scholarly journals Reduction of Photoautotrophic Productivity in the Cyanobacterium Synechocystis sp. Strain PCC 6803 by Phycobilisome Antenna Truncation

2012 ◽  
Vol 78 (17) ◽  
pp. 6349-6351 ◽  
Author(s):  
Lawrence E. Page ◽  
Michelle Liberton ◽  
Himadri B. Pakrasi
Keyword(s):  
Light Harvesting ◽  
Wild Type ◽  
Content Type ◽  
Photosynthetic Productivity ◽  
Mutant Strains ◽  
Light Harvesting Antenna ◽  
Culture Productivity ◽  
Synechocystis Sp ◽  
Pcc 6803

ABSTRACTTruncation of the algal light-harvesting antenna is expected to enhance photosynthetic productivity. The wild type and three mutant strains ofSynechocystissp. strain 6803 with a progressively smaller phycobilisome antenna were examined under different light and CO2conditions. Surprisingly, such antenna truncation resulted in decreased whole-culture productivity for this cyanobacterium.

scholarly journals The Type VI Secretion System Modulates Flagellar Gene Expression and Secretion in Citrobacter freundii and Contributes to Adhesion and Cytotoxicity to Host Cells

2015 ◽  
Vol 83 (7) ◽  
pp. 2596-2604 ◽  
Author(s):  
Liyun Liu ◽  
Shuai Hao ◽  
Ruiting Lan ◽  
Guangxia Wang ◽  
Di Xiao ◽  
...  
Keyword(s):  
Secretion System ◽  
Host Cells ◽  
Target Cells ◽  
Deletion Mutants ◽  
Citrobacter Freundii ◽  
Wild Type ◽  
Type Vi Secretion System ◽  
Content Type ◽  
Type Vi Secretion ◽  
Mutant Strains

The type VI secretion system (T6SS) as a virulence factor-releasing system contributes to virulence development of various pathogens and is often activated upon contact with target cells.Citrobacter freundiistrain CF74 has a complete T6SS genomic island (GI) that containsclpV,hcp-2, andvgrT6SS genes. We constructedclpV,hcp-2,vgr, and T6SS GI deletion mutants in CF74 and analyzed their effects on the transcriptome overall and, specifically, on the flagellar system at the levels of transcription and translation. Deletion of the T6SS GI affected the transcription of 84 genes, with 15 and 69 genes exhibiting higher and lower levels of transcription, respectively. Members of the cell motility class of downregulated genes of the CF74ΔT6SS mutant were mainly flagellar genes, including effector proteins, chaperones, and regulators. Moreover, the production and secretion of FliC were also decreased inclpV,hcp-2,vgr, or T6SS GI deletion mutants in CF74 and were restored upon complementation. In swimming motility assays, the mutant strains were found to be less motile than the wild type, and motility was restored by complementation. The mutant strains were defective in adhesion to HEp-2 cells and were restored partially upon complementation. Further, the CF74ΔT6SS, CF74ΔclpV, and CF74Δhcp-2mutants induced lower cytotoxicity to HEp-2 cells than the wild type. These results suggested that the T6SS GI in CF74 regulates the flagellar system, enhances motility, is involved in adherence to host cells, and induces cytotoxicity to host cells. Thus, the T6SS plays a wide-ranging role inC. freundii.

scholarly journals Data-Driven Models Reveal Mutant Cell Behaviors Important for Myxobacterial Aggregation

mSystems ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Zhaoyang Zhang ◽  
Christopher R. Cotter ◽  
Zhe Lyu ◽  
Lawrence J. Shimkets ◽  
Oleg A. Igoshin
Keyword(s):  
Cell Tracking ◽  
Mutant Cell ◽  
Myxococcus Xanthus ◽  
Data Driven ◽  
Self Organization ◽  
Cell Behavior ◽  
Significant Heterogeneity ◽  
Wild Type ◽  
Content Type ◽  
Mutant Strains

ABSTRACT Single mutations frequently alter several aspects of cell behavior but rarely reveal whether a particular statistically significant change is biologically significant. To determine which behavioral changes are most important for multicellular self-organization, we devised a new methodology using Myxococcus xanthus as a model system. During development, myxobacteria coordinate their movement to aggregate into spore-filled fruiting bodies. We investigate how aggregation is restored in two mutants, csgA and pilC, that cannot aggregate unless mixed with wild-type (WT) cells. To this end, we use cell tracking to follow the movement of fluorescently labeled cells in combination with data-driven agent-based modeling. The results indicate that just like WT cells, both mutants bias their movement toward aggregates and reduce motility inside aggregates. However, several aspects of mutant behavior remain uncorrected by WT, demonstrating that perfect recreation of WT behavior is unnecessary. In fact, synergies between errant behaviors can make aggregation robust. IMPORTANCE Self-organization into spatial patterns is evident in many multicellular phenomena. Even for the best-studied systems, our ability to dissect the mechanisms driving coordinated cell movement is limited. While genetic approaches can identify mutations perturbing multicellular patterns, the diverse nature of the signaling cues coupled to significant heterogeneity of individual cell behavior impedes our ability to mechanistically connect genes with phenotype. Small differences in the behaviors of mutant strains could be irrelevant or could sometimes lead to large differences in the emergent patterns. Here, we investigate rescue of multicellular aggregation in two mutant strains of Myxococcus xanthus mixed with wild-type cells. The results demonstrate how careful quantification of cell behavior coupled to data-driven modeling can identify specific motility features responsible for cell aggregation and thereby reveal important synergies and compensatory mechanisms. Notably, mutant cells do not need to precisely recreate wild-type behaviors to achieve complete aggregation.

scholarly journals Suppressor Mutations in the Study of Photosystem I Biogenesis: sll0088 Is a Previously Unidentified Gene Involved in Reaction Center Accumulation in Synechocystis sp. Strain PCC 6803

2003 ◽  
Vol 185 (13) ◽  
pp. 3878-3887 ◽  
Author(s):  
Jianping Yu ◽  
Gaozhong Shen ◽  
Tao Wang ◽  
Donald A. Bryant ◽  
John H. Golbeck ◽  
...  
Keyword(s):  
Photosystem I ◽  
Point Mutations ◽  
Kanamycin Resistance ◽  
Negative Regulator ◽  
Binding Motif ◽  
Wild Type ◽  
Photoautotrophic Growth ◽  
Suppressor Mutations ◽  
Mutant Strains ◽  
Pcc 6803

ABSTRACT In previous work, some members of our group isolated mutant strains of Synechocystis sp. strain PCC 6803 in which point mutations had been inserted into the psaC gene to alter the cysteine residues to the FA and FB iron-sulfur clusters in the PsaC subunit of photosystem I (J. P. Yu, I. R. Vassiliev, Y. S. Jung, J. H. Golbeck, and L. McIntosh, J. Biol. Chem. 272:8032-8039, 1997). These mutant strains did not grow photoautotrophically due to suppressed levels of chlorophyll a and photosystem I. In the results described here, we show that suppressor mutations produced strains that are capable of photoautotrophic growth at moderate light intensity (20 μmol m−2 s−1). Two separate suppressor strains of C14SPsaC, termed C14SPsaC-R62 and C14SPsaC-R18, were studied and found to have mutations in a previously uncharacterized open reading frame of the Synechocystis sp. strain PCC 6803 genome named sll0088. C14SPsaC-R62 was found to substitute Pro for Arg at residue 161 as the result of a G482→C change in sll0088, and C14SPsaC-R18 was found to have a three-amino-acid insertion of Gly-Tyr-Phe following Cys231 as the result of a TGGTTATTT duplication at T690 in sll0088. These suppressor strains showed near-wild-type levels of chlorophyll a and photosystem I, yet the serine oxygen ligand to FB was retained as shown by the retention of the S ≥ 3/2 spin state of the [4Fe-4S] cluster. The inactivation of sll0088 by insertion of a kanamycin resistance cartridge in the primary C14SPsaC mutant produced an engineered suppressor strain capable of photoautotrophic growth. There was no difference in psaC gene expression or in the amount of PsaC protein assembled in thylakoids between the wild type and an sll0088 deletion mutant. The sll0088 gene encodes a protein predicted to be a transcriptional regulator with sequence similarities to transcription factors in other prokaryotic and eukaryotic organisms, including Arabidopsis thaliana. The protein contains a typical helix-turn-helix DNA-binding motif and can be classified as a negative regulator by phylogenetic analysis. This suggests that the product of sll0088 has a role in regulating the biogenesis of photosystem I.

scholarly journals Novel Functions for Glycosyltransferases Jhp0562 and GalT in Lewis Antigen Synthesis and Variation in Helicobacter pylori

2012 ◽  
Vol 80 (4) ◽  
pp. 1593-1605 ◽  
Author(s):  
Mary Ann Pohl ◽  
Sabine Kienesberger ◽  
Martin J. Blaser
Keyword(s):  
Helicobacter Pylori ◽  
Wild Type ◽  
Sequence Analyses ◽  
Upstream Gene ◽  
Content Type ◽  
Lewis Antigen ◽  
Mutant Strains ◽  
H Pylori

ABSTRACTLewis (Le) antigens are fucosylated oligosaccharides present in theHelicobacter pylorilipopolysaccharide. Expression of these antigens is believed to be important forH. pyloricolonization, since Le antigens also are expressed on the gastric epithelia in humans. A galactosyltransferase encoded by β-(1,3)galTis essential for production of type 1 (Leaand Leb) antigens. The upstream genejhp0562, which is present in many but not allH. pyloristrains, is homologous to β-(1,3)galTbut is of unknown function. BecauseH. pyloridemonstrates extensive intragenomic recombination, we hypothesized that these two genes could undergo DNA rearrangement. A PCR screen and subsequent sequence analyses revealed that the two genes can recombine at both the 5′ and 3′ ends. Chimeric β-(1,3)galT-like alleles can restore function in a β-(1,3)galTnull mutant, but neither native nor recombinantjhp0562can. Mutagenesis ofjhp0562revealed that it is essential for synthesis of both type 1 and type 2 Le antigens. Transcriptional analyses of both loci showed β-(1,3)galTexpression in all wild-type (WT) and mutant strains tested, whereasjhp0562was not expressed injhp0562null mutants, as expected. Sincejhp0562unexpectedly displayed functions in both type 1 and type 2 Le synthesis, we asked whethergalT, part of the type 2 synthesis pathway, had analogous functions in type 1 synthesis. Mutagenesis and complementation analysis confirmed thatgalTis essential for Lebproduction. In total, these results demonstrate thatgalTandjhp0562have functions that cross the expected Le synthesis pathways and thatjhp0562provides a substrate for intragenomic recombination to generate diverse Le synthesis enzymes.

scholarly journals Genetic Evidence for a Molybdopterin-Containing Tellurate Reductase

2013 ◽  
Vol 79 (10) ◽  
pp. 3171-3175 ◽  
Author(s):  
Joanne Theisen ◽  
Gerben J. Zylstra ◽  
Nathan Yee
Keyword(s):  
Genetic Evidence ◽  
Biosynthesis Pathway ◽  
Wild Type ◽  
Transport Pathway ◽  
Content Type ◽  
E Coli ◽  
Reduction Activity ◽  
Mutant Strains ◽  
Molybdate Transport ◽  
K 12

ABSTRACTThe genetic identity and cofactor composition of the bacterial tellurate reductase are currently unknown. In this study, we examined the requirement of molybdopterin biosynthesis and molybdate transporter genes for tellurate reduction inEscherichia coliK-12. The results show that mutants deleted of themoaA,moaB,moaE, ormoggene in the molybdopterin biosynthesis pathway lost the ability to reduce tellurate. Deletion of themodBormodCgene in the molybdate transport pathway also resulted in complete loss of tellurate reduction activity. Genetic complementation by the wild-type sequences restored tellurate reduction activity in the mutant strains. These findings provide genetic evidence that tellurate reduction inE. coliinvolves a molybdoenzyme.

scholarly journals Francisella tularensis Schu S4 Lipopolysaccharide Core Sugar and O-Antigen Mutants Are Attenuated in a Mouse Model of Tularemia

2014 ◽  
Vol 82 (4) ◽  
pp. 1523-1539 ◽  
Author(s):  
Jed A. Rasmussen ◽  
Deborah M. B. Post ◽  
Bradford W. Gibson ◽  
Stephen R. Lindemann ◽  
Michael A. Apicella ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Francisella Tularensis ◽  
Lethal Dose ◽  
Protective Effects ◽  
Wild Type ◽  
Content Type ◽  
O Antigen ◽  
Capsule Production ◽  
Mutant Strains ◽  
Schu S4

ABSTRACTThe virulence factors mediatingFrancisellapathogenesis are being investigated, with an emphasis on understanding how the organism evades innate immunity mechanisms.Francisella tularensisproduces a lipopolysaccharide (LPS) that is essentially inert and a polysaccharide capsule that helps the organism to evade detection by components of innate immunity. Using anF. tularensisSchu S4 mutant library, we identified strains that are disrupted for capsule and O-antigen production. These serum-sensitive strains lack both capsule production and O-antigen laddering. Analysis of the predicted protein sequences for the disrupted genes (FTT1236andFTT1238c) revealed similarity to those forwaa(rfa) biosynthetic genes in other bacteria. Mass spectrometry further revealed that these proteins are involved in LPS core sugar biosynthesis and the ligation of O antigen to the LPS core sugars. The 50% lethal dose (LD50) values of these strains are increased 100- to 1,000-fold for mice. Histopathology revealed that the immune response to theF. tularensismutant strains was significantly different from that observed with wild-type-infected mice. The lung tissue from mutant-infected mice had widespread necrotic debris, but the spleens lacked necrosis and displayed neutrophilia. In contrast, the lungs of wild-type-infected mice had nominal necrosis, but the spleens had widespread necrosis. These data indicate that murine death caused by wild-type strains occurs by a mechanism different from that by which the mutant strains kill mice. Mice immunized with these mutant strains displayed >10-fold protective effects against virulent type AF. tularensischallenge.

scholarly journals The Malic Enzyme Is Required for Optimal Photoautotrophic Growth of Synechocystis sp. Strain PCC 6803 under Continuous Light but Not under a Diurnal Light Regimen

2004 ◽  
Vol 186 (23) ◽  
pp. 8144-8148 ◽  
Author(s):  
Terry M. Bricker ◽  
Shulu Zhang ◽  
Susan M. Laborde ◽  
Paul R. Mayer ◽  
Laurie K. Frankel ◽  
...  
Keyword(s):  
Malic Enzyme ◽  
Continuous Light ◽  
Light Conditions ◽  
Wild Type ◽  
Photoautotrophic Growth ◽  
Light Regimen ◽  
Synechocystis Sp ◽  
Pcc 6803

ABSTRACT A mutation was recovered in the slr0721 gene, which encodes the decarboxylating NADP+-dependent malic enzyme in the cyanobacterium Synechocystis sp. strain PCC 6803, yielding the mutant 3WEZ. Under continuous light, 3WEZ exhibits poor photoautotrophic growth while growing photoheterotrophically on glucose at rates nearly indistinguishable from wild-type rates. Interestingly, under diurnal light conditions (12 h of light and 12 h of dark), normal photoautotrophic growth of the mutant is completely restored.

Interrelation between Cyanophycin Synthesis, L-Arginine Catabolism and Photosynthesis in the Cyanobacterium Synechocystis Sp. Strain PCC 6803

2000 ◽  
Vol 55 (11-12) ◽  
pp. 927-942 ◽  
Author(s):  
Dirk Paul Stephan ◽  
Hans Georg Ruppel ◽  
Elfriede K. Pistorius
Keyword(s):  
Relative Concentration ◽  
Nutrient Deficiency ◽  
Phosphate Limitation ◽  
Physiological Changes ◽  
Wild Type ◽  
Synechocystis Pcc 6803 ◽  
N Source ◽  
Arginine Catabolism ◽  
Synechocystis Sp ◽  
Pcc 6803

ʟ Ultrastructural and imm unocytochemical investigations gave evidence that cyanophycin (multi--arginyl-poly-ʟ-aspartate) granules accumulate in the cyanobacterium Synechocystis sp. strain PCC 6803 under nutrient deficient growth conditions, especially under phosphate limitation. Besides nutrient deficiency, growth of Synechocystis PCC 6803 on ʟ-arginine or ʟ-asparagine as sole N-source also led to high increase of cyanophycin synthesis, while growth on the combination of ʟ-arginine or ʟ-asparagine with nitrate only caused minor cyanophycin accum ulation. Growth of Synechocystis PCC 6803 on ʟ-arginine as sole N-source caused substantial morphological and physiological changes, such as severe thylakoid membrane degradation with partial loss of pigments and photosynthetic activity leading to a phenotype almost like that seen under nutrient deficiency. In contrast to the wild type, the PsbO-free Synechocystis PCC 6803 mutant could grow on ʟ-arginine as sole N-source with only minor morphological and physiological changes. Due to its fairly balanced growth, the mutant accumulated only few cyanophycin granules. ʟ-arginine degrading activity (measured as ornithine and ammonium formation) was high in the PsbO-free mutant but not in the wild type when cells were grown on ʟ-arginine as sole N-source. In both cells types the ʟ-arginine degrading activity was high (although in the PsbO-free mutant about twice as high as in wild type), when cells were grown on ʟ-arginine in combination with nitrate, and as expected very low when cells were grown on nitrate as sole N-source. Thus, net cyanophycin accumulation in Synechocystis PCC 6803 is regulated by the relative concentration of ʟ-arginine to the total nitrogen pool, and the intracellular ʟ-arginine concentration is greatly influenced by the activity of the ʟ-arginine degrading enzyme system which in part is regulated by the activity status of photosystem II. These results suggest a complex interrelation between cyanophycin synthesis, ʟ-arginine catabolism , and in addition photosynthesis in Synechocystis PCC 6803.

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