scholarly journals Characterization of Cell Lysis in Pseudomonas putida Induced upon Expression of Heterologous Killing Genes

1998 ◽  
Vol 64 (12) ◽  
pp. 4904-4911 ◽  
Author(s):  
M. Carmen Ronchel ◽  
Lázaro Molina ◽  
Angela Witte ◽  
Werner Lutbiz ◽  
Søren Molin ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Death ◽  
Pseudomonas Putida ◽  
Membrane Permeability ◽  
Cell Lysis ◽  
Physiological Effects ◽  
Extracellular Medium ◽  
Biological Containment ◽  
Potential Applications

ABSTRACT Active biological containment systems are based on the controlled expression of killing genes. These systems are of interest for thePseudomonadaceae because of the potential applications of these microbes as bioremediation agents and biopesticides. The physiological effects that lead to cell death upon the induction of expression of two different heterologous killing genes in nonpathogenicPseudomonas putida KT2440 derivatives have been analyzed.P. putida CMC4 and CMC12 carry in their chromosomes a fusion of the PA1-04/03 promoter to the Escherichia coli gef gene and the φX174 lysis gene E, respectively. Expression of the killing genes is controlled by the LacI protein, whose expression is initiated from the XylS-dependent Pm promoter. Under induced conditions, killing of P. putidaCMC12 cells mediated by φX174 lysis protein E was faster than that observed for P. putida CMC4, for which the Gef protein was the killing agent. In both cases, cell death occurred as a result of impaired respiration, altered membrane permeability, and the release of some cytoplasmic contents to the extracellular medium.

Characterization of cell death in Escherichia coli mediated by XseA, a large subunit of exonuclease VII

2015 ◽  
Vol 53 (12) ◽  
pp. 820-828 ◽  
Author(s):  
Hyeim Jung ◽  
Junwei Liang ◽  
Yuna Jung ◽  
Dongbin Lim
Keyword(s):  
Escherichia Coli ◽  
Cell Death ◽  
Large Subunit ◽  
Exonuclease Vii

Characterization of the aminopeptidase from Bacillus subtilis as an extracellular enzyme

1972 ◽  
Vol 18 (12) ◽  
pp. 1883-1891 ◽  
Author(s):  
Fred W. Wagner ◽  
A. Chung ◽  
Lee E. Ray
Keyword(s):  
Bacillus Subtilis ◽  
Regulatory Mechanism ◽  
Extracellular Enzyme ◽  
Cell Lysis ◽  
Nitrogen Utilization ◽  
Extracellular Medium ◽  
Cobalt Ions ◽  
C 50 ◽  
Inhibited Enzyme

A strain of Bacillus subtilis produced an aminopeptidase detectable in the cultural fluid and in cell-free extracts. Both extracellular and intracellular aminopeptidases hydrolyzed L-leucyl-β-naphthylamide substrate after activation with cobalt ions. In the cultural fluid, trace amounts of activity were present as early as 12 h, but the highest activity was attained between 36 and 96 h. The addition of lysozyme to cultures less than 36 h old inhibited the production of the aminopeptidase of the cultural fluid, but was less effective in older cultures. This trend was correlated to the Gram-variability of the organisms in the culture. Chloramphenicol and oxytetracycline also inhibited enzyme production without affecting normal cell lysis. These data were interpreted to imply that the aminopeptidase of the cultural fluid did not result from the release of the intracellular aminopeptidase by cell lysis, but that it was produced by viable, metabolizing cells, most probably Gram-negative. Chromatography of the cultural fluid on CM-Sephadex C-50 showed an aminopeptidase characteristic of the extracellular medium. The possible implication of this enzyme as a regulatory mechanism for nitrogen utilization by Bacillus subtilis is discussed.

scholarly journals Curcumin activation of a bacterial mechanosensitive channel underlies its membrane permeability and adjuvant properties

2021 ◽  
Vol 17 (12) ◽  
pp. e1010198
Author(s):  
Robin Wray ◽  
Irene Iscla ◽  
Paul Blount
Keyword(s):  
Membrane Permeability ◽  
Natural Compound ◽  
Bacterial Species ◽  
Antibacterial Properties ◽  
Cell Lysis ◽  
Membrane Permeabilization ◽  
Mechanosensitive Channel ◽  
Bacterial Membrane ◽  
Physiological Effects ◽  
Membrane Tension

Curcumin, a natural compound isolated from the rhizome of turmeric, has been shown to have antibacterial properties. It has several physiological effects on bacteria including an apoptosis-like response involving RecA, membrane permeabilization, inhibiting septation, and it can also work synergistically with other antibiotics. The mechanism by which curcumin permeabilizes the bacterial membrane has been unclear. Most bacterial species contain a Mechanosensitive channel of large conductance, MscL, which serves the function of a biological emergency release valve; these large-pore channels open in response to membrane tension from osmotic shifts and, to avoid cell lysis, allow the release of solutes from the cytoplasm. Here we show that the MscL channel underlies the membrane permeabilization by curcumin as well as its synergistic properties with other antibiotics, by allowing access of antibiotics to the cytoplasm; MscL also appears to have an inhibitory role in septation, which is enhanced when activated by curcumin.

scholarly journals Morphological and Physiological Changes Induced by High Hydrostatic Pressure in Exponential- and Stationary-Phase Cells of Escherichia coli: Relationship with Cell Death

2004 ◽  
Vol 70 (3) ◽  
pp. 1545-1554 ◽  
Author(s):  
Pilar Ma�as ◽  
Bernard M. Mackey
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Cell Death ◽  
Stationary Phase ◽  
Exponential Phase ◽  
Cellular Structures ◽  
Phase Cell ◽  
Physiological Changes ◽  
Extracellular Medium ◽  
Cell Envelopes

ABSTRACT The relationship between a loss of viability and several morphological and physiological changes was examined with Escherichia coli strain J1 subjected to high-pressure treatment. The pressure resistance of stationary-phase cells was much higher than that of exponential-phase cells, but in both types of cell, aggregation of cytoplasmic proteins and condensation of the nucleoid occurred after treatment at 200 MPa for 8 min. Although gross changes were detected in these cellular structures, they were not related to cell death, at least for stationary-phase cells. In addition to these events, exponential-phase cells showed changes in their cell envelopes that were not seen for stationary-phase cells, namely physical perturbations of the cell envelope structure, a loss of osmotic responsiveness, and a loss of protein and RNA to the extracellular medium. Based on these observations, we propose that exponential-phase cells are inactivated under high pressure by irreversible damage to the cell membrane. In contrast, stationary-phase cells have a cytoplasmic membrane that is robust enough to withstand pressurization up to very intense treatments. The retention of an intact membrane appears to allow the stationary-phase cell to repair gross changes in other cellular structures and to remain viable at pressures that are lethal to exponential-phase cells.

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