Cell surface hydrophobicity and its relation to outer membrane proteins of Serratia marcescens

Cell surface hydrophobicity measurement of S. marcescens and its two mutants, one having capacity of overproducing the red pigment prodigiosin, while another carrying no pigment, showed that the hydrophobicity, which always increased with ageing of the cells, was not totally due to the pigment present on the surface. The mutant having no pigment always exhibited higher hydrophobicity than that of two pigmented cells, irrespective of whether the experimented cells were of early log phase or static phase. The outer membrane proteins were isolated and characterized by SDS-polyacrylamide gel. The non-pigmented cell outer membrane showed an extra band of protein (approximately 40 K Da molecular weight) besides the other bands common to those of other two pigmented cells. This extra protein of outer membrane may be responsible for higher surface hydrophobicity of non-pigmented mutant of S. marcescens.