Exogenous Isoleucine and Fatty Acid Shortening Ensure the High Content of Anteiso-C _15:0 Fatty Acid Required for Low-Temperature Growth of Listeria monocytogenes

Abstract

Previous studies have demonstrated that the branched-chain fatty acid anteiso-C 15:0 plays a critical role in the growth of Listeria monocytogenes at low temperatures by ensuring sufficient membrane fluidity. Studies utilizing a chemically defined minimal medium revealed that the anteiso fatty acid precursor isoleucine largely determined the fatty acid profile and fatty acid response of the organism to lowered growth temperature. When isoleucine was sufficient, the fatty acid profile was very uniform, with anteiso fatty acids comprising up to 95% of total fatty acid, and the major fatty acid adjustment to low temperature was fatty acid chain shortening, which resulted in an increase of anteiso-C 15:0 solely at the expense of anteiso-C 17:0 . When isoleucine was not supplied, the fatty acid profile became more complex and was readily modified by leucine, which resulted in a significant increase of corresponding iso fatty acids and an inability to grow at 10°C. Under this condition, the increase of anteiso-C 15:0 at low temperature resulted from the combined effect of increasing the anteiso:iso ratio and chain shortening. A branched-chain ␣-keto acid dehydrogenase-defective strain largely lost the ability to increase the anteiso:iso ratio. Cerulenin, an inhibitor of ␤-ketoacyl-acyl carrier protein synthase (FabF), induced a similar fatty acid chain shortening as low temperature did. We propose that the anteiso precursor preferences of enzymes in the branched-chain fatty acid biosynthesis pathway ensure a high production of anteiso fatty acids, and cold-regulated chain shortening results in a further increase of anteiso-C 15:0 at the expense of anteiso-C 17:0 .

Role and Regulation of Fatty Acid Biosynthesis in the Response of Shewanella piezotolerans WP3 to Different Temperatures and Pressures

“…Therefore, we still have no idea as to how bacteria regulate BCFA to fulfill different requirements. There are studies showing that exogenous BCAA can largely influence the fatty acid profiles in some bacteria (25,55). However, the molecular mechanism for this phenomenon has not been revealed.…”

Role of Branched-Chain Fatty Acids in pH Stress Tolerance in Listeria monocytogenes

“…Thus, these two enzymes, BcaT and Bkd, are critical for BCFA biosynthesis in L. monocytogenes and represent a possible mechanism for stress regulation and modification of FA profiles in this pathogen (8,28,36,37). The differences between the growth rates of BCFA-deficient mutants and the BCFA-competent parent strain under pH stress and the resolution of such differences by the provision of exogenous 2MBA, bypassing the branched-chain ␣-keto acid dehydrogenase step in the biosynthesis of BCFA (49,50), demonstrated the close correlation between membrane BCFA content and the ability of L. monocytogenes to grow under such adverse environmental conditions.…”

“…In L. monocytogenes (49,50) (and also in Bacillus subtilis [12]), such enzymes and their products have vital roles in membrane adaptation to highand low-temperature stress. BCFA synthesis involves the transamination of branched-chain amino acids such as isoleucine, valine, and leucine by a branched-chain amino acid transaminase (BcaT) (12,23) and subsequent oxidative decarboxylation by the branched-chain ␣-keto acid dehydrogenase (Bkd) (8,28,36,37).…”

“…Growth rates of cultures (doubling times per hour of cultures in exponential growth) were calculated (2). Mid-exponential-phase cells were recovered by centrifugation at 8,000 ϫ g for 10 min at 4°C and washed three times with distilled water.The FAs in washed-cell pellets were saponified, methylated, and extracted as described previously (1,49,50). Methyl ester mixtures were separated using an Agilent 5890 dual-tower gas chromatograph with split/splitless injector, flame ionization detector, 25-m by 0.2-mm Ultra 2 capillary column (HewlettPackard), and automatic sampler/integrator and analyzed using an FA identification program (MIDI; Sherlock 4.5 Microbial Identification System).…”

Branched-Chain Fatty Acids Promote Listeria monocytogenes Intracellular Infection and Virulence

“…In this study, we aim to elucidate the contribution of anteiso-BCFA during L. monocytogenes intracellular infection by utilizing the previously characterized cld-2 transposon insertion mutant (1,11,15,26,27) and two independently transduced BKD-deficient mutants in which the cld-2 transposon insertion was transduced into a clean wild-type (WT) background. We show that anteiso-BCFA facilitate intracellular infection of L. monocytogenes by enhancing survival, growth, and phagosomal escape.…”