Membrane Depolarization Sensitizes Pseudomonas aeruginosa Against Tannic Acid.

The use of dietary polyphenols as antimicrobial agents has gained immense popularity in recent years, although few of them-like tannic acid has limited use in this field of research; one of the main reasons is its restricted access through the bacterial membrane. Dissipating the bacterial membrane potential with a sub-lethal dosage of the protonophore, carbonyl cyanide m-chlorophenyl hydrazone, enhanced the tannic acid-cytotoxicity with subsequent inhibition of aerobic respiration in Pseudomonas aeruginosa strains which otherwise exhibited a minimum response to tannic acid. However, ascorbic acid, an antioxidant and bacterial membrane-stabilizing compound, had rescued the cells from both tannic acid- and CCCP-mediated lethality. The results suggested that dispersing the membrane potential with a protonophore can enhance the antibacterial properties of tannic acid.

Subcellular compartmentalization of glutathione peroxidase 1 allelic isoforms differentially impact parameters of energy metabolism.

Specific genetic variations in the gene for the selenium-containing antioxidant protein glutathione peroxidase 1 (GPX1) are associated with the risk of a variety of common diseases, including cancer, diabetes, and cardiovascular disorders. Two common variations have been focused upon, one resulting in leucine or proline at codon 198 and another resulting in 5, 6, or 7 alanine repeats were previously shown to affect the distribution of GPX1 between the cytoplasm and mitochondria. Human MCF7 cells engineered to exclusively express GPX1 with five alanine repeats at amino terminus and proline at codon 198 (A5P) and seven alanine repeats at amino terminus and leucine at codon 198 (A7L), as well as derivatives targeted to the mitochondria by the addition of a mitochondrial localization sequence (mA5P and mA7L) were used to assess the consequences of the expression of these proteins on the cellular redox state and bioenergetics. Ectopic expression of A5P and A7L reduced the levels of reactive oxygen species, and the mitochondrially targeted derivatives exhibited better activity in these assays. Bioenergetics and mitochondrial integrity were assessed by measuring mitochondrial membrane potential, oxygen consumption, adenosine triphosphate (ATP) levels, and the levels of lactate dehydrogenase. The results of these assays indicated distinctively, and sometimes opposing, patterns with regard to differences between the consequences of the expression of A5P, A7L, mA5P, and mA7L. These data provide new information on the consequences of differences in the primary structure and cellular location of GPX1 proteins and contribute to the understanding of how these effects might contribute to human disease.

Revealing the dual role of gallic acid in modulating ampicillin sensitivity of Pseudomonas aeruginosa biofilms.

AIM: To understand the effects of gallic acid (GA) on ampicillin (Amp) sensitive or resistant strain of Pseudomonas sp. and also in modulating the corresponding biofilms. METHODOLOGY: The cell viability was determined by broth dilution, dry weight and CFU assays. Biofilm formation was measured by crystal violet assay while oxygen consumption rate was measured to verify the metabolic status of the cells. The membrane damage and drug efflux/accumulation were studied by fluorimetric assays. RESULTS: GA transformed the Amp resistant cells, both planktonic and biofilms, into highly sensitive one by inducing membrane damage and enhancing accumulation of drug, whereas the Amp sensitive cells gained resistance against Amp. CONCLUSION: Use of GA as an antimicrobial compound should be analyzed more critically depending on the drug dosages, drug sensitivity as well as types of bacterial strains being studied.