RESUMEN
A facultative alkaliphilic protease-producing gram-positive rod-shaped bacteria (EMGA 5) was isolated from mangrove soil and confirmed as Bacillus flexus by the 16S rDNA sequence. Buffering capacity and membrane H+ conductance of this alkaliphilic isolate were investigated for the cells grown at pH 7.2 and 10.5 using acid pulse technique. Suspensions of B. flexus cells grown in poly peptone yeast glucose medium at pH 10.5 exhibited higher cytoplasmic membrane buffering capacity values (70 µmol H+/pH unit/mg protein at pH 9.9) than the cells grown at pH 7.2 (41 µmol H+/pH unit/mg protein at pH 9.9). B. flexus grown aerobically at pH 7.2 showed higher H+ conductance values than the cells grown at pH 10.5 (0.032 µmol H+/s/pH unit/mg protein at pH 9.9 and 0.028 µmol H+/s/pH unit/mg protein at pH 9.8, respectively). The present study revealed that the buffering capacity and membrane H+ conductance of the B. flexus isolates were influenced by pH of the medium.