Identification of a cell-surface located protein with growth at low pH in Bifidobacterium animalis (syn. lactis) Strain Bb12

Bifidobacterium animalis (syn. lactis) has been used as a starter culture in several manufactured product lines including yoghurts and anti-diarrhea tablets. As a starter culture it has been selected through a series of mutations and propogations to make it suitable for use in dairy products. This strain was studied to determine the affect of a sudden decrease in pH or continuous exposure to low pH.

Protein profiles of membrane and cell-surface associated fractions, for growth at both neutral pH (7.0) and mildly acidic conditions were essentially identical. At pH 5.0 an increase was noted in the density of a band around 33kOa. The same band was markedly increased during growth at pH 4.0. A 14 fold increase was observed in the relative amount of the protein present in cultures grown at pH 4.0.

Marked up-regulation of a protein of a protein of approximately 33kOa was a feature of 50S-PAGE gels of cells of Bifidobacterium animalis (syn. lactis) strain VUP Bb 12 grown under strongly acidic conditions.