Optimization of near ultraviolet irradiation conditions for isolation of relaxed mutants ofEscherichia coli

1984 ◽  
Vol 24 (7) ◽  
pp. 495-503 ◽  
Author(s):  
D. Riesenberg ◽  
H. Lang
Keyword(s):  
Ultraviolet Irradiation ◽  
Ofescherichia Coli ◽  
Near Ultraviolet

Changes in polyphosphate composition and localization in Propionibacterium acnes after near-ultraviolet irradiation

1991 ◽  
Vol 37 (7) ◽  
pp. 562-567 ◽  
Author(s):  
B. Kjeldstad ◽  
M. Heldal ◽  
H. Nissen ◽  
S. Bergan ◽  
K. Evjen
Keyword(s):  
Ultraviolet Irradiation ◽  
Propionibacterium Acnes ◽  
Broad Band ◽  
Fluorescence Emission ◽  
Rich Medium ◽  
X Ray ◽  
Dense Granules ◽  
Near Ultraviolet ◽  
Phosphorus And Potassium ◽  
Polyphosphate Granules

Electron microscopy showed that electron-dense granules accumulated in Propionibacterium acnes in larger amounts when the bacteria were grown on a phosphate-rich medium. X-ray microanalysis demonstrated that the granules contained mostly phosphorus and potassium, indicating that the cells contained polyphosphate granules. When cells were grown on a complex Bacto-agar medium, the amount and the size of the polyphosphate granules were reduced. Polyphosphate was also detected with 31P nuclear magnetic resonance (31P-NMR). Of the polyphosphates observed with 31P-NMR, 20% seemed to be located outside the cell membrane. Broad-band near-ultraviolet irradiation (emission maximum 366 nm) corresponding to doses that killed 37% of the cells increased the amount of polyphosphate in cells grown on the phosphate-rich medium. The fluorescent chromophore 4′,6-diamidino-2-phenylindole (DAPI) shifted the fluorescence emission from 478 to 538 nm when bound to polyphosphate and excited at 340 nm. DAPI was used to detect polyphosphates generated after near-ultraviolet irradiation of the cells. Nonirradiated cells showed no increased fluorescence at 538 nm, indicating no polyphosphates, even if polyphosphate is present in the cells. We conclude that DAPI did not have "access" to the intracellular polyphosphate as long as the cells were not light damaged. This observation is important for the interpretation of near-UV damage to cells. Key words: electron and X-ray microscopy, fluorescence, DAPI, 31P-NMR, granule.

Interaction of light quality and temperature on the vegetative reversion of conidiophores in Alternaria cichorii

1983 ◽  
Vol 61 (2) ◽  
pp. 626-630 ◽  
Author(s):  
Demetrios J. Vakalounakis ◽  
Christos Christias ◽  
Nicholaos E. Malathrakis
Keyword(s):  
Blue Light ◽  
Ultraviolet Irradiation ◽  
Light Quality ◽  
Incubation Temperature ◽  
Near Ultraviolet

The development of the conidiophores of the fungus Alternaria cichorii Nattrass was induced by near ultraviolet irradiation (< 340 nm). Temperatures above 25 °C induced a vegetative reversion of conidiophores to sterile hyphae. This reversion was more intense under the influence of blue light (390–530 nm). The extent of vegetative regrowth was proportional to the incubation temperature: the higher the temperature the longer the vegetative regrowth of conidiophores.

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