scholarly journals Triacylglyceride Production and Autophagous Responses in Chlamydomonas reinhardtii Depend on Resource Allocation and Carbon Source

2014 ◽  
Vol 13 (3) ◽  
pp. 392-400 ◽  
Author(s):  
Matthew P. Davey ◽  
Irmtraud Horst ◽  
Giang-Huong Duong ◽  
Eleanor V. Tomsett ◽  
Alexander C. P. Litvinenko ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Membrane Lipids ◽  
N Availability ◽  
Wild Type ◽  
Metabolic Switch ◽  
Content Type ◽  
Carbon Supply ◽  
Microalgal Biodiesel ◽  
In The Wild ◽  
Mutant Cells

ABSTRACT To improve the economic viability of microalgal biodiesel, it will be essential to optimize the productivity of fuel molecules such as triacylglyceride (TAG) within the microalgal cell. To understand some of the triggers required for the metabolic switch to TAG production, we studied the effect of the carbon supply (acetate or CO 2 ) in Chlamydomonas reinhardtii (wild type and the starchless sta6 mutant) grown under low N availability. As expected, initial rates of TAG production were much higher when acetate was present than under strictly photosynthetic conditions, particularly for the sta6 mutant, which cannot allocate resources to starch. However, in both strains, TAG production plateaued after a few days in mixotrophic cultures, whereas under autotrophic conditions, TAG levels continued to rise. Moreover, the reduced growth of the sta6 mutant meant that the greatest productivity (measured as mg TAG liter −1 day −1 ) was found in the wild type growing autotrophically. Wild-type cells responded to low N by autophagy, as shown by degradation of polar (membrane) lipids and loss of photosynthetic pigments, and this was less in cells supplied with acetate. In contrast, little or no autophagy was observed in sta6 mutant cells, regardless of the carbon supply. Instead, very high levels of free fatty acids were observed in the sta6 mutant, suggesting considerable alteration in metabolism. These measurements show the importance of carbon supply and strain selection for lipid productivity. Our findings will be of use for industrial cultivation, where it will be preferable to use fast-growing wild-type strains supplied with gaseous CO 2 under autotrophic conditions rather than require an exogenous supply of organic carbon.

scholarly journals Inactivation of Ca2+/H+Exchanger in Synechocystis sp. Strain PCC 6803 Promotes Cyanobacterial Calcification by Upregulating CO2-Concentrating Mechanisms

2013 ◽  
Vol 79 (13) ◽  
pp. 4048-4055 ◽  
Author(s):  
Hai-Bo Jiang ◽  
Hui-Min Cheng ◽  
Kun-Shan Gao ◽  
Bao-Sheng Qiu
Keyword(s):  
Transcript Level ◽  
Wild Type ◽  
Content Type ◽  
Protein Levels ◽  
Genes Encoding ◽  
In The Wild ◽  
Co2 Concentrating Mechanisms ◽  
Mutant Cells ◽  
Global Carbon ◽  
Pcc 6803

ABSTRACTCyanobacteria are important players in the global carbon cycle, accounting for approximately 25% of global CO2fixation. Their CO2-concentrating mechanisms (CCMs) are thought to play a key role in cyanobacterial calcification, but the mechanisms are not completely understood. InSynechocystissp. strain PCC 6803, a single Ca2+/H+exchanger (Slr1336) controls the Ca2+/H+exchange reaction. We knocked out the exchanger and investigated the effects on cyanobacterial calcification and CCMs. Inactivation ofslr1336significantly increased the calcification rate and decreased the zeta potential, indicating a relatively stronger Ca2+-binding ability. Some genes encoding CCM-related components showed increased expression levels, including thecmpAgene, which encodes the Ca2+-dependent HCO3−transporter BCT1. The transcript level ofcmpAin the mutant was 30 times that in wild type. A Western blot analysis further confirmed that protein levels of CmpA were higher in the mutant than the wild type. Measurements of inorganic carbon fluxes and O2evolution proved that both the net HCO3−uptake rate and the BCT1 transporter supported photosynthetic rate in theslr1336mutant were significantly higher than in the wild type. This would cause the mutant cells to liberate more OH−ions out of the cell and stimulate CaCO3precipitation in the microenvironment. We conclude that the mutation of the Ca2+/H+exchanger inSynechocystispromoted the cyanobacterial calcification process by upregulating CCMs, especially the BCT1 HCO3−transporter. These results shed new light on the mechanism by which CCM-facilitated photosynthesis promotes cyanobacterial calcification.

scholarly journals The Global Nitrogen Regulator NtcA Regulates Transcription of the Signal Transducer PII (GlnB) and Influences Its Phosphorylation Level in Response to Nitrogen and Carbon Supplies in the Cyanobacterium Synechococcus sp. Strain PCC 7942

1999 ◽  
Vol 181 (9) ◽  
pp. 2697-2702 ◽  
Author(s):  
Hyun-Mi Lee ◽  
María Félix Vázquez-Bermúdez ◽  
Nicole Tandeau de Marsac
Keyword(s):  
Nitrogen Availability ◽  
Null Mutant ◽  
Wild Type ◽  
E Coli ◽  
Carbon Supply ◽  
Phosphorylation Level ◽  
In The Wild ◽  
Synechococcus Sp ◽  
Pcc 7942 ◽  
Mutant Cells

ABSTRACT The PII protein is encoded by a unique glnBgene in Synechococcus sp. strain PCC 7942. Its expression has been analyzed in the wild type and in NtcA-null mutant cells grown under different conditions of nitrogen and carbon supply. RNA-DNA hybridization experiments revealed the presence of one transcript species 680 nucleotides long, whatever the nutrient conditions tested. A second transcript species, 620 nucleotides long, absent in the NtcA null mutant, was observed in wild-type cells that were nitrogen starved for 2 h under both high and low CO2and in the presence of nitrate under a high CO2concentration. Primer extension analysis indicated that the two transcript species are generated from two tandem promoters, a ς70 Escherichia coli-type promoter and an NtcA-dependent promoter, located 120 and 53 nucleotides, respectively, from the glnB initiation codon. The NtcA-dependent promoter is up-regulated under the conditions mentioned above, while the ς70 E. coli-type promoter displays constitutive levels of transcripts in the NtcA null mutant and slightly different levels in the wild-type cells, depending on the nitrogen and carbon supplies. In general, a good correlation between the amounts of the two transcript species and that of the PII protein was observed, as revealed by immunodetection with specific antibodies. The phosphorylation level of PII in the wild type is inversely correlated with nitrogen availability and directly correlated with higher CO2 concentration. This regulation is correspondingly less stringent in the NtcA null mutant cells. In contrast, the dephosphorylation of PII is NtcA independent.

scholarly journals Activation of 2,4-Diaminoquinazoline in Mycobacterium tuberculosis by Rv3161c, a Putative Dioxygenase

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
Eduard Melief ◽  
Shilah A. Bonnett ◽  
Edison S. Zuniga ◽  
Tanya Parish
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Type A ◽  
Wild Type ◽  
Metabolite Analysis ◽  
Content Type ◽  
Data Support ◽  
In The Wild

ABSTRACT The diaminoquinazoline series has good potency against Mycobacterium tuberculosis. Resistant isolates have mutations in Rv3161c, a putative dioxygenase. We carried out metabolite analysis on a wild-type strain and an Rv3161c mutant strain after exposure to a diaminoquinazoline. The parental compound was found in intracellular extracts from the mutant but not the wild type. A metabolite consistent with a monohydroxylated form was identified in the wild type. These data support the hypothesis that Rv3161c metabolizes diaminoquinazolines in M. tuberculosis.

Physical and physiological components of the graviresponses of wild-type and mutant Paramecium Tetraurelia

2000 ◽  
Vol 203 (6) ◽  
pp. 1059-1070 ◽  
Author(s):  
U. Nagel ◽  
H. Machemer
Keyword(s):  
Swimming Speed ◽  
Sedimentation Rates ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Centre Of Gravity ◽  
In The Wild ◽  
Type Population ◽  
G Value ◽  
Mutant Cells

Wild-type and the morphological mutant kin 241 of Paramecium tetraurelia showed improved orientation away from the centre of gravity (negative gravitaxis) when accelerations were increased from 1 to 7 g. Gravitaxis was more pronounced in the mutant. A correlation between the efficiency of orientation and the applied g value suggests a physical basis for gravitaxis. Transiently enhanced rates of reversal of the swimming direction coincided with transiently enhanced gravitaxis because reversals occurred more often in downward swimmers than in upward swimmers. The results provide evidence of a physiological modulation of gravitaxis by means of the randomizing effect of depolarization-dependent swimming reversals. Gravity bimodally altered propulsion rates of wild-type P. tetraurelia so that sedimentation was partly antagonized in upward and downward swimmers (negative gravikinesis). In the mutant, only increases in propulsion were observed, although the orientation-dependent sensitivity of the gravikinetic response was the same as in the wild-type population. Observed swimming speed and sedimentation rates in the wild-type and mutant cells were linearly related to acceleration, allowing the determination of gravikinesis as a linear (and so far non-saturating) function of gravity.

scholarly journals Spermidine Inversely Influences Surface Interactions and Planktonic Growth in Agrobacterium tumefaciens

2016 ◽  
Vol 198 (19) ◽  
pp. 2682-2691 ◽  
Author(s):  
Yi Wang ◽  
Sok Ho Kim ◽  
Ramya Natarajan ◽  
Jason E. Heindl ◽  
Eric L. Bruger ◽  
...  
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Biofilm Formation ◽  
Direct Synthesis ◽  
Wild Type ◽  
Cyclic Diguanylate ◽  
Content Type ◽  
Exogenous Addition ◽  
In The Wild ◽  
Growth Requirement ◽  
Transposon Insertions

ABSTRACTIn bacteria, the functions of polyamines, small linear polycations, are poorly defined, but these metabolites can influence biofilm formation in several systems. Transposon insertions in an ornithine decarboxylase (odc) gene inAgrobacterium tumefaciens, predicted to direct synthesis of the polyamine putrescine from ornithine, resulted in elevated cellulose. Null mutants forodcgrew somewhat slowly in a polyamine-free medium but exhibited increased biofilm formation that was dependent on cellulose production. Spermidine is an essential metabolite inA. tumefaciensand is synthesized from putrescine inA. tumefaciensvia the stepwise actions of carboxyspermidine dehydrogenase (CASDH) and carboxyspermidine decarboxylase (CASDC). Exogenous addition of either putrescine or spermidine to theodcmutant returned biofilm formation to wild-type levels. Low levels of exogenous spermidine restored growth to CASDH and CASDC mutants, facilitating weak biofilm formation, but this was dampened with increasing concentrations. Norspermidine rescued growth for theodc, CASDH, and CASDC mutants but did not significantly affect their biofilm phenotypes, whereas in the wild type, it stimulated biofilm formation and depressed spermidine levels. Theodcmutant produced elevated levels of cyclic diguanylate monophosphate (c-di-GMP), exogenous polyamines modulated these levels, and expression of a c-di-GMP phosphodiesterase reversed the enhanced biofilm formation. Prior work revealed accumulation of the precursors putrescine and carboxyspermidine in the CASDH and CASDC mutants, respectively, but unexpectedly, both mutants accumulated homospermidine; here, we show that this requires a homospermidine synthase (hss) homologue.IMPORTANCEPolyamines are small, positively charged metabolites that are nearly ubiquitous in cellular life. They are often essential in eukaryotes and more variably in bacteria. Polyamines have been reported to influence the surface-attached biofilm formation of several bacteria. InAgrobacterium tumefaciens, mutants with diminished levels of the polyamine spermidine are stimulated for biofilm formation, and exogenous provision of spermidine decreases biofilm formation. Spermidine is also essential forA. tumefaciensgrowth, but the related polyamine norspermidine exogenously rescues growth and does not diminish biofilm formation, revealing that the growth requirement and biofilm control are separable. Polyamine control of biofilm formation appears to function via effects on the cellular second messenger cyclic diguanylate monophosphate, regulating the transition from a free-living to a surface-attached lifestyle.

scholarly journals Analysis of flagellar size control using a mutant of Chlamydomonas reinhardtii with a variable number of flagella.

1982 ◽  
Vol 92 (1) ◽  
pp. 170-175 ◽  
Author(s):  
M R Kuchka ◽  
J W Jarvik
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Cell Size ◽  
Size Control ◽  
Variable Number ◽  
Pool Size ◽  
Precursor Protein ◽  
Wild Type ◽  
Protein Pool ◽  
Mutant Cells ◽  
Pool Sizes

A mutant of Chlamydomonas reinhardtii with a variable number of flagella per cell has been used to investigate flagellar size control. The mutant and wild-type do not differ in cell size nor in flagellar length, yet the size of the intracellular pool of flagellar precursor protein can differ dramatically among individual mutant cells, with, for example, triflagellate cells having three times the pool of monoflagellate cells. Because cells of the same size, but with very different pool sizes, have flagella of identical length, it appears that the concentration of the unassembled flagellar precursor protein pool does not regulate flagellar length. The relation between cell size, pool size, and flagellar length has also been investigated for wild-type cells of different sizes and ploidies. Again, flagellar length appears to be maintained independent of pool size or concentration.

scholarly journals Alterations of Metabolic and Lipid Profiles in Polymyxin-ResistantPseudomonas aeruginosa

2018 ◽  
Vol 62 (6) ◽  
Author(s):  
Mei-Ling Han ◽  
Yan Zhu ◽  
Darren J. Creek ◽  
Yu-Wei Lin ◽  
Dovile Anderson ◽  
...  
Keyword(s):  
Lipid A ◽  
Therapeutic Option ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Wild Type ◽  
Metabolomics Data ◽  
Content Type ◽  
In The Wild ◽  
High Level ◽  
Acyl Coenzyme A

ABSTRACTMultidrug-resistantPseudomonas aeruginosapresents a global medical challenge, and polymyxins are a key last-resort therapeutic option. Unfortunately, polymyxin resistance inP. aeruginosahas been increasingly reported. The present study was designed to define metabolic differences between paired polymyxin-susceptible and -resistantP. aeruginosastrains using untargeted metabolomics and lipidomics analyses. The metabolomes of wild-typeP. aeruginosastrain K ([PAK] polymyxin B MIC, 1 mg/liter) and its pairedpmrBmutant strains, PAKpmrB6and PAKpmrB12(polymyxin B MICs of 16 mg/liter and 64 mg/liter, respectively) were characterized using liquid chromatography-mass spectrometry, and metabolic differences were identified through multivariate and univariate statistics. PAKpmrB6and PAKpmrB12, which displayed lipid A modifications with 4-amino-4-deoxy-l-arabinose, showed significant perturbations in amino acid and carbohydrate metabolism, particularly the intermediate metabolites from 4-amino-4-deoxy-l-arabinose synthesis and the methionine salvage cycle pathways. The genomics result showed a premature termination (Y275stop) inspeE(encoding spermidine synthase) in PAKpmrB6, and metabolomics data revealed a decreased intracellular level of spermidine in PAKpmrB6compared to that in PAKpmrB12. Our results indicate that spermidine may play an important role in high-level polymyxin resistance inP. aeruginosa. Interestingly, bothpmrBmutants had decreased levels of phospholipids, fatty acids, and acyl-coenzyme A compared to those in the wild-type PAK. Moreover, the more resistant PAKpmrB12mutant exhibited much lower levels of phospholipids than the PAKpmrB6mutant, suggesting that the decreased phospholipid level was associated with polymyxin resistance. In summary, this study provides novel mechanistic information on polymyxin resistance inP. aeruginosaand highlights its impacts on bacterial metabolism.

Enhanced sodium-dependent extrusion of magnesium in mutant cells established from a mouse renal tubular cell line

2005 ◽  
Vol 289 (4) ◽  
pp. F742-F748 ◽  
Author(s):  
Masaru Watanabe ◽  
Masato Konishi ◽  
Ichiro Ohkido ◽  
Senya Matsufuji
Keyword(s):  
Culture Media ◽  
Cell Types ◽  
Renal Tubular Cell ◽  
Wild Type ◽  
Tubular Cells ◽  
Renal Tubular Cells ◽  
In The Wild ◽  
Renal Tubular ◽  
Mutant Cells ◽  
Very High

To study the regulatory mechanisms of intracellular Mg2+ concentration ([Mg2+]i) in renal tubular cells as well as in other cell types, we established a mutant strain of mouse renal cortical tubular cells that can grow in culture media with very high extracellular Mg2+ concentrations ([Mg2+]o > 100 mM: 101Mg-tolerant cells). [Mg2+]i was measured with a fluorescent indicator furaptra (mag-fura 2) in wild-type and 101Mg-tolerant cells. The average level of [Mg2+]i in the 101Mg-tolerant cells was kept lower than that in the wild-type cells either at 51 mM or 1 mM [Mg2+]o. When [Mg2+]o was lowered from 51 to 1 mM, the decrease in [Mg2+]i was significantly faster in the 101Mg-tolerant cells than in the wild-type cells. These differences between the 101Mg-tolerant cells and the wild-type cells were abolished in the absence of extracellular Na+ or in the presence of imipramine, a known inhibitor of Na+/Mg2+ exchange. We conclude that Na+-dependent Mg2+ transport activity is enhanced in the 101Mg-tolerant cells. The enhanced Mg2+ extrusion may prevent [Mg2+]i increase to higher levels and may be responsible for the Mg2+ tolerance.

scholarly journals FadD Is Required for Utilization of Endogenous Fatty Acids Released from Membrane Lipids

2011 ◽  
Vol 193 (22) ◽  
pp. 6295-6304 ◽  
Author(s):  
Ángel Pech-Canul ◽  
Joaquina Nogales ◽  
Alfonso Miranda-Molina ◽  
Laura Álvarez ◽  
Otto Geiger ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Stationary Phase ◽  
Free Fatty Acids ◽  
Sinorhizobium Meliloti ◽  
Membrane Lipids ◽  
Membrane Phospholipids ◽  
Content Type ◽  
Fatty Acid Transporter ◽  
In The Wild

FadD is an acyl coenzyme A (CoA) synthetase responsible for the activation of exogenous long-chain fatty acids (LCFA) into acyl-CoAs. Mutation offadDin the symbiotic nitrogen-fixing bacteriumSinorhizobium melilotipromotes swarming motility and leads to defects in nodulation of alfalfa plants. In this study, we found thatS. melilotifadDmutants accumulated a mixture of free fatty acids during the stationary phase of growth. The composition of the free fatty acid pool and the results obtained after specific labeling of esterified fatty acids with a Δ5-desaturase (Δ5-Des) were in agreement with membrane phospholipids being the origin of the released fatty acids.Escherichia colifadDmutants also accumulated free fatty acids released from membrane lipids in the stationary phase. This phenomenon did not occur in a mutant ofE. coliwith a deficient FadL fatty acid transporter, suggesting that the accumulation of fatty acids infadDmutants occurs inside the cell. Our results indicate that, besides the activation of exogenous LCFA, in bacteria FadD plays a major role in the activation of endogenous fatty acids released from membrane lipids. Furthermore, expression analysis performed withS. melilotirevealed that a functional FadD is required for the upregulation of genes involved in fatty acid degradation and suggested that in the wild-type strain, the fatty acids released from membrane lipids are degraded by β-oxidation in the stationary phase of growth.

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