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Title: Rola bakterii endofitycznych w fitoremediacji gleb skażonych związkami ropopochodnymi
Authors: Pawlik, Małgorzata
Advisor: Piotrowska-Seget, Zofia
Keywords: bakterie endofityczne; fitoremediacja; gleba - zanieczyszczenie; produkty naftowe
Issue Date: 2018
Publisher: Katowice : Uniwersytet Śląski
Abstract: Recent attention has been paid to the endophytic bacteria which live inside plant tissues without causing any apparent symptoms of diseases. These bacteria display a broad range of symbiotic interactions with their host. Several studies demonstrated that endophytes may significantly increase effectiveness of phytoremediation of soils polluted by petroleum hydrocarbons. The highest potential have hydrocarbon-degrading endophytic bacteria with multiple plant growth-promoting mechanisms and ability to survive in contaminated soil and to colonize plant tissues. The aims of this study were to isolate and characterise crude oil-degrading endophytic bacteria from different tissues of the birdsfoot trefoil (Lotus corniculatus), evening primrose (Oenothera biennis) and tall hawkweed (Hieracium piloselloides). These plants were collected in the highly-polluted area around the refinery in Czechowice- Dziedzice. The diversity and richness of microbiome of birdsfoot trefoil and tall hawkweed were assessed by 454 pyrosequencing. Furthermore, the biochemical traits considered as plant growth-promoting mechanisms of endophytes and their ability to grow on media containing crude oil, diesel oil, n-hexadecane, as sole carbon sources were evaluated. The selected strains were used as inoculum in the phytoremediation experiment. Based on morphological characteristics, in total 44 crude oil-degrading endophytic bacteria were isolated from the interior tissues of three plants. The isolates possessed numerous mechanisms supporting plant growth, which allowed them to be included in the group of plant growth promoting endophytes (PGPE). All selected endophytes synthetized indole-3-acetic acid (IAA) at varying levels, and most of them had the ability to produce cellulolytic enzymes (> 40%). More than 80% of endophytes were found to be motile. PCR analyses revealed that catabolic genes that are associated with hydrocarbon degradation pathways were widespread in the tested strains. The isolates were identified based on sequencing of their 16S rDNA genes. Gammaproteobacteria comprised the majority of the isolated strains and were the predominant group in the investigated plant species. Bacterial isolates belonging to the genus Rhizobium and Rhodococcus were the most abundant in the tissues of O. biennis. Pseudomonas sp. was the most often isolated from L. corniculatus and H. piloselloides. The metagenomics analysis showed that Proteobacteria, Actinobacteria and Firmicutes were the most abundant phyla in all samples. The highest bacterial diversity was revealed in roots of H. piloselloides, while the lowest diversity was observed in roots of L. corniculatus. The predominance of Alphaproteobacteria was driven by the high abundance of mentioned phyla. The impact of endophytic bacteria Rhodococcus erythropolis 5WK and Rhizobium sp. 10WK on petroleum hydrocarbons removal efficiency during phytoremediation with Lolium perenne was evaluated. In the phytoremediation experiment, two inoculation techniques: (1) soil inoculation (SI); (2) seeds pre-inoculation followed by soil inoculation (PI), were used. After 75 days of phytoremediation, the highest TPH removal (19.1%). was observed in the soil, where a consortium of strains and seed pre-inoculation method with soil inoculation (PI+5WK+10WK) were used. Multivariate statistical analysis showed that the method of strains inoculation significantly affected TPH removal and biomass production. Both strains were able to colonize the soil and interior plant tissues (roots and shoots), and their introduction into the soil caused only short-term changes in the total number and abundance of aliphatic hydrocarbon-degrading autochthonous microbial community in soil. Presented results have a high cognitive, scientific and potentially practical significance. Characterised endophytic bacteria may be useful in further research of both a basic and practical nature, on bioremediation and phytoremediation of soils contaminated with petroleum hydrocarbons. In addition, results obtained in this project allowed to complement the knowledge about the abundance and biodiversity of the endophytic bacteria associated with plants growing spontaneously on heavily polluted environments
Appears in Collections:Rozprawy doktorskie (WNP)

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