scholarly journals Effect of spaceflight on Pseudomonas aeruginosa final cell density is modulated by nutrient and oxygen availability

2013 ◽  
Vol 13 (1) ◽  
pp. 241 ◽  
Author(s):  
Wooseong Kim ◽  
Farah K Tengra ◽  
Jasmine Shong ◽  
Nicholas Marchand ◽  
Hon Chan ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Density ◽  
Oxygen Availability ◽  
Final Cell Density

Reduction of Selenite and Detoxification of Elemental Selenium by the Phototrophic BacteriumRhodospirillum rubrum

1999 ◽  
Vol 65 (11) ◽  
pp. 4734-4740 ◽  
Author(s):  
J. Kessi ◽  
M. Ramuz ◽  
E. Wehrli ◽  
M. Spycher ◽  
R. Bachofen
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Cell Density ◽  
Culture Medium ◽  
Rhodospirillum Rubrum ◽  
Buoyant Density ◽  
Elemental Selenium ◽  
Selenite Reduction ◽  
Final Cell Density ◽  
Cell Densities

ABSTRACT The effect of selenite on growth kinetics, the ability of cultures to reduce selenite, and the mechanism of detoxification of selenium were investigated by using Rhodospirillum rubrum. Anoxic photosynthetic cultures were able to completely reduce as much as 1.5 mM selenite, whereas in aerobic cultures a 0.5 mM selenite concentration was only reduced to about 0.375 mM. The presence of selenite in the culture medium strongly affected cell division. In the presence of a selenite concentration of 1.5 mM cultures reached final cell densities that were only about 15% of the control final cell density. The cell density remained nearly constant during the stationary phase for all of the selenite concentrations tested, showing that the cells were not severely damaged by the presence of selenite or elemental selenium. Particles containing elemental selenium were observed in the cytoplasm, which led to an increase in the buoyant density of the cells. Interestingly, the change in the buoyant density was reversed after selenite reduction was complete; the buoyant density of the cells returned to the buoyant density of the control cells. This demonstrated that R. rubrum expels elemental selenium across the plasma membrane and the cell wall. Accordingly, electron-dense particles were more numerous in the cells during the reduction phase than after the reduction phase.

scholarly journals Modulation of Pseudomonas aeruginosa Quorum Sensing by Glutathione

2019 ◽  
Vol 201 (9) ◽  
Author(s):  
Hui Zhou ◽  
Meizhen Wang ◽  
Nicole E. Smalley ◽  
Maxim Kostylev ◽  
Amy L. Schaefer ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Quorum Sensing ◽  
Cell Density ◽  
Redox State ◽  
Gene Activation ◽  
Cellular Redox ◽  
Content Type ◽  
Cellular Redox State

ABSTRACT Pseudomonas aeruginosa uses quorum sensing (QS) to regulate the production of a battery of secreted products. At least some of these products are shared among the population and serve as public goods. When P. aeruginosa is grown on casein as the sole carbon and energy source, the QS-induced extracellular protease elastase is required for growth. We isolated a P. aeruginosa variant, which showed increased production of QS-induced factors after repeated transfers in casein broth. This variant, P. aeruginosa QS*, had a mutation in the glutathione synthesis gene gshA. We describe several experiments that show a gshA coding variant and glutathione affect the QS response. The P. aeruginosa QS transcription factor LasR has a redox-sensitive cysteine (C79). We report that GshA variant cells with a LasR C79S substitution show a similar QS response to that of wild-type P. aeruginosa. Surprisingly, it is not LasR but the QS transcription factor RhlR that is more active in bacteria containing the variant gshA. Our results demonstrate that QS integrates information about cell density and the cellular redox state via glutathione levels. IMPORTANCE Pseudomonas aeruginosa and other bacteria coordinate group behaviors using a chemical communication system called quorum sensing (QS). The QS system of P. aeruginosa is complex, with several regulators and signals. We show that decreased levels of glutathione lead to increased gene activation in P. aeruginosa, which did not occur in a strain carrying the redox-insensitive variant of a transcription factor. The ability of P. aeruginosa QS transcription factors to integrate information about cell density and cellular redox state shows these transcription factors can fine-tune levels of the gene products they control in response to at least two types of signals or cues.

scholarly journals Potential of Acidithiobacillus ferrooxidans to Grow on and Bioleach Metals from Mars and Lunar Regolith Simulants under Simulated Microgravity Conditions

2021 ◽  
Vol 9 (12) ◽  
pp. 2416
Author(s):  
Anna H. Kaksonen ◽  
Xiao Deng ◽  
Christina Morris ◽  
Himel Nahreen Khaleque ◽  
Luis Zea ◽  
...  
Keyword(s):  
Cell Density ◽  
Acidithiobacillus Ferrooxidans ◽  
Simulated Microgravity ◽  
Lunar Regolith ◽  
Terrestrial Gravity ◽  
Final Cell Density ◽  
Earth Gravity ◽  
Microgravity Conditions ◽  
Abiotic Controls ◽  
Martian Regolith

The biomining microbes which extract metals from ores that have been applied in mining processes worldwide hold potential for harnessing space resources. Their cell growth and ability to extract metals from extraterrestrial minerals under microgravity environments, however, remains largely unknown. The present study used the model biomining bacterium Acidithiobacillus ferrooxidans to extract metals from lunar and Martian regolith simulants cultivated in a rotating clinostat with matched controls grown under the influence of terrestrial gravity. Analyses included assessments of final cell count, size, morphology, and soluble metal concentrations. Under Earth gravity, with the addition of Fe3+ and H2/CO2, A. ferrooxidans grew in the presence of regolith simulants to a final cell density comparable to controls without regoliths. The simulated microgravity appeared to enable cells to grow to a higher cell density in the presence of lunar regolith simulants. Clinostat cultures of A. ferrooxidans solubilised higher amounts of Si, Mn and Mg from lunar and Martian regolith simulants than abiotic controls. Electron microscopy observations revealed that microgravity stimulated the biosynthesis of intracellular nanoparticles (most likely magnetite) in anaerobically grown A. ferrooxidans cells. These results suggested that A. ferrooxidans has the potential for metal bioleaching and the production of useful nanoparticles in space.

scholarly journals Ethanol Stimulates Trehalose Production through a SpoT-DksA-AlgU-Dependent Pathway inPseudomonas aeruginosa

2019 ◽  
Vol 201 (12) ◽  
Author(s):  
Colleen E. Harty ◽  
Dorival Martins ◽  
Georgia Doing ◽  
Dallas L. Mould ◽  
Michelle E. Clay ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Cell Density ◽  
Sigma Factor ◽  
Strong Support ◽  
Transcriptional Response ◽  
Exponential Phase ◽  
Fermentation Products ◽  
Content Type ◽  
In Cells

ABSTRACTPseudomonas aeruginosafrequently resides among ethanol-producing microbes, making its response to the microbially produced concentrations of ethanol relevant to understanding its biology. Our transcriptome analysis found that genes involved in trehalose metabolism were induced by low concentrations of ethanol, and biochemical assays showed that levels of intracellular trehalose increased significantly upon growth with ethanol. The increase in trehalose was dependent on the TreYZ pathway but not other trehalose-metabolic enzymes (TreS or TreA). The sigma factor AlgU (AlgT), a homolog of RpoE in other species, was required for increased expression of thetreZgene and trehalose levels, but induction was not controlled by the well-characterized proteolysis of its anti-sigma factor, MucA. Growth with ethanol led to increased SpoT-dependent (p)ppGpp accumulation, which stimulates AlgU-dependent transcription oftreZand other AlgU-regulated genes through DksA, a (p)ppGpp and RNA polymerase binding protein. Ethanol stimulation of trehalose also required acylhomoserine lactone (AHL)-mediated quorum sensing (QS), as induction was not observed in a ΔlasRΔrhlRstrain. A network analysis using a model, eADAGE, built from publicly availableP. aeruginosatranscriptome data sets (J. Tan, G. Doing, K. A. Lewis, C. E. Price, et al., Cell Syst 5:63–71, 2017, https://doi.org/10.1016/j.cels.2017.06.003) provided strong support for our model in whichtreZand coregulated genes are controlled by both AlgU- and AHL-mediated QS. Consistent with (p)ppGpp- and AHL-mediated quorum-sensing regulation, ethanol, even when added at the time of culture inoculation, stimulatedtreZtranscript levels and trehalose production in cells from post-exponential-phase cultures but not in cells from exponential-phase cultures. These data highlight the integration of growth and cell density cues in theP. aeruginosatranscriptional response to ethanol.IMPORTANCEPseudomonas aeruginosais often found with bacteria and fungi that produce fermentation products, including ethanol. At concentrations similar to those produced by environmental microbes, we found that ethanol stimulated expression of trehalose-biosynthetic genes and cellular levels of trehalose, a disaccharide that protects against environmental stresses. The induction of trehalose by ethanol required the alternative sigma factor AlgU through DksA- and SpoT-dependent (p)ppGpp. Trehalose accumulation also required AHL quorum sensing and occurred only in post-exponential-phase cultures. This work highlights how cells integrate cell density and growth cues in their responses to products made by other microbes and reveals a new role for (p)ppGpp in the regulation of AlgU activity.

scholarly journals Expression of Alcaligenes eutrophusFlavohemoprotein and Engineered VitreoscillaHemoglobin-Reductase Fusion Protein for Improved Hypoxic Growth ofEscherichia coli

2000 ◽  
Vol 66 (1) ◽  
pp. 98-104 ◽  
Author(s):  
Alexander D. Frey ◽  
James E. Bailey ◽  
Pauli T. Kallio
Keyword(s):  
Escherichia Coli ◽  
Cell Density ◽  
Product Formation ◽  
Gene Encoding ◽  
Final Cell Density ◽  
E Coli ◽  
Amino Terminal ◽  
Positive Effects ◽  
Cell Densities ◽  
Carboxy Terminal

ABSTRACT Expression of the vhb gene encoding hemoglobin fromVitreoscilla sp. (VHb) in several organisms has been shown to improve microaerobic cell growth and enhance oxygen-dependent product formation. The amino-terminal hemoglobin domain of the flavohemoprotein (FHP) of the gram-negative hydrogen-oxidizing bacterium Alcaligenes eutrophus has 51% sequence homology with VHb. However, like other flavohemoglobins and unlike VHb, FHP possesses a second (carboxy-terminal) domain with NAD(P)H and flavin adenine dinucleotide (FAD) reductase activities. To examine whether the carboxy-terminal redox-active site of flavohemoproteins can be used to improve the positive effects of VHb in microaerobic Escherichia coli cells, we fused sequences encoding NAD(P)H, FAD, or NAD(P)H-FAD reductase activities of A. eutrophus in frame after the vhb gene. Similarly, the gene for FHP was modified, and expression cassettes encoding amino-terminal hemoglobin (FHPg), FHPg-FAD, FHPg-NAD, or FHP activities were constructed. Biochemically active heme proteins were produced from all of these constructions in Escherichia coli, as indicated by their ability to scavenge carbon monoxide. The presence of FHP or of VHb-FAD-NAD reductase increased the final cell density of transformed wild-type E. coli cells approximately 50 and 75%, respectively, for hypoxic fed-batch culture relative to the control synthesizing VHb. Approximately the same final optical densities were achieved with the E. coli strains expressing FHPg and VHb. The presence of VHb-FAD or FHPg-FAD increased the final cell density slightly relative to the VHb-expressing control under the same cultivation conditions. The expression of VHb-NAD or FHPg-NAD fusion proteins reduced the final cell densities approximately 20% relative to the VHb-expressing control. The VHb-FAD-NAD reductase-expressing strain was also able to synthesize 2.3-fold more recombinant β-lactamase relative to the VHb-expressing control.

scholarly journals Factors controlling the proliferative rate, final cell density, and life span of bovine vascular smooth muscle cells in culture.

1981 ◽  
Vol 89 (3) ◽  
pp. 568-578 ◽  
Author(s):  
D Gospodarowicz ◽  
K Hirabayashi ◽  
L Giguère ◽  
J P Tauber
Keyword(s):  
Smooth Muscle ◽  
Growth Factor ◽  
Cell Growth ◽  
Vascular Smooth Muscle ◽  
Life Span ◽  
Cell Density ◽  
Synthetic Medium ◽  
Density Lipoprotein ◽  
Lower Growth ◽  
Final Cell Density

Low density vascular smooth muscle (VSM) cell cultures maintained on extracellular-matrix(ECM)-coated dishes and plated in the presence of either plasma or serum will proliferate actively when serum-containing medium is replaced by a synthetic medium supplemented with three factors: high density lipoprotein (HDL, 250 micrograms protein/ml); insulin (2.5 micrograms/ml) or somatomedin C (10 ng/ml); and fibroblast growth factor (FGF, 100 ng/ml) or epidermal growth factor (EGF, 50 ng/ml). The omission of any of these three factors from the synthetic medium results in a lower growth rate of the cultures, as well as in a lower final cell density once cultures reach confluence. When cells are plated in the total absence of serum, transferrin (10 micrograms/ml) is also required to induce optimal cell growth. The effects of the substrate and medium supplements on the life span of VSM cultures have also been analyzed. Cultures maintained on plastic and exposed to medium supplemented with 5% bovine serum underwent 15 generations. However, when maintained on ECM-coated dishes the serum-fed cultures had a life span of at least 88 generations. Likewise, when cultures were maintained in a synthetic medium supplemented with HDL and either FGF or EGF, an effect on the tissue culture life span by the substrate was observed. Cultures maintained on plastic underwent 24 generations, whereas those maintained on ECM-coated dishes could be passaged repeatedly for 58 generations. These experiments demonstrate the influence of the ECM-substrate only in promoting cell growth but also in increasing the longevity of the cultures.

Kinetic modeling of rhamnolipid production by Pseudomonas aeruginosa PAO1 including cell density-dependent regulation

2014 ◽  
Vol 98 (16) ◽  
pp. 7013-7025 ◽  
Author(s):  
Marius Henkel ◽  
Anke Schmidberger ◽  
Markus Vogelbacher ◽  
Christian Kühnert ◽  
Janina Beuker ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Density ◽  
Kinetic Modeling ◽  
Pseudomonas Aeruginosa Pao1 ◽  
Density Dependent ◽  
Rhamnolipid Production ◽  
Density Dependent Regulation

scholarly journals Ethanol stimulates trehalose production through a SpoT-DksA-AlgU dependent pathway in Pseudomonas aeruginosa

2019 ◽  
Author(s):  
Colleen E. Harty ◽  
Dorival Martins ◽  
Georgia Doing ◽  
Dallas L. Mould ◽  
Michelle E. Clay ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Cell Density ◽  
Sigma Factor ◽  
Strong Support ◽  
Transcriptional Response ◽  
Exponential Phase ◽  
Fermentation Products ◽  
Acylhomoserine Lactone ◽  
Antisigma Factor

AbstractPseudomonas aeruginosa frequently resides among ethanol-producing microbes, making its response to these microbially-produced concentrations of ethanol relevant to understanding its biology. Our ranscriptome analysis found that the genes involved in trehalose metabolism were induced by low concentrations of ethanol, and levels of intracellular trehalose increased significantly upon growth with ethanol. The increase in trehalose was dependent on the TreYZ pathway, but not other trehalose metabolic enzymes TreS or TreA. The sigma factor AlgU (AlgT), a homolog of RpoE in other species, was required for increased expression of the treZ gene and trehalose levels, but induction was not controlled by the well-characterized proteolysis of its antisigma factor MucA. Growth with ethanol led to increased SpoT-dependent (p)ppGpp accumulation, which stimulates AlgU-dependent transcription of treZ and other AlgU-regulated genes through DksA, a (p)ppGpp and RNA polymerase binding protein. Ethanol stimulation of trehalose also required acylhomoserine lactone (AHL)-mediated quorum sensing, as induction was not observed in a ΔlasRΔrhlR strain. A network analysis using a model, eADAGE, built from publicly available P. aeruginosa transcriptome datasets (1) provided strong support for our model that treZ and co-regulated genes are controlled by both AlgU and AHL-mediated QS (QS). Consistent with (p)ppGpp and AHL-mediated quorum sensing regulation, ethanol, even when added at the time of culture inoculation, stimulated treZ transcript levels and trehalose production in cells from post-exponential phase cultures but not from exponential phase cultures. These data highlight the integration of growth and cell density cues in the P. aeruginosa transcriptional response to ethanol.ImportancePseudomonas aeruginosa is often found with bacteria and fungi that produce fermentation products including ethanol. At concentrations similar to those produced by environmental microbes, we found that ethanol stimulated expression of trehalose biosynthetic genes and cellular levels of trehalose, a disaccharide that protects against environmental stresses. The induction of trehalose by ethanol required the alternative sigma factor AlgU through DksA and SpoT-dependent (p)ppGpp. Trehalose accumulation also required AHL quorum sensing and only occurred in post-exponential phase cultures. This work highlights how cells integrate cell-density and growth cues in their responses to products made by other microbes and a reveals a new role for (p)ppGpp in the regulation of AlgU activity.

Sign in / Sign up

Export Citation Format

Share Document