我国霍乱弧菌的脂肪酸分型研究

目的 对脂肪酸分型方法在霍乱弧菌菌株鉴定、菌株相似性分析等方面的应用价值进行评价。方法 选取了分离自我国的两个主要致病血清群的194株霍乱弧菌菌株（1961年以来的El Tor型和1992年以来的O139群）,提取脂肪酸,应用MIDI公司的脂肪酸分型系统,进行数据分析。结果 检测的所有菌株都含有的脂肪酸成分有13种。霍乱弧菌的判断符合率为88.6%。二维聚类分析没有成明显可区分的群, O139群霍乱弧菌的脂肪酸组成与O1群的相似,产毒与非产毒霍乱弧菌的脂肪酸成分没有显著差异。结论 脂肪酸分型对弧菌种的快速鉴定有应用价值,对霍乱弧菌的现场分离鉴定有辅助意义,在小样本暴发资料的研究中能够反映菌株之间的亲缘关系,但其对霍乱弧菌种属内的各种特征性菌群不具有鉴别能力。     

Chemotaxonomic characterization of rice seedling blight complex using fatty acid methyl ester (FAME) profiles

Rice seedling blight is an important disease caused by a complex of fungi that include Fusarium, Rhizopus, Pythium, and Trichoderma species. A modified MIDI method was used for extraction of fatty acids from these causal pathogens, and fatty acid methyl ester (FAME) profiles were characterized. Factors that might affect fatty acid production, such as period of culture and saponification in extraction, were also evaluated. A total of 14 fatty acids were detected, and FAME profiles showed quantitative and qualitative variations by discriminant analysis and principal component analysis. Genus-specific FAME profiles consisting of the types of fatty acid produced and remarkable components of individual fatty acids were observed. The possibility of application as chemotaxonomic methods based on the FAME profiles for diagnosis of the rice seedling blight complex is also discussed.     

Isolation and characterization of fatty acid methyl ester (FAME)‐producing Streptomyces sp. S161 from sheep (Ovis aries) faeces

An actinomycete producing oil‐like mixtures was isolated and characterized. The strain was isolated from sheep faeces and identified as Streptomyces sp. S161 based on 16S rRNA gene sequence analysis. The strain showed cellulase and xylanase activities. The ¹H nuclear magnetic resonance (NMR) spectra of the mixtures showed that the mixtures were composed of fatty acid methyl esters (52·5), triglycerides (13·7) and monoglycerides (9·1) (mol.%). Based on the gas chromatography–mass spectrometry (GC‐MS) analysis, the fatty acid methyl esters were mainly composed of C14‐C16 long‐chain fatty acids. The results indicated that Streptomyces sp. S161 could produce fatty acid methyl esters (FAME) directly from starch. To our knowledge, this is the first isolated strain that can produce biodiesel (FAME) directly from starch.

Significance and Impact of the Study

Nowadays, production of biodiesel is based on plant oils, animal fats, algal oils and microbial oils. Lipid mostly consists of triacylglycerols (TAG), and conversion of these lipids into fatty acid short‐chain alcohol esters (methanol or ethanol) is the final step in biodiesel production. In this study, an oil‐producing Streptomyces strain was isolated from sheep faeces. The oil was composed of C₁₄‐C₁₆ long‐chain fatty acid methyl esters, triglycerides and monoglycerides. This is the first isolated strain‐producing biodiesel (FAME) directly from starch. Due to showing cellulase and xylanase activities, the strain would be helpful for converting renewable lignocellulose into biodiesel directly.     

Subgrouping of bacterial populations by cellular fatty acid composition

Abstract The cellular fatty acid composition of six bacterial species isolated from the seeds and leaves of sugar beet ( Beta vulgaris ) and from soil were analysed. The quantitative data from the fatty acid methyl ester (FAME) profiles were highly reproducible. Numerical analysis of Xanthomonas maltophilia . FAME profiles sub-grouped strains according to when they were isolated in the growing season. The analytical method used was sensitive enough to differentiate strains of Klebsiella terrigena isolated from either soil or leaves. The results from this study confirm reports that analyses of bacterial FAME composition were rapid to perform, specific and allowed differentiation of strains within the same species.     

Chemotaxonomy of heterocystous cyanobacteria using FAME profiling as species markers

The fatty acid methyl ester (FAME) analysis of the 12 heterocystous cyanobacterial strains showed different fatty acid profiling based on the presence/absence and the percentage of 13 different types of fatty acids. The major fatty acids viz. palmitic acid (16:0), hexadecadienoic acid (16:2), stearic acid (18:0), oleic acid (18:1), linoleic (18:2), and linolenic acid (18:3) were present among all the strains except Cylindrospermum musicola where oleic acid (18:1) was absent. All the strains showed high levels of polyunsaturated fatty acid (PUFAs; 41-68.35%) followed by saturated fatty acid (SAFAs; 1.82-40.66%) and monounsaturated fatty acid (0.85-24.98%). Highest percentage of PUFAs and essential fatty acid (linolenic acid; 18:3) was reported in Scytonema bohnerii which can be used as fatty acid supplement in medical and biotechnological purpose. The cluster analysis based on FAME profiling suggests the presence of two distinct clusters with Euclidean distance ranging from 0 to 25. S. bohnerii of cluster I was distantly related to the other strains of cluster II. The genotypes of cluster II were further divided into two subclusters, i.e., IIa with C. musicola showing great divergence with the other genotypes of IIb which was further subdivided into two groups. Subsubcluster IIb(1) was represented by a genotype, Anabaena sp. whereas subsubcluster IIb(2) was distinguished by two groups, i.e., one group having significant similarity among their three genotypes showed distant relation with the other group having closely related six genotypes. To test the validity of the fatty acid profiles as a marker, cluster analysis has also been generated on the basis of morphological attributes. Our results suggest that FAME profiling might be used as species markers in the study of polyphasic approach based taxonomy and phylogenetic relationship.     

A High-Throughput Fatty Acid Profiling Screen Reveals Novel Variations in Fatty Acid Biosynthesis in Chlamydomonas reinhardtii and Related Algae

Analysis of fatty acid methyl esters (FAMEs) by gas chromatography (GC) is a common technique for the quantitative and qualitative analysis of acyl lipids. Methods for FAME preparation are typically time-consuming and labor-intensive and require multiple transfers of reagents and products between reaction tubes and autosampler vials. In order to increase throughput and lower the time and materials costs required for FAME preparation prior to GC analysis, we have developed a method in which 10-to-20-mg samples of microbial biomass are transferred to standard GC autosampler vials, transesterified using an emulsion of methanolic trimethylsulfonium hydroxide and hexane, and analyzed directly by GC without further sample handling. This method gives results that are essentially identical to those obtained by the more labor- and material-intensive FAME preparation methods, such as transmethylation with methanolic HCl. We applied this method to the screening of laboratory and environmental isolates of the green alga Chlamydomonas for variations in fatty acid composition. This screening method facilitated two novel discoveries. First, we identified a common laboratory strain of C. reinhardtii, CC-620, completely lacking all ω-3 fatty acids normally found in this organism and showed that this strain contains an inactivating mutation in the CrFAD7 gene, encoding the sole ω-3 desaturase activity in this organism. Second, we showed that some species of Chlamydomonas make Δ6-unsaturated polyunsaturated fatty acids (PUFA) rather than the Δ5 species normally made by the previously characterized laboratory strains of Chlamydomonas, suggesting that there is species-specific variation in the regiospecificity and substrate selectivity of front-end desaturases in this algal genus.     

Comparison of two fatty acid analysis protocols to characterize and differentiate Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici

The utility of fatty acid methyl ester (FAME) profiles for characterization and differentiation of isolates of Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici was investigated. Two fatty acid analysis protocols of the normal (MIDI) and a modified MIDI method were used for their utility. Only the modified MIDI method allowed a clear differentiation between F. oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicislycopersici. FAME profiles using the modified MIDI method gave the most consistent and reproducible analyzed fatty acid data. Evaluation of the FAME profiles based on cluster analysis and principal-component analysis revealed that FAME profiles from tested isolates were correlated with the same vegetative compatibility groups (VCGs) compared to the same races in F. oxysporum f. sp. lycopersici. Results indicated that FAME profiles could be an additional tool useful for characterizing isolates and forma species of F. oxysporum obtained from tomato.     

Congruence of ribosomal DNA sequencing, fatty acid methyl ester profiles and morphology for characterization of the genus Rhizophagus (arbuscular mycorrhiza fungus)

Difficulties in obtaining sterile axenic cultures and heterogeneity in nuclear-encoded ribosomal DNA (n-rDNA) sequences within a single arbuscular mycorrhizal spore make genetic analysis of arbuscular mycorrhizal fungi (AMF) a complicated task, and currently available methods of genotyping are inadequate for identification to the species level. Therefore, we applied a multipronged approach on different isolates grown in root organ culture (ROC) belonging to the genus Rhizophagus which were not characterized at species level. Each strain was characterized using the fatty acid methyl ester profile (FAME), partial sequencing of a small subunit-internal transcribed spacer (SSU-ITS) and a large subunit (LSU) region of n-rDNA, and morphological examination of spores. Neighbor-joining trees obtained from the SSU-ITS rDNA sequences were broadly similar to those obtained from the LSU rDNA sequences. FAME profiles of the same isolates used for molecular characterization were obtained using fatty acid datasets, and results were compared to a neighbor-joining tree of n-rDNA sequence. Based on the results of these studues, a combination of morphology, biomarkers (FAME), and molecular sequencing (of highly variable D1-D2 of LSU and ITS) is recommended for phylogenetic analysis and characterization of species/strain of Glomeromycota.     

Polyphasic taxonomy of symbiotic rhizobia from wild leguminous plants growing in Egypt

About 20 strains of rhizobia from wild legumes were characterized based on numerical analysis of phenotypic characteristics, nodulating ability, fatty acid methyl esters (FAME) and SDS-PAGE profiles of whole cell proteins. FAME analysis revealed that palmitic (16:0), stearic (18:0) and arachidonic (20:0) were detected in most of wild-legume rhizobia, the latter being uncommon in fatty acid profiles of Rhizobium and Sinorhizobium. Numerical analysis of FAME classified strains of wild-legume rhizobia into 9 clusters and one heterogeneous group. There was both agreement and disagreement with the clustering data based on phenotypic analysis and FAME analysis. Four strains were grouped together in the same cluster based on both methods. However, 4 another strains, which were placed in one cluster of phenotypic analysis, were distributed in several clusters after FAME analysis. SDS-PAGE of whole-cell proteins revealed that the rhizobial strains exhibited protein profiles with peptide bands ranging from 5-19 band per profile and showed molar mass of 110-183 kDa. As in the case of FAME analysis, numerical analysis of protein bands was compared with clustering of phenotypic analysis. Agreement of the two methods was obvious when clustering some strains but conflicted in the classification of some other strains. However, integration of the three methods could be the basis of a polyphasic taxonomy. The twenty strains of wild-legume rhizobia were finally classified as follows: 12 strains related to Rhizobium leguminosarum, 5 strains related to Sinorhizobium meliloti and 3 strains to Rhizobium spp. Rhizobia nodulating wild herb legumes are among indigenous strains nodulating crop legumes in cultivated as well as noncultivated lands.     

<Emphasis Type="Italic">Fremyella diplosiphon</Emphasis> as a Biodiesel Agent: Identification of Fatty Acid Methyl Esters via Microwave-Assisted Direct In Situ Transesterification

Increasing concerns on environmental and economic issues linked to fossil fuel use has driven great interest in cyanobacteria as third-generation biofuel agents. In this study, the biodiesel potential of a model photosynthetic cyanobacterium, Fremyella diplosiphon, was identified by fatty acid methyl esters (FAME) via direct transesterification. Total lipids in wild type (Fd33) and halotolerant (HSF33-1 and HSF33-2) strains determined by gravimetric analysis yielded 19% cellular dry weight (CDW) for HSF33-1 and 20% CDW for HSF33-2, which were comparable to Fd33 (18% CDW). Gas chromatography-mass spectrometry detected a high ratio of saturated to unsaturated FAMEs (2.48–2.61) in transesterified lipids, with methyl palmitate being the most abundant (C16:0). While theoretical biodiesel properties revealed high cetane number and oxidative stability, high cloud and pour point values indicated that fuel blending could be a viable approach. Significantly high FAME abundance in total transesterified lipids of HSF33-1 (40.2%) and HSF33-2 (69.9%) relative to Fd33 (25.4%) was identified using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry, indicating that robust salt stress response corresponds to higher levels of extractable FAME. Alkanes, a key component in conventional fuels, were present in F. diplosiphon transesterified lipids across all strains confirming that natural synthesis of these hydrocarbons is not inhibited during biodiesel production. While analysis of photosynthetic pigments and phycobiliproteins did not reveal significant differences, FAME abundance varied significantly in wild type and halotolerant strains indicating that photosynthetic pathways are not the sole factors that determine fatty acid production. We characterize the potential of F. diplosiphon for biofuel production with FAME yields in halotolerant strains higher than the wild type with no loss in photosynthetic pigmentation.     

Characterization of soybean bradyrhizobia for which serogroup affinities have not been identified

The USDA, ARS National Rhizobium Germplasm Collection contains 143 accessions of slow-growing soybean strains among which there are 17 distinct serological groups. However, 11 strains appear to have no serological affinity with the 17 serogroups. Therefore, we determined whether these strains were diverse and examined their phylogenetic placement. Nine strains formed nitrogen-fixing symbioses with soybean indicating that these accessions were not contaminants. We concluded from results of amplified fragment length polymorphism (AFLP) analysis, using 3 selective primers with 8 strains, that they were genetically dissimilar. Nine strains were examined for their fatty acid composition using fatty acid methyl ester (FAME) derivatives. The FAME results with 5 strains and serotype strains of Bradyrhizobium elkanii were similar, while results with each of the remaining 2 pairs were either similar to the type strain of Bradyrhizobium japonicum (USDA 6) or to USDA 110. Evolutionary history of 9 strains was reconstructed from sequence divergence of a combination of the complete 16S rRNA gene, the internally transcribed spacer region, and about 400 bases of the 5' end of the 23S rRNA gene. Placement of 5 strains was nested within B. elkanii, 2 with USDA 110, and the other 2 with USDA 6. We concluded that soybean isolates that cannot be placed within one of the 17 established serogroups are phenotypically and genetically as diverse as the serotype strains.     

Study on intraspecific diversity of Ralstonia solanacearum strains in West Malaysia using whole cell fatty acid analysis

Abstract

Surveys were conducted between the years of 2005 and 2006 at several locations in the northern, central and southern parts of West Malaysia to study the polymorphism of Ralstonia solanacearum strains. These sites included vegetables and farms with known hosts of the pathogen, such as banana, tomato, eggplant, chili and tobacco. Samples were collected from the suspected wilted plants and weeds, including soil and water samples, in selected areas. The bacterium was isolated in all samples using semi-selective tetrazolium chloride medium (TZC). The bacteria strains were detected by using the BIOLOG identification system and were confirmed by nested-PCR. Fatty Acid Methyl Esters (FAME) profiling was performed to determine polymorphism among 58 bacterial isolates. The results showed that the fatty acid composition varied for all R. solanacearum isolates. Grouping of R. solanacearum isolates by fatty acid composition suggested that the existence of distinct groups that were significantly related to host of bacteria but low correlation between fatty acid profiles and biovar or sampling site was detected. A unique FAME profile was found among the strains that have been isolated from banana.     

Characterization of Armillaria spp. from peach orchards in the southeastern United States using fatty acid methyl ester profiling

Limited information is available regarding the composition of cellular fatty acids in Armillaria and the extent to which fatty acid profiles can be used to characterize species in this genus. Fatty acid methyl ester (FAME) profiles generated from cultures of A. tabescens, A. mellea, and A. gallica consisted of 16–18 fatty acids ranging from 12–24 carbons in length, although some of these were present only in trace amounts. Across the three species, 9-cis,12-cis-octadecadienoic acid (9,12-C18:2), hexadecanoic acid (16:0), heneicosanoic acid (21:0), 9-cis-octadecenoic acid (9-C18:1), and 2-hydroxy-docosanoic acid (OH-22:0) were the most abundant fatty acids. FAME profiles from different thallus morphologies (mycelium, sclerotial crust, or rhizomorphs) displayed by cultures of A. gallica showed that thallus type had no significant effect on cellular fatty acid composition (P > 0.05), suggesting that FAME profiling is sufficiently robust for species differentiation despite potential differences in thallus morphology within and among species. The three Armillaria species included in this study could be distinguished from other lignicolous basidiomycete species commonly occurring on peach (Schizophyllum commune, Ganoderma lucidum, Stereum hirsutum, and Trametes versicolor) on the basis of FAME profiles using stepwise discriminant analysis (average squared canonical correlation = 0.953), whereby 9-C18:1, 9,12-C18:2, and 10-cis-hexadecenoic acid (10-C16:1) were the three strongest contributors. In a separate stepwise discriminant analysis, A. tabescens, A. mellea, and A. gallica were separated from one another based on their fatty acid profiles (average squared canonical correlation = 0.924), with 11-cis-octadecenoic acid (11-C18:1), 9-C18:1, and 2-hydroxy-hexadecanoic acid (OH-16:0) being most important for species separation. When fatty acids were extracted directly from mycelium dissected from naturally infected host tissue, the FAME-based discriminant functions developed in the preceding experiments classified all samples (n = 16) as A. tabescens; when applied to cultures derived from the same naturally infected samples, all unknowns were similarly classified as A. tabescens. Thus, FAME species classification of Armillaria unknowns directly from infected tissues may be feasible. Species designation of unknown Armillaria cultures by FAME analysis was identical to that indicated by IGS-RFLP classification with AluI.     

Increasing unsaturated fatty acid contents in Escherichia coli by coexpression of three different genes

Biodiesel is an interesting alternative energy source and is used as substitute for petroleum-based diesel. Microorganisms have been used for biodiesel production due to their significant environmental and economic benefits. However, few researches have investigated the regulation of fatty acid composition of these microbial diesels. Fatty acid biosynthesis in Escherichia coli has provided a paradigm for other bacteria and plants. By overexpressing two genes (fabA and fabB) associated with unsaturated fatty acid (UFA) synthesis in E. coli, we have engineered an efficient producer of UFAs. Saturated fatty acid (SFA) contents decreased from 50.2% (the control strain) to 34.6% (the recombinant strain overexpressing fabA and fabB simultaneously) and the ratio of cis-vaccenate (18:1Δ11), a major UFA in E. coli, reached 51.1% in this recombinant strain. When an Arabidopsis thaliana thioesterase (AtFatA) was coexpressed with these two genes, 0.19 mmol l⁻¹ fatty acids was produced by this E. coli strain after 18-h culture under shake-flask conditions. Free fatty acids made up about 37.5% of total fatty acid concentration in this final engineered strain carrying fabA, fabB, and AtFatA, and the ratio of UFA/SFA reached 2.3:1. This approach offers a means to improve the fatty acid composition of microdiesel and might pave the way for production of biodiesel equivalents using engineered microorganisms in the near future.     

Rapid GC analysis of cellular fatty acids for characterizing Lactobacillus sake and Lact. curvatus strains of meat origin

A rapid procedure based on the gas chromatographic analysis of cellular fatty acids was used to differentiate between strains of Lactobacillus sake and Lact. curvatus isolated from dry salami. All strains had very similar fatty acid profiles except four of them which lacked C19 cycl acid, but neither this feature nor other differences in single fatty acid contents could be successfully correlated with the biochemical discrimination of Lact. sake from Lact. curvatus . When, however, strains were compared on the basis of the total content of fatty acids with 18 carbon atoms divided by that with 16 carbon atoms, a very good correlation with strain characterization by classical methods was achieved. It was concluded that selected cellular fatty acid ratios might be useful for characterizing phylogenetically related strains of lactic acid bacteria.     

Heterogeneous diacylglycerol acyltransferase expression enhances lipids and PUFA in Chlorella species

Algae have been explored for renewable energy, nutraceuticals, and value-added products. However, low lipid yield is a significant impediment to its commercial viability. Genetic engineering can improve the fatty acid profile of algae without compromising its growth. This study introduced the diacylglycerol acyltransferase (BnDGAT) gene from Brassica napus into Chlorella sorokiniana-I, a fast-growing and thermotolerant natural strain isolated from wastewater, which increased its intracellular lipid accumulation. Hygromycin-resistant cells were selected, and enhanced green florescence protein fluorescence was used to distinguish pure transgenic cell lines from mixed cultures. Compared to the wild type, BnDGAT expression in transgenic C. sorokiniana-I caused a threefold increase in non-polar lipid and a twofold increase in polyunsaturated fatty acids. Nile red staining reaffirmed the presence of higher intracellular lipid bodies in transgenic cells. There was a substantial alteration in the fatty acid profile of transgenic alga expressing BnDGAT. The non-essential omega 9 (C18: 1) fatty acid decreased (5%–7% from 18%), while alpha-linolenic acid, an essential omega 3 fatty acid (C18: 3), was increased (23%–24% from 11%). This study substantiates a valuable strategy for enhancing essential omega-3 fatty acids and neutral lipids to improve its nutritional value for animal feed. The increased lipid productivity should reduce the cost of producing fatty acid methyl esters (FAME). Improved FAME quality should address the clouding issues in cold regions.     

Characterization of Neutrophilic Fe(II)-Oxidizing Bacteria Isolated from the Rhizosphere of Wetland Plants and Description of Ferritrophicum radicicola gen. nov. sp. nov., and Sideroxydans paludicola sp. nov.

Iron deposits (Fe plaque) on wetland plant roots contain abundant microbial populations, including Fe(II)-oxidizing bacteria (FeOB) that have not been cultured previously. In this study, 4 strains of Fe plaque-associated FeOB were isolated from 4 species of wetland plants. All 4 isolates grew in tight association with Fe-oxides, but did not form any identifiable Fe-oxide structures. All strains were obligate lithotrophic Fe(II)-oxidizers that were microaerobic, and were unable to use other inorganic or organic energy sources. One strain, BrT, was shown to fix ¹⁴ CO ₂ at a rate consistent with its requirement for total cell carbon. The doubling times for the strains varied between 9.5 and 15.8 hours. The fatty acid methyl ester (FAME) profiles of 2 strains, BrT and CCJ, revealed that 16:0, 15:1 isoG, and 14:0 were dominant fatty acids. Phylogenetic analysis of the 16S rRNA gene indicated that all the strains were Betaproteobacteria. Two of the strains, BrT and Br-1 belong to a new species, Sideroxydans paludicola; a third strain, LD-1, is related to Sideroxydans lithotrophicus, a recently described species of FeOB. The fourth isolate, Ferritrophicum radicicola, represented a new genus in a new order of Betaproteobacteria, the Ferritrophicales. There are no other cultured isolates in this order. A small subunit rRNA gene-based, cultivation-independent analysis of Typha latifolia collected from a wetland revealed terminal restriction fragment profiles (tRFLP) consistent with the presence of these bacteria in the rhizosphere. These novel organisms likely play an important role in Fe(II) oxidation kinetics and Fe cycling within many terrestrial and freshwater environments.     

Thermal effects on the blood respiratory properties of southern bluefin tuna, Thunnus maccoyii

Fasting-induced changes in fatty acid composition have been reported to occur within the body lipids of several types of animals; however, little is known about the changes in fatty acid profiles exhibited by reptiles subjected to prolonged fasting. This study characterizes the fatty acid profiles of six reptile species subjected to sublethal periods of fasting lasting 0, 56, 112, and 168 days. Analyses of fatty acid methyl esters (FAMEs) conducted on the total body lipids of rattlesnakes (Crotalus atrox), ratsnakes (Elaphe obsoleta), pythons (Python regius), boas (Boa constrictor), true vipers (Bitis gabonica), and monitor lizards (Varanus exanthematicus) revealed that all of the species exhibited similar characteristic changes in their fatty acid profiles during starvation stress. According to ANOVAs, the four most effective indicators of the onset of starvation were significant increases in the [1] fatty acid unsaturation index as well as ratios of [2] linoleic to palmitoleic acid, [3] oleic to palmitic, and [4] arachidonic to total fatty acid concentrations. The results of this study suggest that FAME analyses might be useful for identifying nutritional stress and/or starvation among squamate reptiles; however, forthcoming studies will be required to validate the generality of these responses. I also review the potential limitations of this approach, and suggest experiments that will be important for future applications of FAME analyses. Ultimately, it is hoped that FAME analyses can be used in conjunction with current practices as an additional tool to characterize the prevalence of starvation experienced by free-living reptiles.     

Production of 7,10-dihydroxy-8(<Emphasis Type="Italic">E</Emphasis>)-octadecenoic acid from olive oil by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> PR3

Microbial modification of naturally occurring materials is one of the efficient ways to add new values to them. Hydroxylation of free unsaturated fatty acids by microorganism is a good example of those modifications. Among microbial strains studied for that purpose, a new bacterial isolate Pseudomonas aeruginosa PR3 has been well studied to produce several hydroxy fatty acids from different unsaturated fatty acids. Of those hydroxy fatty acids, 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was efficiently produced from oleic acid by strain PR3. However, it was highly plausible to use vegetable oil containing oleic acid rather than free oleic acid as a substrate for DOD production by strain PR3. In this study, we firstly tried to use olive oil containing high content of oleic acid as a substrate for DOD production. DOD production from olive oil was confirmed by structural determination with GC, TLC, and GC/MS analysis. DOD production yield from olive oil was 53.5%. Several important environmental factors were also tested. Galactose and glutamine were optimal carbon and nitrogen sources, and magnesium ion was critically required for DOD production from olive oil. Results from this study demonstrated that natural vegetable oils containing oleic acid could be used as efficient substrate for the production of DOD by strain PR3.     

Fatty acid methyl ester (FAME) profiles as measures of soil microbial community structure

Analysis of fatty acid methyl ester (FAME) profiles extracted from soils is a rapid and inexpensive procedure that holds great promise in describing soil microbial community structure without traditional reliance on selective culturing, which seems to severely underestimate community diversity. Interpretation of FAME profiles from environmental samples can be difficult because many fatty acids are common to different microorganisms and many fatty acids are extracted from each soil sample. We used principal components (PCA) and cluster analyses to identify similarities and differences among soil microbial communities described using FAME profiles. We also used PCA to identify particular FAMEs that characterized soil sample clusters. Fatty acids that are found only or primarily in particular microbial taxa-marker fatty acids-were used in conjunction with these analyses. We found that the majority of 162 soil samples taken from a conventionally-tilled corn field had similar FAME profiles but that about 20% of samples seemed to have relatively low, and that about 10% had relatively high, bacterial:fungal ratios. Using semivariance analysis we identified 21:0 iso as a new marker fatty acid. Concurrent use of geostatistical and FAME analyses may be a powerful means of revealing other potential marker FAMEs. When microbial communities from the same samples were cultured on R2A agar and their FAME profiles analyzed, there were many differences between FAME profiles of soil and plated communities, indicating that profiles of FAMEs extracted from soil reveal portions of the microbial community not culturable on R2A. When subjected to PCA, however, a small number of plated communities were found to be distinct due to some of the same profile characteristics (high in 12:0 iso, 15:0 and 17:1 ante A) that identified soil community FAME profiles as distinct. Semivariance analysis indicated that spatial distributions of soil microbial populations are maintained in a portion of the microbial community that is selected on laboratory media. These similarities between whole soil and plated community FAME profiles suggest that plated communities are not solely the result of selection by the growth medium, but reflect the distribution, in situ, of the dominant, culturable soil microbial populations.