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1.
Ting Wei Tee Anupam Chowdhury Costas D. Maranas Jacqueline V. Shanks 《Biotechnology and bioengineering》2014,111(5):849-857
Increasing demand for petroleum has stimulated industry to develop sustainable production of chemicals and biofuels using microbial cell factories. Fatty acids of chain lengths from C6 to C16 are propitious intermediates for the catalytic synthesis of industrial chemicals and diesel‐like biofuels. The abundance of genetic information available for Escherichia coli and specifically, fatty acid metabolism in E. coli, supports this bacterium as a promising host for engineering a biocatalyst for the microbial production of fatty acids. Recent successes rooted in different features of systems metabolic engineering in the strain design of high‐yielding medium chain fatty acid producing E. coli strains provide an emerging case study of design methods for effective strain design. Classical metabolic engineering and synthetic biology approaches enabled different and distinct design paths towards a high‐yielding strain. Here we highlight a rational strain design process in systems biology, an integrated computational and experimental approach for carboxylic acid production, as an alternative method. Additional challenges inherent in achieving an optimal strain for commercialization of medium chain‐length fatty acids will likely require a collection of strategies from systems metabolic engineering. Not only will the continued advancement in systems metabolic engineering result in these highly productive strains more quickly, this knowledge will extend more rapidly the carboxylic acid platform to the microbial production of carboxylic acids with alternate chain‐lengths and functionalities. Biotechnol. Biotechnol. Bioeng. 2014;111: 849–857. © 2014 Wiley Periodicals, Inc. 相似文献
2.
Fatty alcohols have numerous commercial applications, including their use as lubricants, surfactants, solvents, emulsifiers, plasticizers, emollients, thickeners, and even fuels. Fatty alcohols are currently produced by catalytic hydrogenation of fatty acids from plant oils or animal fats. Microbial production of fatty alcohols may be a more direct and environmentally-friendly strategy since production is carried out by heterologous enzymes, called fatty acyl-CoA reductases, able to reduce different acyl-CoA molecules to their corresponding primary alcohols. Successful examples of metabolic engineering have been reported in Saccharomyces cerevisiae and Escherichia coli in which the production of fatty alcohols ranged from 1.2 to 1.9 g/L, respectively. Due to their metabolic advantages, oleaginous yeasts are considered the best hosts for production of fatty acid-derived chemicals. Some of these species can naturally produce, under specific growth conditions, lipids at high titers (>50 g/L) and therefore provide large amounts of fatty acyl-CoAs or fatty acids as precursors. Very recently, taking advantage of such features, over 8 g/L of C16–C18 fatty alcohols have been produced in Rhodosporidium toruloides. In this review we summarize the different metabolic engineering strategies, hosts and cultivation conditions used to date. We also point out some future trends and challenges for the microbial production of fatty alcohols. 相似文献
3.
An engineered reversal of the β-oxidation cycle was exploited to demonstrate its utility for the synthesis of medium chain (6–10-carbons) ω-hydroxyacids and dicarboxylic acids from glycerol as the only carbon source. A redesigned β-oxidation reversal facilitated the production of medium chain carboxylic acids, which were converted to ω-hydroxyacids and dicarboxylic acids by the action of an engineered ω-oxidation pathway. The selection of a key thiolase (bktB) and thioesterase (ydiI) in combination with previously established core β-oxidation reversal enzymes, as well as the development of chromosomal expression systems for the independent control of pathway enzymes, enabled the generation of C6–C10 carboxylic acids and provided a platform for vector based independent expression of ω-functionalization enzymes. Using this approach, the expression of the Pseudomonas putida alkane monooxygenase system, encoded by alkBGT, in combination with all β-oxidation reversal enzymes resulted in the production of 6-hydroxyhexanoic acid, 8-hydroxyoctanoic acid, and 10-hydroxydecanoic acid. Following identification and characterization of potential alcohol and aldehyde dehydrogenases, chnD and chnE from Acinetobacter sp. strain SE19 were expressed in conjunction with alkBGT to demonstrate the synthesis of the C6–C10 dicarboxylic acids, adipic acid, suberic acid, and sebacic acid. The potential of a β-oxidation cycle with ω-oxidation termination pathways was further demonstrated through the production of greater than 0.8 g/L C6–C10 ω-hydroxyacids or about 0.5 g/L dicarboxylic acids of the same chain lengths from glycerol (an unrelated carbon source) using minimal media. 相似文献
4.
《Process Biochemistry》2014,49(6):989-995
Rhamnolipids are surface-active molecules produced by Pseudomonas aeruginosa as congener mixtures. They are considered “green” alternatives to synthetic surfactants used in industrial, remediation and pharmaceutical applications. Optimizing yield as well as controlling congener distribution are necessary steps for successful commercialization of rhamnolipids. This study used a mixture of glucose and fatty acids of different chain length (C12–C22) and saturation (C18:1 and C18:2) to produce monorhamnolipids and determine the effect of fatty acid substrates on rhamnolipid yield, percent carbon conversion and congener distribution. Results show that 1% glucose + 0.25% stearic acid (C18) produced the greatest yield (2.1 g L−1) compared to other glucose–fatty acid combinations (0.8–1.8 g L−1). Various glucose + C18 ratios were then tested to optimize yield and percent substrate carbon conversion to monorhamnolipid. Results revealed a positive linear correlation between the mass percent of C18 used and the percent carbon conversion. A mass percent of 67% C18 was optimal resulting in a 44% carbon conversion and a yield of 13.7 g L−1 monorhamnolipid. For all fatty acid substrates tested, the RhaC10C10 was the most abundant and RhaC10C12:1 was the least abundant of the four major congeners produced. However, the relative amount of RhaC10C8 and RhaC10C12 congeners was dependent on several factors: in general, fatty acid substrates with relatively short chain length (C12 and C14), unsaturated fatty acid substrate (C18:2), and longer cultivation time resulted in a higher RhaC10C8/RhaC10C12 ratio. These findings will assist in mass production of monorhamnolipids and controlling the specific congeners produced. 相似文献
5.
Cell growth and lipid production of a marine microalga Nannochloropsis oceanica DUT01 were investigated, and fresh medium replacement with different ratios to promote long term cell growth and lipid accumulation was also tested. The highest lipid content reached 64% in nitrogen deplete f/2 medium containing 37.5 mg/L NaNO3 combined with 1/5 fresh medium replacement, however, the highest lipid titer (0.6 g/L) and lipid productivity (31 mg/L/d) were achieved using BG11 medium containing 1.5 g/L NaNO3, taking advantage of 1/5 fresh medium replacement as well, which corresponded to the maximum biomass production of 1.4 g/L, highlighting the importance of high biomass accumulation for efficient lipid production. When biomass compositions were monitored throughout the culture, decreased protein content was found to be coupled with increased lipid production, whereas relatively stable carbohydrate content was observed. The fatty acids in the lipid of N. oceanica DUT01 comprise over 65% saturated fatty acids and monounsaturated acids (i.e. palmitic acid (C16:0) and oleic acid (C18:1)), suggesting that N. oceanica DUT01 is a promising candidate for biodiesel production. Interestingly, very high content of hexadecadienoic acid (C16:2, about 26–33%) was produced by DUT01, which distinguished this microalga with other microalgae strains reported so far. 相似文献
6.
The functions of two long-chain fatty acid CoA ligase genes (facl) in crude oil-degrading Geobacillus thermodenitrificans NG80-2 were characterized. Facl1 and Facl2 encoded by GTNG_0892 and GTNG_1447 were expressed in Escherichia coli and purified as His-tagged fusion proteins. Both enzymes utilized a broad range of fatty acids ranging from acetic acid (C2) to melissic acid (C30). The most preferred substrates were capric acid (C10) for Facl1 and palmitic acid (C16) for Facl2, respectively. Both enzymes had an optimal temperature of 60 °C, an optimal pH of 7.5, and required ATP as a cofactor. Thermostability of the enzymes and effects of metal ions, EDTA, SDS and Triton X-100 on the enzyme activity were also investigated. When NG80-2 was cultured with crude oil rather than sucrose as the sole carbon source, upregulation of facl1 and facl2 mRNA was observed by real time RT-PCR. This is the first time that the activity of fatty acid CoA ligases toward long-chain fatty acids up to at least C30 has been demonstrated in bacteria. 相似文献
7.
Branched-chain fatty acids (BCFAs) are key precursors of branched-chain fuels, which have cold-flow properties superior to straight chain fuels. BCFA production in Gram-negative bacterial hosts is inherently challenging because it competes directly with essential and efficient straight-chain fatty acid (SCFA) biosynthesis. Previously, Escherichia coli strains engineered for BCFA production also co-produced a large percentage of SCFA, complicating efficient isolation of BCFA. Here, we identified a key bottleneck in BCFA production: incomplete lipoylation of 2-oxoacid dehydrogenases. We engineered two protein lipoylation pathways that not only restored 2-oxoacid dehydrogenase lipoylation, but also increased BCFA production dramatically. E. coli expressing an optimized lipoylation pathway produced 276 mg/L BCFA, comprising 85% of the total free fatty acids (FFAs). Furthermore, we fine-tuned BCFA branch positions, yielding strains specifically producing ante-iso or odd-chain iso BCFA as 77% of total FFA, separately. When coupled with an engineered branched-chain amino acid pathway to enrich the branched-chain α-ketoacid pool, BCFA can be produced from glucose at 181 mg/L and 72% of total FFA. While E. coli can metabolize BCFAs, we demonstrated that they are not incorporated into the cell membrane, allowing our system to produce a high percentage of BCFA without affecting membrane fluidity. Overall, this work establishes a platform for high percentage BCFA production, providing the basis for efficient and specific production of a variety of branched-chain hydrocarbons in engineered bacterial hosts. 相似文献
8.
《Process Biochemistry》2014,49(5):725-731
In this study, the yeast strain P10 which was identified to be a member of Aureobasidium pullulans var. melanogenum isolated from the mangrove ecosystems was found to be able to accumulate high content of oil in its cells. After optimization of the medium for lipid production and cell growth by the yeast strain P10, it was found that 8.0 g of glucose per 100 ml, 0.02 g of yeast extract per 100 ml, 0.02 g of ammonium sulfate per 100 ml, pH 6.0 in the medium were the most suitable for lipid production. During 10-l fermentation, a titer was 66.3 g oil per 100 g of cell dry weight, cell mass was 1.3 g per 100 ml, a yield was 0.11 g of oil per g of consumed sugar and a productivity was 0.0009 g of oil per g of consumed sugar per h within 120 h. At the same time, only 0.07 g of reducing sugar per 100 ml was left in the fermented medium. The compositions of the fatty acids produced were C16:0 (26.7%), C16:1(1.7%), C18:0 (6.1%), C18:1 (44.5%), and C18:2 (21.0%). The biodiesel produced from the extracted lipid could be burnt well. 相似文献
9.
Microbially produced lipids like triacylglycerols or fatty acid ethyl esters are currently of great interest as fuel replacements or other industrially relevant compounds. They can even be produced by non-oleaginous microbes, like Escherichia coli, upon metabolic engineering. However, there is still much room for improvement regarding the yield for a competitive microbial production of lipids or biofuels. We genetically engineered E. coli by expressing fadD, fadR, pgpB, plsB and ‘tesA in combination with atfA from Acinetobacter baylyi. A total fatty acid contents of up to 16% (w/w) was obtained on complex media, corresponding to approximately 9% (w/w) triacylglycerols and representing the highest titers of fatty acids and triacylglycerols obtained in E. coli under comparable cultivation conditions, so far. To evaluate further possibilities for an optimization of lipid production, ten promising bacterial wax ester synthase/acyl-Coenzyme A:diacylglycerol acyltransferases were tested and compared. While highest triacylglycerol storage was achieved with AtfA, the mutated variant AtfA-G355I turned out to be most suitable for fatty acid ethyl ester biosynthesis and enabled an accumulation of approx. 500 mg/L without external ethanol supplementation. 相似文献
10.
Valeric acid and 2-methylbutyric acid serve as chemical intermediates for a variety of applications such as plasticizers, lubricants and pharmaceuticals. The commercial process for their production uses toxic intermediates like synthesis gas and relies on non-renewable petroleum-based feedstock. In this work, synthetic metabolic pathways were constructed in Escherichia coli for the renewable production of these chemicals directly from glucose. The native leucine and isoleucine biosynthetic pathways in E. coli were expanded for the synthesis of valeric acid and 2-methylbutyric acid (2MB) respectively by the introduction of aldehyde dehydrogenases and 2-ketoacid decarboxylases. Various aldehyde dehydrogenases and 2-ketoacid decarboxylases were investigated for their activities in the constructed pathways. Highest titers of 2.59 g/L for 2-mthylbutyric acid and 2.58 g/L for valeric acid were achieved in shake flask experiments through optimal combinations of these enzymes. This work demonstrates the feasibility of renewable production of these high volume aliphatic carboxylic acids. 相似文献
11.
Alkanes of defined carbon chain lengths can serve as alternatives to petroleum-based fuels. Recently, microbial pathways of alkane biosynthesis have been identified and enabled the production of alkanes in non-native producing microorganisms using metabolic engineering strategies. The chemoautotrophic bacterium Cupriavidus necator has great potential for producing chemicals from CO2: it is known to have one of the highest growth rate among natural autotrophic bacteria and under nutrient imbalance it directs most of its carbon flux to the synthesis of the acetyl-CoA derived polymer, polyhydroxybutyrate (PHB), (up to 80% of intracellular content). Alkane synthesis pathway from Synechococcus elongatus (2 genes coding an acyl-ACP reductase and an aldehyde deformylating oxygenase) was heterologously expressed in a C. necator mutant strain deficient in the PHB synthesis pathway. Under heterotrophic condition on fructose we showed that under nitrogen limitation, in presence of an organic phase (decane), the strain produced up to 670 mg/L total hydrocarbons containing 435 mg/l of alkanes consisting of 286 mg/l of pentadecane, 131 mg/l of heptadecene, 18 mg/l of heptadecane, and 236 mg/l of hexadecanal. We report here the highest level of alka(e)nes production by an engineered C. necator to date. We also demonstrated the first reported alka(e)nes production by a non-native alkane producer from CO2 as the sole carbon source. 相似文献
12.
《Process Biochemistry》2010,45(7):1121-1126
In this study, we found that Rhodotorula mucilaginosa TJY15a could accumulate 48.8% (w/w) oil from hydrolysate of inulin and its cell dry weight reached 14.8 g/l during the batch cultivation while it could accumulate 48.6% (w/w) oil and 52.2% (w/w) oil from hydrolysate of extract of Jerusalem artichoke tubers and its cell dry weight reached 14.4 g/l and 19.5 g/l during the batch and fed-batch cultivations, respectively. At the end of the fed-batch cultivation, only 0.04% of reducing sugar and 0.08% of total sugar were left in the fermented medium. Over 87.6% of the fatty acids from the yeast strain TJY15a cultivated in the hydrolysate of extract of Jerusalem artichoke tubers was C16:0, C18:1 and C18:2, especially C18:1 (54.7%). Therefore, the results show that hydrolysates of inulin and extract of Jerusalem artichoke tubers were also the good materials for single cell oil production. 相似文献
13.
Fatty alcohols are important components of surfactants and cosmetic products. The production of fatty alcohols from sustainable resources using microbial fermentation could reduce dependence on fossil fuels and greenhouse gas emission. However, the industrialization of this process has been hampered by the current low yield and productivity of this synthetic pathway. As a result of metabolic engineering strategies, an Escherichia coli mutant containing Synechococcus elongatus fatty acyl-ACP reductase showed improved yield and productivity. Proteomics analysis and in vitro enzymatic assays showed that endogenous E. coli AdhP is a major contributor to the reduction of fatty aldehydes to fatty alcohols. Both in vitro and in vivo results clearly demonstrated that the activity and expression level of fatty acyl-CoA/ACP reductase is the rate-limiting step in the current protocol. In 2.5-L fed-batch fermentation with glycerol as the only carbon source, the most productive E. coli mutant produced 0.75 g/L fatty alcohols (0.02 g fatty alcohol/g glycerol) with a productivity of up to 0.06 g/L/h. This investigation establishes a promising synthetic pathway for industrial microbial production of fatty alcohols. 相似文献
14.
《生物化学与生物物理学报:生物膜》2018,1860(2):481-490
In this work, modifications of cell membrane fluidity, fatty acid composition and fatty acid biosynthesis-associated genes of Escherichia coli ATCC 25922 (E. coli) and Staphylococcus aureus ATCC 6538 (S. aureus), during growth in the presence of naringenin (NAR), one of the natural antibacterial components in citrus plants, was investigated. Compared to E. coli, the growth of S. aureus was significantly inhibited by NAR in low concentrations. Combination of gas chromatography–mass spectrometry with fluorescence polarization analysis revealed that E. coli and S. aureus cells increased membrane fluidity by altering the composition of membrane fatty acids after exposure to NAR. For example, E. coli cells produced more unsaturated fatty acids (from 18.5% to 43.3%) at the expense of both cyclopropane and saturated fatty acids after growth in the concentrations of NAR from 0 to 2.20 mM. For S. aureus grown with NAR at 0 to 1.47 mM, the relative proportions of anteiso-branched chain fatty acids increased from 37.2% to 54.4%, whereas iso-branched and straight chain fatty acids decreased from 30.0% and 33.1% to 21.6% and 23.7%, respectively. Real time q-PCR analysis showed that NAR at higher concentrations induced a significant down-regulation of fatty acid biosynthesis-associated genes in the bacteria, with the exception of an increased expression of fabA gene. The minimum inhibitory concentration (MIC) of NAR against these two bacteria was determined, and both of bacteria underwent morphological changes after exposure to 1.0 and 2.0 MIC. 相似文献
15.
Jens-Ole Bartz Jochen Blom Hans-Jürgen Busse Jacques B. Mvie Martin Hardt Patrick Schubert Thomas Wilke Alexander Goessmann Gottfried Wilharm Jennifer Bender Peter Kämpfer Stefanie P. Glaeser 《Systematic and applied microbiology》2018,41(2):73-84
Two Gram-stain-negative, facultative anaerobic, motile, rod-shaped strains, S-B4-1UT and JOB-63a, forming small whitish transparent colonies on marine agar, were isolated from a sponge of the genus Haliclona. The strains shared 99.7% 16S rRNA gene sequence identity and a DNA-DNA hybridization value of 100%, but were differentiated by genomic fingerprinting using rep-PCRs. 16S rRNA gene sequence phylogeny placed the strains as a sister branch to the monophyletic genus Endozoicomonas (Oceanospirillales; Gammaproteobacteria) with 92.3–94.3% 16S rRNA gene sequence similarity to Endozoicomonas spp., 91.9 and 92.1% to Candidatus Endonucleobacter bathymodiolin, and 91.9 to 92.1% to the type strains of Kistimonas spp. Core genome based phylogeny of strain S-B4-1UT confirmed the phylogenetic placement. Major fatty acids were summed feature 3 (C16:1 ω7c/C16:1 ω6c) and 8 (C18:1 ω7c/C18:1 ω6c) followed by C10:0 3-OH, C16:0, and C18:0. The G + C content was 50.1–51.4 mol%. The peptidoglycan diamino acid of strain S-B4-1UT was meso-diaminopimelic acid, the predominant polyamine spermidine, the major respiratory quinone ubiquinone Q-9; phosphatidylethanolamine, phosphatidylglycerol and phosphatidylserine were major polar lipids. Based on the clear phylogenetic distinction, the genus Parendozoicomonas gen. nov. is proposed, with Parendozoicomonas haliclonae sp. nov. as type species and strain S-B4-1UT (= CCM 8713T = DSM 103671T = LMG 29769T) as type strain and JOB-63a as a second strain of the species. Based on the 16S rRNA gene sequence phylogeny of the Oceanospirillales within the Gammaproteobacteria, the Endozoicomonaceae fam. nov. is proposed including the genera Endozoicomonas, Parendozoicomonas, and Kistimonas as well as the Candidatus genus Endonucleobacter. 相似文献
16.
Biosynthesis of ethyl caproate and other short ethyl esters catalyzed by cutinase in organic solvent
《Journal of Molecular Catalysis .B, Enzymatic》2009,61(3-4):178-185
The main objective of this work was to study the enzymatic synthesis of short chain ethyl esters, a group of relevant aroma molecules, by Fusarium solani pisi cutinase in an organic solvent media (iso-octane), and to assess the influence of different parameters on the reaction yield.Cutinase displayed high initial esterification rates in iso-octane, which amounted to 1.15 μmol min−1 mg−1 for ethyl butyrate (C4 acid chain) and 1.06 μmol min−1 mg−1 for ethyl valerate (C5 acid chain). High product yields, 84% for ethyl butyrate and 96% for ethyl valerate, were observed after 6 h of reaction, for an initial equimolar concentration of substrates (0.1 M).The highest product yield (97%) was observed for ethyl caproate (C6) synthesis, a compound which is a part of natural apple and pineapple flavour, for an alcohol:acid molar ratio of 2 (0.2 M ethanol concentration).Cutinase affinity for short chain length carboxylic acids (C4–C6) in ester synthesis in iso-octane confirmed previous observations in reversed micellar system. 相似文献
17.
Jun-lian Gao Pengbo Sun Xiao-hong Sun Shuai Tong Hui Yan Mei-lin Han Xiao-jie Mao Jian-guang Sun 《Systematic and applied microbiology》2018,41(6):604-610
Four bacterial strains designated 410T, 441, 695T and 736 were isolated from maize root in Beijing, P. R. China. Based on 16S rRNA gene phylogeny, the four strains formed two clusters in the genus Caulobacter. Since strain 441 was a clonal variety of strain 410T, only three strains were selected for further taxonomic studies. The whole genome average nucleotide identity (ANI) value between strains 410T and 695T was 94.65%, and both strains shared less than 92.10% ANI values with their close phylogenetic neighbors Caulobacter vibrioides DSM 9893T, Caulobacter segnis ATCC 21756T and Caulobacter flavus CGMCC 1.15093T. Strains 410T and 695T contained Q-10 as the sole ubiquinone and their major fatty acids were C16:0, 11-methyl C18:1ω 0, 11-methyl C18: 1ω7c, summed feature 3 (C16:1ω7c and/or C16:1ω 1ω7c and/or C16: 1ω6c) and summed feature 8 (C18:1ω7c and/or C18:1ω 1ω7c and/or C18: 1ω6c). Their major polar lipids consisted of glycolipids and phosphatidylglycerol, and phenotypic tests differentiated them from their closest phylogenetic neighbors. Based on the results obtained, it is proposed that the three strains represent two novel species, for which the names Caulobacter zeae sp. nov. (type strain 410T = CGMCC 1.15991 = DSM 104304) and Caulobacter radicis sp. nov. (type strain 695T = CGMCC 1.16556 = DSM 106792) are proposed. 相似文献
18.
《Systematic and applied microbiology》2019,42(3):291-301
A taxonomic study of 24 Gram-stain-negative rod-shaped bacteria originating from the Antarctic environment is described. Phylogenetic analysis using 16S rRNA gene sequencing differentiated isolated strains into two groups belonging to the genus Flavobacterium. Group I (n = 20) was closest to Flavobacterium aquidurense WB 1.1-56T (98.3% 16S rRNA gene sequence similarity) while group II (n = 4) showed Flavobacterium hydatis DSM 2063T as its nearest neighbour (98.5–98.9% 16S rRNA gene sequence similarity). Despite high 16S rRNA gene sequence similarity, these two groups represented two distinct novel species as shown by phenotypic traits and low genomic relatedness assessed by rep-PCR fingerprinting, DNA-DNA hybridization and whole-genome sequencing. Common to representative strains of both groups were the presence of major menaquinone MK-6 and sym-homospermidine as the major polyamine. Common major fatty acids were C15:0 iso, C15:1 iso G, C15:0 iso 3-OH, C17:0 iso 3OH and Summed Feature 3 (C16:1 ω7c/C16:1 ω6c). Strain CCM 8828T (group I) contained phosphatidylethanolamine, three unidentified lipids lacking a functional group, three unidentified aminolipids and single unidentified glycolipid in the polar lipid profile. Strain CCM 8825T (group II) contained phosphatidylethanolamine, eight unidentified lipids lacking a functional group, three unidentified aminolipids and two unidentified glycolipids in the polar lipid profile. These characteristics corresponded to characteristics of the genus Flavobacterium. The obtained results showed that the analysed strains represent novel species of the genus Flavobacterium, for which the names Flavobacterium circumlabens sp. nov. (type strain CCM 8828T = P5626T = LMG 30617T) and Flavobacterium cupreum sp. nov. (type strain CCM 8825T = P2683T = LMG 30614T) are proposed. 相似文献
19.
David R. Singleton Janice Lee Allison N. Dickey Aaron Stroud Elizabeth H. Scholl Fred A. Wright Michael D. Aitken 《Systematic and applied microbiology》2018,41(5):460-472
Four bacterial strains identified as members of the Acidovorax genus were isolated from two geographically distinct but similarly contaminated soils in North Carolina, USA, characterized, and their genomes sequenced. Their 16S rRNA genes were highly similar to those previously recovered during stable-isotope probing (SIP) of one of the soils with the polycyclic aromatic hydrocarbon (PAH) phenanthrene. Heterotrophic growth of all strains occurred with a number of organic acids, as well as phenanthrene, but no other tested PAHs. Optimal growth occurred aerobically under mesophilic temperature, neutral pH, and low salinity conditions. Predominant fatty acids were C16:1ω7c/C16:1ω6c, C16:0, and C18:1ω7c, and were consistent with the genus. Genomic G + C contents ranged from 63.6 to 64.2%. A combination of whole genome comparisons and physiological analyses indicated that these four strains likely represent a single species within the Acidovorax genus. Chromosomal genes for phenanthrene degradation to phthalate were nearly identical to highly conserved regions in phenanthrene-degrading Delftia, Burkholderia, Alcaligenes, and Massilia species in regions flanked by transposable or extrachromosomal elements. The lower degradation pathway for phenanthrene metabolism was inferred by comparisons to described genes and proteins. The novel species Acidovorax carolinensis sp. nov. is proposed, comprising the four strains described in this study with strain NA3T as the type strain (=LMG 30136, =DSM 105008). 相似文献
20.
《Systematic and applied microbiology》2019,42(4):488-494
Four endophytic bacterial strains were isolated from root, stem and leaf of maize planted in different regions of northern China. The four strains possessed almost identical 16S rRNA gene sequences. However, REP-PCR fingerprint patterns discriminated that they were not from one clonal origin. Furthermore, the average nucleotide identity (ANI) values among them were higher than 95%, suggesting they all belong to one species. Based on 16S rRNA gene phylogeny, the four strains were clustered together with Pantoea rodasii LMG 26273T and Pantoea rwandensis LMG 26275T, but on a separate branch. Multilocus sequence analysis (MLSA) indicated that the four strains form a novel Pantoea species. Authenticity of the novel species was confirmed by ANI comparisons between strain 596T and its closest relatives, since obtained values were considerably below the proposed thresholds for the species delineation. The genome size of 596T was 5.1Mbp, comprising 4896 predicted genes with DNA G + C content of 57.8 mol%. The respiratory quinone was ubiquinone-8 (Q-8) and the polar lipid profile consisted of phosphatidylethanolamin, diphosphatidylglycerol, phosphatidylglycerol, unidentified aminophospholipid and unidentified phospholipid. The major fatty acids of strain 596T were C16:0, summed feature 2 (C12:0 aldehyde), summed feature 3 (C16:1ω7c and/or C16:1ω6c) and summed feature 8 (C18:1ω7c and/or C18:1ω6c). Based on phylogenetic, genomic, phenotypic and chemotaxonomic data, the four isolates are considered to represent a novel species of the genus Pantoea, for which the name Pantoea endophytica sp. nov., is proposed, with 596T (= DSM 100,785T = CGMCC 1.15280T) as type strain. 相似文献