Uptake and utilization of n-octacosane and n-nonacosane by Arthrobacter nicotianae KCC B35

Arthrobacter nicotianae KCC B35 isolated from blue-green mats densely covering oil sediments along the Arabian Gulf coast grew well on C₁₀ to C₄₀ n -alkanes as sole sources of carbon and energy. Growth on C₂₀ to C₄₀ alkanes was even better than on C₁₀ to C₁₈ alkanes. Biomass samples incubated for 6 h with n -octacosane (C₂₈) or n -nonacosane (C₂₉) accumulated these compounds as the predominant constituent alkanes of the cell hydrocarbon fractions. The even chain hexadecane C₁₆ and the odd chain pentadecane C₁₅ were the second dominant constituent alkanes in C₂₈ and C₂₉ incubated cells, respectively. n -Hexadecane-incubated cells accumulated in their lipids higher proportions of C₁₆-fatty acids than control cells not incubated with hydrocarbons. On the other hand, C₂₈ and C₂₉-incubated cells did not contain any fatty acids with the equivalent chain lengths, but the fatty acid patterns of the cell lipids suggest that there should have been mid-chain oxidation of these very long chain alkanes. This activity qualifies A. nicotianae KCC B35 to be used in cocktails for bioremediating environments polluted with heavy oil sediments.     

Effect of non-target cells on the sensitivity of the PCR for Escherichia coli O157 : H7

The fatty acid composition from mycelia of Streptomyces hygroscopicus strains was studied. A significant proportion of C_{18 : 2} was found in cultures. High levels of C_{16 : 0}, iso-C_{16 : 0} and C_{18 : 1} were also detected in all S. hygroscopicus strains. The different representatives of S. hygroscopicus had almost the same proportion of unsaturated fatty acids. Certain shifts in the amount of iso, anteiso and straight-chain fatty acids in some cultures were revealed. This might be explained by the adaptation capability of strains belonging to one species to form a variety of available fatty acids determined by particular cell membrane composition favouring certain antibiotic biosynthesis.     

Degradation of crude oil by Acinetobacter calcoaceticus and Alcaligenes odorans

Two types of Indian crude oil (Bombay High and Gujarat) were tested for their biodegradability by Acinetobacter calcoaceticus and Alcaligenes odorans. Acinetobacter calcoaceticus S30 and Alc. odorans P20 degraded Bombay High crude oil by 50% and 45%, while only 29% and 37% of Gujarat crude oil (heavy crude oil) was degraded by these isolates, respectively. Acinetobacter calcoaceticus and Alc. odorans in combination deraded 58% and 40% of Bombay High and Gujarat crude oils, respectively, which were significantly higher than that of by individual cultures. Acinetobacter calcoaceticus S30 degraded more of the alkanes fraction than the aromatics fraction of both crude oils. GC fingerprinting of alkane fraction showed major degradation of heptadecane (C₁₇), octadecane (C₁₈), nonadecane (C₁₉), eicosane (C₂₀), docosane (C₂₂), tricosane (C₂₃) and tetracosane (C₂₄) of crude oil, while the Alc. odorans P20 degraded alkanes and aromatics equally. The asphaltenic component increased in both types of crude oil after biodegradation. The two strains grew very well on n -alkane up to C₃₃ as well as on pristane (branched-chain alkane) but could not grow on cycloalkanes. Acinetobacter calcoaceticus S30 could not grow on pure polycyclic aromatic hydrocarbon (PAH) compounds except naphthalene but Alc. odorans P20 could grow on anthracene, phenanthrene, dibenzothiophene, fluorene, fluoranthene, pyrene and chrysene.     

Carbon isotope ratios of plants and occurrences of C4 species under different soil moisture regimes in arid region of Northwest China

Carbon isotope ratio of leaf dry matter, δ ¹³C, was measured on species occurring within Baiyin desert community, consisting of valley, slope and ridge microhabitats, and within Shandan desert community, consisting of Gobi desert and seasonal flooded creek microhabitats, in Northwest China. δ ¹³C of C₃ species increased with a decrease in soil water availability, suggesting that water-use efficiency (WUE) increased with decreasing soil moisture, whereas for all C₄ species, δ ¹³C tended to decrease with decreasing soil water availability, suggesting that WUE also increased with decreasing soil moisture. Above results indicated that water-use pattern was conservative under drought for C₄ and C₃ plants. In this present study, C₄ species' occurrences within different microhabitats were investigated and C₄ plants were observed to be absent and/or scarce within relatively lower soil moisture microhabitats, whereas they occurred and/or even had a high abundance within relatively higher soil moisture microhabitats, suggesting limited moisture available was a key factor of limiting C₄ distribution in arid region of Northwest China.     

Cellular fatty acid composition in moderately halophilic Gram-negative rods

The fatty acid compositions for 40 strains of moderately halophilic Gram-negative rods were determined by gas-liquid chromatography. The strains studied were included in the genera: Vibrio, Deleya, Alteromonas, Chromobacterium, Flavobac-terium and Pseudomonas. Although there were quantitative differences all strains showed more or less similar spectra of fatty acids ranging from C₁₂ to C₂₀ chain. The major fatty acid species were C_16:0, C_16:1 and C_18:1. Most striking was the predominance of the C_18:1 component, the major fatty acid in extracts of 29 of the 40 strains.     

Chromosome numbers of C3 and C4 variants within the species Alloteropsis sernialata (R.Br.) Hitchc. (Poaceae)

FREAN, M. L. & MARKS, E., 1988. Chromosome numbers of C₃ and C₄ variants within the species Alloteropais semialata (R.Br.) Hitch. (Poaceae). In a study of mid-lamina leaf sections, different variants of A. semialata were found to have C₃ or C₄ anatomy. The C₄ leaf showed a specialized photosynthetic vascular bundle sheath not present in the C₃ form. Chromosome counts made from pollen mother cell squashes showed that the C₃ form of A. semialata is a fertile diploid 2n = 2x = 18 and the C₄ form, a fertile allohexaploid 2n = 6x = 54. The cytological evidence suggests that the two forms should be considered as separate species.     

Antimicrobial activity of some alkyltrimethylammonium bromides

n-Alkyltrimethylammonium bromides (CnTAB) have been synthesized with n-alkyl chain lengths of between C₅ and C₂₂. Antimicrobial activity was assessed as growth inhibitory activity (MIC) towards seven representative strains of micro-organisms and as bacterial activity towards Staphylococcus aureus, Saccharomyces cerevisiae and Pseudomonas aeruginosa . These data indicated that whilst the level of activity was generally parabolically related to n-alkyl chain length, separate dependencies existed for short (n < 10) and long (n > 10) chain substituents, with disproportionately large increases in activity, in the order of three log cycles, occurring as substituent chain lengths increased from n = 10 to n = 12. This is interpreted in terms of distinct mechanisms of action, binding site and/or physicochemical properties for extreme members of the series.     

The origins and diversification of C4 grasses and savanna-adapted ungulates

C₄ grasses constitute the main component of savannas and are pervasive in other dry tropical ecosystems where they serve as the main diet for grazing animals. Among potential factors driving C₄ evolution of grasses, the interaction between grasses and grazers has not been investigated. To evaluate if increased grazing pressure may have selected for higher leaf silica production as the grasses diverged, we reconstructed the phylogeny of all 800 genera of the grass family with both molecular (combined multiplastid DNA regions) and morphological characters. Using molecular clocks, we also calculated the age and number of origins of C₄ clades and found that shifts from C₃ to C₄ photosynthesis occurred at least 12 times starting 30.9 million years ago and found evidence that the most severe drop in atmospheric carbon dioxide in the late Oligocene (between 33 and 30 million years ago) matches the first origin of C₄ photosynthesis in Chloridoideae. By combining fossil and phylogenetic data for ungulates and implementing a randomization procedure, our results showed that the appearance of C₄ grass clades and ungulate adaptations to C₄-dominated habitats match significantly in time. An increase of leaf epidermal density of silica bodies was found to correspond to postulated shifts in diversification rates in the late Miocene [24 significant shifts in diversification ( P <0.05) were detected between 23 and 3.7 million years ago]. For aristidoid and chloridoid grasses, increased grazing pressure may have selected for a higher leaf epidermal silica production in the late Miocene.     

Unusual glycoconjugates in the oesophagus of a tilapine polyhybrid

The aim of this work is to elucidate the glycoconjugate composition of the secretory products of the oesophageal mucous cells in a tilapine polyhybrid. Lectin histochemistry gave evidence of the presence of β-galactose, α-N-acetylgalactosamine and sialic acid residues in the terminal position. The majority of sialic acid belongs to short side chains; a few sialic acid residues are acetylated at the C₇ and/or C₈ and/or C₉ level. The heterogeneity of the carbohydrate chains may mask potential receptor sites for micro-organisms and hamper the formation of multiple bonds.     

Distribution of C3 and C4 grasses along an altitudinal gradient in Central Argentina

The distribution pattern of C₃ and C₄ grasses was studied in eight sites located between 350 m and 2100 m along an altitudinal gradient in Central Argentina. Of 139 taxa fifty-nine are C₃ and eighty C₄. Species of the C₃ tribes (Stipeae, Poeae, Meliceae, Aveneae, Bromeae and Triticeae) and C₃ Paniceae species increase in number at higher elevations; only one C₃ species was found below 650 m. C₄ Aristideae, Pappophoreae, Eragrostideae, Cynodonteae, Andropogoneae and Paniceae increase at lower altitudes. The floristic crossover point is at about 1500 m; the ground cover cross-over point is at about 1000 m. Analysis of the relationships between % C₄ species along the gradient and nine climatic and environmental variables showed the highest correlation with July mean temperature, but all temperature variables show highly significant correlations with % C₄. Correlation with annual rainfall is lower but also significant. These results are consistent with previous research showing the relative importance of C₄ grasses as temperature increases. C₃ species make a high contribution to relative grass coverage below the C₃/C₄ floristic crossover point but are rare below 1000 m.     

Photorespiration in C4 grasses remains slow under drought conditions

The CO₂-concentrating mechanism present in C₄ plants decreases the oxygenase activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and, consequently, photorespiratory rates in air. Under drought conditions, the intercellular CO₂ concentration may decrease and cause photorespiration to increase. The C₄ grasses Paspalum dilatatum Poiret, Cynodon dactylon (L.) Pers. and Zoysia japonica Steudel were grown in soil and drought was imposed by ceasing to provide water. Net CO₂ assimilation ( A ) and stomatal conductance to water vapour decreased with leaf dehydration. Decreased carbon and increased oxygen isotope composition were also observed under drought. The response of A to CO₂ suggested that the compensation point was zero in all species irrespective of the extent of drought stress. A slight decrease of A as O₂ concentration increased above 10% provided evidence for slow photorespiratory gas exchanges. Analysis of amino acids contained in the leaves, particularly the decrease of glycine after 30 s in darkness, supported the presence of slow photorespiration rates, but these were slightly faster in Cynodon dactylon than in Paspalum dilatatum and Zoysia japonica . Although the contents of glycine and serine increased with dehydration and mechanistic modelling of C₄ photosynthesis suggested slightly increased photorespiration rates in proportion to photosynthesis, the results provide evidence that photorespiration remained slow under drought conditions.     

Ozone induced emissions of biogenic VOC from tobacco: relationships between ozone uptake and emission of LOX products

Volatile organic compound (VOC) emissions from tobacco ( Nicotiana tabacum L. var. Bel W3) plants exposed to ozone (O₃) were investigated using proton-transfer-reaction mass-spectrometry (PTR-MS) and gas chromatography mass-spectrometry (GC-MS) to find a quantitative reference for plants' responses to O₃ stress. O₃ exposures to illuminated plants induced post-exposure VOC emission bursts. The lag time for the onset of volatile C₆ emissions produced within the octadecanoid pathway was found to be inversely proportional to O₃ uptake, or more precisely, to the O₃ flux density into the plants. In cases of short O₃ pulses of identical duration the total amount of these emitted C₆ VOC was related to the O₃ flux density into the plants, and not to ozone concentrations or dose–response relationships such as AOT 40 values. Approximately one C₆ product was emitted per five O₃ molecules taken up by the plant. A threshold flux density of O₃ inducing emissions of C₆ products was found to be (1.6 ± 0.7) × 10⁻⁸ mol m⁻² s⁻¹.     

Seasonal differences in photosynthesis between the C3 and C4 subspecies of Alloteropsis semialata are offset by frost and drought

The regional abundance of C₄ grasses is strongly controlled by temperature, however, the role of precipitation is less clear. Progress in elucidating the direct effects of photosynthetic pathway on these climate relationships is hindered by the significant genetic divergence between major C₃ and C₄ grass lineages. We addressed this problem by examining seasonal climate responses of photosynthesis in Alloteropsis semialata , a unique grass species with both C₃ and C₄ subspecies. Experimental manipulation of rainfall in a common garden in South Africa tested the hypotheses that: (1) photosynthesis is greater in the C₄ than C₃ subspecies under high summer temperatures, but this pattern is reversed at low winter temperatures; and (2) the photosynthetic advantage of C₄ plants is enhanced during drought events. Measurements of leaf gas exchange over 2 years showed a significant photosynthetic advantage for the C₄ subspecies under irrigated conditions from spring through autumn. However, the C₄ leaves were killed by winter frost, while photosynthesis continued in the C₃ plants. Unexpectedly, the C₄ subspecies also lost its photosynthetic advantage during natural drought events, despite greater water-use efficiency under irrigated conditions. This study highlights previously unrecognized roles for climatic extremes in determining the ecological success of C₃ and C₄ grasses.     

Effects of age, supra-ambient oxygen and repeated assays on acetylene reduction and root respiration in pea

An open flow-through gas system was used to investigate the effect of plant age on nitrogenase activity in relation to root respiration (measured as CO₂ release) and supra-ambient O₂ levels in 24- to 51-day-old, nodulated Pisum sativum L. cv. Bodil. The effect of assaying plants repeatedly was also studied. The respiratory efficiency of nitrogenase [mol CO₂ (mol C₂H₄)⁻¹] and the relative decline in nitrogenase (EC 1.7.99.2) activity in response to introduction of C₂H₂ in the gas stream were unaffected by plant age. In contrast, the nitrogenase-linked respiration as a proportion of total root respiration increased with time. Accordingly, the specific respiration linked-to growth and maintenace of the noduled root system decreased with time. C₂H₂ reduction and root respiration were increased by supra-ambient O₂ levels, but the tolerance to high O₂ concentrations seemed to decrease with plant age. Repeated C₂H₂ assays on the same plants decreased their rate of growth and N accumulation: in addition, nitrogenase activity and root respiration were somewhat negatively affected. The results indicate that results from experiments with plants of different ages cannot always be directly compared, and that repeated C₂H₂ assays on the same plants should be applied with caution in physiological work.     

Enhanced degradation of petrol (Slovene diesel) in an aqueous system by immobilized Pseudomonas fluorescens

The rate of degradation of n -alkanes C₁₂-C₁₈, in petrol (Slovene diesel) in an aqueous system, by free and immobilized Pseudomonas fluorescens in shaking flasks was investigated. Cells were immobilized to a biosupport, Biofix, and a biosorbant, Drizit. Analysis of cellular growth of the free and immobilized bacteria over 8 d of incubation with diesel as the sole carbon source, showed a reduction in the lag phase in the immobilized cultures in comparison to the free system. The free system degraded 52·3% of C₁₂ and 11·6% of C₁₃, but C₁₄-C₁₈ were not degraded. In comparison to the free system and diesel which had not been exposed to experimental conditions (unexposed), the immobilized systems degraded significantly more of C₁₃-C₁₈. Biofix-immobilized cells degraded 14·8% of C₁₂ and an average of 53·5% of C₁₃-C₁₈. Drizit-immobilized cells degraded 24·5% of C₁₂, 52·4% of C₁₃ and an average of 91·2% of C₁₄-C₁₈. This study shows the successful use of immobilized bacteria technology to enhance the degradation of diesel in an aqueous system.     

The C system of cattle blood groups. 1. Additional factors in the system

Four additional cattle blood group antigenic factors, provisionally termed Fl, F6, F10 and F15, were shown to belong to the C system. Factor Fl appears to be a linear subtype of C"(initially designated F2, or P1B1). It is suggested that future international nomenclature should adopt C", and C"₂ in place of Fl and C . No phenogroup was found to include C" together with C₂ or C₁, but a few phenogroups lack the three factors. Thus C₁, C₂ and C"do not form a closed system within the C system as concluded by Duniec et al. (1973). The effectiveness of the additional factors to uncover the genetic variability of the C system, and to translate phenotypes into genotypes is exemplified in the Charolais breed.     

Anaerobic utilization of alkylbenzenes and n-alkanes from crude oil in an enrichment culture of denitrifying bacteria affiliating with the beta-subclass of Proteobacteria

Denitrifying bacteria were enriched from freshwater sediment with added nitrate as electron acceptor and crude oil as the only source of organic substrates. The enrichment cultures were used as laboratory model systems for studying the degradative potential of denitrifying bacteria with respect to crude oil constituents, and the phylogenetic affiliation of denitrifiers that are selectively enriched with crude oil. The enrichment culture exhibited two distinct growth phases. During the first phase, bacteria grew homogeneously in the aqueous phase, while various C₁–C₃ alkylbenzenes, but no alkanes, were utilized from the crude oil. During the second phase, bacteria also grew that formed aggregates, adhered to the crude oil layer and emulsified the oil, while utilization of n -alkanes (C₅ to C₁₂) from the crude oil was observed. During growth, several alkylbenzoates accumulated in the aqueous phase, which were presumably formed from alkylbenzenes. Application of a newly designed, fluorescently labelled 16S rRNA-targeted oligonucleotide probe specific for the Azoarcus / Thauera group within the β-subclass of Proteobacteria revealed that the majority of the enriched denitrifiers affiliated with this phylogenetic group.     

Fatty acids of leaf wax esters in Coincya Rouy (Brassicaceae)

A total of 46 populations belonging to the genus Coincya Ruoy (Brassicaceae) from the Iberian Peninsula was examined for their wax ester fatty acids composition. Size of ester fatty acids in the genus Coincya varies between 14 and 28 carbon atoms. This series is dominated by acids with an even number of carbon atoms. The most abundant acids are Ojg, C^y, C^^o and C₂₆ among evens and C₁₇ and C₂₁ among odds. A positive correlation was observed between chemical composition and environmental adaptation, and also with certain morphological characters. Changes relate to low temperatures or to high relative humidity, and there is a positive correlation between chemical composition and leaf glaucousness.     

Arabidopsis CER8 encodes LONG-CHAIN ACYL-COA SYNTHETASE 1 (LACS1) that has overlapping functions with LACS2 in plant wax and cutin synthesis

Plant cuticle is an extracellular lipid-based matrix of cutin and waxes, which covers aerial organs and protects them from many forms of environmental stress. We report here the characterization of CER8 / LACS1 , one of nine Arabidopsis long-chain acyl-CoA synthetases thought to activate acyl chains. Mutations in LACS1 reduced the amount of wax in all chemical classes on the stem and leaf, except in the very long-chain fatty acid (VLCFA) class wherein acids longer than 24 carbons (C₂₄) were elevated more than 155%. The C₁₆ cutin monomers on lacs1 were reduced by 37% and 22%, whereas the C₁₈ monomers were increased by 28% and 20% on stem and leaf, respectively. Amounts of wax and cutin on a lacs1-1 lacs2-3 double mutant were much lower than on either parent, and lacs1-1 lacs2-3 had much higher cuticular permeability than either parent. These additive effects indicate that LACS1 and LACS2 have overlapping functions in both wax and cutin synthesis. We demonstrated that LACS1 has synthetase activity for VLCFAs C₂₀–C₃₀, with highest activity for C₃₀ acids. LACS1 thus appears to function as a very long-chain acyl-CoA synthetase in wax metabolism. Since C₁₆ but not C₁₈ cutin monomers are reduced in lacs1 , and C₁₆ acids are the next most preferred acid (behind C₃₀) by LACS1 in our assays, LACS1 also appears to be important for the incorporation of C₁₆ monomers into cutin polyester. As such, LACS1 defines a functionally novel acyl-CoA synthetase that preferentially modifies both VLCFAs for wax synthesis and long-chain (C₁₆) fatty acids for cutin synthesis.