Buffering capacity and H+ membrane conductance of gram-negative bacteria

Buffering capacity and membrane H+ conductance were examined in seven Gram-negative species: Aquaspirillum serpens, Pseudomonas aeruginosa, Alcaligenes faecalis, Escherichia coli, Salmonella typhimurium, Proteus mirabilis and Aeromonas hydrophila. All strains of Enterobacteriaceae studied here showed a decrease in both parameters as the external pH increased, over the pH range studied. The other four species presented an increase in buffering capacity and membrane conductance to protons as the external pH increased from 5.5 to 7.0.