scholarly journals Oxygen-Dependent Regulation of Bacterial Lipid Production

2015 ◽  
Vol 197 (9) ◽  
pp. 1649-1658 ◽  
Author(s):  
Kimberly C. Lemmer ◽  
Alice C. Dohnalkova ◽  
Daniel R. Noguera ◽  
Timothy J. Donohue

ABSTRACTUnderstanding the mechanisms of lipid accumulation in microorganisms is important for several reasons. In addition to providing insight into assembly of biological membranes, lipid accumulation has important applications in the production of renewable fuels and chemicals. The photosynthetic bacteriumRhodobacter sphaeroidesis an attractive organism to study lipid accumulation, as it has the ability to increase membrane production at low O2tensions. Under these conditions,R. sphaeroidesdevelops invaginations of the cytoplasmic membrane to increase its membrane surface area for housing of the membrane-bound components of its photosynthetic apparatus. Here we use fatty acid levels as a reporter of membrane lipid content. We show that, under low-O2and anaerobic conditions, the total fatty acid content per cell increases 3-fold. We also find that the increases in the amount of fatty acid and photosynthetic pigment per cell are correlated as O2tensions or light intensity are changed. To ask if lipid and pigment accumulation were genetically separable, we analyzed strains with mutations in known photosynthetic regulatory pathways. While a strain lacking AppA failed to induce photosynthetic pigment-protein complex accumulation, it increased fatty acid content under low-O2conditions. We also found that an intact PrrBA pathway is required for low-O2-induced fatty acid accumulation. Our findings suggest a previously unknown role ofR. sphaeroidestranscriptional regulators in increasing fatty acid and phospholipid accumulation in response to decreased O2tension.IMPORTANCELipids serve important functions in living systems, either as structural components of membranes or as a form of carbon storage. Understanding the mechanisms of lipid accumulation in microorganisms is important for providing insight into the assembly of biological membranes and additionally has important applications in the production of renewable fuels and chemicals. In this study, we investigate the ability ofRhodobacter sphaeroidesto increase membrane production at low O2tensions in order to house its photosynthetic apparatus. We demonstrate that this bacterium has a mechanism to increase lipid content in response to decreased O2tension and identify a transcription factor necessary for this response. This is significant because it identifies a transcriptional regulatory pathway that can increase microbial lipid content.

mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Christopher W. Lennon ◽  
Kimberly C. Lemmer ◽  
Jessica L. Irons ◽  
Max I. Sellman ◽  
Timothy J. Donohue ◽  
...  

ABSTRACTDksA is a global regulatory protein that, together with the alarmone ppGpp, is required for the “stringent response” to nutrient starvation in the gammaproteobacteriumEscherichia coliand for more moderate shifts between growth conditions. DksA modulates the expression of hundreds of genes, directly or indirectly. Mutants lacking a DksA homolog exhibit pleiotropic phenotypes in other gammaproteobacteria as well. Here we analyzed the DksA homolog RSP2654 in the more distantly relatedRhodobacter sphaeroides, an alphaproteobacterium. RSP2654 is 42% identical and similar in length toE. coliDksA but lacks the Zn finger motif of theE. coliDksA globular domain. Deletion of the RSP2654 gene results in defects in photosynthetic growth, impaired utilization of amino acids, and an increase in fatty acid content. RSP2654 complements the growth and regulatory defects of anE. colistrain lacking thedksAgene and modulates transcriptionin vitrowithE. coliRNA polymerase (RNAP) similarly toE. coliDksA. RSP2654 reduces RNAP-promoter complex stabilityin vitrowith RNAPs fromE. coliorR. sphaeroides, alone and synergistically with ppGpp, suggesting that even though it has limited sequence identity toE. coliDksA (DksAEc), it functions in a mechanistically similar manner. We therefore designate the RSP2654 protein DksARsp. Our work suggests that DksARsphas distinct and important physiological roles in alphaproteobacteria and will be useful for understanding structure-function relationships in DksA and the mechanism of synergy between DksA and ppGpp.IMPORTANCEThe role of DksA has been analyzed primarily in the gammaproteobacteria, in which it is best understood for its role in control of the synthesis of the translation apparatus and amino acid biosynthesis. Our work suggests that DksA plays distinct and important physiological roles in alphaproteobacteria, including the control of photosynthesis inRhodobacter sphaeroides. The study of DksARsp, should be useful for understanding structure-function relationships in the protein, including those that play a role in the little-understood synergy between DksA and ppGpp.


2009 ◽  
Vol 21 (1) ◽  
pp. 154 ◽  
Author(s):  
M. Barcelo-Fimbres ◽  
G. E. Seidel

The objective of this experiment was to evaluate lipid accumulation and embryonic development of bovine morulae treated with different chemicals. A total of 2619 slaughterhouse oocytes from heifers and mature cows were matured in CDM medium (similar to SOF) plus 0.5% fatty acid-free BSA and hormones (M-CDM) for 23 h at 38.5°C in 5% CO2 in air. Frozen–thawed sperm were centrifuged through a Percoll gradient and co-cultured with matured oocytes for 18 h in F-CDM (CDM+heparin). Zygotes were cultured at 38.5°C in 5% CO2/5% O2/90% N2 in CDM-1 with nonessential amino acids, 10 μm EDTA, 0.5% fatty acid free BSA, and 0.5 mm fructose. After 60 h, resulting 8-cell embryos were cultured 120 h in CDM-2 (CDM-1+essential amino acids and 2 mm fructose). A factorial design was used with 7 treatments, 2 ovary sources (cows v. heifers), and 3 bulls (A, B and C) replicated twice for each bull (6 replicates). At Day 2.5 embryo cleavage and 8-cell rates were evaluated, and on Day 6 a total of 755 morulae were randomly assigned to the 7 treatments (control, 2 and 8 mm caffeine, 1 and 4 μm epinephrine, and 10 and 40 μm forskolin). To quantify lipid accumulation, Day 7 blastocysts were fixed and stained with 1 μg mL–1 Nile red dye, after which a digital photograph of the equatorial part of the embryo (including the inner cell mass) was taken at 200×, and fluorescence intensity was measured with Image Pro software from 0 to 255 shades for each pixel (0 = no lipids; 255 = greatest lipid accumulation), as previously reported (Biol. Reprod. 2007 (Suppl. 1), 87–88). Data were analyzed by ANOVA. No differences in cleavage rates (75 v. 68 ± 3.6%) or eight cell rates (61 ± v. 57 ± 2.8%) were found for heifer v. cow oocytes (P > 0.1); however, blastocyst rates per oocyte and per 8-cell embryo were greater for cows than heifers (20 v. 10 ± 2.1%, and 68 v. 35 ± 3.8%, respectively; P < 0.05). Treatments: 2 and 8 mm caffeine produced fewer blastocysts per morula than 1 and 4 μm epinephrine, 10 and 40 μm forskolin and the control (39, 5 v. 54, 49, 48, 54 and 52 ± 5.8%; respectively) (P < 0.01). More lipid content was found in whole embryos and trophoblast of heifer-derived than cow blastocysts (P < 0.05), and forskolin resulted in less lipid content than control, caffeine- and epinephrine-treated morulae in whole embryos, embryonic mass and trophoblasts (P < 0.05; Table 1). In conclusion, mature cows were a better source of oocytes than feedlot heifers for embryonic development. High doses of caffeine were detrimental to embryos, and the addition of the lypolitic agent forskolin reduced lipid content relative to control, caffeine and epinephrine-treated embryos. Table 1.Main effect treatment means of lipid content (arbitrary fluorescence units)


PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11217
Author(s):  
Chin Sze Yee ◽  
Victor Tosin Okomoda ◽  
Fakriah Hashim ◽  
Khor Waiho ◽  
Siti Rozaimah Sheikh Abdullah ◽  
...  

This study investigated the effect of co-culturing microalgae with a floc-forming bacterium. Of the six microalgae isolated from a biofloc sample, only Thalassiosira weissflogii, Chlamydomonas sp. and Chlorella vulgaris were propagated successfully in Conway medium. Hence, these species were selected for the experiment comparing microalgae axenic culture and co-culture with the floc-forming bacterium, Bacillus infantis. Results obtained showed that the co-culture had higher microalgae biomass compared to the axenic culture. A similar trend was also observed concerning the lipid content of the microalgae-bacterium co-cultures. The cell number of B. infantis co-cultured with T. weissflogii increased during the exponential stage until the sixth day, but the other microalgae species experienced a significant early reduction in cell density of the bacteria at the exponential stage. This study represents the first attempt at co-culturing microalgae with B. infantis, a floc-forming bacterium, and observed increased biomass growth and lipid accumulation compared to the axenic culture.


Author(s):  
John L. Dahl ◽  
Wayne Gatlin III ◽  
Phuong M. Tran ◽  
Cody S. Sheik

A fast-growing, non-chromogenic, acid-fast-staining bacterium (DL90T) was isolated from a peat bog in northern Minnesota. On the basis of 16S rRNA gene sequence similarity (99.8 % identity with Mycolicibacterium septicum and 98 % with Mycolicibacterium peregrinum ) and chemotaxonomic data (fatty acid content), strain DL90T represents a member of the genus Mycolicibacterium . Physiological tests (growth curves, biofilm formation, antibiotic sensitivity, colony morphologies and heat tolerance) and biochemical analysis (arylsulfatase activity and fatty acid profiles) distinguish DL90T from its closest relative M. septicum . Phylogenomic reconstruction of the ‘Fortuitium–Vaccae’ clade, digital DNA–DNA hybridization (DDH) values of 61 %, and average nucleotide identity (ANI) values of approximately 95 % indicate that DL90T is likely to be diverged from M. septicum . Thus, we propose that DL90T represents a novel species, given the name Mycolicibacterium nivoides with the type strain being isolate DL90T (=JCM 32796T=NCCB 100660T).


Author(s):  
Xiao Liu ◽  
Dan Zhang ◽  
Jianhui Zhang ◽  
Yuhong Chen ◽  
Xiuli Liu ◽  
...  

Microalgae are considered to be a highly promising source for the production of biodiesel. However, the regulatory mechanism governing lipid biosynthesis has not been fully elucidated to date, and the improvement of lipid accumulation in microalgae is essential for the effective production of biodiesel. In this study,LEAFY COTYLEDON1 (LEC1)fromArabidopsis thaliana, a transcription factor (TF) that affects lipid content, was transferred intoChlorella ellipsoidea. Compared with wild-type (WT) strains, the total fatty acid content and total lipid content ofAtLEC1transgenic strains were significantly increased by 24.20–32.65 and 22.14–29.91%, respectively, under mixotrophic culture conditions and increased by 24.4–28.87 and 21.69–30.45%, respectively, under autotrophic conditions, while the protein content of the transgenic strains was significantly decreased by 18.23–21.44 and 12.28–18.66%, respectively, under mixotrophic and autotrophic conditions. Fortunately, the lipid and protein content variation did not affect the growth rate and biomass of transgenic strains under the two culture conditions. According to the transcriptomic data, the expression of 924 genes was significantly changed in the transgenic strain (LEC1-1). Of the 924 genes, 360 were upregulated, and 564 were downregulated. Based on qRT-PCR results, the expression profiles of key genes in the lipid synthesis pathway, such asACCase,GPDH,PDAT1, andDGAT1, were significantly changed. By comparing the differentially expressed genes (DEGs) regulated byAtLEC1inC. ellipsoideaandArabidopsis, we observed that approximately 59% (95/160) of the genes related to lipid metabolism were upregulated inAtLEC1transgenicChlorella. Our research provides a means of increasing lipid content by introducing exogenous TF and presents a possible mechanism ofAtLEC1regulation of lipid accumulation inC. ellipsoidea.


2006 ◽  
Vol 86 (2) ◽  
pp. 279-290 ◽  
Author(s):  
P. S. Mir ◽  
S. Bittman ◽  
D. Hunt ◽  
T. Entz ◽  
B. Yip

In order to explore the value of herbage for the production of ruminant products with a high content of conjugated linoleic acid (CLA), a study was undertaken to determine the content of fatty acids that can be hydrogenated [hydrogenatable fatty acids (HFA)] in herbage of three cool-season forage grasses, orchardgrass (OG), perennial ryegrass (PRG) and tall fescue (TF). Dry matter (DM) yield, lipid content (ether extract) and fatty acid concentration (weight percent of detected fatty acids) on five sampling dates in the spring of 2004 were determined. HFA is the available substrate for the production and deposition of fatty acid bioconversion products in ruminants that consume the grass. Fatty acid content of the grasses was estimated as the product of fatty acids concentration (weight percent) and lipid content (ether extract), while HFA was estimated as the sum of the content of C18:1, C18:2 and C18:3. The DM yield of the three species of grasses increased (P < 0.05) between Mar. 29 and Apr. 28, after which the increase was observed for TF followed by PRG. However, the lipid content decreased in all the grasses over the 140 d of sampling. Although concentration of the saturated fatty acids and C18:1 and C18:2 increased over the sampling period, the content did not alter substantially. In OG samples, C18:2 concentrations were higher (P < 0.05) than those in PRG or TF in all samples. The concentration and content of C18:3 was highest (P < 0.05) in all the forages, but declined progressively. Results indicate that the availability of HFA is greatest in OG and PRG, especially in the early samples, but DM yields are low; however, later in the season TF produces more DM but with substantially reduced lipid and HFA content. Key words: Orchard grass, perennial ryegrass, tall fescue, hydrogenatable fatty acids, conjugated linoleic acid, ruminants


2010 ◽  
Vol 88 (12) ◽  
pp. 1157-1165 ◽  
Author(s):  
Samyra L. Buzelle ◽  
Maísa P. Santos ◽  
Amanda M. Baviera ◽  
Carbene F. Lopes ◽  
Maria A.R. Garófalo ◽  
...  

The amount of triacylglycerol (TAG) that accumulates in adipose tissue depends on 2 opposing processes: lipogenesis and lipolysis. We have previously shown that the weight and lipid content of epididymal (EPI) adipose tissue increases in growing rats fed a low-protein, high-carbohydrate (LPHC) diet for 15 days. The aim of this work was to study the pathways involved in lipogenesis and lipolysis, which ultimately regulate lipid accumulation in the tissue. De novo fatty acid synthesis was evaluated in vivo and was similar for rats fed an LPHC diet or a control diet; however, the LPHC-fed rats had decreased lipoprotein lipase activity in the EPI adipose tissue, which suggests that there was a decreased uptake of fatty acids from the circulating lipoproteins. The LPHC diet did not affect synthesis of glycerol-3-phosphate (G3P) via glycolysis or glyceroneogenesis. Glycerokinase activity — i.e., the phosphorylation of glycerol from the hydrolysis of endogenous TAG to form G3P — was also not affected in LPHC-fed rats. In contrast, adipocytes from LPHC animals had a reduced lipolytic response when stimulated by norepinephrine, even though the basal adipocyte lipolytic rate was similar for both of the groups. Thus, the results suggest that the reduction of lipolytic activity stimulated by norepinephrine seems essential for the TAG increase observed in the EPI adipose tissue of LPHC animals, probably by impairment of the process of activation of lipolysis by norepinephrine.


2021 ◽  
Vol 22 (3) ◽  
pp. 1304
Author(s):  
Hang Su ◽  
Jia Feng ◽  
Junping Lv ◽  
Qi Liu ◽  
Fangru Nan ◽  
...  

The oleaginous microalgae species Chlorococcum sphacosum GD is a promising feedstock for biodiesel production from soil. However, its metabolic mechanism of lipid production remains unclear. In this study, the lipid accumulation and metabolism mechanisms of Chlorococcum sphacosum GD were analyzed under salt stress based on transcriptome sequencing. The biomass and lipid content of the alga strain were determined under different NaCl concentrations, and total RNA from fresh cells were isolated and sequenced by HiSeq 2000 high throughput sequencing technology. As the salt concentration increased in culture medium, the algal lipid content increased but the biomass decreased. Following transcriptome sequencing by assembly and splicing, 24,128 unigenes were annotated, with read lengths mostly distributed in the 200–300 bp interval. Statistically significant differentially expressed unigenes were observed in different experimental groups, with 2051 up-regulated genes and 1835 down-regulated genes. The lipid metabolism pathway analysis showed that, under salt stress, gene-related fatty acid biosynthesis (ACCase, KASII, KAR, HAD, FATA) was significantly up-regulated, but some gene-related fatty acid degradation was significantly down-regulated. The comprehensive results showed that salt concentration can affect the lipid accumulation and metabolism of C. sphacosum GD, and the lipid accumulation is closely related to the fatty acid synthesis pathway.


2021 ◽  
Vol 8 ◽  
Author(s):  
Xin Tang ◽  
Xiaoqi Sun ◽  
Xuxu Wang ◽  
Hao Zhang ◽  
Yong Q. Chen ◽  
...  

Mortierella alpina has a strong capacity for lipid accumulation. Isocitrate dehydrogenase (IDH) plays an important role in affecting the flow of intracellular carbon sources and reducing power NADPH for lipid biosynthesis. In this study, the effect of various IDHs (NAD+- and NADP+-specific) in M. alpina on the lipid accumulation was investigated through homologous overexpression. The results showed that the transcription level and enzyme activity of the IDHs from M. alpina (MaIDHs) in homologous overexpressing strains were higher than those of the control strain, but that their biomass was not significantly different. Among the various NAD+-specific MaIDH1/2/3 overexpression, NAD+-MaIDH3 reduced total lipid content by 12.5%, whereas overexpression NAD+-MaIDH1 and NAD+-MaIDH2 had no effect on fatty acid content. Intracellular metabolites analysis indicated that the overexpression NAD+-MaIDH3 strain had reduced the fatty acid accumulation, due to its greater carbon flux with the tricarboxylic acid cycle and less carbon flux with fatty acid biosynthesis. For the NADP+-MaIDH4/5/6 recombinant strains overexpressing only NADP+-MaIDH4 enhanced the total fatty acid content by 8.2%. NADPH analysis suggested that this increase in lipid accumulation may have been due to the great reducing power NADPH is produced in this recombinant strain. This study provides theoretical basis and guidance for the analysis of the mechanism of IDH function and the potential to improve lipid production in M. alpina.


2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Songcui Wu ◽  
Wenhui Gu ◽  
Aiyou Huang ◽  
Yuanxiang Li ◽  
Manoj Kumar ◽  
...  

Abstract Background Numerous studies have shown that stress induction and genetic engineering can effectively increase lipid accumulation, but lead to a decrease of growth in the majority of microalgae. We previously found that elevated CO2 concentration increased lipid productivity as well as growth in Phaeodactylum tricornutum, along with an enhancement of the oxidative pentose phosphate pathway (OPPP) activity. The purpose of this work directed toward the verification of the critical role of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the OPPP, in lipid accumulation in P. tricornutum and its simultaneous rapid growth rate under high-CO2 (0.15%) cultivation. Results In this study, G6PDH was identified as a target for algal strain improvement, wherein G6PDH gene was successfully overexpressed and antisense knockdown in P. tricornutum, and systematic comparisons of the photosynthesis performance, algal growth, lipid content, fatty acid profiles, NADPH production, G6PDH activity and transcriptional abundance were performed. The results showed that, due to the enhanced G6PDH activity, transcriptional abundance and NAPDH production, overexpression of G6PDH accompanied by high-CO2 cultivation resulted in a much higher of both lipid content and growth in P. tricornutum, while knockdown of G6PDH greatly decreased algal growth as well as lipid accumulation. In addition, the total proportions of saturated and unsaturated fatty acid, especially the polyunsaturated fatty acid eicosapentaenoic acid (EPA; C20:5, n-3), were highly increased in high-CO2 cultivated G6PDH overexpressed strains. Conclusions The successful of overexpression and antisense knockdown of G6PDH well demonstrated the positive influence of G6PDH on algal growth and lipid accumulation in P. tricornutum. The improvement of algal growth, lipid content as well as polyunsaturated fatty acids in high-CO2 cultivated G6PDH overexpressed P. tricornutum suggested this G6PDH overexpression-high CO2 cultivation pattern provides an efficient and economical route for algal strain improvement to develop algal-based biodiesel production.


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