Correlation of carotenoid production, decreased membrane fluidity, and resistance to oleic acid killing in Staphylococcus aureus 18Z

Abstract

Staphylococcus aureus is susceptible to killing by host-derived fatty acids. Studies were performed to test for a correlation between carotenoid production by S. aureus and protection against oleic acid. Oleic acid killing of cells grown in carotenoid expression medium was determined as the dosage of oleic acid in 2 M NaCl-2 mM EDTA that would kill 20% of the cells in 60 min at 37°C (i.e., the 20% lethal dose). Compared with the wild-type strain (18Z), a carotenoid-deficient mutant strain (18Z-76) and strain 18Z grown in a medium that suppressed carotenoid production both showed increased sensitivity to oleic acid. Spontaneous revertants of strain 18Z-76 that regained the ability to produce carotenoids were as resistant to oleic acid as the wild-type strain. Oleic acid was shown by fluorescence polarization to decrease polarization values. Lower polarization values indicate a more-fluid membrane. To determine whether protection against oleic acid killing might depend on carotenoid stabilization of membranes, fluorescence polarization values were determined for strains showing different levels of carotenoid production. An indirect correlation was found between membrane fluidity and carotenoid production. We were able to conclude that there is a direct correlation between carotenoid production (i.e., cell pigmentation), cell membrane stability, and resistance to oleic acid-induced cell killing.

Impact of oleic acid (cis-9-octadecenoic acid) on bacterial viability and biofilm production inStaphylococcus aureus

“…As carotenoids were shown to have a direct protective effect against oleic acid killing in S. aureus (Xiong & Kapral, 1992), this raises the question of a potential influence of oleic acid on sigB signaling. In agreement with previous studies showing the effects of oleic acid on planktonic bacteria (Chamberlain et al, 1991;Xiong & Kapral, 1992;Xiong et al, 1993), our live/dead experiments performed with planktonic UAMS-1 and its DsigB mutant suggest a sigB-dependent resistance against oleic acid killing. However, the adherent bacterial population was affected by oleic acid independently of sigB expression as shown by the transcript levels of asp23 used to indirectly quantify the active form of SigB (Senn et 2005).…”

“…Despite several in vitro studies that analyzed the effects of oleic acid on S. aureus (Chamberlain et al, 1991;Xiong & Kapral, 1992;Xiong et al, 1993), the potential of oleic acid as a bactericidal agent on S. aureus remains controversial.…”

Expression of novel carotenoid biosynthesis genes from Enterococcus gilvus improves the multistress tolerance of Lactococcus lactis

“…Carotenoids are lipophilic agents that are incorporated into the bacterial membrane. Chamberlain et al (1991) reported that carotenoids could influence cell membrane fluidity and decrease the sensitivity of Staph. aureus to oleic acid.…”

Adaptive changes in geranylgeranyl pyrophosphate synthase gene expression level under ethanol stress conditions inOenococcus oeni

“…Chamberlain et al . () reported that carotenoids could influence cell membrane fluidity and decrease the sensitivity of S. aureus to oleic acid. This finding implies that carotenoid production in LAB also may lead to changes in membrane fluidity.…”