Physicochemical Effects of Long Chain Fatty Acids on Bacterial Cells and their Protoplasts

Abstract

Fatty acids of chain length > C,, induced lysis of protoplasts at pH 7.4 when the concentration was nearly bactericidd. At p H 6, lauric and linoleic acids produced lysis above bactericidal concentrations but, at pH 8, lysk was produced by the same acids below bactericidal concentrations. The lysis was immediate a t p H 8, but at pH 6 the effect was preceded by contraction of protoplasts. At pH 7.4 the order of lytic activity between individual fatty acids was similar to that of bactericidal activity and the response of protoplasts of Bacillwr megaterium relative to those of 2Mimcoccus lyeodeikticus reflected differences in bactericidal sensitivity though whole cells were much less sensitive to fatty acid-induced leakage effects then protoplasts. Reversal agents antagonized the lysis of protoplasts by fatty acids. A physicochemical basis for the action of fatty acids and reversal agents on protoplasts and whole cells is discussed.ANTIBACTERIAL EIWECTS of long chain fatty acids have already been discussed in relation to bactericidal activity and physicochemical properties in solution (Galbraith, Miller, Paton & Thompson, 1971 ;Galbraith & Miller, 1973a).Several workers have produced evidence which suggests that antibacterial compounds with lipophilic and hydrophilic properties act on the cytoplasmic membrane (Hugo, 1967; Salton, 1968). The most convenient method of investigating the interaction between these antibacterial compounds and the bacterial membrane involves the use of protoplasts and spheroplasts. Gilby & Few (1957, 1960) have demonstrated the lysis of protoplasts by surface active agents and correlated the lytic activity with antibacterial activity on whole bacterial cells. In previous work with long chain fatty acids (Galbraith & Miller, 1973a) the reversible uptake of 14C labelled fatty acids by bacterial cells and protoplasts also indicated that the probable site of action of the fatty acids was the cytoplasmic membrane and so in the present work the lysis of protoplasts has been studied in order to investigate the relationship between antibacterial action and phyaicochemical activity on the membrane. The studies have included the effects of pH, aliphatic chain length, reversal agents and the sensitivity of the individual bacterial species which were used to determine bactericidal activity and uptake. An attempt was also made to investigate the physicochemical effects of fatty acids on whole cells in order to determine whether the overall response is similar to that found with protoplasts in the absence of the cell wall. Materials and MethodsCultures and media The organisms used were Bacillus megaterium NCIB 9521 and Micrococcus lysodeiktieus NCIB 9278. Bacterial suspensions and protoplasts of B. megaterium were prepared [6471

Antimicrobial Activity of Saturated Fatty Acids and Fatty Amines against Methicillin-Resistant Staphylococcus aureus

“…The outer membrene of gram-negative bacteria behaves as a entry barrier against fatty acids, but the cell wall of gram-positive bacteria may adsorb and transport fatty acids into the inner membrane. 31,32) At 4 fold the MIC, lauric acid produced a bactericidal effect after 6 h of incubation (Fig. 1A).…”

Characterization of the extracellular bactericidal factors of rat alveolar lining material.

“…Lysis of the pneumococcal cell wall by detergents, although visually impressive, is not necessary for pneumococcal killing (12). At suitable concentrations FFA can cause leakage and even lysis of bacterial cell membranes (46,47) as well as various cellular metabolic effects, including inhibition of respiratory activity, effects on transportation of amino acids, and uncoupling of oxidative phosphorlization (48)(49)(50). Although our present and previous work suggests that FFA in rat surfactant alter pneumococcal cell membrane permeability, the exact mechanism of killing is not known.…”

Assessment of sediment toxicity during anaerobic biodegradation of vegetable oil using Microtox® and Hyalella azteca bioassays

“…Although clay can effectively transfer vegetable oil from the water to sediments where anaerobic degradation of vegetable oil can occur, the metabolic intermediates of degradation (especially free long-chain fatty acids), may be toxic to microorganisms due to their ability to disrupt cell membranes and membrane-dependent processes (Galbraith and Miller, 1973;Cherrington et al, 1991). Free long-chain fatty acids have been reported to be toxic to a wide variety of microorganisms in anaerobic digestion systems (Hanaki et al, 1981;Koster and Cramer, 1987;Rinzema et al, 1994;Hwu et al, 1996;Lalman and Bagley, 2001;Pereira et al, 2001Pereira et al, , 2003a.…”