| Popis: |
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. |
