Physiological role of phosphatidylcholine in the Pseudomonas putida A ATCC 12633 response to tetradecyltrimethylammonium bromide and aluminium

Aims:  To evaluate the effect of tetradecyltrimethylammonium bromide (TTAB) and aluminium stresses on the phospholipid (PL) composition of Pseudomonas putida A ATCC 12633.
Methods and Results:  Pseudomonas putida were grown with TTAB in the presence or absence of AlCl₃, and the PL composition was analysed. The presence of TTAB resulted in an increase in phosphatidylglycerol and phosphatidic acid levels (6- and 20-fold, respectively) with respect to the levels in cells grown without the surfactant. With AlCl₃, phosphatidylcholine (PC) increased (threefold) and cell-free extracts contained approximately threefold more phosphatidylcholine synthase activities than extracts without AlCl₃, indicating that the PC level is dependent upon activation of this enzyme.
Conclusions:  The negative charges of the headgroups of PL are the primary membrane-associated factors for the response to TTAB. PC are involved in cellular responses to binding Al³⁺ and should be viewed as a temporary reservoir of available Al³⁺ to allow a more efficient utilization of TTAB by Ps. putida .
Significance and Impact of the Study:  The changes in the PL of Ps. putida in the presence of TTAB and AlCl₃ indicate that different responses are utilized by bacteria to maintain optimal PL composition in the presence of such environmental pollutants.     

Lipids of Salmonella typhimurium and Escherichia coli: structure and metabolism

The nature and quantity of the phospholipids of Salmonella typhimurium and Escherichia coli K-12 have been examined. The main classes of phospholipids, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin have been completely characterized. Four minor compounds have been detected: phosphatidylserine, phosphatidic acid, and two partially characterized lipids. The phospholipid composition of the two organisms is quite similar, the only difference is the absence of one of the minor components and a decreased level of all components in E. coli. A study of the turnover of the phosphate in the phospholipids demonstrated no turnover in phosphatidylethanolamine, a slow turnover in phosphatidylglycerol, and a slow turnover in cardiolipin with, possibly, a transfer of phosphate from phosphatidylglycerol to cardiolipin. The amino acid phenylalanine is shown to become incorporated intact into lipidic compounds which have been partially characterized. Methods for the isolation and separation of lipids have been examined for their utility with these bacteria.     

Intrinsic and acquired resistance to quaternary ammonium compounds in food-related Pseudomonas spp

AIMS: To determine the sensitivity of a strain used for disinfectants testing (Pseudomonas aeruginosa ATCC 15442) and food-associated isolates to benzalkonium chloride and didecyl dimethylammonium chloride (DDAC). To determine whether the increase in bacterial resistance after adaptation to DDAC can be associated with phenotypic changes. To test the activity of alternative disinfectants to eliminate resistant Pseudomonas spp. METHODS AND RESULTS: Pseudomonas aeruginosa ATCC 15442 was among the most resistant strains tested using a bactericidal suspension test. Growth of a sensitive Ps. fluorescens in gradually higher concentrations of DDAC resulted in stable higher resistance and to some cross-resistance to several antibacterial agents, with the exception of disinfectants containing chloramine T, glutaraldehyde or peracetic acid. It was shown by microscopy that adaptation was followed by loss of flagella, and slime formation. Removal of the slime by sodium dodecyl sulphate resulted in partial loss of the acquired resistance. CONCLUSIONS: Pseudomonas spp. may adapt to survive against higher concentrations of quaternary ammonium compounds (QACs), but resistant strains can be eliminated with chemically unrelated disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: The work supports the rotation of disinfectants in food processing environments for avoiding the development of bacterial resistance to QACs. The alternating disinfectants should be chosen carefully, because of possible cross-resistance.     

Transfer of phosphatidic acid between microsomal and mitochondrial outer and inner membranes

A protein fraction from rat liver cytoplasm, precipitable at 50-95% saturation of ammonium sulphate, binds phosphatidic acid from mitochondrial and microsomal membranes. Protein-bound phosphatidic acid was eluted from Sephadex G-75 in fractions corresponding to a molecular weight of about 10 000. No such binding was observed with mitochondrial soluble proteins, either total or precipitated with ammonium sulphate between 50 and 95% saturation. The transfer of phosphatidic acid from microsomes to mitochondria was increased by liver cytoplasmic proteins precipitable at 50-95% saturation of ammonium sulphate but not with mitochondrial soluble proteins. This increase by cytoplasmic proteins was pronounced in 200 mM sucrose but was negligible in 100 mM KCI where the spontaneous transfer was quite high. Cytoplasmic proteins stimulated the synthesis of cardiolipin and phosphatidylglycerol in mitochondria deprived of the outer membrane but not in intact mitochondria when phosphatidic acid was supplied either by microsomes or liposomes. It is suggested that the transfer of phosphatidic acid from the outer to the inner mitochondrial membrane is not mediated by transfer proteins but occurs either by direct contact of the membranes or as free diffusion through the aqueous phase.     

Analysis of pectate lyases produced by soft rot bacteria associated with spoilage of vegetables.

Isoelectric focusing (IEF) profiles of pectate lyases (PLs) produced by five different groups of soft rot bacteria were analyzed by using the combined techniques of thin-layer polyacrylamide gel IEF and agarose-pectate overlay activity staining. Four strains of soft rot Erwinia spp. produced three or more PL isozymes. All of eight Pseudomonas viridiflava strains examined produced one single PL with a pI of 9.7. All 10 of Pseudomonas fluorescens strains produced two PLs; the major one had a pI of 10.0 and the minor one had a pI of 6.7. A single PL with a pI of greater than or equal to 10.0 was detected in one strain each of Xanthomonas campestris and Cytophaga johnsonae. PLs of six representative strains were purified from culture supernatants by ammonium sulfate precipitation and anion-exchange chromatography. All purified PL samples macerated potato slices, but to different degrees. The Mrs of alkaline PLs produced by P. viridiflava, P. fluorescens, X. campestris, and C. johnsonae were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 42,000, 41,000, 41,500, and 35,000, respectively. IEF profiles of PLs were distinct among the bacterial species. Profiles of non-Erwinia spoilage bacteria were considerably simpler than those of Erwinia spp. The PL with an alkaline pI appeared to be the principal or the sole enzymatic factor involved in tissue maceration caused by most strains of soft rot bacteria.     

Analysis of pectate lyases produced by soft rot bacteria associated with spoilage of vegetables

Isoelectric focusing (IEF) profiles of pectate lyases (PLs) produced by five different groups of soft rot bacteria were analyzed by using the combined techniques of thin-layer polyacrylamide gel IEF and agarose-pectate overlay activity staining. Four strains of soft rot Erwinia spp. produced three or more PL isozymes. All of eight Pseudomonas viridiflava strains examined produced one single PL with a pI of 9.7. All 10 of Pseudomonas fluorescens strains produced two PLs; the major one had a pI of 10.0 and the minor one had a pI of 6.7. A single PL with a pI of greater than or equal to 10.0 was detected in one strain each of Xanthomonas campestris and Cytophaga johnsonae. PLs of six representative strains were purified from culture supernatants by ammonium sulfate precipitation and anion-exchange chromatography. All purified PL samples macerated potato slices, but to different degrees. The Mrs of alkaline PLs produced by P. viridiflava, P. fluorescens, X. campestris, and C. johnsonae were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 42,000, 41,000, 41,500, and 35,000, respectively. IEF profiles of PLs were distinct among the bacterial species. Profiles of non-Erwinia spoilage bacteria were considerably simpler than those of Erwinia spp. The PL with an alkaline pI appeared to be the principal or the sole enzymatic factor involved in tissue maceration caused by most strains of soft rot bacteria.     

Lipid composition of the electron transport membrane of Haemophilus parainfluenzae

The principal lipids associated with the electron transport membrane of Haemophilus parainfluenzae are phosphatidylethanolamine (78%), phosphatidylmonomethylethanolamine (0.4%), phosphatidylglycerol (18%), phosphatidylcholine (0.4%), phosphatidylserine (0.4%), phosphatidic acid (0.2%), and cardiolipin (3.0%). Phospholipids account for 98.4% of the extractible fatty acids. There are no glycolipids, plasmalogens, alkyl ethers, or lipo amino acid esters in the membrane lipids. Glycerol phosphate esters derived from the phospholipids by mild alkaline methanolysis were identified by their staining reactions, mobility on paper and ion-exchange column chromatography, and by the molar glycerol to phosphate ratios. Eleven diacyl phospholipids can be separated by two-dimensional thin-layer chromatography. Each lipid served as a substrate for phospholipase D, and had a fatty acid to phosphate ratio of 2:1. Each separated diacyl phospholipid was deacylated and the glycerol phosphate ester was identified by paper chromatography in four solvent systems. Of the 11 separated phospholipids, 3 were phosphatidylethanolamines, 2 were phosphatidylserines, and 2 were phosphatidylglycerols. Phosphatidylcholine, cardiolipin, and phosphatidic acid were found at a single location. Phosphatidylmonomethylethanolamine was found with the major phosphatidylethanolamine. Three distinct classes of phospholipids are separable according to their relative fatty acid compositions. (i) The trace lipids consist of two phosphatidylethanolamines, two phosphatidylserines, phosphatidylcholine, phosphatidic acid, and a phosphatidylglycerol. Each lipid represents less than 0.3% of the total lipid phosphate. These lipids are characterized by high proportions of the short (C(10) to C(14)) and long (C(19) to C(22)) fatty acids with practically no palmitoleic acid. (ii) The major phospholipids (93% of the lipid phosphate) are phosphatidylethanolamine, phosphatidylmonomethylethanolamine, and phosphatidylglycerol. These lipids contain a low proportion of the short (C(19)) fatty acids. Palmitic and palmitoleic acids represent over 80% of the total fatty acids. (iii) The fatty acid composition of the cardiolipin is intermediate between the other two classes. Both palmitoleic and the longer fatty acids represent a significant proportion of the total fatty acid.     

Biodegradation of didecyldimethylammonium chloride by Pseudomonas fluorescens TN4 isolated from activated sludge

Bacteria that degrade didecyldimethylammonium chloride (DDAC) were isolated from activated sludge from a municipal sewage treatment plant by enrichment culture with DDAC as a sole carbon source. One of the isolates, Pseudomonas fluorescens TN4, degraded DDAC to produce decyldimethylamine and subsequently, dimethylamine, as the intermediates. The TN4 strain also assimilated the other quaternary ammonium compounds (QACs), alkyltrimethyl- and alkylbenzyldimethyl-ammonium salts, but not alkylpyridinium salts. TN4 was highly resistant to these QACs and degraded them by an N-dealkylation process. These data mean that there are some QAC-resistant and QAC-degrading bacteria such as TN4 in the environment.     

Agmatine transport into spinal nerve terminals is modulated by polyamine analogs

Because alpha-synuclein (Snca) has a role in brain lipid metabolism, we determined the impact that Snca deletion had on whole brain lipid composition. We analysed masses of individual phospholipid (PL) classes and neutral lipid mass as well as PL acyl chain composition in brains from wild-type and Snca-/- mice. Although total brain PL mass was not altered, cardiolipin and phosphatidylglycerol mass decreased 16% and 27%, respectively, in Snca-/- mice. In addition, no changes were observed in plasmalogen or polyphosphoinositide mass. In ethanolamine glycerophospholipids and phosphatidylserine, docosahexaenoic acid (22 : 6n-3) was decreased 7%, while 16 : 0 was increased 1.1-fold and 1.4-fold, respectively. Surprisingly, brain cholesterol, cholesteryl ester, and triacylglycerol mass were increased 1.1-fold, 1.6-fold, and 1.4-fold, respectively in Snca-/- mice. In isolated myelin, cholesterol mass was also increased 1.3-fold, but because there was also a net increase in myelin PL mass, the cholesterol to PL ratio was unaltered. No changes in the expression of cholesterogenic enzymes were observed, suggesting these did not account for the observed changes in cholesterol. These data extend our previous results in astrocytes and kinetic studies in vivo demonstrating a role for Snca in brain lipid metabolism and demonstrate a clear impact on brain neutral lipid metabolism.     

Daptomycin resistance in enterococci is associated with distinct alterations of cell membrane phospholipid content

Background

The lipopeptide antibiotic, daptomycin (DAP) interacts with the bacterial cell membrane (CM). Development of DAP resistance during therapy in a clinical strain of Enterococcus faecalis was associated with mutations in genes encoding enzymes involved in cell envelope homeostasis and phospholipid metabolism. Here we characterized changes in CM phospholipid profiles associated with development of DAP resistance in clinical enterococcal strains.

Methodology

Using two clinical strain-pairs of DAP-susceptible and DAP-resistant E. faecalis (S613 vs. R712) and E. faecium (S447 vs. R446) recovered before and after DAP therapy, we compared four distinct CM profiles: phospholipid content, fatty acid composition, membrane fluidity and capacity to be permeabilized and/or depolarized by DAP. Additionally, we characterized the cell envelope of the E. faecium strain-pair by transmission electron microscopy and determined the relative cell surface charge of both strain-pairs.

Principal Findings

Both E. faecalis and E. faecium mainly contained four major CM PLs: phosphatidylglycerol (PG), cardiolipin, lysyl-phosphatidylglycerol (L-PG) and glycerolphospho-diglycodiacylglycerol (GP-DGDAG). In addition, E. faecalis CMs (but not E. faecium) also contained: i) phosphatidic acid; and ii) two other unknown species of amino-containing PLs. Development of DAP resistance in both enterococcal species was associated with a significant decrease in CM fluidity and PG content, with a concomitant increase in GP-DGDAG. The strain-pairs did not differ in their outer CM translocation (flipping) of amino-containing PLs. Fatty acid content did not change in the E. faecalis strain-pair, whereas a significant decrease in unsaturated fatty acids was observed in the DAP-resistant E. faecium isolate R446 (vs S447). Resistance to DAP in E. faecium was associated with distinct structural alterations of the cell envelope and cell wall thickening, as well as a decreased ability of DAP to depolarize and permeabilize the CM.

Conclusion

Distinct alterations in PL content and fatty acid composition are associated with development of enterococcal DAP resistance.     

Decreased cardiolipin synthesis corresponds with cytochrome c release in palmitate-induced cardiomyocyte apoptosis

Apoptosis has been identified recently as a component of many cardiac pathologies. However, the potential triggers of programmed cell death in the heart and the involvement of specific metabolic pathway(s) are less well characterized. Detachment of cytochrome c from the mitochondrial inner membrane is a necessary first step for cytochrome c release into the cytosol and initiation of apoptosis. The saturated long chain fatty acid, palmitate, induces apoptosis in rat neonatal cardiomyocytes and diminishes content of the mitochondrial anionic phospholipid, cardiolipin. These changes are accompanied by 1) acyl chain saturation of phosphatidic acid and phosphatidylglycerol, 2) large increases in the levels of these two phospholipids, and 3) a decline in cardiolipin synthesis. Although cardiolipin synthase activity is unchanged, saturated phosphatidylglycerol is a poor substrate for this enzyme. Under these conditions, decreased cardiolipin synthesis and release of cytochrome c are directly and significantly correlated. The results suggest that phosphatidylglycerol saturation and subsequent decreases in cardiolipin affect the association of cytochrome c with the inner mitochondrial membrane, directly influencing the pathway to cytochrome c release and subsequent apoptosis.     

Changes in Membrane Fatty Acid Composition of Pseudomonas aeruginosa in Response to UV-C Radiations

The changes in lipid composition enable the micro-organisms to maintain membrane functions in the face of environmental fluctuations. The relationship between membrane fatty acid composition and UV-C stress was determined for mid-exponential phase and stationary phase Pseudomonas aeruginosa. The total lipids were obtained by dichloromethane/methanol (3:1) and were quantified by GC. The TLC analysis of phospholipids showed the presence of three major fractions phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. Significant modifications, as manifested by an increase of UFA, were obtained. Interestingly, this microorganism showed a remarkable capacity for recovery from the stressful effects of UV-C.     

Lipid-protein interactions in ADP-ATP carrier/egg phosphatidylcholine recombinants studied by spin-label ESR spectroscopy

The stoichiometry and specificity of lipid-protein interaction, as well as the lipid exchange rates at the protein interface, have been determined from the electron spin resonance spectra of spin-labeled lipids in reconstituted complexes of the mitochondrial ADP-ATP carrier with egg phosphatidylcholine. With the exception of cardiolipin and phosphatidic acid, the lipids studied are found to compete for approximately 50 sites at the intramembranous surface of the protein dimer. This number of first-shell lipid sites is unusually large for a protein of this size. The specificity for the protein is in the order stearic acid approximately phosphatidic acid approximately cardiolipin greater than phosphatidylserine greater than phosphatidylglycerol approximately phosphatidylcholine, with the maximum association constant relative to phosphatidylcholine being approximately 4. The selectivity for anionic lipids was partially screened with increasing ionic strength, but to a lesser extent for cardiolipin and phosphatidic acid than for stearic acid. Only in the case of phosphatidylserine was the selectivity reduced at high ionic strength to a level close to that for phosphatidylcholine. The off rates for lipid exchange at the protein surface were independent of lipid/protein ratio and correlated in a reciprocal fashion with the different lipid selectivities, varying from 5 x 10(6) s-1 for stearic acid at low ionic strength to 2 x 10(7) s-1 for phosphatidylcholine and phosphatidylglycerol. The off rates for cardiolipin were unusually low in comparison with the observed selectivity, and indicated the existence of a special population of sites (ca. 30% of the total) for cardiolipin, at which the exchange rate was very low.(ABSTRACT TRUNCATED AT 250 WORDS)     

Features of phospholipid composition of marine proteobacteria of Pseudoalteromonas species

The study of the phospholipid composition of 14 type strains of marine proteobacteria of the genus Pseudoalteromonas showed that phospholipids are the main polar lipid constituents of membranes in these proteobacteria. The phospholipid patterns of the strains studied were found to be similar and involved five phospholipids typical of gram-negative bacteria, namely, phosphatidylethanolamine, phosphatidylglycerol, bisphosphatidic acid, lysophosphatidylethanolamine, and phosphatidic acid. The major phospholipids were phosphatidylethanolamine and phosphatidylglycerol, which add up to 89-97% of total phospholipids; bisphosphatidic acid was dominant among minor phospholipids. The prevalence of phosphatidylethanolamine (62-77% of total phospholipids) and the absence of diphosphatidylglycerol are the characteristic features of most bacteria of this genus. As in Escherichia coli, the phospholipid composition of the marine proteobacteria depended on the presence of magnesium in the medium.     

Specific interaction of cytosolic and mitochondrial glyoxalase II with acidic phospholipids in form of liposomes results in the inhibition of the cytosolic enzyme only

Kinetics of cytosolic recombinant human glyoxalase II and bovine liver mitochondrial glyoxalase II were studied in the presence of liposomes made of different phospholipids (PLs). Neutral PLs such as egg phosphatidylcholine or dipalmitoylphosphatidylcholine did not affect the enzymatic activity of either enzymatic form. Liposomes made of dioleoyl phosphatidic acid or cardiolipin or phosphatidylserine also did not affect the enzymatic activity of mitochondrial glyoxalase II. Conversely, these negatively charged PLs exerted noncompetitive inhibition on cytosolic glyoxalase II only, dioleoyl phosphatidic acid and bovine brain phosphatidylserine exerting the highest and lowest inhibition, respectively. Binding studies, carried out by using a resonant mirror biosensor, revealed that liposomes made of negatively charged PLs interact specifically with both enzymatic forms of glyoxalase II, whereas interactions were not detected with neutral PLs. Once bound on glyoxalase II, negatively charged liposomes could not be removed by 3 M NaCl, suggesting that interactions between glyoxalase II and negatively charged PLs, besides ionic, may be also hydrophobic. These data suggest a possible role of negatively charged phospholipids in the regulation of level of lactoylglutathione in the cell. The data are also discussed in terms of a possible regulation of reduced glutathione supply to mitochondria.     

Identification of Unusual Phospholipid Fatty Acyl Compositions of Acanthamoeba castellanii

Acanthamoeba are opportunistic protozoan pathogens that may lead to sight-threatening keratitis and fatal granulomatous encephalitis. The successful prognosis requires early diagnosis and differentiation of pathogenic Acanthamoeba followed by aggressive treatment regimen. The plasma membrane of Acanthamoeba consists of 25% phospholipids (PL). The presence of C20 and, recently reported, 28- and 30-carbon fatty acyl residues is characteristic of amoeba PL. A detailed knowledge about this unusual PL composition could help to differentiate Acanthamoeba from other parasites, e.g. bacteria and develop more efficient treatment strategies. Therefore, the detailed PL composition of Acanthamoeba castellanii was investigated by ³¹P nuclear magnetic resonance spectroscopy, thin-layer chromatography, gas chromatography, high performance liquid chromatography and liquid chromatography-mass spectrometry. Normal and reversed phase liquid chromatography coupled with mass spectrometric detection was used for detailed characterization of the fatty acyl composition of each detected PL. The most abundant fatty acyl residues in each PL class were octadecanoyl (18∶0), octadecenoyl (18∶1 Δ9) and hexadecanoyl (16∶0). However, some selected PLs contained also very long fatty acyl chains: the presence of 28- and 30-carbon fatty acyl residues was confirmed in phosphatidylethanolamine (PE), phosphatidylserine, phosphatidic acid and cardiolipin. The majority of these fatty acyl residues were also identified in PE that resulted in the following composition: 28∶1/20∶2, 30∶2/18∶1, 28∶0/20∶2, 30∶2/20∶4 and 30∶3/20∶3. The PL of amoebae are significantly different in comparison to other cells: we describe here for the first time unusual, very long chain fatty acids with Δ⁵-unsaturation (30∶3^5,21,24) and 30∶2^21,24 localized exclusively in specific phospholipid classes of A. castellanii protozoa that could serve as specific biomarkers for the presence of these microorganisms.     

Lipidomic analysis of phospholipids from human mammary epithelial and breast cancer cell lines

Alterations of phospholipid (PL) profiles have been associated to disease and specific lipids may be involved in the onset and evolution of cancer; yet, analysis of PL profiles using mass spectrometry (MS) in breast cancer cells is a novel approach. Previously, we reported a lipidomic analysis of PLs from mouse mammary epithelial and breast cancer cells using off‐line thin layer chromatography (TLC)‐MS, where several changes in PL profile were found to be associated with the degree of malignancy of cells. In the present study, lipidomic analysis has been extended to human mammary epithelial cells and breast cancer cell lines (MCF10A, T47‐D, and MDA‐MB‐231), using TLC‐MS, validated by hydrophilic interaction liquid chromatography‐MS. Differences in phosphatidylethanolamine (PE) content relative to total amount of PLs was highest in non‐malignant cells while phosphatidic acid was present with highest relative abundance in metastatic cells. In addition, the following differences in PL molecular species associated to cancer phenotype, metastatic potential, and cell morphology were found: higher levels of alkylacyl PCs and phosphatidylinositol (PI; 22:5/18:0) were detected in migratory cells, epithelial cells had less unsaturated fatty acyl chains and shorter aliphatic tails in PE and sphingomyelin classes, while PI (18:0/18:1) was lowest in non‐malignant cells compared to cancer cells. To date, information about PL changes in cancer progression is scarce, therefore results presented in this work will be useful as a starting point to define possible PLs with prospective as biomarkers and disclose metabolic pathways with potential for cancer therapy. J. Cell. Physiol. 228: 457–468, 2013. © 2012 Wiley Periodicals, Inc.     

Phospholipids of marine proteobacteria of the genusPseudoalteromonas

The study of the phospholipid composition of 14 type strains of marine proteobacteria of the genusPseudoalteromonas showed that phospholipids are the main polar lipid constituents of membranes in these proteobacteria. The phospholipid patterns of the strains studied were found to be similar and involved five phospholipids typical of gram-negative bacteria, namely, phosphatidylethanolamine, phosphatidylglycerol, bisphosphatidic acid, lysophosphatidylethanolamine, and phosphatidic acid. The major phospholipids were phosphatidylethanolamine and phosphatidylglycerol, which add up to 89–97% of the total phospholipids; bisphosphatidic acid was dominant among minor phospholipids. The prevalence of phosphatidylethanolamine (62–77% of the total phospholipids) and the absence of diphosphatidylglycerol are the characteristic features of most bacteria of this genus. As inEscherichia coli, the phospholipid composition of the marine proteobacteria depended on the presence of magnesium in the medium.     

Isolation and characterization of a Pseudomonas putida strain able to grow with trimethyl-1,2-dihydroxy-propyl-ammonium as sole source of carbon, energy and nitrogen

Trimethyl-1,2-dihydroxypropyl-ammonium (TM) originates from the hydrolysis of the parent esterquat surfactant, which is widely used as softener in fabric care. Based on test procedures mimicking complex biological systems, TM is supposed to degrade completely when reaching the environment. However, no organisms able to degrade TM were isolated nor has the degradation pathway been elucidated so far. We isolated a Gram-negative rod able to grow with TM as sole source of carbon, energy and nitrogen. The strain reached a maximum specific growth rate of 0.4(h-1) when growing with TM as the sole source of carbon, energy and nitrogen. TM was degraded to completion and surplus nitrogen was excreted as ammonium into the growth medium. A high percentage of the carbon in TM (68% in continuous culture and 60% in batch culture) was combusted to CO2 resulting in a low yield of 0.54 mg cell dry weight per mg carbon during continuous cultivation and 0.73 mg cell dry weight per mg carbon in batch cultures. Choline, a natural structurally related compound, served as a growth substrate, whereas a couple of similar other quaternary aminoalcohols also used in softeners did not. The isolated bacterium was identified by 165-rDNA sequencing as a strain of Pseudomonas putida with a difference of only one base pair to P. putida DSM 291T. Despite their high identity, the reference strain P. putida DSM 291T was not able to grow with TM and the two strains differed even in shape when growing on the same medium. This is the first microbial isolate able to degrade a quaternary ammonium softener head group to completion. Previously described strains growing on quaternary ammonium surfactants (decyltrimethylammonium, hexadecyltrimethylammonium and didecyldimethylammonium) either excreted metabolites or a consortium of bacteria was required for complete degradation.