Abstrakt: | The aim of this study was to investigate the effects of
phenol on fatty acid composition of Pseudomonas
vesicularis and Pseudomonas sp. JS150 strains introduced
into sterile L1, L2 and G soils and in Pseudomonas-
inoculated non-sterile soils. Phenol was added to all
soils at the concentration of 1.7 mg g–1, 3.3 mg g–1 and
5.0 mg g–1. Simultaneously, the survival of both strains
introduced into soils was estimated. The investigations
were conducted in four separate experimental arrangements.
The first comprised sterile soils with introduced
Pseudomonas vesicularis strain, the second — sterile
soils with Pseudomonas sp. JS150, the third-sterile soils
containing the mixture of these strains and the fourth —
Pseudomonas-inoculated non-sterile soils. FAMEs extracted
from these soils at the following sampling days
were analysed by GC method and identified using software
Sherlock, 3,90.
It was found that phenol degradation by Pseudomonas
vesicularis or/and Pseudomonas sp. JS150 depended
on type of soil, phenol contamination and inoculum
composition. The highest phenol removal at each concentration
in L1, L2 and G soils was observed when
bacteria were used as a mixture, phenol was metabolized
slower by Pseudomonas sp. JS150 and much
slower by Pseudomonas vesicularis. It was also demonstrated
that independently on inoculum composition
phenol degradation rate varied depending on type of
soil. In G soil with the highest amount of organic matter
phenol degradation proceeded faster than in L1 soil with
intermediate amount of organic matter and in L2 soil
with the lowest amount of organic matter. Obtained results
also indicated that increasing dose of phenol made
its biodegradation much longer. On the basis of bacterial
counts it was showed that Pseudomonas sp. JS150
strain better survived both in phenol-polluted and the
unpolluted soils in comparison with Pseudomonas
vesicularis. Bioaugmentation with Pseudomonas
vesicularis and Pseudomonas sp. JS150 strain in all
soils resulted in the increase of effectiveness of phenol
removal as compared to control samples. It indicated
that the interactions between autochtonous bacteria and
strains introduced into soils were synergic.
The analyses of fatty acid percentages and composition
in bacterial cells showed that they regulated of
membrane fluidity and permeability in response to actual phenol concentration in soil. The first reaction of
both strains in the presence of phenol added was de
novo synthesis and changes in composition of saturated,
straight-chain and branched fatty acids at the beginning
days of experiment. While the phenol concentration decreased
above 50% of dose used cyclopropane fatty acid
19:0 cy ω10c from these cells was isolated. In turn, the
abundance of hydroxy fatty acids in that time decreased
or they were not present in FAMEs profiles. The ratio
of saturated/unsaturated fatty acids appeared the useful
marker for rate of phenol degradation by Pseudomonas
vesicularis or/and Pseudomonas sp. JS150. At the first
days of experiment when phenol concentration in soils
was high saturated/unsaturated ratio increased. It highest
value was calculated generally at day when the abundance
of 19:0 cy ω10c fatty acid was the highest
whereas at the following days simultaneously with phenol
removal it decreased. The value of sat/unsat ratio
varied in response to the type of soil, inoculum composition
and dose of phenol added. The similar correlations
between phenol concentration, the presence of
19:0 cy ω10c fatty acid and value of sat/unsat ratio were
observed in phenol amended and Pseudomonas-inoculated
soils and phenol amended but not-inoculated soils.
The abundance of saturated, straight-chain and branched
fatty acids changed also in these soils but the changes
were significantly lower as compared to sterile soils
with introduced of Pseudomonas vesicularis or/and
Pseudomonas sp. JS150 strains. In turn, the amount of
hydroxy fatty acids isolated from these soils remained at
the similar level. It indicates that adaptive mechanisms
to the presence of phenol were similar both in laboratory
selective of Pseudomonas vesicularis and Pseudomonas
sp. JS150 strains and in other species of bacteria
naturally existing in soil.
It was confirmed that MIDI-FAME method could be
used to monitor the progress of phenol elimination from
soil. On the basis of fatty acid profiles and analysis of
value of sat/unsat ratio it is possible to estimate if degradation
of phenol by microorganisms in soil proceeds
and the presence and abundance of 19:0 cy ω10c fatty
acid indicate the progress of this process. For this reason,
they may be good biomarkers of phenol contaminated
environments. |