scholarly journals Gene expression under low-oxygen conditions in the cyanobacterium Synechocystis sp. PCC 6803 demonstrates Hik31-dependent and -independent responses

Microbiology ◽  
2011 ◽  
Vol 157 (2) ◽  
pp. 301-312 ◽  
Author(s):  
Tina C. Summerfield ◽  
Sowmya Nagarajan ◽  
Louis A. Sherman
Keyword(s):  
Ribosomal Proteins ◽  
Chlorophyll Biosynthesis ◽  
Large Set ◽  
Wild Type ◽  
Low Oxygen ◽  
Knockout Mutant ◽  
Gene Encoding ◽  
Ps Ii ◽  
Oxygen Conditions ◽  
Pcc 6803

We have investigated the response of the cyanobacterium Synechocystis sp. PCC 6803 during growth at very low O2 concentration (bubbled with 99.9 % N2/0.1 % CO2). Significant transcriptional changes upon low-O2 incubation included upregulation of a cluster of genes that contained psbA1 and an operon that includes a gene encoding the two-component regulatory histidine kinase, Hik31. This regulatory cluster is of particular interest, since there are virtually identical copies on both the chromosome and plasmid pSYSX. We used a knockout mutant lacking the chromosomal copy of hik31 and studied differential transcription during the aerobic–low-O2 transition in this ΔHik31 strain and the wild-type. We observed two distinct responses to this transition, one Hik31 dependent, the other Hik31 independent. The Hik31-independent responses included the psbA1 induction and genes involved in chlorophyll biosynthesis. In addition, there were changes in a number of genes that may be involved in assembling or stabilizing photosystem (PS)II, and the hox operon and the LexA-like protein (Sll1626) were upregulated during low-O2 growth. This family of responses mostly focused on PSII and overall redox control. There was also a large set of genes that responded differently in the absence of the chromosomal Hik31. In the vast majority of these cases, Hik31 functioned as a repressor and transcription was enhanced when Hik31 was deleted. Genes in this category encoded both core and peripheral proteins for PSI and PSII, the main phycobilisome proteins, chaperones, the ATP synthase cluster and virtually all of the ribosomal proteins. These findings, coupled with the fact that ΔHik31 grew better than the wild-type under low-O2 conditions, suggested that Hik31 helps to regulate growth and overall cellular homeostasis. We detected changes in the transcription of other regulatory genes that may compensate for the loss of Hik31. We conclude that Hik31 regulates an important series of genes that relate to energy production and growth and that help to determine how Synechocystis responds to changes in O2 conditions.

scholarly journals A cbb3-Type Cytochrome C Oxidase Contributes to Ralstonia solanacearum R3bv2 Growth in Microaerobic Environments and to Bacterial Wilt Disease Development in Tomato

2010 ◽  
Vol 23 (8) ◽  
pp. 1042-1052 ◽  
Author(s):  
Jennifer Colburn-Clifford ◽  
Caitilyn Allen
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Wilt Disease ◽  
Wild Type ◽  
Low Oxygen ◽  
Tomato Root ◽  
Bacterial Wilt Disease ◽  
Oxygen Conditions

Ralstonia solanacearum race 3 biovar 2 (R3bv2) is an economically important soilborne plant pathogen that causes bacterial wilt disease by infecting host plant roots and colonizing the xylem vessels. Little is known about R3bv2 behavior in the host rhizosphere and early in bacterial wilt pathogenesis. To explore this part of the disease cycle, we used a novel taxis-based promoter-trapping strategy to identify pathogen genes induced in the plant rhizosphere. This screen identified several rex (root exudate expressed) genes whose promoters were upregulated in the presence of tomato root exudates. One rex gene encodes an assembly protein for a high affinity cbb3-type cytochrome c oxidase (cbb3-cco) that enables respiration in low-oxygen conditions in other bacteria. R3bv2 cbb3-cco gene expression increased under low-oxygen conditions, and a cbb3-cco mutant strain grew more slowly in a microaerobic environment (0.5% O2). Although the cco mutant could still wilt tomato plants, symptom onset was significantly delayed relative to the wild-type parent strain. Further, the cco mutant did not colonize host stems or adhere to roots as effectively as wild type. These results suggest that R3bv2 encounters low-oxygen environments during its interactions with host plants and that the pathogen depends on this oxidase to help it succeed in planta.

scholarly journals Pseudomonas aeruginosa Ethanol Oxidation by AdhA in Low-Oxygen Environments

2019 ◽  
Vol 201 (23) ◽  
Author(s):  
Alex W. Crocker ◽  
Colleen E. Harty ◽  
John H. Hammond ◽  
Sven D. Willger ◽  
Pedro Salazar ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Alcohol Dehydrogenase ◽  
Ethanol Oxidation ◽  
Physiological Role ◽  
Wild Type ◽  
Low Oxygen ◽  
Content Type ◽  
Anoxic Conditions ◽  
Oxygen Conditions ◽  
Acetate Accumulation

ABSTRACT Pseudomonas aeruginosa has a broad metabolic repertoire that facilitates its coexistence with different microbes. Many microbes secrete products that P. aeruginosa can then catabolize, including ethanol, a common fermentation product. Here, we show that under oxygen-limiting conditions P. aeruginosa utilizes AdhA, an NAD-linked alcohol dehydrogenase, as a previously undescribed means for ethanol catabolism. In a rich medium containing ethanol, AdhA, but not the previously described PQQ-linked alcohol dehydrogenase, ExaA, oxidizes ethanol and leads to the accumulation of acetate in culture supernatants. AdhA-dependent acetate accumulation and the accompanying decrease in pH promote P. aeruginosa survival in LB-grown stationary-phase cultures. The transcription of adhA is elevated by hypoxia and under anoxic conditions, and we show that it is regulated by the Anr transcription factor. We have shown that lasR mutants, which lack an important quorum sensing regulator, have higher levels of Anr-regulated transcripts under low-oxygen conditions than their wild-type counterparts. Here, we show that a lasR mutant, when grown with ethanol, has an even larger decrease in pH than the wild type (WT) that is dependent on both anr and adhA. The large increase in AdhA activity is similar to that of a strain expressing a hyperactive Anr-D149A variant. Ethanol catabolism in P. aeruginosa by AdhA supports growth on ethanol as a sole carbon source and electron donor in oxygen-limited settings and in cells growing by denitrification under anoxic conditions. This is the first demonstration of a physiological role for AdhA in ethanol oxidation in P. aeruginosa. IMPORTANCE Ethanol is a common product of microbial fermentation, and the Pseudomonas aeruginosa response to and utilization of ethanol are relevant to our understanding of its role in microbial communities. Here, we report that the putative alcohol dehydrogenase AdhA is responsible for ethanol catabolism and acetate accumulation under low-oxygen conditions and that it is regulated by Anr.

scholarly journals A Novel “Oxygen-induced” Greening Process in a Cyanobacterial Mutant Lacking the Transcriptional Activator ChlR Involved in Low-oxygen Adaptation of Tetrapyrrole Biosynthesis

2013 ◽  
Vol 289 (3) ◽  
pp. 1841-1851 ◽  
Author(s):  
Rina Aoki ◽  
Yuto Hiraide ◽  
Hisanori Yamakawa ◽  
Yuichi Fujita
Keyword(s):  
Fluorescence Spectra ◽  
Tetrapyrrole Biosynthesis ◽  
Wild Type ◽  
Low Oxygen ◽  
Promising Alternative ◽  
Photoautotrophic Growth ◽  
Oxygen Conditions ◽  
Almost All ◽  
Low Temperature Fluorescence Spectra ◽  
Chl Biosynthesis

ChlR activates the transcription of the chlAII-ho2-hemN operon in response to low-oxygen conditions in the cyanobacterium Synechocystis sp. PCC 6803. Three genes in the operon encode low-oxygen-type enzymes to bypass three oxygen-dependent reactions in tetrapyrrole biosynthesis. A chlR-lacking mutant, ΔchlR, shows poor photoautotrophic growth due to low chlorophyll (Chl) content under low-oxygen conditions, which is caused by no induction of the operon. Here, we characterized the processes of etiolation of ΔchlR cells in low-oxygen conditions and the subsequent regreening of the etiolated cells upon exposure to oxygen, by HPLC, Western blotting, and low-temperature fluorescence spectra. The Chl content of the etiolated ΔchlR cells incubated under low-oxygen conditions for 7 days was only 10% of that of the wild-type with accumulation of almost all intermediates of the magnesium branch of Chl biosynthesis. Both photosystem I (PSI) and photosystem II (PSII) were significantly decreased, accompanied by a preferential decrease of antenna Chl in PSI. Upon exposure to oxygen, the etiolated ΔchlR cells resumed to produce Chl after a short lag (∼2 h), and the level at 72 h was 80% of that of the wild-type. During this novel “oxygen-induced” greening process, the PSI and PSII contents were largely increased in parallel with the increase in Chl contents. After 72 h, the PSI content reached ∼50% of the wild-type level in contrast to the full recovery of PSII. ΔchlR provides a promising alternative system to investigate the biogenesis of PSI and PSII.

Characterization of the Light-Induced Oxygen Gas Exchange from the IC 2 Deletion Mutant of Synechocystis PCC 6803 Lacking the Photosystem II 33 kDa Extrinsic Protein

1993 ◽  
Vol 48 (3-4) ◽  
pp. 224-233 ◽  
Author(s):  
V. A. Boichenko ◽  
V. V. Klimov ◽  
S. R. Mayes ◽  
J. Barber
Keyword(s):  
Water Splitting ◽  
Oxygen Evolution ◽  
Oxygen Exchange ◽  
Wild Type ◽  
Exchange Reactions ◽  
Synechocystis Pcc 6803 ◽  
Ps Ii ◽  
Aerobic Conditions ◽  
Ps I ◽  
Pcc 6803

Abstract The absence of the extrinsic Mn-stabilizing 33 kDa protein in the IC 2 mutant of Synechocystis PCC 6803 disturbs the redox cycling of the water splitting system and retards the formation of its higher S-states (I. Vass, K. Cook, S. Deak, S. R. Mayes, and J. Barber, Biochim. Biophys. Acta 1102, 195-201 (1992)). We have performed analyses of the flashinduced oxygen exchange in the mutated cyanobacterium to clarify further the role of the 33 kDa protein. Under aerobic conditions, both the wild type and IC2 mutant show a relatively slow signal of oxygen rise on the first flash which is increased about twice by the addition of 10 μᴍ DCMU and significantly diminished by lowering the oxygen concentration in the medium. According to action spectra measurements, this mode of apparent oxygen release is mediated by PS I and can be attributed to a light induced inhibition of respiratory activity. In contrast to the wild type, having the usual oxygen evolution flash pattern with a periodicity of four, the IC2 mutant shows a binary oscillation pattern of flash-induced respiratory oxygen exchange at a flash frequency 10 Hz, being dampened with DCMU or by a lower flash frequency (< 1 Hz). Oxygen evolution due to water splitting is clearly seen in the IC2 mutant when background far-red illumination is applied to saturate the signal due to respiratory inhibition, but a quadruple oscillatory component of flash-induced oxygen evolution appears only in the presence of artificial electron acceptors under partial aerobic conditions. The mutant possesses a higher PS I/PS II ratio compared to the wild type, as judged from both the flashinduced yields and quantum efficiencies of the steady-state rates of the oxygen exchange reactions. Estimates of antenna sizes indicate about a 20% decrease of optical cross-section at 675 nm of the PS II unit in IC2 mutants in comparison with the wild type. It is suggested that the absence of the 33 kDa protein leads to a modification of the PS II assembly and because of the slowing down of the S-state cycle, the rate of cyclic electron flow around PS II is enhanced. It seems that the absence of the 33 kDa protein in Synechocystis 6803 also disturbs energy transfer between adjacent PS II core complexes and may also alter their association with the phycobilisomes.

scholarly journals Hydrogen Production by the Unicellular, Diazotrophic Cyanobacterium Cyanothece sp. Strain ATCC 51142 under Conditions of Continuous Light

2010 ◽  
Vol 76 (13) ◽  
pp. 4293-4301 ◽  
Author(s):  
Hongtao Min ◽  
Louis A. Sherman
Keyword(s):  
Hydrogen Production ◽  
Nitrogenase Activity ◽  
Continuous Light ◽  
Hydrogenase Activity ◽  
Strain Atcc ◽  
Nitrogen Fixing ◽  
Low Oxygen ◽  
Ps Ii ◽  
Oxygen Conditions ◽  
Metabolic Conditions

ABSTRACT We report on the hydrogen production properties of the unicellular, diazotrophic cyanobacterium Cyanothece sp. strain ATCC 51142. This organism has a versatile metabolism and can grow in the presence or absence of combined nitrogen and can grow photosynthetically or mixotrophically and heterotrophically in the presence of glycerol. The strain produces a bidirectional hydrogenase (encoded by the hox genes), an uptake hydrogenase (hupLS), and nitrogenase (nifHDK). We demonstrated hydrogen production by both the hydrogenase and the nitrogenase under appropriate metabolic conditions. The highest rates of hydrogen production were produced under nitrogen-fixing conditions when cells were grown and incubated under continuous light conditions, in either the presence or absence of glycerol. Under such nitrogen-fixing conditions, we have achieved rates of 300 μmol H2/mg chloramphenicol (Chl)/hr during the first 24 h of incubation. The levels of H2 measured were dependent upon the incubation conditions, such as sparging with argon, which generated anaerobic conditions. We demonstrated that the same conditions led to high levels of H2 production and N2 fixation, indicating that low-oxygen conditions favor nitrogenase activity for both processes. The levels of hydrogen produced by the hydrogenase are much lower, typically 5 to 10 μmol H2/mg Chl/hr. Hydrogenase activity was dependent upon electron transport through photosystem II (PS II), whereas nitrogenase activity was more dependent on PS I, as well as on respiration. Although cells do not double under the incubation conditions when sparged with argon to provide a low-oxygen environment, the cells are metabolically active, and hydrogen production can be inhibited by the addition of chloramphenicol to inhibit protein synthesis.

scholarly journals Cytochrome cM downscales photosynthesis under photomixotrophy in Synechocystis sp. PCC 6803

2019 ◽  
Author(s):  
Daniel Solymosi ◽  
Dorota Muth-Pawlak ◽  
Lauri Nikkanen ◽  
Duncan Fitzpatrick ◽  
Ravendran Vasudevan ◽  
...  
Keyword(s):  
Photosynthetic Apparatus ◽  
Wild Type ◽  
Gene Encoding ◽  
Transport Chain ◽  
Similar Phenotype ◽  
Photosynthetic Microorganisms ◽  
Photosynthesis And Respiration ◽  
Pcc 6803

AbstractPhotomixotrophy is a metabolic state, which enables photosynthetic microorganisms to simultaneously perform photosynthesis and metabolism of imported organic carbon substrates. This process is complicated in cyanobacteria, since many, including Synechocystis sp. PCC 6803, conduct photosynthesis and respiration in an interlinked thylakoid membrane electron transport chain. Under photomixotrophy, the cell must therefore tightly regulate electron fluxes from photosynthetic and respiratory complexes. In this study, we show via characterization of photosynthetic apparatus and the proteome, that photomixotrophic growth results in a gradual reduction of the plastoquinone pool in wild-type Synechocystis, which fully downscales photosynthesis over three days of growth. This process is circumvented by deleting the gene encoding cytochrome cM (CytM), a cryptic c-type heme protein widespread in cyanobacteria. ΔCytM maintained active photosynthesis over the three day period, demonstrated by high photosynthetic O2 and CO2 fluxes and effective yields of Photosystem II and Photosystem I. Overall, this resulted in a higher growth rate than wild-type, which was maintained by accumulation of proteins involved in phosphate and metal uptake, and cofactor biosynthetic enzymes. While the exact role of CytM has not been determined, a mutant deficient in the thylakoid-localised respiratory terminal oxidases and CytM (ΔCox/Cyd/CytM) displayed a similar phenotype under photomixotrophy to ΔCytM, demonstrating that CytM is not transferring electrons to these complexes, which has previously been suggested. In summary, the obtained data suggests that CytM may have a regulatory role in photomixotrophy by reducing the photosynthetic capacity of cells.One sentence summaryThe cryptic, highly conserved cytochrome cM completely blocks photosynthesis in Synechocystis under three days of photomixotrophy, possibly by suppressing CO2 assimilation.

scholarly journals Deficiency of mitoribosomal S10 protein affects translation and splicing in Arabidopsis mitochondria

2019 ◽  
Author(s):  
Malgorzata Kwasniak-Owczarek ◽  
Urszula Kazmierczak ◽  
Artur Tomal ◽  
Pawel Mackiewicz ◽  
Hanna Janska
Keyword(s):  
Protein Synthesis ◽  
Translational Control ◽  
Ribosomal Proteins ◽  
Regulatory Element ◽  
Mitochondrial Gene ◽  
Ribosome Profiling ◽  
Translation Efficiency ◽  
Wild Type ◽  
Gene Encoding ◽  
Related Proteins

Abstract The ribosome is not only a protein-making machine, but also a regulatory element in protein synthesis. This view is supported by our earlier data showing that Arabidopsis mitoribosomes altered due to the silencing of the nuclear RPS10 gene encoding mitochondrial ribosomal protein S10 differentially translate mitochondrial transcripts compared with the wild-type. Here, we used ribosome profiling to determine the contribution of transcriptional and translational control in the regulation of protein synthesis in rps10 mitochondria compared with the wild-type ones. Oxidative phosphorylation system proteins are preferentially synthesized in wild-type mitochondria but this feature is lost in the mutant. The rps10 mitoribosomes show slightly reduced translation efficiency of most respiration-related proteins and at the same time markedly more efficiently synthesize ribosomal proteins and MatR and TatC proteins. The mitoribosomes deficient in S10 protein protect shorter transcript fragments which exhibit a weaker 3-nt periodicity compared with the wild-type. The decrease in the triplet periodicity is particularly drastic for genes containing introns. Notably, splicing is considerably less effective in the mutant, indicating an unexpected link between the deficiency of S10 and mitochondrial splicing. Thus, a shortage of the mitoribosomal S10 protein has wide-ranging consequences on mitochondrial gene expression.

scholarly journals Increased Production of Zeaxanthin and Other Pigments by Application of Genetic Engineering Techniques toSynechocystis sp. Strain PCC 6803

2000 ◽  
Vol 66 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Delphine Lagarde ◽  
Laurent Beuf ◽  
Wim Vermaas
Keyword(s):  
Mutant Strain ◽  
Fold Increase ◽  
Carotenoid Biosynthesis ◽  
Carotenoid Content ◽  
Wild Type ◽  
Gene Encoding ◽  
Genes Encoding ◽  
In The Wild ◽  
Β Carotene ◽  
Pcc 6803

ABSTRACT The psbAII locus was used as an integration platform to overexpress genes involved in carotenoid biosynthesis inSynechocystis sp. strain PCC 6803 under the control of the strong psbAII promoter. The sequences of the genes encoding the yeast isopentenyl diphosphate isomerase (ipi) and theSynechocystis β-carotene hydroxylase (crtR) and the linked Synechocystis genes coding for phytoene desaturase and phytoene synthase (crtP andcrtB, respectively) were introduced intoSynechocystis, replacing the psbAII coding sequence. Expression of ipi, crtR, andcrtP and crtB led to a large increase in the corresponding transcript levels in the mutant strains, showing that the psbAII promoter can be used to drive transcription and to overexpress various genes in Synechocystis. Overexpression of crtP and crtB led to a 50% increase in the myxoxanthophyll and zeaxanthin contents in the mutant strain, whereas the β-carotene and echinenone contents remained unchanged. Overexpression of crtR induced a 2.5-fold increase in zeaxanthin accumulation in the corresponding overexpressing mutant compared to that in the wild-type strain. In this mutant strain, zeaxanthin becomes the major pigment (more than half the total amount of carotenoid) and the β-carotene and echinenone amounts are reduced by a factor of 2. However, overexpression of ipi did not result in a change in the carotenoid content of the mutant. To further alter the carotenoid content of Synechocystis, the crtOgene, encoding β-carotene ketolase, which converts β-carotene to echinenone, was disrupted in the wild type and in the overexpressing strains so that they no longer produced echinenone. In this way, by a combination of overexpression and deletion of particular genes, the carotenoid content of cyanobacteria can be altered significantly.

scholarly journals Pseudomonas aeruginosaethanol oxidation by AdhA in low oxygen environments

2019 ◽  
Author(s):  
Alex W. Crocker ◽  
Colleen E. Harty ◽  
John H. Hammond ◽  
Sven D. Willger ◽  
Pedro Salazar ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Alcohol Dehydrogenase ◽  
Ethanol Oxidation ◽  
Physiological Role ◽  
Wild Type ◽  
Low Oxygen ◽  
Anoxic Conditions ◽  
Oxygen Conditions ◽  
Acetate Accumulation ◽  
Culture Supernatants

AbstractPseudomonas aeruginosahas a broad metabolic repertoire that facilitates its co-existence with different microbes. Many microbes secrete products thatP. aeruginosacan then catabolize, including ethanol, a common fermentation product. Here, we show that under oxygen limiting conditionsP. aeruginosautilizes AdhA, an NAD-linked alcohol dehydrogenase, as a previously undescribed means for ethanol catabolism. In a rich medium containing ethanol, AdhA, but not the previously described PQQ-linked alcohol dehydrogenase, ExaA, oxidizes ethanol and leads to the accumulation of acetate in culture supernatants. AdhA-dependent acetate accumulation, and the accompanying decrease in pH, promotesP. aeruginosasurvival in LB-grown stationary phase cultures. The transcription ofadhAis elevated by hypoxia and in anoxic conditions, and we show that it is regulated by the Anr transcription factor. We have shown thatlasRmutants have higher levels of Anr-regulated transcripts in low oxygen conditions compared to their wild type counterparts. Here, we show that alasRmutant, when grown with ethanol, has an even larger decrease in pH than WT that is dependent on bothanrandadhA. The large increase in AdhA activity similar to that of a strain expressing a hyperactive Anr-D149A variant. Ethanol catabolism inP. aeruginosaby AdhA supports growth on ethanol as a sole carbon source and electron donor in oxygen-limited settings and in cells growing by denitrification in anoxic conditions. This is the first demonstration of a physiological role for AdhA in ethanol oxidation inP. aeruginosa.ImportanceEthanol is a common product of microbial fermentation, and thePseudomonas aeruginosaresponse to and utilization of ethanol is relevant to our understanding of its role in microbial communities. Here, we report that the putative alcohol dehydrogenase, AdhA, is responsible for ethanol catabolism and acetate accumulation in low oxygen conditions and that it is regulated by Anr.

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