The lytic mechanism of
Sphaerotilus natans by nonionic surfactant, polyoxyethylene dodecyl ether was investigated. The microscopic appearance of
S. natans was not significantly altered by the dose of the surfactant. The cell protein permeated through the outer and inner membrane after lysis, however the endotoxin of outer membrane was not detected in the bulk solution. The ion strength in the bulk solution had no effect on the lysis and the permeation of the cell protein had no connection with the change of osmotic pressure. These results indicated that the nonionic surfactant caused only partial destruction of the outer membrane.
The lytic abilities of nonionic surfactants were dependent upon the carbon number of hydrophobic chain, although the HLB were the same. Nonionic surfactants with 12-15 carbons in their hydrophobic chain lysed
S. natans quickly. Contrary, that with 27 carbons was not capable of lysing
S. natans. It was suggested that nonionic surfactant that have a shorter hydrophobic chain than that of phospholipid in the cell membrane and membrane had a high ability of lysis.
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