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Response of birch and alder root endophytes as well as rhizosphere and bulk soil microorganisms to heavy metal pollution

Złoch M., Kowalkowski T., Szymańska S., Hrynkiewicz K.

Polish Journal of Ecology

2014

Vol. 62, nr 1

37--53

Research on soil microorganisms associated with plant roots (endophytes) and their outside habitats (rhizosphere, soil) under exposure to high concentrations of heavy metals in the environment may contribute to an increased knowledge about the effects of unfavorable pollutants in the natural ecosystem and improve the efficiency of remediation processes of degraded soils. The main goal of our study was to evaluate properties of microbial populations inhabiting different but spatially closed habitats: interior of the tree roots – endophytes (Betula pendula L. and Alnus glutinosa L.), rhizosphere and soil not influenced by plant roots at two heavy metal polluted areas in southern Poland where the content of cadmium, lead and zinc ranged 9.2–14.9, 26.2–75.1 and 1080–1559 mg∙kg-1 of dried soil, respectively. In our experiment, we analyzed their density as well as determined the total metabolic activity and ability for utilization of different carbon sources. The density of endophytes (5.76–7.16 log10 c.f.u. × g dw-1) was higher than the density of bacteria inhabiting outside habitats – the rhizosphere and soil (5.43–5.91 and 5.08–5.57 log10 c.f.u. × g dw-1, respectively) and was not affected by heavy metal content. However, the total metabolic activity of endophytic populations was strongly influenced by the physicochemical properties of the soil and was significantly lower at more contaminated site. In general, the metabolic activity of endophytes was ~15 times lower than the activity of rhizobacteria and at the same level or lower than the activity of soil microorganisms. Discriminant analysis revealed a higher utilization of α-Cyclodextrin and D-Xylose by microorganisms isolated from more polluted test site. The use of an artificial neural network (ANN) followed by principal component analysis (PCA) allowed the distinguishing of preferences in the utilization of carbon sources by microorganisms due to tree species but not the zone of isolation – endophytes, rhizosphere, soil. Our study revealed no significant impact of the metal concentrations present in the soil on the density of microorganisms (bacteria and fungi) inhabiting three analyzed zones (interior of the roots, rhziosphere, soil); however, their total metabolic activity was decreased in more contaminated site. Since the density of endophytes was higher compared to the number of bacteria present in the outside habitats (rhizosphere and soil), and their total metabolic activity was in general lower, we suggest a high specialization of microorganisms associated with the cellular spaces of plant roots compared to other microbial populations.

Wpływ bakterii ryzosferowych na zmianę liczebności drobnoustrojów w rędzinie wapiennej świeżo skażonej mieszaniną wielopierścieniowych węglowodorów aromatycznych z olejem napędowym

Gałązka A., Król M., Perzyński A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

2009

z. 56 [268]

35-47

Przedstawiono badania wpływu ochronnego szczepów Azospirillum spp. i Pseudomonas stutzeri na liczebność mikrobiologiczną w rędzinie wapiennej świeżo skażonej mieszaniną WWA i ON. Po zastosowaniu szczepienia roślin stwierdzono statystycznie istotny wzrost liczby drobnoustrojów glebowych (ogólnej liczby bakterii, promieniowców, bakterii amonifikacyjnych, proteolitycznych, celulolitycznych, rozkładających fosforany oraz kopiotrofów i oligotrofów) oraz statystycznie znaczny spadek ogólnej liczby grzybów. Stwierdzono ponadto stymulujący wpływ oleju napędowego w dawkach O,1 i 1 % na wzrost liczby wymienionych drobnoustrojów.

Rhizodegradation is the breakdown of organic contaminants in soil by soil dwelling microbes which is enhanced by the rhizospheres presence. The soil used in the experiment was collected from 0-30 cm layer in the uncontaminated area of agricultural use (Mięćmierz, Kazimierz Dolny, Poland). Pot experiment was conducted to evaluate the number of microorganisms in rendzina freshly contaminated with PAH's, diesel fuel and mixtures of PAH's and diesel fuel using inoculation of meadow feascue with rhizospheric bacteria Azospirillum spp. and Pseudomonas stutzeri. The strains of Azospirillum spp. and Pseudomonas stutzeri were able to nitrogen fix and degrade PAH's as the only source of carbon and energy. Experiment was carried out as a chamber pot study. Plants had been cultivated for 30 days and then harvested. The total number of various bacteria (ammonifiying, proteolitic, able to degrade phosphorus, copiotrophic, oligotrophic), actinomycetes and fungi in soil before and after vegetation period of investigated soil were the basis for the determination of the effectiveness of the inoculation of plants with Azospirillum spp. and Pseudomonas stutzeri. This research has confirmed higher total number of microorganisms after increase on total number of fungi in rendzina after inoculation of plants with all doses of P AH' s: total number of bacteria, actinomycetes and lower number of fungi. Statistically important decrease of total number of different bacteria and actinomycetes and statistically important increase on total number of fungi in rendzina after grown of meadow feascus inoculated with Azospirillum spp. and Pseudomonas stutzeri were observed together with increase of pollution doses. Number of different bacteria and actinomycetes were statistically higher in soils polluted with diesel fuel at the doses 0, I and 1 %. The differences in concentration between the inoculated or non-inoculated soils indicate that the presence of plant roots, in addition to the period of time, contributes to grown and adaptation of Azospirillum spp. and Pseudomonas stutzeri to a soil freshly polluted with P AH' s and diesel fuel.