Photosynthetic performance in cyanobacteria with increased sulphide tolerance: an analysis comparing wild-type and experimentally derived strains

AbstractSulphide is proposed to have influenced the evolution of primary stages of oxygenic photosynthesis in cyanobacteria. However, sulphide is toxic to most of the species of this phylum, except for some sulphide-tolerant species showing various sulphide-resistance mechanisms. In a previous study, we found that this tolerance can be induced by environmental sulphidic conditions, in which two experimentally derived strains with an enhanced tolerance to sulphide were obtained from Microcystis aeruginosa, a sensitive species, and Oscillatoria, a sulphide-tolerant genus. We have now analysed the photosynthetic performance of the wild-type and derived strains in the presence of sulphide to shed light on the characteristics underlying the increased tolerance. We checked whether the sulphide tolerance was a result of higher PSII sulphide resistance and/or the induction of sulphide-dependent anoxygenic photosynthesis. We observed that growth, maximum quantum yield, maximum electron transport rate and photosynthetic efficiency in the presence of sulphide were less affected in the derived strains compared to their wild-type counterparts. Nevertheless, in 14C photoincoporation assays, neither Oscillatoria nor M. aeruginosa exhibited anoxygenic photosynthesis using sulphide as an electron donor. On the other hand, the content of photosynthetic pigments in the derived strains was different to that observed in the wild-type strains. Thus, an enhanced PSII sulphide resistance appears to be behind the increased sulphide tolerance displayed by the experimentally derived strains, as observed in most natural sulphide-tolerant cyanobacterial strains. However, other changes in the photosynthetic machinery cannot be excluded.

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Influences of Histone Stoichiometry on the Target Site Preference of Retrotransposons Ty1 and Ty2 in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/142.3.761 ◽

1996 ◽

Vol 142 (3) ◽

pp. 761-776 ◽

Cited By ~ 2

Author(s):

Lori A Rinckel ◽

David J Garfinkel

Keyword(s):

Saccharomyces Cerevisiae ◽

Promoter Region ◽

Target Site ◽

Site Preference ◽

Wild Type ◽

Histone Proteins ◽

Protein Levels ◽

In The Wild ◽

Type Strains ◽

Orientation Bias

Abstract In Saccharomyces cerevisiae, the target site specificity of the retrotransposon Ty1 appears to involve the Ty integration complex recognizing chromatin structures. To determine whether changes in chromatin structure affect Ty1 and Ty2 target site preference, we analyzed Ty transposition at the CAN1 locus in mutants containing altered levels of histone proteins. A Δhta1-htb1 mutant with decreased levels of H2A and H2B histone proteins showed a pattern of Ty1 and Ty2 insertions at CAN1 that was significantly different from that of both the wild-type and a Δhta2-htb2 mutant, which does not have altered histone protein levels. Altered levels of H2A and H2B proteins disrupted a dramatic orientation bias in the CAN1 promoter region. In the wild-type strains, few Ty1 and Ty2 insertions in the promoter region were oriented opposite to the direction of CAN1 transcription. In the Δhta1-htb1 background, however, numerous Ty1 and Ty2 insertions were in the opposite orientation clustered within the TATA region. This altered insertion pattern does not appear to be due to a bias caused by selecting canavanine resistant isolates in the different HTA1-HTB1 backgrounds. Our results suggest that reduced levels of histone proteins alter Ty target site preference and disrupt an asymmetric Ty insertion pattern.

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Identification and molecular characterization of a Chlamydomonas reinhardtii mutant that shows a light intensity dependent progressive chlorophyll deficiency

F1000Research ◽

10.12688/f1000research.2-142.v1 ◽

2013 ◽

Vol 2 ◽

pp. 142

Author(s):

Phillip B Grovenstein ◽

Darryel A Wilson ◽

Kathryn D Lankford ◽

Kelsey A Gaston ◽

Surangi Perera ◽

...

Keyword(s):

Light Intensity ◽

Insertional Mutagenesis ◽

Protoporphyrin Ix ◽

Model Organism ◽

Genomic Region ◽

Oxygenic Photosynthesis ◽

Autotrophic Growth ◽

Wild Type ◽

Light Intensities ◽

In The Wild

The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms. These tetrapyrroles are synthesized via a common branched pathway that involves mainly nuclear encoded enzymes. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg2+ into protoporphyrin IX (PPIX, proto) to form Magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. The GUN4 (genomes uncoupled 4) protein is not essential for the MgChel activity but has been shown to significantly stimulate its activity. We have isolated a light sensitive mutant, 6F14, by random DNA insertional mutagenesis. 6F14 cannot tolerate light intensities higher than 90-100 μmol photons m-2 s-1. It shows a light intensity dependent progressive photo-bleaching. 6F14 is incapable of photo-autotrophic growth under light intensity higher than 100 μmol photons m-2 s-1. PCR based analyses show that in 6F14 the insertion of the plasmid outside the GUN4 locus has resulted in a genetic rearrangement of the GUN4 gene and possible deletions in the genomic region flanking the GUN4 gene. Our gun4 mutant has a Chl content very similar to that in the wild type in the dark and is very sensitive to fluctuations in the light intensity in the environment unlike the earlier identified Chlamydomonas gun4 mutant. Complementation with a functional copy of the GUN4 gene restored light tolerance, Chl biosynthesis and photo-autotrophic growth under high light intensities in 6F14. 6F14 is the second gun4 mutant to be identified in C. reinhardtii. Additionally, we show that our two gun4 complements over-express the GUN4 protein and show a higher Chl content per cell compared to that in the wild type strain.

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A Transposon Story: From TE Content to TE Dynamic Invasion of Drosophila Genomes Using the Single-Molecule Sequencing Technology from Oxford Nanopore

Cells ◽

10.3390/cells9081776 ◽

2020 ◽

Vol 9 (8) ◽

pp. 1776

Author(s):

Mourdas Mohamed ◽

Nguyet Thi-Minh Dang ◽

Yuki Ogyama ◽

Nelly Burlet ◽

Bruno Mugat ◽

...

Keyword(s):

Single Molecule ◽

Wild Type ◽

Sequencing Data ◽

Short Read ◽

Short Read Sequencing ◽

Sequencing Technologies ◽

Oxford Nanopore ◽

In The Wild ◽

Successive Generations ◽

Type Strains

Transposable elements (TEs) are the main components of genomes. However, due to their repetitive nature, they are very difficult to study using data obtained with short-read sequencing technologies. Here, we describe an efficient pipeline to accurately recover TE insertion (TEI) sites and sequences from long reads obtained by Oxford Nanopore Technology (ONT) sequencing. With this pipeline, we could precisely describe the landscapes of the most recent TEIs in wild-type strains of Drosophila melanogaster and Drosophila simulans. Their comparison suggests that this subset of TE sequences is more similar than previously thought in these two species. The chromosome assemblies obtained using this pipeline also allowed recovering piRNA cluster sequences, which was impossible using short-read sequencing. Finally, we used our pipeline to analyze ONT sequencing data from a D. melanogaster unstable line in which LTR transposition was derepressed for 73 successive generations. We could rely on single reads to identify new insertions with intact target site duplications. Moreover, the detailed analysis of TEIs in the wild-type strains and the unstable line did not support the trap model claiming that piRNA clusters are hotspots of TE insertions.

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Resistance mechanism development to the topoisomerase-I inhibitor Hoechst 33342 byLeishmania donovani

Parasitology ◽

10.1017/s0031182005007328 ◽

2005 ◽

Vol 131 (2) ◽

pp. 197-206 ◽

Cited By ~ 2

Author(s):

J.-F. MARQUIS ◽

I. HARDY ◽

M. OLIVIER

Keyword(s):

Mammalian Cells ◽

Topoisomerase I ◽

Resistance Mechanism ◽

Resistance Mechanisms ◽

Drug Accumulation ◽

Wild Type ◽

Hoechst 33342 ◽

In The Wild ◽

Energy Dependent

The bisbenzimidazole compound Hoechst 33342 (Ho342) has been identified as a specific Topoisomerase-I (Topo-I) inhibitor in mammalian cells. More recently, we have reported the ability of Ho342 to targetL. donovaniTopo-I, leading to parasite growth inhibitionin vitroby mechanisms involving DNA breakage and apoptosis-like phenomenon. As the Ho342 lead molecule (2,5′-Bi-1H-benzimidazole) can be used as a starting structure for derivative compounds more effective againstLeishmania, defining the Ho342 resistance mechanism(s) inLeishmaniarepresents an important strategic tool. In the present study, we selected resistant parasites to Ho342 (LdRHo.300). While we observed an increase of the Topo-I gene expression correlated by a higher Topo-I DNA relaxation activity, the Topo-I genes (LdTOP1AandLdTOP1B) sequencing did not reveal any mutation for the resistant parasites. Moreover, our results on Ho342 cellular accumulation suggested the presence of a potential energy-dependent Ho342 transporter in the wild-type parasite, and that an alteration of this transporter has occurred inLdRHo.300, leading to an altered drug accumulation. Collectively, Ho342 resistance characterization provided results supporting that the resistance developed byLdRHo.300involves complex mechanisms, most likely dominated by an altered drug accumulation, providing new insight in the Ho342 resistance mechanisms.

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Influence of double-stranded RNAs on growth, sporulation, pathogenicity, and survival of Chalara elegans

Canadian Journal of Botany ◽

10.1139/b95-109 ◽

1995 ◽

Vol 73 (7) ◽

pp. 1001-1009 ◽

Cited By ~ 9

Author(s):

Zamir K. Punja

Keyword(s):

Plant Pathogen ◽

Dry Weight ◽

Complete Loss ◽

Thielaviopsis Basicola ◽

Wild Type ◽

C Elegans ◽

Chalara Elegans ◽

In The Wild ◽

Rna Fragments ◽

Type Strains

Three strains of Chalara elegans from diverse geographical areas that contained multiple (4 or 5) double-stranded RNA fragments were compared with spontaneously derived cultures from these strains that were either partially cured or completely free of dsRNA. In the wild-type strains, presence of the dsRNAs was found to significantly enhance phialospore production and pigmentation of colonies, whereas radial growth and mycelial dry weight accumulation were reduced. The rate and overall percentage of phialospore germination on 1% Noble water agar were also significantly reduced by the presence of the dsRNAs. In two partially cured strains (only one 2.8-kb fragment remaining), pathogenicity to various plant tissues was significantly enhanced when compared with the wild-type strains containing multiple dsRNA. However, survival in field soil was enhanced in one strain and reduced in the other. In the completely cured strain, the loss of multiple dsRNA fragments was associated with enhanced growth, reduced phialospore production, and a complete loss of pathogenicity and capability for survival in soil. These results indicate that the effects of dsRNAs in C. elegans vary with the strain. In general, the presence of multiple dsRNAs in this fungus enhanced sporulation, altered colony morphology, and reduced growth and pathogenicity. However, since the complete loss of dsRNA was found to eliminate pathogenicity and reduce survival, it suggests that some dsRNA fragments in C. elegans may confer an advantage to this soil-borne facultative plant pathogen. Key words: black root rot, soil-borne plant pathogen, Thielaviopsis basicola.

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In VitroActivity of Ceftazidime-Avibactam Combination inIn VitroCheckerboard Assays

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04146-14 ◽

2014 ◽

Vol 59 (2) ◽

pp. 1138-1144 ◽

Cited By ~ 23

Author(s):

Johanna Berkhout ◽

Maria J. Melchers ◽

Anita C. van Mil ◽

Wright W. Nichols ◽

Johan W. Mouton

Keyword(s):

Antibacterial Activity ◽

Enterobacter Cloacae ◽

Resistance Mechanisms ◽

Maximum Effect ◽

Wild Type ◽

Dependent Effect ◽

Content Type ◽

Resistant Strains ◽

Type Strains

ABSTRACTTo evaluate thein vitroeffects of the combination of ceftazidime and avibactam on the MICs of both compounds, checkerboard assays were performed for 81 clinical strains, including 55Enterobacteriaceaestrains (32Klebsiella pneumoniae, 19Escherichia coli, 1Citrobacter freundii, and 3Enterobacter cloacae) and 26 strains ofPseudomonas aeruginosa, all with known resistance mechanisms such as extended-spectrum β-lactamases (ESBLs) and carbapenemases, phenotypically or molecularly determined. Phenotypically ceftazidime-resistant strains (n= 69) were analyzed in more detail. For theEnterobacteriaceaestrains, a concentration-dependent effect of avibactam was found for most strains with a maximum effect of avibactam at a concentration of 4 mg/liter, which decreased all ceftazidime MICs to ≤4 mg/liter. Avibactam alone also showed antibacterial activity (the MIC50and MIC90being 8 and 16 mg/liter, respectively). For the ceftazidime-resistantP. aeruginosastrains, considerable inhibition of β-lactamases by avibactam was acquired at a concentration of 4 mg/liter, which decreased all ceftazidime MICs except one to ≤8 mg/liter (the CLSI and EUCAST susceptible breakpoint). Increasing the concentration of avibactam further decreased the MICs, resulting in a maximum effect for most strains at 8 to 16 mg/liter. In summary, for most strains, the tested addition of avibactam of 4 mg/liter restored the antibacterial activity of ceftazidime to a level comparable to that of wild-type strains, indicating full inhibition, and strains became susceptible according to the EUCAST and CLSI criteria. Based on thesein vitrodata, avibactam is a promising inhibitor of different β-lactamases, including ESBLs and carbapenemases.

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Cloning of the chromosomal determinants encoding hemolysin production and mannose-resistant hemagglutination in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.152.3.1241-1247.1982 ◽

1982 ◽

Vol 152 (3) ◽

pp. 1241-1247

Author(s):

H Berger ◽

J Hacker ◽

A Juarez ◽

C Hughes ◽

W Goebel

Keyword(s):

Escherichia Coli ◽

High Frequency ◽

Wild Type ◽

Chromosomal Dna ◽

Genetic Determinants ◽

E Coli ◽

Gene Banks ◽

In The Wild ◽

K 12 ◽

Type Strains

We have cloned the chromosomal hemolysin determinants from Escherichia coli strains belonging to the four O-serotypes O4, O6, O18, and O75. The hemolysin-producing clones were isolated from gene banks of these strains which were constructed by inserting partial Sau3A fragments of chromosomal DNA into the cosmid pJC74. The hemolytic cosmid clones were relatively stable. The inserts were further subcloned either as SalI fragments in pACYC184 or as BamHI-SalI fragments in a recombinant plasmid (pANN202) containing cistron C (hlyC) of the plasmid-encoded hemolysin determinant. Detailed restriction maps of each of these determinants were constructed, and it was found that, despite sharing overall homology, the determinants exhibited minor specific differences in their structure. These appeared to be restricted to cistron A (hlyA), which is the structural gene for hemolysin. In the gene banks of two of these hemolytic strains, we could also identify clones which carried the genetic determinants for the mannose-resistant hemagglutination antigens Vb and VIc. Both of these fimbrial antigens were expressed in the E. coli K-12 clones to an extent similar to that observed in the wild-type strains. These recombinant cosmids were rather unstable, and, in the absence of selection, segregated at a high frequency.

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Identification and molecular characterization of the second Chlamydomonas gun4 mutant, gun4-II

F1000Research ◽

10.12688/f1000research.2-142.v2 ◽

2013 ◽

Vol 2 ◽

pp. 142

Author(s):

Phillip B Grovenstein ◽

Darryel A Wilson ◽

Kathryn D Lankford ◽

Kelsey A Gaston ◽

Surangi Perera ◽

...

Keyword(s):

Light Intensity ◽

Insertional Mutagenesis ◽

Protoporphyrin Ix ◽

Model Organism ◽

Genomic Region ◽

Oxygenic Photosynthesis ◽

Autotrophic Growth ◽

Wild Type ◽

Light Intensities ◽

In The Wild

The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in photosynthesis and respiration. These tetrapyrroles are synthesized via a common branched pathway that involves mainly enzymes, encoded by nuclear genes. One of the enzymes in the pathway is Mg chelatase (MgChel). MgChel catalyzes insertion of Mg2+ into protoporphyrin IX (PPIX, proto) to form Magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. The GUN4 (genomes uncoupled 4) protein is not essential for the MgChel activity but has been shown to significantly stimulate its activity. We have isolated a light sensitive mutant, 6F14, by random DNA insertional mutagenesis. 6F14 cannot tolerate light intensities higher than 90-100 μmol photons m-2 s-1. It shows a light intensity dependent progressive photo-bleaching. 6F14 is incapable of photo-autotrophic growth under light intensity higher than 100 μmol photons m-2 s-1. PCR based analyses show that in 6F14 the insertion of the plasmid outside the GUN4 locus has resulted in a genetic rearrangement of the GUN4 gene and possible deletions in the genomic region flanking the GUN4 gene. Our gun4 mutant has a Chl content very similar to that in the wild type in the dark and is very sensitive to fluctuations in the light intensity in the environment unlike the earlier identified Chlamydomonas gun4 mutant. Complementation with a functional copy of the GUN4 gene restored light tolerance, Chl biosynthesis and photo-autotrophic growth under high light intensities in 6F14. 6F14 is the second gun4 mutant to be identified in C. reinhardtii. Additionally, we show that our two gun4 complements over-express the GUN4 protein and show a higher Chl content per cell compared to that in the wild type strain.

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Lipopolysaccharides: structure, function and bacterial identification

OCL ◽

10.1051/ocl/2020025 ◽

2020 ◽

Vol 27 ◽

pp. 31

Author(s):

Martine Caroff ◽

Alexey Novikov

Keyword(s):

Lipid A ◽

Biological Molecules ◽

Gram Negative Bacteria ◽

Bacterial Identification ◽

Wild Type ◽

Core Oligosaccharide ◽

Lipid Moiety ◽

In The Wild ◽

Main Components ◽

Type Strains

Lipopolysaccharides (LPS) are the main components of the outer membrane of Gram-negative bacteria. They are glycolipids containing a lipid moiety called lipid A, more often made of a bis-phosphorylated glucosamine disaccharide, carrying fatty acids in ester and amide linkages. Lipid A is linked to a core oligosaccharide of about 10 sugars, substituted in the wild-type strains, by long-chain oligosaccharide repetitive units, extending outside the bacteria and representing their main antigens. In addition to determine the serotype of the bacterium, LPS are highly potent biological molecules, capable of eliciting at the level of minute amounts, beneficial, as well as deleterious activities.

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Freeze-substituted fungal cells of Nectria haematococca: A comparison of the macroconidial walls of the adhesion-competent wild type with an adhesion-reduced mutant

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160996 ◽

1990 ◽

Vol 48 (3) ◽

pp. 688-689

Author(s):

Thecan Caesar-Ton That ◽

Lynn Epstein

Keyword(s):

Freeze Substitution ◽

Uranyl Acetate ◽

Wild Type ◽

Nectria Haematococca ◽

Fruit Extract ◽

Dialysis Tubing ◽

Tube Emergence ◽

Contrast Microscopy ◽

In The Wild ◽

Freeze Damage

Nectria haematococca mating population I (anamorph, Fusarium solani) macroconidia attach to its host (squash) and non-host surfaces prior to germ tube emergence. The macroconidia become adhesive after a brief period of protein synthesis. Recently, Hickman et al. (1989) isolated N. haematococca adhesion-reduced mutants. Using freeze substitution, we compared the development of the macroconidial wall in the wild type in comparison to one of the mutants, LEI.Macroconidia were harvested at 1C, washed by centrifugation, resuspended in a dilute zucchini fruit extract and incubated from 0 - 5 h. During the incubation period, wild type macroconidia attached to uncoated dialysis tubing. Mutant macroconidia did not attach and were collected on poly-L-lysine coated dialysis tubing just prior to freezing. Conidia on the tubing were frozen in liquid propane at 191 - 193C, substituted in acetone with 2% OsO4 and 0.05% uranyl acetate, washed with acetone, and flat-embedded in Epon-Araldite. Using phase contrast microscopy at 1000X, cells without freeze damage were selected, remounted, sectioned and post-stained sequentially with 1% Ba(MnO4)2 2% uranyl acetate and Reynold’s lead citrate. At least 30 cells/treatment were examined.

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