Regulation of the synthesis of unsaturated fatty acids by growth temperature in Bacillus subtilis (original) (raw)
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Coupling of Fatty Acid and Phospholipid Synthesis in Bacillus subtilis
Journal of Bacteriology, 2007
and this study investigated their roles in gram-positive phospholipid metabolism through the analysis of conditional knockout strains in the Bacillus subtilis model system. The depletion of PlsX led to the cessation of both fatty acid synthesis and phospholipid synthesis. The inactivation of PlsY also blocked phospholipid synthesis, but fatty acid formation continued due to the appearance of acylphosphate intermediates and fatty acids arising from their hydrolysis. Phospholipid synthesis ceased following PlsC depletion, but fatty acid synthesis continued at a high rate, leading to the accumulation of fatty acids arising from the dephosphorylation of 1-acylglycerol-3-P followed by the deacylation of monoacylglycerol. Analysis of glycerol 3-P acylation in B. subtilis membranes showed that PlsY was an acylphosphate-specific acyltransferase, whereas PlsC used only acyl-ACP as an acyl donor. PlsX was found in the soluble fraction of disrupted cells but was associated with the cell membrane in intact organisms. These data establish that PlsX is a key enzyme that coordinates the production of fatty acids and membrane phospholipids in B. subtilis.
Microbiology-sgm, 1998
A Bacillus subtilis strain was constructed in which the operon accBC, encoding the biotin carboxyl carrier protein (BCCP) and biotin carboxylase (BC) subunits of acetyl-CoA carboxylase (ACC), was placed under the control of the IPTGinducible promoter spac. A reduction in the levels of BCCP resulted in a decrease of de novo fatty acid synthesis and in the total content of membrane fatty acids. This strain was dependent upon the presence of IPTG for a normal growth phenotype. Growth was specifically restored by supplying exogenous long branched-chain fatty acids in the medium, indicating that the inducerdependent phenotype was specifically related to a conditional block in fatty acid biosynthesis. The strain showed a strong decrease in sporulation frequency when it was induced to sporulate in an IPTG-free medium. Germination and outgrowth were both delayed in spores of the mutant obtained in the absence of IPTG. (1995). The genes encoding the biotin carboxyl carrier protein and biotin carboxylase subunits of Bacillus subtilis acetyl coenzyme A carboxylase, the first enzyme of fatty acid synthesis.
Journal of Bacteriology, 2009
Lipoic acid is an essential cofactor required for the function of key metabolic pathways in most organisms. We report the characterization of a Bacillus subtilis mutant obtained by disruption of the lipA (yutB) gene, which encodes lipoyl synthase (LipA), the enzyme that catalyzes the final step in the de novo biosynthesis of this cofactor. The function of lipA was inferred from the results of genetic and physiological experiments, and this study investigated its role in B. subtilis fatty acid metabolism. Interrupting lipoate-dependent reactions strongly inhibits growth in minimal medium, impairing the generation of branched-chain fatty acids and leading to accumulation of copious amounts of straight-chain saturated fatty acids in B. subtilis membranes. Although depletion of LipA induces the expression of the ⌬5 desaturase, controlled by a two-component system that senses changes in membrane properties, the synthesis of unsaturated fatty acids is insufficient to support growth in the absence of precursors for branched-chain fatty acids. However, unsaturated fatty acids generated by deregulated overexpression of the ⌬5 desaturase functionally replaces lipoic acid-dependent synthesis of branched-chain fatty acids. Furthermore, we show that the cold-sensitive phenotype of a B. subtilis strain deficient in ⌬5 desaturase is suppressed by isoleucine only if LipA is present.
DNA supercoiling and thermal regulation of unsaturated fatty acid synthesis in Bacillus subtilis
Molecular Microbiology, 1994
Bacillus subtilis growing at 37 C synthesizes, almost exclusively, saturated fatty acids. However, when a culture growing at 37 C is transferred to 20 C, the synthesis of unsaturated fatty acids is induced. The addition of the DNA gyrase inhibitor novobiocin specifically prevented the induction of unsaturated fatty acid synthesis at 20 C. Furthermore, it was determined that piasmid DNA isolated from ceils growing at 20 C was significantly more negatively supercoiled than the equivalent DNA isolated from celts growing at 37 C. The overall results agree with the hypothesis that an increase in DNA supercoiling associated with a temperature downshift could regulate the unsaturated fatty acids synthesis in 8. subtilis.
Bacillus subtilis acyl carrier protein is encoded in a cluster of lipid biosynthesis genes
Journal of Bacteriology, 1996
A cluster of Bacillus subtilis fatty acid synthetic genes was isolated by complementation of an Escherichia coli fabD mutant encoding a thermosensitive malonyl coenzyme A-acyl carrier protein transacylase. The B. subtilis genomic segment contains genes that encode three fatty acid synthetic proteins, malonyl coenzyme A-acyl carrier protein transacylase (fabD), 3-ketoacyl-acyl carrier protein reductase (fabG), and the N-terminal 14 amino acid residues of acyl carrier protein (acpP). Also present is a sequence that encodes a homolog of E. coli plsX, a gene that plays a poorly understood role in phospholipid synthesis. The B. subtilis plsX gene weakly complemented an E. coli plsX mutant. The order of genes in the cluster is plsX fabD fabG acpP, the same order found in E. coli, except that in E. coli the fabH gene lies between plsX and fabD. The absence of fabH in the B. subtilis cluster is consistent with the different fatty acid compositions of the two organisms. The amino acid sequen...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1973
The present study evaluates the unsaturated fatty acid requirement in Escherichia coli. A derivative of a double mutant defective both in unsaturated fatty acid biosynthesis and in fatty acid degradation has been selected which grows equally well o n anteisopentadecanoate (12-Me-14: 0) or cis-A 9-octadecenoate (cis-A 9_ 18 : 1). When this strain is grown for many generations on 12-Me-14:0, there is extensive incorporation of this analogue into the membrane phospholipid and essentially no detectable unsaturated fatty acids residues in any lipid-containing structures of the cell envelope. Secondly, as the maximal growth temperature of E. coli is approached, the minimum content of unsaturated fatty acid required by this strain for growth decreases to a few percent and is associated with the appearance of substantial amounts of 12:0 (8%) and 14:0 (50%) in the phospholipid. These experiments demonstrate that the cis unsaturated fatty acids of E. eoli phospholipids can be replaced by residues which possess no special electronic configuration. Hence, the unsaturated fatty acids do not participate in specific interactions with other membrane components but serve a general role of controlling the packing of paraffin chains in the membrane bilayer.
Quantitative effects of unsaturated fatty acids in microbial mutants
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1977
The ability of a series of 18 carbon acetylenic fatty acids to fulfill the unsaturated fatty acid requirements of Escherichia coli and Saccharomyces cereuisiae was investigated. Despite their high melting points (>4O"C), several isomers of the acetylenic fatty acids were as efficient or more efficient in supporting growth than the analogous fatty acid having a cis-double bond. The efficiencies of the different positional isomers in supporting cell proliferation varied from essentially 0 cells per fmol for the 2-5 and 13-17 isomers to high values when the acetylenic bond was near the center of the chain: e.g. 45 E. coli and 5.5 S. cereuisiae cells/fmol for the 10 isomer. A striking ineffectiveness of the 9 isomer was observed with E. coli. The 7, 8 and 10 isomers were at least lo-fold more efficient than any of the other positional isomers in supporting the growth of E. colt In contrast, the 9 isomer was among the most effective acetylenic fatty acids tested with the yeast mutant. Chromatographic analysis of the extracted lipids indicated that each of the acetylenic isomers tested (except A2 and A3) could be esterified by the prokaryotic and eukaryotic microorganisms. The content of unsaturated plus cyclopropane acids observed when growth ceased in E. coli cultures supplemented with gro~h-limiting concentrations of the acetylenic fatty acids ranged from approx. 15 mol% for the 8 isomer to approx. 35 mol% for the 14 and 17 isomers. The 8-11 isomers were observed to be esterified predominantly at the two position in phosphatidylethanolamine of E. coli and in phosphatidylcholine of S. cereuisiae.
Applied and Environmental Microbiology, 2013
⌬5 and ⌬10, as well as ⌬5,10 diunsaturated fatty acids. Through sequence homology searches, we identified two open reading frames (ORFs) encoding a putative ⌬5 desaturase and a fatty acid acyl-lipid desaturase in the B. cereus ATCC 14579 genome, and these were named BC2983 and BC0400, respectively. Functional characterization of ORFs BC2983 and BC0400 by means of heterologous expression in Bacillus subtilis confirmed that they both encode acyl-lipid desaturases that use phospholipids as the substrates and have ⌬5 and ⌬10 desaturase activities. Thus, these ORFs were correspondingly named desA (⌬5 desaturase) and desB (⌬10 desaturase). We established that DesA utilizes ferredoxin and flavodoxins (Flds) as electron donors for the desaturation reaction, while DesB preferably employs Flds. In addition, increased amounts of UFAs were found when B. subtilis expressing B. cereus desaturases was subjected to a cold shock treatment, indicating that the activity or the expression of these enzymes is upregulated in response to a decrease in growth temperature. This represents the first work reporting the functional characterization of fatty acid desaturases from B. cereus.