Lipid Formation by Aqueous Fischer-Tropsch-Type Synthesis over a Temperature Range of 100 to 400 °C

The formation of lipid compounds during anaqueous Fischer-Tropsch-type reaction was studied withsolutions of oxalic acid as the carbon and hydrogensource. The reactions were conducted in stainlesssteel vessels by heating the oxalic acid solution atdiscrete temperatures from 100 to 400 °C, atintervals of 50 °C for two days each. Themaximum lipid yield, especially for oxygenatedcompounds, is in the window of 150–250 °C. At atemperature of 100 °C only a trace amount oflipids was detected. At temperatures above150 °C the lipid components ranged from C₁₂to >C₃₃ and included n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanals, n-alkanones, n-alkanes, andn-alkenes, all with essentially no carbon numberpreference. The n-alkanes increased inconcentration over the oxygenated compounds attemperatures of 200 °C and above, with a slightreduction in their carbon number ranges due tocracking. It was also noted that the n-alkanoicacids increased while n-alkanols decreased withincreasing temperature above 200 °C. Attemperatures above 300 °C synthesis competeswith cracking and reforming reactions. At 400 °Csignificant cracking was observed and polynucleararomatic hydrocarbons and their alkylated homologswere detected. The results of this work suggest thatthe formation of lipid compounds by aqueous FTTreactions proceeds by insertion of a CO group at theterminal end of a carboxylic acid functionality toform n-oxoalkanoic acids, followed by reductionto n-alkanoic acids, to n-alkanals, thento n-alkanols. The n-alkenes areintermediate homologs for n-alkan-2-ones andn-alkanes. This proposed mechanism for aqueousFTT synthesis differs from the surface-catalyzedstepwise FT process (i.e., gaseous) of polymerization of methylene reported in the literature.     

Composition of soluble cuticular lipids and water permeability of cuticular membranes from Citrus leaves

Water permeability and composition of soluble cuticular lipids of isolated cuticular membranes from leaves of Citrus aurantium L. were investigated for 3 successive years. The average water permeability coefficient determined using 169 cuticular membranes was 1.09·10^–7 cm s^–1 with a standard deviation of 0.78·10^–7 cm s^–1. There were no significant differences in water permeability between years. Cuticular membranes are characterized by a great variability in water permeability both within and between years. Both water permeability of individual membranes and variability between membranes are shown to be determined by soluble cuticular lipids contained within the cuticular membranes. The soluble cuticular lipids of Citrus leaves are composed of fatty acids, primary alcohols, esters, and hydrocarbons. They occur in amounts of 9.84 g cm^–2, which represents approx. 3% of the total mass of isolated cuticular membranes. The specific weight of cuticular membranes (365.4 g cm^–1) and total amount of soluble cuticular lipids did not vary significantly between years. Significant differences were observed for the amounts and composition of the constituent classes of lipids. Six homologues comprise 86% of the fatty acids (C₁₆; C₁₈; C₁₉; C₂₁; C₂₄; C₂₆), 83% of the primary alcohols (C₂₄; C₂₆; C₂₈; C₃₀; C₃₂; C₃₄) and 88% of the esters (C₃₆; C₃₈; C₄₀; C₄₁; C₄₂; C₄₄). Eleven major homologues amount only to 62% of the total hydrocarbons (C₁₆; C₁₇; C₁₈; C₂₀; C₂₆; C₂₇; C₂₉; C₃₀; C₃₁; C₃₂; C₃₃). Variability in the composition of soluble cuticular lipids between years was much smaller than variability of water permeability and, therefore, no relation between composition of soluble cuticular lipids and water permeability could be found. It is suggested that this may be due to the fact that the lipid composition observed represents the averages of 20 to 30 membranes analyzed so that differences between individual membranes may have been leveled out.Abbreviations CM cuticular membranes - MX polymer matrix - P_d permeability coefficient for diffusion of water - SCL soluble cuticular lipids - MES morpholinoethane sulphonic acid     

The impact of short rotation coppice on the concentrations of aliphatic soil lipids

The aim was to investigate how short rotation coppice (SRC) on arable soil in Northern Germany altered the concentrations of soil lipids, and thus, soil organic matter (SOM) quality. The concentrations of organic C and aliphatic lipids were determined in the litter and underlying soil layers under two willow (Salix caprea × viminalis clone 6, S. viminalis clone 78–183) and two poplar (Populus trichocarpa × deltoides cv. Beaupré, P. nigra × maximowiczii cv. Max 4) clones at a 14-year-old SRC and a permanent arable reference site. High organic C concentrations in the topsoil under S. viminalis and P. trichocarpa × deltoides agreed with high concentrations of long C-chain saturated n-alkanoic acids, n-alkanols and n-alkanes. These disproportionally higher concentrations of long C-chain saturated n-alkanoic acids (factor 3.6) and n-alkanols (factor 3.8) under S. viminalis and of n-alkanols (factor 3.9) under P. trichocarpa × deltoides than in an arable reference treatment indicated a lower microbial decomposability and, thus, a clone-specific accumulation of these SOM constituents. The clone-specific enrichments in long C-chain saturated n-alkanoic acids, n-alkanols and n-alkanes indicate that clone selection may be an approach to additional long-term storage of atmosphere CO₂ in the form of stable SOM under SRC.     

Effect of cell lipid composition on the formation of nonspecific antibiotic resistance in alkanotrophic rhodococci

The antibiotic resistance and lipid composition of rhodococci grown in rich organic media with gaseous or liquidn-alkanes were studied. Hydrocarbon-grown rhodococci exhibited an increased resistance to a wide range of antibiotics (aminoglycosides, linkosamides, macrolides, β-lactams, and aromatic compounds). The enhanced antibiotic resistance of rhodococci grown onn-alkanes correlated with an increased content of total cell lipids (up to 14–28%) and saturated straight-chain fatty acids (C_16:0, C_18:0, C_21:0) and was accompanied by the appearance of cardiolipin and phosphatidylglycerol in cells. These lipid compounds are supposed to promote the formation of nonspecific antibiotic resistance in rhodococci by decreasing the permeability of their cell envelope to antibiotics.     

A comparative study into the chemical constitution of cutins and suberins from Picea abies (L.) Karst., Quercus robur L., and Fagus sylvatica L.

The compositions of BF₃/CH₃OH depolymerisates of cutins and suberins from leaf and periderm samples from Picea abies [L.] Karst., Quercus robur L., and Fagus sylvatica L., respectively, were determined by quantitative capillary gas chromatography/mass spectroscopy. Long-chain monobasic, -hydroxymonobasic, dihydroxymonobasic, trihydroxymonobasic and epoxyhydroxymonobasic alkanoic acids constituted the major aliphatic monomers of leaf cutins. The total amounts of cutin monomers ranged from 629 mg · m^–2 (Fagus) to 1350 mg · m^–2 (Quercus). Cutin composition and amounts did not significantly differ between current year and three-year-old needles of Picea. Trans-esterification of periderm samples yielded a much greater variety of aliphatic monomers than obtained from cutins. In addition to the substance classes found with cutins, suberin depolymerisates also contained , -dibasic acids while dihydroxymonobasic acids were lacking. Depolymerisates from periderms taken from different locations on a Picea tree did not differ significantly in their relative composition. The results are discussed in terms of the distinctive characteristics of the aliphatic portions of cutins and suberins, respectively. Discriminant analysis is applied for formulating a quantitative and inarbitrary classification rule for cutins and suberins. The precision, statistical significance and robustness of this classification rule are tested by employing it to a large set of compositional data (70 plant species) from the literature. The relevance of data obtained by depolymerization methods for elucidating the physical structure of cutins and suberins in situ is evaluated.To whom correspondence should be addressedThe authors are indebted to Drs. J. Winkler and H. Krause (Laboratorium für Strukturchemie des Fachbereichs Chemie, Biologie und Geowissenschaften, Technische Universität München, Garching, FRG) for performing capillary gas chromatography-mass spectrometry and their valuable help in the identification of cutin and suberin constituents. The work was supported by grants from the Deutsche Forschungsgemeinschaft and the Bayerisches Staatsministerium für Unterricht, Kultus, Wissenschaft und Kunst.     

Degradation of long-chain n-alkanes by the yeast Candida maltosa

Summary The yeast Candida maltosa precultivated on liquid n-alkanes utilized different solid n-alkanes (especially C₂₀–C₂₅) in the presence of pristane as an organic phase with rates comparable to, or somewhat larger than, those of liquid n-alkanes. Analysis of cellular fatty acids indicated an assimilation of solid n-alkanes via monoterminal oxidation. The resulting fatty acids with substrate chain length were chain-shortened by C₂ units down to an optimal range of chain length from C₁₆ to C₁₈ and incorporated into cellular, lipids directly or after desaturation. The intermediates of chain-shortening with numbers of carbon atoms higher than C₁₈, as well as the unusually long-chain fatty acids of substrate chain length, were detected in trace amounts only. Even-carbon-numbered and odd-numbered fatty acids predominated in experiments with evenchain and odd-chain n-alkanes, respectively. Studies with cerulenin indicated that de novo synthesis of fatty acids was negligible. Oxidation of solid n-alkanes by the yeast C. maltosa yielded fatty acid patterns similar to those of cells grown on liquid n-alkanes.     

Application of Two‐Way Hierarchical Cluster Analysis for the Identification of Similarities between the Individual Lipid Fractions of Lucilia sericata

The composition of the cuticular and internal lipids of larvae and pupae of Lucilia sericata was studied using chromatographic techniques. The lipids from both stages of L. sericata had similar free fatty acid (FFA) profiles and also contained alcohols and cholesterol. The range of the number of C‐atoms detected for these classes of compounds was to some extent similar in larvae and pupae, but the relative amounts of each class differed between stages. Saturated as well as unsaturated FFAs with even and odd numbered C‐atom chains were present in both cuticular and internal lipids. The alcohol fractions of L. sericata were represented by free, straight‐chain primary alcohols containing an even number of C‐atoms. The lipid composition of male and female L. sericata adults and the hydrocarbon composition of all stages of L. sericata had previously been analyzed. To have a full overview of the lipid composition and to identify similarities or dissimilarities between the individual lipid fractions in this insect species, two‐way hierarchical cluster analysis (HCA) was performed using also the data from these previous publications. The content of FFA 18 : 1 (n‐9) was noticed to be very high in the cuticular fractions of larvae and pupae as well as in all internal fractions (male, female, larvae, and pupae) and low in the cuticular fractions of male and female imago. The contents of FFAs 16 : 0 and 16 : 1 (n‐9), cholesterol, and the n‐alkanes n‐C₃₁, n‐C₂₉, n‐C₂₇, n‐C₂₅, and n‐C₂₃ varied between particular fractions, whereas the amounts of other compounds were similar in all fractions.     

Thermodynamic analysis of nonelectrolyte sorption in plant cuticles: The effects of concentration and temperature on sorption of 4-nitrophenol

The sorption of 4-nitrophenol (4-NP) in enzymatically isolated cuticles ofLycopersicon esculentum fruits andFicus elastica leaves was studied as a function of temperature and solute concentration. Plots of the concentrations of 4-NP sorbed in the cuticle versus the equilibrium concentrations in the aqueous phase gave linear isotherms at low concentrations that tended to approach plateaus at higher sorbate concentrations ( 10 mmol·kg^-1). At low concentrations of sorbed 4-NP, cuticles have sorptive properties similar to those of organic solvents which are able to form intermolecular hydrogen bonds, while at higher concentrations their solid nature becomes apparent. During sorption of 4-NP the cutin matrix swells and new sorption sites are successively formed. The partition coefficients of 4-NP in the system cuticle/buffer are functions of temperature and concentration. At high sorbate concentrations (approx. 1 mol·kg^-1) they approach a value of 1. Different sorptive properties were observed for the cutin regions normally encrusted with soluble cuticular lipids (SCL) and those without SCL. Increasing temperature augmented the number of sorption sites in the cutin ofLycopersicon while no effect was observed withFicus. The changes of partial molar free energy (G ^o _tr), enthalpy (H ^o _tr), and entropy (S ^o _tr) for the phase transfer of 4-NP also depended on sorbate concentration: H ^o _tr and S ^o _tr were negative and steeply decreased at high sorbate concentrations. This is due to solute-solute interactions replacing solute-cutin interactions at high concentrations resulting in solid precipitates of solute within the cutin matrix. This formation of ordered solid domaines starting from a small number of nonelectrolyte molecules interacting with the cutin is proposed as a model for the intracuticular deposition of SCL.Abbreviations CM cuticular membrane - MX polymer matrix membrane - 4-NP 4-nitrophenol - SCL soluble cuticular lipids     

<Emphasis Type="Italic">n</Emphasis>-Alkanes variability in the diazotrophic cyanobacterium <Emphasis Type="Italic">Anabaena cylindrica</Emphasis> in response to NaCl stress

n-Alkanes pattern in response to NaCl stress has been studied in the cyanobacterium Anabaena cylindrica. Saturated hydrocarbons were separated and identified by gas chromatography-mass spectrometry (GC-MS) using serially coupled capillary column. Light chain n-alkanes in the range of C₉–C₁₇ (43%) and heavy chain n-alkanes in range of C₁₇–C₂₃ (34%) and C₂₃–C₃₁ (23%) were identified as the major components of total hydrocarbons in the NaCl adapted cells of A. cylindrica. In contrast, NaCl-untreated cells of A. cylindrica had dominance of only long chain n-alkanes in the range of C₂₃–C₃₁ comprising about 94% of its total n-alkanes. The persistence of high level (43%) of short chain n-alkanes (C₉–C₁₇) in NaCl adapted cells of A. cylindrica as compared to its negligible level (0.2%) in NaCl untreated counterpart clearly indicates that NaCl stress causes the A. cylindrica to shift towards the synthesis of short chain n-alkanes.     

Carbon and hydrogen isotopic fractionation during lipid biosynthesis in a higher plant (Cryptomeria japonica)

Compound-specific carbon and hydrogen isotopic compositions of lipid biomolecules (n-alkanes, n-alkanoic acids, n-alkanols, sesquiterpenes, diterpenes, phytol, diterpenols and β-sitosterol), extracted from Cryptomeria japonica leaves, were determined in order to understand isotopic fractionations occurring during lipid biosynthesis in this species. All lipid biomolecules were depleted in both ¹³C and D relative to bulk tissue and ambient water, respectively. n-Alkyl lipids associated with the acetogenic pathway were depleted in ¹³C relative to bulk tissue by 2.4-9.9‰ and depleted in D relative to ambient water by 91-152‰. C₁₅- and C₃₀-isoprenoid lipids (sesquiterpenes, squalene and β-sitosterol) associated with the mevalonic-acid pathway are depleted in ¹³C relative to bulk tissue by 1.7-3.1‰ and depleted in D relative to ambient water by 212-238‰. C₂₀-isoprenoid lipids (phytol and diterpenoids) associated with the non-mevalonic-acid pathway were depleted in ¹³C relative to bulk tissue by 4.6-5.9‰ and depleted in D relative to ambient water by 238-303‰. Phytol was significantly depleted in D by amounts up to 65‰ relative to other C₂₀ isoprenoid lipids. The acetogenic, mevalonic-acid and non-mevalonic-acid pathways were clearly discriminated using a cross-plot between the carbon and hydrogen isotopic fractionations.     

Chemotaxonomic Implications of the n‐Alkane Composition and the Nonacosan‐10‐ol Content in Picea omorika,Pinus heldreichii,and Pinus peuce

The n‐alkane composition and the nonacosan‐10‐ol content in the needle cuticular waxes of Serbian spruce (Picea omorika), Bosnian pine (Pinus heldreichii), and Macedonian pine (Pinus peuce) were compared. The amount of nonacosan‐10‐ol in the needle waxes of P. omorika was higher than those in P. heldreichii and P. peuce. The range of n‐alkanes was also wider in P. omorika (C₁₈–C₃₅) than in P. heldreichii and P. peuce (C₁₈–C₃₃). The dominant n‐alkanes were C₂₉ in the needle waxes of P. omorika, C₂₃, C₂₇, and C₂₅ in those of P. heldreichii, and C₂₉, C₂₅, C₂₇, and C₂₃ in those of P. peuce. The waxes of P. omorika contained higher amounts of n‐alkanes C₂₉, C₃₁, and C₃₃, while those of P. heldreichii and P. peuce had higher contents of n‐alkanes C₂₁, C₂₂, C₂₃, C₂₄, and C₂₆. The principal component analysis of the contents of nine n‐alkanes showed a clear separation of the Serbian spruce populations from those of the two investigated pine species, which partially overlapped. The separation of the species was due to high contents of the n‐alkanes C₂₉ and C₃₁ (P. omorika), C₁₉, C₂₀, C₂₁, C₂₂, C₂₃, and C₂₄ (P. heldreichii), and C₂₈ (P. peuce). Cluster analysis also showed a clear separation between the P. omorika populations on one side and the P. heldreichii and P. peuce populations on the other side. The n‐alkane and terpene compositions are discussed in the light of their usefulness in chemotaxonomy as well as with regard to the biogeography and phylogeny of these rare and endemic conifers.     

Ontogenetic and seasonal development of wax composition and cuticular transpiration of ivy (Hedera helix L.) sun and shade leaves

The ontogenetic and seasonal development of wax composition and cuticular transpiration of sun and shade leaves of ivy (Hedera helix L.) was analysed by investigating leaves varying in age between 4 and 202 d. It was discovered that the total amount of solvent-extractable wax was composed of two distinct fractions, separable by column chromatography: (i) a less polar or apolar monomeric wax fraction consisting of the typical linear, long-chain aliphatics usually described as cuticular wax components and (ii) a polar, oligomeric wax fraction consisting of primary alcohols and acids mostly esterified to C₁₂-, C₁₄- and C₁₆-ω-hydroxyfatty acids. The apolar wax fraction, which could be analysed directly by gas chromatography coupled with mass spectrometry (GC-MS), exhibited pronounced seasonal changes in composition. Wax amounts in the apolar fraction reached a maximum after about 30 d and gradually decreased again during the remaining period of the season investigated. In contrast, the polar wax fraction, which was analysable by GC-MS only after transesterification, rapidly increased early in the season, reaching a plateau after 40 d, and then remained constant during the rest of the season. Thus, total amounts of solvent-extractable cuticular waxes, which can be determined gravimetrically, will only be detected by GC-MS after fractionation and transesterification, a methodological approach rarely applied in the past in cuticular wax analysis. Additionally, investigation of the cutin polymer matrix after depolymerisation through transesterification, revealed that only those primary alcohols and acids forming an essential part of the apolar and the polar wax fractions were esterified during the investigated season and incorporated in increasing amounts into the cutin polymer matrix (matrix-bound wax fraction). Thus, it can be concluded that a complete analysis of cuticular wax of ivy and its seasonal development can only be achieved if all the relevant fractions (i) the less polar or apolar, (ii) the polar and (iii) the wax fraction bound to the cutin polymer matrix are investigated. Cuticular transpiration rapidly decreased within the first 30 d and essentially remained constant during the rest of the season. Thus, changes in cuticular water permeability were closely correlated with the most prominent changes in wax amounts and composition occurring during the first 30 d of ontogenetic leaf development. However, during the remainder of the year, up to 202 d, cuticular transport properties remained constant, although significant quantitative and qualitative changes in cuticular wax composition continued to occur. Thus, our study clearly demonstrated that there will be no simple relationship between chemical composition of cuticular waxes and transport properties of isolated ivy leaf cuticles. Received: 2 March 1998 / Accepted: 26 June 1998     

Water permeability of plant cuticles

Using the system vapor/membrane/liquid, permeability coefficients of cuticular transpiration (P _ct) were determined as functions of water activity in the vapor (a _wv). Enzymatically isolated cuticular membranes (CM) of Citrus aurantium L. and nonisolated CM of onion bulb scales and eggplant fruits were investigated. P _ct of Citrus and eggplant CM decreased with decreasing a _wv, while permeability coefficients of CM of onion were independent of a _wv. Extraction of soluble cuticular lipids (SCL) from the CM of Citrus increased permeability coefficients by a factor of approximately 500. This extraction had no effect on the dependence of P _ct on a _wv.Treating cuticular membranes as a resistance network consisting of SCL and the polymer matrix, it is shown that the permeability of onion CM is determined by the resistance of the SCL arranged in series with the polymer matrix. In this type of CM liquid and vapor are separated by a continuous, nonporous layer of SCL, and the driving force of transpiration is the gradient of partial pressure of water vapor across the SCL layer. In the CM of Citrus and eggplant, the SCL layer is traversed by polar pores that swell or shrink depending on a _wv. However, liquid continuity is maintained across these membranes down to a _wv=0.22, the lowest value used. In this type of membrane the driving force of transpiration is the water potential gradient across the membrane.Abbreviations CM cuticular membrane - MX polymer matrix - SCL soluble cuticular lipids - HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid - MES (N-morpholino)ethane sulfonic acid - SADH succinic acid 2,2-dimethyl hydrazide     

Production of poly(3-hydroxyalkanoates) by a bacterium of the genus Alcaligenes utilizing long-chain fatty acids

Summary The synthesis of poly(3-hydroxyalkanoates) [P(3HA)] by a new Alcaligenes species was investigated. The new species was grown on various carbon sources such as n-alkanoic acids of carbon numbers ranging from C₂ to C₂₂, plant oils and animal fats, and accumulated P(3HA) within the cells. When the bacterium was cultured in mineral media containing sodium salts of n-alkanoic acids, the homopolymer of poly(3-hydroxybutyrate) [P(3HB)] was produced from n-alkanoates of even carbon numbers, whereas the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate units [P(3HB-co-3HV)] was produced from n-alkanoates of odd carbon numbers. Relatively high yields of both dry cells and P(3HA) were obtained by the use of n-alkanoates from C₁₂ to C₁₆ as the sole carbon source. Correspondence to: Y. Doi     

Extractive compounds of birch buds (<Emphasis Type="Italic">Betula pendula</Emphasis> Roth.): II. Carbonyl compounds and oxides. Esters

This is the first report devoted to study of the hydrocarbon composition of the extract of buds of European birch Betula pendula (family Betulacea). We have identified saturated (C₁₆ to C₂₈, even number of carbon atoms) and unsaturated (linoleic and linolenic) fatty acids, β-caryophyllene, α-humulene, and the components of epicuticular waxes of cover scales, such as n-alkanes (C₂₁ to C₂₆), esters of fatty acids (C₁₆ to C₂₈, even number of carbon atoms), and fatty alcohols (C₁₈ to C₃₀, even number of carbon atoms). The gas chromatographic retention indices of all identified compounds have been determined.     

植物角质层蜡质的化学组成研究综述

角质层是植物与外界的第一接触面,而角质层蜡质则是由位于角质层外的外层蜡质和深嵌在角质层中的内层蜡质两部分构成。植物角质层蜡质成分极其复杂,具有重要的生理功能。综述了有关植物角质层蜡质的化学组成信息,探讨了目前植物角质层蜡质化学成分研究中存在的一些问题,展望了角质层蜡质成分的研究前景。     

Leaf n‐Alkanes as Characters Differentiating Coastal and Continental Juniperus deltoides Populations from the Balkan Peninsula

The composition of the cuticular n‐alkanes isolated from the leaves of nine populations of Juniperus deltoides R.P.Adams from continental and coastal areas of the Balkan Peninsula was characterized by GC‐FID and GC/MS analyses. In the leaf waxes, 14 n‐alkane homologues with chain‐lengths ranging from C₂₂ to C₃₅ were identified. n‐Tritriacontane (C₃₃) was dominant in the waxes of all populations, but variations between the populations in the contents of all n‐alkanes were observed. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses) were used to investigate the diversity and variability of the cuticular‐leaf‐n‐alkane patterns of the nine J. deltoides populations. This is the first report on the n‐alkane composition for this species. The multivariate statistical analyses evidenced a high correlation of the leaf‐n‐alkane pattern with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon.     

Assimilation of hydrocarbons

When cultivating different yeast genera on the mixture of C₁₁−C₂₃ n-alkanes with predominant C₁₆ and C₁₇ content C₁₆ and C₁₇ fatty acids predominated in the synthetized cell fat. Besides these C_11∶0, C_15∶0 and C_18∶1 fatty acids were also present in higher quantities in all strains tested. This conclusion is in agreement with results of the residualn-alkanes estimation where during the fermentation most of the C₁₆ and C₁₇ hydrocarbons decreased from the original hydrocarbon mixture. From these experiments it can be provisionally concluded that the qualitative composition of the cell fat is not dependent on the yeast strain investigated, the amount of fat on the dry weight basis depends on the strain.     

<Emphasis Type="Italic">n</Emphasis>-Alkane assimilation and <Emphasis Type="Italic">tert</Emphasis>-butyl alcohol (TBA) oxidation capacity in <Emphasis Type="Italic">Mycobacterium austroafricanum</Emphasis> strains

Mycobacterium austroafricanum IFP 2012, which grows on methyl tert-butyl ether (MTBE) and on tert-butyl alcohol (TBA), the main intermediate of MTBE degradation, also grows on a broad range of n-alkanes (C₂ to C₁₆). A single alkB gene copy, encoding a non-heme alkane monooxygenase, was partially amplified from the genome of this bacterium. Its expression was induced after growth on n-propane, n-hexane, n-hexadecane and on TBA but not after growth on LB. The capacity of other fast-growing mycobacteria to grow on n-alkanes (C₁ to C₁₆) and to degrade TBA after growth on n-alkanes was compared to that of M. austroafricanum IFP 2012. We studied M. austroafricanum IFP 2012 and IFP 2015 able to grow on MTBE, M. austroafricanum IFP 2173 able to grow on isooctane, Mycobacterium sp. IFP 2009 able to grow on ethyl tert-butyl ether (ETBE), M. vaccae JOB5 (M. austroaafricanum ATCC 29678) able to degrade MTBE and TBA and M. smegmatis mc2 155 with no known degradation capacity towards fuel oxygenates. The M. austroafricanum strains grew on a broad range of n-alkanes and three were able to degrade TBA after growth on propane, hexane and hexadecane. An alkB gene was partially amplified from the genome of all mycobacteria and a sequence comparison demonstrated a close relationship among the M. austroafricanum strains. This is the first report suggesting the involvement of an alkane hydroxylase in TBA oxidation, a key step during MTBE metabolism.     

Variations of the Composition of the Leaf Cuticular Wax among Chinese Populations of Plantago major

Plantago major L. grows in a very wide range of regions in China and exhibits great variations among populations. The analysis of the cuticular‐wax composition provides a potential approach to classify populations of P. major confronting different environmental conditions. Twelve populations of P. major and five populations of P. depressa Willd ., distributed over regions with average annual temperatures ranging from ?2.0 to 18.4°, were sampled, the variation of the composition of their cuticular waxes was analyzed, and their values of average chain length (ACL) and carbon preference index (CPI) were calculated. Great intra‐ and interspecies variations were observed for the total wax contents. The average annual temperature of the habitats was significantly correlated with the relative contents of the dominant n‐alkanes with an odd number of C‐atoms, but not with the wax contents. With an increasing average annual temperature, the relative contents of n‐alkanes C₂₉ and C₃₁ decreased, whereas those of C₃₃ and C₃₅ as well as the values of ACL_total and ACL_27–33 increased. Cluster analysis based on the pattern of the n‐alkane distribution allowed to clearly separate the populations of P. major according to the average annual temperature of their habitats, but not to separate the populations of the two species. Hence, the pattern of the n‐alkane distribution might be a good taxonomic marker for P. major at the intraspecies level, but not at the interspecies level. Nevertheless, a small difference between the populations of the two species was observed concerning the values of ACL_total and CPI_total, implying the potential use of these indices for the classification of the populations of the two species at the interspecies level.