The effect of anthocyanin- and proanthocyanidin-rich fractions isolated from cranberry juice was studied for their antibacterial activity against nine bacterial strains. Activity was assessed by the agar diffusion assay. Staphylococcus aureus ATCC 6538 was the only strain to exhibit some susceptibility to four out of 10 anthocyanin-rich fractions tested. A variable susceptibility of S. aureus, Enterococcus faecalis ATCC 10541, and Micrococcus luteus ATCC 9341 to proanthocyanidin- rich fractions was also observed. Streptococcus mutans strains as well as Escherichia coli ATCC 10538 and Pseudomonas aeruginosa ATCC 27853 were not susceptible to any of the cranberry juice samples or fractions at the tested concentrations. There was no clear correlation between Gram-positive or Gram-negative bacterial susceptibility to cranberry juice. In this work, the role of cranberry juice anthocyanic and proanthocyanic fractions upon bacterial viability is discussed.

Streptococcus mutans membrane-bound P-and F-type ATPases are responsible for H + extrusion from the cytoplasm thus keeping intracellular pH appropriate for cell metabolism. Toluene-permeabilized bacterial cells have long been used to study total membrane-bound ATPase activity, and to compare the properties of ATPase in situ with those in membrane-rich fractions. The aim of the present research was to determine if toluene permeabilization can significantly modify the activity of membranebound ATPase of both F-type and P-type. ATPase activity was assayed discontinuously by measuring phosphate release from ATP as substrate. Treatment of S. mutans membrane fractions with toluene reduced total ATPase activity by approximately 80% and did not allow differentiation between F-and P-type ATPase activities by use of the standard inhibitors vanadate (3 µM) and oligomycin (4 µg/mL). Transmission electron microscopy shows that, after S. mutans cells permeabilization with toluene, bacterial cell wall and plasma membrane are severely injured, causing cytoplasmic leakage. As a consequence, loss of cell viability and disruption of H + extrusion were observed. These data suggest that treatment of S. mutans with toluene is an efficient method for cell disruption, but care should be taken in the interpretation of ATPase activity when toluene-permeabilized cells are used, because results may not reflect the real P-and F-type ATPase activities present in intact cell membranes. The mild conditions used for the preparation of membrane fractions may be more suitable to study specific ATPase activity in the presence of biological agents, since this method preserves ATPase selectivity for standard inhibitors.