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Osmotic stress on dilution of acid injured Escherichia coli O157:H7
Author(s) -
Jordan K. N.,
Hall S.,
McClure P. J.
Publication year - 1999
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1046/j.1365-2672.1999.00543.x
Subject(s) - diluent , osmotic concentration , dilution , glycerol , sucrose , osmotic shock , sorbitol , sodium , sugar , mannitol , chromatography , osmotic pressure , biochemistry , chemistry , food science , escherichia coli , biology , nuclear chemistry , physics , organic chemistry , gene , thermodynamics
To determine surviving numbers of Escherichia coli from cultures or food systems, dilution with 0·1% peptone is regularly used. Higher numbers of survivors could be obtained from an acid‐treated culture if 0·5 mol l −1 sucrose was added to the 0·1% peptone. Sorbitol, glucose or sodium chloride, but not glycerol, could be used in place of sucrose. Using electron microscopy distinct differences could be seen between acid‐treated and untreated cells. The osmolarity of the diluents ranged from 5 to 500 mosmol kg −1 H 2 O for the 0·5 mol l −1 sugar or glycerol solutions, to about 1000 mosmol kg −1 H 2 O for the salt solution. Maximum recovery diluent has an osmolarity of about 300 mosmol kg −1 H 2 O and resulted in recovery of similar numbers of injured cells as a 0·5 mol l −1 solution of sugar in 0·1% peptone. Taking into account the observed damage to acid‐treated cells and the differences in osmolarity of the diluents, it is likely that dilution in 0·1% peptone imposed additional stress on the acid‐injured cells which caused further cell damage. Dilution in a more osmotically stable solution alleviated this osmotic stress.