Influence of phenols on growth and membrane permeability of free and immobilized Escherichia coli

Abstract

The inhibition of the exponential growth of Escherichia coli K-12 by different phenolic compounds was examined. Cells entrapped in calcium alginate showed a greater tolerance than cells grown in suspension. The extent of inhibition of growth of the immobilized cells depended on the period of growth in the gel matrix. After the addition of bacteriostatic concentrations of phenol or 4-chlorophenol, a dose-dependent efflux of metabolites such as ATP and of K+ ions was elicited. Provided that glucose was supplied as an energy substrate, a reaccumulation of K+ ions at low phenol concentrations was observed. The restoration of the membrane gradient for K+ always preceded the continuation of growth in the presence of the toxic compounds. Compared with free cells, those cells immobilized and grown in alginate suffered a smaller loss of cations after the addition of 4-chlorophenol. The reestablishment of gradients was observed at higher concentrations of the pollutants with entrapped cells than with free cells. Corresponding to the increase in tolerance, the membrane damage was reduced in cells grown in immobilized form for longer times. These data offer a mechanistic explanation of the protection of immobilized microorganisms from phenolic solvents. The data point to the membrane as an important cell component in the toxicity of these pollutants.

Influence of pH and the degree of protonation on the inhibitory effect of fatty acids in the ruminal methanogenMethanobrevibacter ruminantiumstrain M1

“…Leakage of K + is an indicator of impaired cell envelope integrity because it is accumulated in the cytoplasm of methanogens in exchange for Na + (Sprott and Jarrell 1981). Cellular ATP efflux was investigated as it is known to coincide with the leakage of K + and the dissipation of cell membrane potential after exposure to antimicrobials in bacteria (Heipieper et al 1991;Aronsson et al 2005;Higgins et al 2005). For the first time, we used this functional indicator in Archaea and showed that it can indeed be applied as another sign of a destroyed cell envelope as it coincided with K + leakage.…”

Potassium uptake and retention by Oceanomonas baumannii at low water activity in the presence of phenol

“…In mid-exponential growth phase, aliquots (10 ml) of cultures were harvested and centrifuged. The K content of the cells was determined by the method of Heipieper et al [15]. The cell pellet was disrupted by boiling in 5 ml of 5% trichloroacetic acid, and debris removed by centrifugation.…”

“…Published by Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 -1 0 9 7 ( 0 1 ) 0 0 4 3 6 -0 pieper et al [15] found that when E. coli K-12 was subjected to increasing phenol concentration the K content of the cells decreased signi¢cantly. This suggested that phenol had compromised the cell membrane, leading to the loss of metabolites.…”

Emerging tools, enabling technologies, and future opportunities for the bioproduction of aromatic chemicals

“…90,91 As has also been reported for other hydrophobic, membrane accumulating species, such interactions lead to membrane swelling and increased fluidity, 92,93 ultimately resulting in membrane leakage, 94 modified membrane protein activity, 95 and dissipation of the transmembrane proton gradient which in turn impacts cellular energy status, intracellular pH, and chemical homeostasis. [96][97][98][99][100] Production of styrene in E. coli, for example, was found to induce membrane damage and leakage (contrastingly, exogenous addition of styrene triggered little change in membrane integrity). 101 In addition to this common and general mechanism, inhibition imposed by aromatics can also further depend upon structural and functional group diversity.…”