scholarly journals Using extracellular polymeric substances (EPS)-producing cyanobacteria for the bioremediation of heavy metals: do cations compete for the EPS functional groups and also accumulate inside the cell?

Microbiology ◽  
2011 ◽  
Vol 157 (2) ◽  
pp. 451-458 ◽  
Author(s):  
Sara Pereira ◽  
Ernesto Micheletti ◽  
Andrea Zille ◽  
Arlete Santos ◽  
Pedro Moradas-Ferreira ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Extracellular Polymeric Substances ◽  
Metal Removal ◽  
Ultrastructural Changes ◽  
Wild Type ◽  
Mutual Inhibition ◽  
Biotechnological Potential ◽  
Surrounding Environment ◽  
In The Wild ◽  
Mutant Cells

Many cyanobacteria produce extracellular polymeric substances (EPS) mainly of polysaccharidic nature. These EPS can remain associated to the cell surface as sheaths, capsules and/or slimes, or be liberated into the surrounding environment as released polysaccharides (RPS). The ability of EPS-producing cyanobacteria to remove heavy metals from aqueous solutions has been widely reported in the literature, focusing mainly on the biotechnological potential. However, the knowledge of the effects of the metals in the cell's survival/growth is still scarce, particularly when they are simultaneously exposed to more than one metal. This work evaluated the effects of different concentrations of Cu2+ and/or Pb2+ in the growth/survival of Gloeothece sp. PCC 6909 and its sheathless mutant Gloeothece sp. CCY 9612. The results obtained clearly showed that both phenotypes are more severely affected by Cu2+ than Pb2+, and that the mutant is more sensitive to the former metal than the wild-type. Evident ultrastructural changes were also observed in the wild-type and mutant cells exposed to high levels (10 mg l−1) of Cu2+. Moreover, in bi-metal systems, Pb2+ was preferentially removed compared with Cu2+, being the RPS of the mutant that is the most efficient polysaccharide fraction in metal removal. In these systems, the simultaneous presence of Cu2+ and Pb2+ caused a mutual inhibition in the adsorption of each metal.

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.

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 Isolation of theCAR1Gene fromSaccharomyces cerevisiaeand Analysis of Its Expression

1982 ◽  
Vol 2 (12) ◽  
pp. 1514-1523 ◽  
Author(s):  
Roberta A. Sumrada ◽  
Terrance G. Cooper
Keyword(s):  
Nitrogen Source ◽  
Wild Type ◽  
Polyadenylated Rna ◽  
Regulatory Mutations ◽  
In The Wild ◽  
Steady State Levels ◽  
Nitrogen Repression ◽  
Dna Fragment ◽  
Cloned Gene ◽  
Mutant Cells

We isolated theCARIgene fromSaccharomyces cerevisiaeon a recombinant plasmid and localized it to a 1.58-kilobase DNA fragment. The cloned gene was used as a probe to analyze polyadenylated RNA derived from wild-type and mutant cells grown in the presence and absence of an inducer. Wild-type cells grown without the inducer contained very little polyadenylated RNA capable of hybridizing to the isolatedCAR1gene. A 1.25-kilobaseCAR1-specific RNA species was markedly increased, however, in wild-type cells grown in the presence of inducer and in constitutive, regulatory mutants grown without it. NoCAR1-specific RNA was observed when one class of constitutive mutant was grown in medium containing a good nitrogen source, such as asparagine. Two other mutants previously shown to be resistant to nitrogen repression contained large quantities ofCAR1RNA regardless of the nitrogen source in the medium. These data point to a qualitative correlation between the steady-state levels ofCAR1-specific, polyadenylated RNA and the degree of arginase induction and repression observed in the wild type and in strains believed to carry regulatory mutations. Therefore, they remain consistent with our earlier suggestion that arginase production is probably controlled at the level of gene expression.

scholarly journals A temperature-sensitive mutation of the Schizosaccharomyces pombe gene nuc2+ that encodes a nuclear scaffold-like protein blocks spindle elongation in mitotic anaphase.

1988 ◽  
Vol 106 (4) ◽  
pp. 1171-1183 ◽  
Author(s):  
T Hirano ◽  
Y Hiraoka ◽  
M Yanagida
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Gradient Centrifugation ◽  
Metaphase Plate ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Wild Type ◽  
In The Wild ◽  
Spindle Elongation ◽  
Mutant Cells

A temperature-sensitive mutant nuc2-663 of the fission yeast Schizosaccharomyces pombe specifically blocks mitotic spindle elongation at restrictive temperature so that nuclei in arrested cells contain a short uniform spindle (approximately 3-micron long), which runs through a metaphase plate-like structure consisting of three condensed chromosomes. In the wild-type or in the mutant cells at permissive temperature, the spindle is fully extended approximately 15-micron long in anaphase. The nuc2' gene was cloned in a 2.4-kb genomic DNA fragment by transformation, and its complete nucleotide sequence was determined. Its coding region predicts a 665-residues internally repeating protein (76.250 mol wt). By immunoblots using anti-sera raised against lacZ-nuc2+ fused proteins, a polypeptide (designated p67; 67,000 mol wt) encoded by nuc2+ is detected in the wild-type S. pombe extracts; the amount of p67 is greatly increased when multi-copy or high-expression plasmids carrying the nuc2+ gene are introduced into the S. pombe cells. Cellular fractionation and Percoll gradient centrifugation combined with immunoblotting show that p67 cofractionates with nuclei and is enriched in resistant structure that is insoluble in 2 M NaCl, 25 mM lithium 3,5'-diiodosalicylate, and 1% Triton but is soluble in 8 M urea. In nuc2 mutant cells, however, soluble p76, perhaps an unprocessed precursor, accumulates in addition to insoluble p67. The role of nuc2+ gene may be to interconnect nuclear and cytoskeletal functions in chromosome separation.

The in vivo role of annexin VII (synexin): characterization of an annexin VII-deficient Dictyostelium mutant indicates an involvement in Ca(2+)-regulated processes

1995 ◽  
Vol 108 (5) ◽  
pp. 2065-2076 ◽  
Author(s):  
V. Doring ◽  
F. Veretout ◽  
R. Albrecht ◽  
B. Muhlbauer ◽  
C. Schlatterer ◽  
...  
Keyword(s):  
Developmental Cycle ◽  
Cell Fractionation ◽  
Wild Type ◽  
Camp Phosphodiesterase ◽  
In The Wild ◽  
Extracellular Camp ◽  
Mutant Cells

Dictyostelium discoideum cells harbor two annexin VII isoforms of 47 and 51 kDa which are present throughout development. In immunofluorescence and cell fractionation studies annexin VII was found in the cytoplasm and on the plasma membrane. In gene disruption mutants lacking both annexin VII isoforms growth, pinocytosis, phagocytosis, chemotaxis and motility were not significantly impaired under routine laboratory conditions, and the cells were able to complete the developmental cycle on bacterial plates. On non-nutrient agar plates development was delayed by three to four hours and a significant number of aggregates was no longer able to form fruiting bodies. Exocytosis as determined by measuring extracellular cAMP phosphodiesterase, alpha-fucosidase and alpha-mannosidase activity was unaltered, the total amounts of these enzymes were however lower in the mutant than in the wild type. The mutant cells were markedly impaired when they were exposed to low Ca2+ concentrations by adding EGTA to the nutrient medium. Under these conditions growth, motility and chemotaxis were severely affected. The Ca2+ concentrations were similar in mutant and wild-type cells both under normal and Ca2+ limiting conditions; however, the distribution was altered under low Ca2+ conditions in SYN-cells. The data suggest that annexin VII is not required for membrane fusion events but rather contributes to proper Ca2+ homeostasis in the cell.

scholarly journals The Clp Proteases of Bacillus subtilisAre Directly Involved in Degradation of Misfolded Proteins

2000 ◽  
Vol 182 (11) ◽  
pp. 3259-3265 ◽  
Author(s):  
Elke Krüger ◽  
Elke Witt ◽  
Steffen Ohlmeier ◽  
Renate Hanschke ◽  
Michael Hecker
Keyword(s):  
Immunogold Labeling ◽  
Misfolded Proteins ◽  
Turnover Rates ◽  
Wild Type ◽  
Heat Stress Response ◽  
Clp Proteases ◽  
In The Wild ◽  
Ultrathin Cryosections ◽  
Mutant Cells

ABSTRACT The presence of the heat stress response-related ATPases ClpC and ClpX or the peptidase ClpP in the cell is crucial for tolerance of many forms of stress in Bacillus subtilis. Assays for detection of defects in protein degradation suggest that ClpC, ClpP, and ClpX participate directly in overall proteolysis of misfolded proteins. Turnover rates for abnormal puromycyl peptides are significantly decreased in clpC, clpP, and clpXmutant cells. Electron-dense aggregates, most likely due to the accumulation of misfolded proteins, were noticed in studies of ultrathin cryosections in clpC and clpP mutant cells even under nonstress conditions. In contrast, in the wild type orclpX mutants such aggregates could only be observed after heat shock. This phenomenon supports the assumption thatclpC and clpP mutants are deficient in the ability to solubilize or degrade damaged and aggregated proteins, the accumulation of which is toxic for the cell. By using immunogold labeling with antibodies raised against ClpC, ClpP, and ClpX, the Clp proteins were localized in these aggregates, showing that the Clp proteins act at this level in vivo.

scholarly journals The d-Alanine Residues ofStaphylococcus aureus Teichoic Acids Alter the Susceptibility to Vancomycin and the Activity of Autolytic Enzymes

2000 ◽  
Vol 44 (10) ◽  
pp. 2845-2847 ◽  
Author(s):  
Andreas Peschel ◽  
Cuong Vuong ◽  
Michael Otto ◽  
Friedrich Götz
Keyword(s):  
Structural Changes ◽  
Cell Envelope ◽  
Glycopeptide Antibiotics ◽  
Wild Type ◽  
Teichoic Acids ◽  
In The Wild ◽  
Autolytic Activity ◽  
Increased Sensitivity ◽  
High Concentrations ◽  
Mutant Cells

ABSTRACT Recently, Staphylococcus aureus strains with intermediate resistance to vancomycin, the antibiotic of last resort, have been described. Multiple changes in peptidoglycan turnover and structure contribute to the resistance phenotype. Here, we describe that structural changes of teichoic acids in the cell envelope have a considerable influence on the susceptibility to vancomycin and other glycopeptides. S. aureus cells lackingd-alanine esters in teichoic acids exhibited an at least threefold-increased sensitivity to glycopeptide antibiotics. Furthermore, the autolytic activity of the d-alanine mutant was reduced compared to the wild-type, and the mutant was more susceptible to the staphylolytic enzyme lysostaphin. Vancomycin inhibited autolysis at very high concentrations but neither in the wild-type nor in the mutant was the autolytic activity influenced in the range of the MIC. Mutant cells had a considerably higher capacity to bind vancomycin.

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.

Calcium release from Synechocystis cells induced by depolarization of the plasma membrane: MscL as an outward Ca2+ channel

Microbiology ◽  
2003 ◽  
Vol 149 (5) ◽  
pp. 1147-1153 ◽  
Author(s):  
Lyudmila V. Nazarenko ◽  
Igor M. Andreev ◽  
Alexander A. Lyukevich ◽  
Tatiana V. Pisareva ◽  
Dmitry A. Los
Keyword(s):  
Plasma Membrane ◽  
Calcium Release ◽  
Channel Blocker ◽  
Membrane Depolarization ◽  
Wild Type ◽  
Exact Function ◽  
Intracellular Ca ◽  
In The Wild ◽  
Mechanosensitive Ion Channel ◽  
Mutant Cells

Cells of the cyanobacterium Synechocystis sp. PCC 6803 are equipped with a mechanosensitive ion channel MscL that is located in their plasma membrane. However, the exact function of the channel in this freshwater cyanobacterium is unknown. This study shows that cells of Synechocystis are capable of releasing Ca2+ in response to depolarization of the plasma membrane by the K+ ionophore valinomycin in the presence of K+ or by tetraphenylphosphonium (TPP+). A fluorescent dye, diS-C3-(5), sensitive to membrane potential and the metallochromic Ca2+ indicator arsenazo III were used to follow the plasma membrane depolarization and the Ca2+ release, respectively. The Ca2+ release from wild-type cells was temperature-dependent and it was strongly inhibited by the Ca2+ channel blocker verapamil and by the mechanosensitive channel blocker amiloride. In MscL-deficient cells, Ca2+ release was about 50 % of that from the wild-type cells. The mutant cells had lost temperature sensitivity of Ca2+ release completely. However, verapamil and amiloride inhibited Ca2+ release from these cells in same manner as in the wild-type cells. This suggests the existence of additional Ca2+ transporters in Synechocystis, probably of a mechanosensitive nature. Evidence for the putative presence of intracellular Ca2+ stores in the cells was obtained by following the increase in fluorescence intensity of the Ca2+ indicator chlortetracycline. These results suggest that the MscL of Synechocystis might operate as a verapamil/amiloride-sensitive outward Ca2+ channel that is involved in the plasma-membrane depolarization-induced Ca2+ release from the cells under temperature stress conditions.

Sign in / Sign up

Export Citation Format

Share Document