title: Selection of pH buffers for use in conductimetric microbiological assays.
abstract: Many metabolic activities of micro-organisms lead to changes in the pH value of cultures and consequently pH buffer compounds are potentially a major source of conductivity changes in cultures. To maximize changes in conductivity associated with microbial growth the pH buffer-associated changes should occur in a direction that reinforces those due to other metabolic activities. In agreement with this, studies with Escherichia coli showed that fermentation of glucose and aerobic growth on L-alanine yielded greater changes in the conductivity of media containing Tris(hydroxymethyl)aminomethane or L-histidine buffers than in a medium containing phosphate buffer, whereas aerobic growth on glucose or succinate yielded greater changes with phosphate buffer than with Tris(hydroxymethyl)aminomethane or L-histidine buffers. Criteria for the selection of appropriate pH buffer compounds are presented.
mesh_terms: D000332:Aerobiosis; D000409:Alanine / Q000378:metabolism; D000693:Anaerobiosis; D002021:Buffers; D003217:Conductometry; D003470:Culture Media; D004553:Electric Conductivity; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism; D014325:Tromethamine / Q000378:metabolism
chemical_list: D002021:Buffers; D003470:Culture Media; D010710:Phosphates; D013386:Succinates; D014325:Tromethamine; D006639:Histidine; D005947:Glucose; D000409:Alanine