in the absence of NaCl showed a typical profile of chain length between C31 and C38 of the MA (Fig. 3). No saturated MA could be detected, and the unsaturation varied between monounsaturated and triple unsaturated MA with 35:3 being the predominant MA. In the presence of NaCl, the MA profile showed significant modifications when compared to the control cells. These changes can be expressed as the average chain length (ACL) of the MA as well as the unsaturation index (UI) which is the average amount of double bonds present in fatty acid chains (Kaszycki et al. 2013). Thus, the higher the UI is, the more fluid the cell wall becomes due to a lower melting temperature of the corresponding MA. In the present study, both ACL and UI values decreased with increasing salt concentration up to 1.5 M NaCl but an increase was observed for higher salt concentrations (Fig. 4).Fig. 3

View Article: PubMed Central - PubMed

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.

No MeSH data available.