Abstract
添加NaCl或sucrose於plate count broth (PCB)中用於培養 Deinococcus radiodurans IR會造成菌液生長特性的變化，包括偽生長延 滯期(pseudo -lag phase) 的出現、菌體倍增時間( doubling time)之增 加，及最大生長量(maximum growth)之降低。同時原本為4聯的IR細胞會 隨之導致多聯性細胞的形成。由於NaCl和sucrose 對IR細胞培養的生長及 細胞聯數的影響的程度正好反應於此二者在PCB 中所造成的滲透壓值，此 暗示了這些對IR生理的反應，可能源於滲透壓的影響。我們在PCB 中天加 造成上述等值滲透壓值之glycerol用於培養IR，卻不見生長效應及細胞聯 數的顯著變化，而由於glycerol為油溶性溶質(permeating solute)所以 此結果暗示細胞內外的滲透壓差可能才是上述滲透壓影響IR生各種生理效 應的原因。另外，用於調結離子強度的抗滲透壓劑 (osmoprotectant) 如glycine betaine proline choline 並不會改變滲透壓對IR細胞的影 響，且細胞內的鉀含量也不因細胞聯數的改變而有顯著的差異。如上兩項 結果更可支持NaCl或sucrose的添加培養對IR生長效應的影響可由細胞內 外滲透壓差所造成的推論。 It was found that addition of NaCl and sucrose into Deinococcus radiodurans IR culture affects its growth. The effects include the appearance of a pseudo-lag phase, a longer doubling time, a decrease in maximum growth, and an increase of cell multiplicity. It was found that cell- multiplicity of D. radiodurans IR seems to depend on osmolarity of the growth medium. High concentration of glycerol (1.5 M) in the growth medium does not inhibit the growth or increase the cell- multiplicity of this bacterium. Since glycerol is a permeating solute, the difference of the osmolarity across the plasma membrane seems to be the factor that inhibits the growth of D. radiodurans IR and increases its cell-multiplicity. Besides, osmoprotectants (glycine betaine, proline, and choline) which protect the cell from the increasing of intracellular ionic strengh, do not reduce the growth inhibition caused by osmotic strengh in D. radiodurans IR. The potassium concentration, which is changed in other bacteria due to the presence of NaCl in the medium, was the same in D. radiodurans IR with different cell- multiplicity. Those results further support the theory that the effect of NaCl or sucrose on D. radiodurans IR is due to the difference of osmolarity across the plasma membrane.