Effects of Growth Pressure and Temperature on Fatty Acid Composition of a Barotolerant Deep-Sea Bacterium

The effects of pressure and temperature on the fatty acid composition in a barotolerant deep-sea bacterium that had branched-chain fatty acids were examined. The major fatty acids of the strain at atmospheric pressure were iso-C_15:0, C_16:1, iso-C_17:0, and iso-C_17:1. As the growth pressure increased, the proportion of unsaturated fatty acid increased because of an increase in the proportion of iso-C_17:1. On the other hand, as the growth temperature decreased, the proportion of unsaturated fatty acid increased because of the increase in the proportion of C_16:1 and C_18:1.     

Oleaginous yeast Meyerozyma guilliermondii shows fermentative metabolism of sugars in the biosynthesis of ethanol and converts raw glycerol and cheese whey permeate into polyunsaturated fatty acids

We studied the biotechnological potential of the recently isolated yeast Meyerozyma guilliermondii BI281A to produce polyunsaturated fatty acids and ethanol, comparing products yields using glucose, raw glycerol from biodiesel synthesis, or whey permeate as substrates. The yeast metabolism was evaluated for different C/N ratios (100:1 and 50:1). Results found that M. guilliermondii BI281A was able to assimilate all tested substrates, and the most efficient conversion obtained was observed using raw glycerol as carbon source (C/N ratio 50:1), concerning biomass formation (5.67 g·L⁻¹) and lipid production (1.04 g·L⁻¹), representing 18% of dry cell weight. Bioreactors experiments under pH and aeration-controlled conditions were conducted. Obtained fatty acids were composed of ~67% of unsaturated fatty acids, distributed as palmitoleic acid (C_16:1, 9.4%), oleic acid (C_18:1, 47.2%), linoleic acid (C_{18:2 n−6}, 9.6%), and linolenic acid (C_{18:3 n−3}, 1.3%). Showing fermentative metabolism, which is unusual for oleaginous yeasts, M. guilliermondii produced 13.7 g·L⁻¹ of ethanol (yields of 0.27) when growing on glucose medium. These results suggest the promising use of this uncommonly studied yeast to produce unsaturated fatty acids and ethanol using cheap agro-industrial residues as substrates in bioprocess.     

Poly-extremotolerant bacterium isolated from reverse osmosis reject: an implication toward waste water management

We demonstrate the tolerance of bacterial strain SM2014 to various unsustainable conditions and suggest its implication in waste water management. Its sustainability to reverse osmosis pressure (2.1 MPa) during desalination, and survival percentage of 73 % under hyperbaric conditions (pressure tension of 3.1 MPa under absolute oxygen atmosphere) confirmed its pressure tolerance. The growth of this strain at pH 9 or 10 and at 60 °C alone or in combination revealed its unique physiology as poly-extremotolerant strain. As an adaptive mechanism, the ratio of saturated to unsaturated fatty acids changed with growth conditions. Under poly-extreme condition long chain saturated fatty acid (C_18:0, C_16:0, C_14:0, C_12:0) predominated at the expense of unsaturated fatty acids. The nucleotide BLAST of 16S rRNA gene sequence of strain SM2014 with the NCBI gene bank sequences showed its close identity to Bacillus licheniformis with a similarity match of 94 %. The secretion of industrially valuable enzymes proteinase, lipase and amylase under such harsh conditions further signified potential of this strain as a source of extremozymes. Its unique characteristics underscore its relevance in waste water management.     

Photosynthesis,lipids and proteins in the cyanobacteriumSynechocystis PCC 6803 as affected by temperature

The cyanobacteriumSynechocystis PCC 6803 was grown photoautotrophically in an inorganic medium at constant growth temperatures of 20, 38 (control) or 43°C for 9 h. The up and down-shift of cultivation temperature decreased the growth as measured by culture absorbance and chlorophylla content. However, high temperature slightly increased the oxygen evolution while temperature lower than control inhibited oxygen evolution during the whole incubation period. The protein synthesis studied by¹⁴C-labeled protein declined under low temperature by about 50%. The fatty acid pattern is characterized as lacking in C₂₀/C₂₂ acids but containing large amounts of C₁₆ and C₁₈ polyunsaturated fatty acids, 16:2 and 18:3 in particular. The lower temperature increased the percentage of monounsaturated fatty acids while higher temperature increased the saturated fatty acid content in total lipids and lipid classes studied.     

Structure and composition of hydrocarbons and fatty acids from a marine blue-green alga,Synechococcus sp.

The major hydrocarbons of Synechococcus sp., a marine blue-green alga isolated from the Gulf of Mexico, were identified as 1-nonadecene and 1,14-nonadecadiene. The content of 1-nonadecene increased with culture age from about 0.5 mg/g dry weight in young cells to about 2.3 mg/g dry weight in old cells, while the content of 1,14-nonadecadiene remained constant with culture age at about 1 mg/g dry weight. Both [1-¹⁴C]acetate and [2-¹⁴C]acetate were incorporated to equal extents into the hydrocarbons. [1-¹⁴C]Stearate was incorporated into the hydrocarbons, but [³H]arachidate was not. The fatty acids of Synechococcus sp. were typical of blue-green algae, consisting of C_16:0, C_16:1, C_16:1, C_16:0, C_18:0, C_18:1, C_18:2 and C_18:3 fatty acids were detected. The hexadecenoic acid was shown to be 9-C_16:1 while the octadecenoic acid was a mixture of 93% 11-C_18:1 and 7% 9-C_18:1. The fatty acid content increased during the first 4 days of growth and then decreased slightly.     

Membranes of Tetrahymena: III. The effect of temperature on membrane core structures and fatty acid composition of Tetrahymena cells

Membrane core structures as revealed by the freeze-etch electron microscopy and the fatty acid composition measured by gas-liquid chromatography have been analyzed in Tetrahymena cells exposed to low temperature for varying periods.When cells were grown to mid-log phase at the optimal growth temperature of 28 °C and then chilled to 10 °C, cell division was inhibited. However, within 16 h the cells adapted to the low temperature.Chilling effected drastic structural alterations in the cores of different membrane types (membranes of the pellicula, the alveolar sacs, the endoplasmic reticulum and the nuclei). In all cases, there was a segregation of smooth faces from particle-rich faces in the fracture planes. However, the native membrane state, i.e. like that of cells grown at 28 °C, reappeared when the cells adapted to the low temperature.The total lipids of Tetrahymena cells contained primarily even-numbered fatty acids ranging from C₁₂ to C₁₈, but we also detected appreciable amounts of C₂₀ acids; this has not been reported before. During the initial phase of chilling, when cell division is inhibited, about 50% of the saturated fatty acids were replaced by unsaturated fatty acids, primarily monoenoic, dienoic and trienoic acids.We conclude that the structural recovery of the membranes in chilled Tetrahymena cells is accomplished by a desaturation of membrane fatty acids. This is discussed with respect to membrane “fluidity”.     

The Metabolism of the Germinating Oil Palm (Elaeis guineensis) Seedling : In Vivo Studies

The metabolism of ¹⁴C-labeled fatty acids and triacylglycerols was followed in intact germinating oil palm seedlings as well as in tissue slices. In the germinating seedling, the shoot contained a normal pattern of membrane fatty acids (mainly C₁₆, C_18:1, C_18:2) but the kernel contained about 68% C₁₂ and C₁₄ fatty acids. Haustorium fatty acids were intermediate between the two. [¹⁴C]Acetate was actively metabolized by shoot and haustorium slices but not so actively by the kernel. Approximately 9% to 17% was converted to water-soluble substances, 4% to 6% to CO₂, and 0.5% to 5.9% to lipids. The fatty acids synthesized in the shoot and haustorium were mainly C₁₆, C₁₈, and C_18:1 fatty acids but in the kernel about 18% to 32% of the ¹⁴C-fatty acids were C₁₂ fatty acids.

[¹⁴C]Lauric acid was absorbed and metabolized by haustorium slices and by the haustorium in intact seedlings; it was partly esterified to triacylglycerols and also converted to water-soluble substances and insoluble tissue material. In contrast, tri-[¹⁴C]laurin was absorbed but not metabolized. The haustorium also absorbed other fatty acids but the longer chain (C₁₆ and C₁₈) fatty acids were not esterified or metabolized further. Preincubation of the haustorium with plant hormones or in the presence of kernel tissue did not alter its inactivity towards tri-[¹⁴C]laurin.

When tri-[¹⁴C]laurin or [¹⁴C]lauric acid were injected into the seed or the shoot, there was no movement or radioactivity to other parts of the seedling. When injected into the shoot, but not into the seed, tri-[¹⁴C] laurin was hydrolyzed and partly metabolized to water-soluble substances.

     

Ultrastructure,composition of neutral lipids and their fatty acids of Candida tropicalis strain D-2 mutants resistant to the polyene antibiotic nystatin

This report deals with data on the cell ultrastructure of Candida tropicals strain D-2 mutants resistant to the polyene antibiotic, nystatin, and with an analysis of the fractional composition of neutral lipids and their fatty acids. The ultrastructural organization of the mutant cells is characterized by thickening of the cell wall and formation of invaginations into the cytoplasm, the appearance of new formations, large vacuoles, and reduction of the system of mitochondrial cristae. Lipids of nys^r mutants differ from those of the nys^s variant in having a decreased content of steroids and some fractions of neutral lipids. Certain nys^r mutants manifest difference in the relative amounts of saturated and unsaturated fatty acids (C_16:0, C_16:1, C_18:0, C_18:1).     

Photosynthetic performance at low temperature of Bouteloua gracilis Lag., a high-altitude C4 grass from the Rocky Mountains, USA

The mechanisms controlling the photosynthetic performance of C₄ plants at low temperature were investigated using ecotypes of Bouteloua gracilis Lag. from high (3000 m) and low (1500 m) elevation sites in the Rocky Mountains of Colorado. Plants were grown in controlled‐environment cabinets at a photon flux density of 700 μ mol m^?2 s^?1 and day/night temperatures of 26/16 °C or 14/7 °C. The thermal response of the net CO₂ assimilation rate (A) was evaluated using leaf gas‐exchange analysis and activity assays of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPCase) and pyruvate,orthophosphate dikinase (PPDK). In both ecotypes, a reduction in measurement temperature caused the CO₂‐saturated rate of photosynthesis to decline to a greater degree than the initial slope of A versus the intercellular CO₂ response, thereby reducing the photosynthetic CO₂ saturation point. As a consequence, A in normal air was CO₂‐saturated at sub‐optimal temperatures. Ecotypic variation was low when grown at 26/16 °C, with the major difference between the ecotypes being that the low‐elevation plants had higher A; however, the ecotypes responded differently when grown at cool temperature. At temperatures below the thermal optimum, A in high‐elevation plants grown at 14/7 °C was enhanced relative to plants grown at 26/16 °C, while A in low‐elevation plants grown at 14/7 °C was reduced compared to 26/16 °C‐grown plants. Photoinhibition at low growth temperature was minor in both ecotypes as indicated by small reductions in dark‐adapted F_v/F_m. In both ecotypes, the activity of Rubisco was equivalent to A below 17 °C but well in excess of A above 25 °C. Activities of PEPCase and PPDK responded to temperature in a similar proportion relative to Rubisco, and showed no evidence for dissociation that would cause them to become principal limitations at low temperature. Because of the similar temperature response of Rubisco and A, we propose that Rubisco is a major limitation on C₄ photosynthesis in B. gracilis below 17 °C. Based on these results and for theoretical reasons associated with how C₄ plants use Rubisco, we further suggest that Rubisco capacity may be a widespread limitation upon C₄ photosynthesis at low temperature.     

Stable Carbon Isotope Ratios of Lipid Biomarkers of Sulfate-Reducing Bacteria

We examined the potential use of natural-abundance stable carbon isotope ratios of lipids for determining substrate usage by sulfate-reducing bacteria (SRB). Four SRB were grown under autotrophic, mixotrophic, or heterotrophic growth conditions, and the δ¹³C values of their individual fatty acids (FA) were determined. The FA were usually ¹³C depleted in relation to biomass, with Δδ¹³C_{(FA − biomass)} of −4 to −17‰; the greatest depletion occurred during heterotrophic growth. The exception was Desulfotomaculum acetoxidans, for which substrate limitation resulted in biomass and FA becoming isotopically heavier than the acetate substrate. The δ¹³C values of FA in Desulfotomaculum acetoxidans varied with the position of the double bond in the monounsaturated C₁₆ and C₁₈ FA, with FA becoming progressively more ¹³C depleted as the double bond approached the methyl end. Mixotrophic growth of Desulfovibrio desulfuricans resulted in little depletion of the i17:1 biomarker relative to biomass or acetate, whereas growth with lactate resulted in a higher proportion of i17:1 with a greater depletion in ¹³C. The relative abundances of 10Me16:0 in Desulfobacter hydrogenophilus and Desulfobacterium autotrophicum were not affected by growth conditions, yet the Δδ¹³C_{(FA − substrate)} values of 10Me16:0 were considerably greater during autotrophic growth. These experiments indicate that FA δ¹³C values can be useful for interpreting carbon utilization by SRB in natural environments.     

Effect of light intensity on the proximate biochemical and fatty acid composition of Isochrysis sp. and Nannochloropsis oculata for use in tropical aquaculture

The total protein, carbohydrate, lipid and ash compositions, and fatty acid contents of two species of marine microalgae, the eustigmatophyte Nannochloropsis oculata (formerly ‘Chlorella sp., Japan’) and the chrysophyte Isochrysis sp. (Tahitian) used in tropical Australian mariculture, were studied. The microalgae were grown under a range of culture conditions (41 and 601 laboratory culture, 3001 bag culture, and 80001 outdoor culture) and four light regimes (100 to 107 μ E m⁻² s⁻¹, 240 to 390 μ E m⁻² s⁻¹, 340 to 620 μ E m⁻² s⁻¹, and 1100 to 1200 μE m⁻² s⁻¹ respectively) to determine the effect of light intensity on the chemical composition of large scale outdoor cultures. Laboratory and bag cultures were axenic and cultured in Walne medium while outdoor cultures were grown in a commercial medium designed for optimum nutrition in tropical outdoor aquaculture operations. Change in growth medium and photon flux density produced only small changes in the proximate biochemical composition of both algae. N. oculata and Isochrysis sp. both showed a trend towards slightly lower carbohydrate and higher chlorophyll a in shaded outdoor culture. Isochrysis sp. showed significant concentrations of the essential polyunsaturated fatty acid 22:6(n−3) (docosahexaenoic acid) from 5.3 to 10.3% of total fatty acid, and 20:5(n−3) (eicosapentaenoic acid) ranged from 0.6 to 4.1%. In contrast, N. oculata had high concentrations of 20:5(n−3) (17.8 to 39.9%) and only traces of 22:6(n−3). The fatty acid composition of Isochrysis sp. grown at high photon flux density (1100–1200 μE m⁻² s⁻¹) under outdoor culture showed a decrease in the percentage of several highly unsaturated fatty acids, including 20:5(n−3), and an increase in 22:6(n−3). N. oculata showed a similar decrease in the percentage of 20:5(n−3). High light intensity caused a decrease in the ratio of total C₁₆ unsaturated fatty acids to saturated 16:0 in N. oculata, and a decrease in the ratio of total C₁₈ unsaturated fatty acids to saturated 18:0 together with a decrease in the ratio of total unsaturated fatty acids to total saturated fatty acids in both microalgae.     

Agro-industrial oily wastes as substrates for PHA production by the new strain Pseudomonas aeruginosa NCIB 40045: Effect of culture conditions

Production of poly(3-hydroxyalkaonates) (PHA) by Pseudomonas aeruginosa 42A2 from agro-industrial oily wastes was studied. PHA accumulation, throughout the cell cycle, was observed as intracellular accumulation associated to polyphosphate granules. A 54.6% PHA accumulation was obtained when technical oleic acid (TOA) was used as carbon source. Molecular weight of the polymer was 54.7 Da. The polymer was amorphous, with glass transition at −47.5 °C and thermal degradation at 293 °C. PHA production and monomer composition were affected by K_La and temperature. The most relevant characteristic of the polymer produced at low aeration rates (K_La, 0.06 s⁻¹) were the unusual C_14:2 (13%) and the increase of C_12:1 (42.2%). The highest amount of unsaturated monomers was found in the polymer produced at 18 °C (64.4%).PHA accumulation ranged between 66.1% when waste-free fatty acids from soybean oil (WFFA) were used as carbon substrate, 29.4% when waste frying oil (WFO) was used and 16.8% when glucose was used. Depending on the substrate supplied a wide range of components was observed. Major saturated or unsaturated components of the polymer found were C_10:0, C_12:0 and C_8:0 or C_12:1 and C_14:1, respectively. When glucose was used as carbon substrate C_9:0, C_11:0 and C_16:0 were found.     

Fatty acid exchange of phospholipids in membranes of rat heart

Incorporation of ¹⁴C fatty acids in phospholipids of plasma membranes and sarcoplasmic reticulum of rat heart was studied. Mainly phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were labelled. Our studies showed that the incorporation of unsaturated fatty acids (oleic and linoleic acid) was higher than for saturated fatty acids (palmitic and stearic acid). The range of uptake was between 0.2 and 2.2 nmol·mg⁻¹ protein·h⁻¹ and 0.5–7.4 nmol·μgatom⁻¹ P₁·h⁻¹, respectively. Uptake of activity in individual phospholipids (measured after separation on TLC) was calculated as percentage of total activity. Incorporation in phosphatidylcholine was higher than in phosphatidylethanolamine. Phosphatidylcholine showed an increasing sequence for the following fatty acids: C_18:0 < C_16:0 < C_18:0 < C_18:2. However, phosphatidylethanolamine showed a decreasing sequence for the incorporation of the same fatty acids. Labelling of PC was always greater than for PE, except for stearic acid which was better incorporated into phosphatidylethanolamine. Uptake of the same fatty acid into phospholipids of sarcoplasmic reticulum was always higher than uptake into plasma membranes. As incorporation of fatty acids bound to albumin was studied in isolated membranes of rat heart, the addition of ATP and CoASH was an absolute requirement.     

Microbial fatty acid specificity

Strains ofRhodotorula sp.,Candida spp. andLangermania sp. cultivated on polyunsaturated oil preferentially incorporated more unsaturated fatty acids. These fatty acids were used mainly for growth needs whereas the saturated ones accumulated in the microbial cell. The cellular oil and the remaining oil in the culture had a lower degree of unsaturation as compared to the initial oil, and a modified fatty acid composition.Candida lipolytica, in a chemostat continuous culture, incorporated C₁₈ fatty acids in the order of C_18:3>C_18:2>C_18:1>C_18:0, and accumulated mostly the saturated ones. The specific productivity of the cellular oil and of the oil remaining in the culture medium was 0.036 and 0.487 gg⁻¹ h⁻¹, respectively, at dilution rateD=0.2/h.     

Fatty acids of monogalactosyl diglycerides from Citrus

Fatty acids in vesicular and leaf monogalactosyl diglycerides (MGDG) of citrus were studied. Vesicular MGDG contained front 94.4 to 97.3% C₁₆, C_16:1, C_18:1, C_18:2, and C_18:3; whereas leaf MGDG contained ca 90% C_18:3, 3% C₁₆ and 1.8 to 9.5% C_18:2. Species varied considerably in their percentages of vesicular C_18:2, C1_8:3 and to a lesser degree, C_16:1 and C_18:1 fatty acids with lemons being the most distinctive. Branched fatty acids were present to the extent of 5.6% in vesicular and to only 0.1% in leaf MGDG.     

Effects of Temperature on Composition and Cell Volume of Candida utilis

Candida utilis NCYC 321 was grown in steady-state culture in a chemostat under glucose limitation or NH₄⁺ limitation at temperatures of 30, 25, 20, and 15 C and at dilution rates (equal to growth rates) in the range of 0.35 to 0.05 hr⁻¹. Deoxyribonucleic acid contents of cells grown under the various conditions remained approximately constant, but the contents of several other cell components varied. Over the range of 30 to 15 C, the greatest differences were in the ribonucleic acid (RNA) and protein contents of cells grown under NH₄⁺ limitation, which increased as the temperature was decreased. The contents of other components, particularly adenosine triphosphate in cells grown under glucose limitation, varied more when the cells were grown at different rates at a fixed temperature. Cells grown at a fixed rate under NH₄⁺ limitation increased in volume as the temperature was decreased below 30 C. The increase in volume was closely correlated with increases in the proportions of RNA and protein in the dry weight of cells. Cells grown under glucose limitation showed much smaller increases in volume; these increases were poorly correlated with the increased RNA content and hardly at all with the increased protein content. Increases in volume with a decrease in growth temperature from 30 to 20 C were also demonstrated in cells grown under phosphate limitation and to a much smaller extent in cells grown under glycerol limitation. The increased RNA synthesized at low temperatures by cells grown under NH₄⁺ limitation was found almost exclusively in the 40,000 × g supernatant fluid, but only about 40% of it sedimented at 100,000 × g. Cells grown at a fixed rate under NH₄⁺ limitation synthesized less total carbohydrate when the temperature was decreased from 30 to 15 C. This decrease was mainly in the trichloroacetic acid-soluble fraction (probably trehalose) and in the intracellular hot alkali-soluble glucan (probably glycogen). Cells grown at a fixed rate under glucose limitation showed a small increase in carbohydrate content as the temperature was decreased from 30 to 15 C.     

Ruminococcus faecis sp. nov., isolated from human faeces

Bacterial strain Eg2^T, an anaerobic, Gram-positive, non-motile, and non-spore-forming coccus, was isolated from human faeces. The optimal temperature for its growth was 37°C. Oxidase activity was negative, but catalase activity was positive. The strain was able to hydrolyze esculin and to produce acids from the fermentation of several substrates, including glucose. Lactic and acetic acids were the main products of glucose fermentation. The major fatty acids present in this strain were C_16:0, C_14:0, and C_18:1 cis11 DMA. The G+C content was 43.4 mol%. Based on the 16S rRNA gene sequence, strain Eg2^T was closely related to species of the genus Ruminococcus (96.3% similarity to R. torques and 96.2% similarity to R. lactaris), and its taxonomic position was placed within the Clostridium cluster XIVa. Based on phenotypic, chemotaxonomic, genotypic, and phylogenetic evidence, we propose that this novel strain be assigned to the genus Ruminococcus and be named Ruminococcus faecis sp. nov. The type strain is Eg2^T (=KCTC 5757^T =JCM 15917^T).     

Leishmania species: fatty acid composition of promastigotes

The fatty acid composition of the total lipid fractions of five different Leishmania organisms grown on Eagle's medium was determined by gas chromatography. The major fatty acids identified in the total lipid fractions of L. donovani, L. tropica major, L. tropica minor, L. tropica (England strain), and L. enriettii were C_12:0, C_13:0, C_14:0, C_15:0, C_16:0, C_17:0, C_18:0, C_18:1, C_18:2, and C_18:3. The statistical differences among the fatty acid methyl esters of different Leishmania organisms are discussed.Gas chromatographic analysis of the fatty acid methyl esters of the total lipid fractions of the original Eagle's medium and the media after harvesting of various Leishmania species revealed the presence of C_18:3 fatty acid in the total lipid fraction of the medium of L. donovani and the complete absence of 18-carbon unsaturated fatty acids in the total lipid fraction of the medium of L. enriettii. The use of such differences in the differentiation of various Leishmania species is discussed.     

Further evidence for an elongation-decarboxylation mechanism in the biosynthesis of paraffins in leaves

In isolated tobacco leaves l-valine-U-¹⁴C gave rise to labeled even-numbered isobranched fatty acids containing 16 to 26 carbon atoms and iso C₂₉, iso C₃₁, and iso C₃₃ paraffins. l-Isoleucine-U-¹⁴C on the other hand produced labeled odd-numbered anteiso C₁₇ to C₂₇ fatty acids and anteiso C₃₀ and C₃₂ paraffins. Trichloroacetic acid inhibited the incorporation of isobutyrate into C₂₀ and higher fatty acids and paraffins without affecting the synthesis of the C₁₆ and C₁₈ fatty acids. Thus the very long branched fatty acids are biosynthetically related to the paraffins. In Senecio odoris leaves acetate-1-¹⁴C was incorporated into the paraffins (mainly n-C₃₁) only in the epidermis although acetate was readily incorporated into fatty acids in the mesophyll tissue. Similarly only the epidermal tissue incorporated acetate into fatty acids longer than C₁₈ suggesting that the epidermis is the site of synthesis of both paraffins and the very long fatty acids. In broccoli leaves n-C₁₂ acid labeled with ¹⁴C in the carboxyl carbon and ³H in the methylene carbons was incorporated into C₂₉ paraffin without the loss of ¹⁴C relative to ³H. Since n-C₁₈ acid is known to be incorporated into the paraffin without loss of carboxyl carbon these results suggest that the condensation of C₁₂ acid with C₁₈ acid is not responsible for n-C₂₉ paraffin synthesis in this tissue. Thus all the experimental evidence thus far obtained strongly suggests that elongation of fatty acids followed by decarboxylation is the most likely pathway for paraffin biosynthesis in leaves.     

Diversity of Yeasts from Puddles in the Vicinity of Midre Lovénbreen Glacier, Arctic and Bioprospecting for Enzymes and Fatty Acids

A total of 132 yeast strains were characterised from 4 sediment samples collected from small puddles in the vicinity of Midre Lovénbreen glacier, Arctic. Based on the D1/D2 domain sequence similarity, the isolates could be categorised into 6 groups. The nearest phylogenetic neighbour of groups I to VI were identified as Cryptococcus gastricus, Cryptococcus terricolus, Rhodotorula muscorum, Mrakia psychrophila, Mrakia gelida and Rhodotorula glacialis, respectively. Strains representative of the six groups were psychrophilic and salt tolerant but varied in their ability to produce cold-active extracellular enzymes such as lipase, protease, pectinase, cellulase and amylase. C_{18:1 (w9C)} and C_{18:2 (w9,12C)} were the only two fatty acids common to all the yeasts and branched and (or) unsaturated fatty acids increased in yeasts growing at 8°C compared to 22°C, probably as an adaptation to low temperature. The present study establishes that psychrophilic yeasts are predominant in Arctic and could be used as work horses to produce cold-active enzymes and poly unsaturated fatty acids which have been implicated in low temperature adaptation and also for their use in biotechnology.