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Fatty
acids of bacterial membranes as a biomarker of aromatic compounds
toxicity
Abstract: In
all bacteria fatty acids are found as a major component of their
membrane lipids. The well-known spectrum of bacterial fatty
acids comprises saturated, cis,
trans-monounsaturated,
diunsaturated, cyclopropane, hydroxyl and methyl-branched fatty
acids. Recently a new type has been found as membrane constituents
— polyunsaturated fatty acids.
The physical properties of bacterial
membranes are determined by the composition of fatty acids. Some
membrane active agents, including aromatic compounds, have a
strong influence on membrane fluidity. These compounds dissolve in
the cell membrane disturbing its integrity and affecting
specific permeabilization. The hydrophobicity of an aromatic
compound, expressed as its logP value, is a good indicator of its
toxicity. Microorganisms however can adapt to many organic
compounds by changing of their membrane fluidity. They can modify
degree of saturation of fatty acids, the average chain length and
the protein content. This mechanism is called “homeoviscosic
adaptation”. One of the key processes in the adaptation of
some Pseudomonas, Vibrio and Escherichia
coli strains, enabling them to tolerate aromatic
compounds, appears to be the isomerization of cis
— into trans-unsaturated fatty acids.
The
analysis of microbial membrane lipids, specifically phospholipid
fatty acids (PLFA) is a powerful tool for monitoring the
microbial responses to changes in their environment. Phospholipids
are extracted directly from environmental samples to characterise
microorganisms within their communities. Microbial PLFA analysis
provides quantitative insight into three important attributes of
microbial communities, viable biomass, community structure and
metabolic activity. Certain pollutants induce changes in some PLFA
components such as ratio of saturated to unsaturated fatty acids,
ratio of trans to cis-monoenoic
unsaturated fatty acids, and the content of cyclopropane fatty
acids. It might function as an indicator for the toxicity of many
aromatic pollutants, particularly during in situ
bioremediation and biotransformation processes.
1. Introduction.
2. Fatty acids of bacterial membranes. 3. Influence of
aromatic compounds on bacterial membranes. 4. Adaptation
mechanisms of bacteria to aromatic compounds. 5. Utility of fatty
acids as biomarkers in environmental studies. 5.1. Isolation
of phospholipid fatty acids (PLFA). 5.2. Analysis of
phospholipid fatty acids (PLFA). 6. Summary
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Agnieszka
Mrozik i Sylwia Łabużek
Katedra Biochemii Uniwersytetu Śląskiego
Ul. Jagiellońska 28, 40-032 Katowice
e-mail:
amrozik@us.edu.pl
Zofia Piotrowska-Seget
Katedra Mikrobiologii Uniwersytetu Śląskiego
Ul.
Jagiellońska 28, 40-032 Katowice
Wpłynęło w lutym
2002
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