Search

Decades of intensive discharge from industrial activities into coastal systems has resulted in the accumulation of a variety of persistent organic pollutants (POPs) in marine waters and sediments, having detrimental impacts on aquatic ecosystems and the resident biota. POPs are among the most hazardous chemicals originating from industrial activities due to their biotoxicity and resistance to environmental degradation. Bacterial communities are known to break down many of these aromatic compounds, and different members of naturally occurring bacterial consortia have been described to work in syntrophic association to thrive in heavily contaminated waters and sediments, making them potential candidates as bioindicators of environmental pollution. In this study environmental, sampling was combined with chemical analysis of pollutants and high-resolution sequencing of bacterial communities using Next Generation Sequencing molecular biology tools. The aim of the present study was to describe the bacterial communities from marine sediments containing high loads of POPs and to identify relevant members of the resident microbial communities that may act as bioindicators of contamination. Marine sediments were collected from a coastal bay area of the Baltic Sea historically influenced by intense industrial activity, including metal smelting, oil processing, and pulp and paper production. Different types of POPs were detected at high concentrations. Fiberbank sediments, resulting from historic paper industry activity, were found to harbour a clearly distinct bacterial community including a number of bacterial taxa capable of cellulolytic and dechlorination activities. Our findings indicate that specific members of the bacterial communities thrive under increasing levels of POPs in marine sediments, and that the abundances of certain taxa correlate with specific POPs (or groups), which could potentially be employed in monitoring, status assessment and environmental management purposes.

Northern peatlands are often dominated by ericaceous shrub species which rely on ericoid mycorrhizal fungi (ERM) for access to organic sources of nutrients, such as nitrogen (N) and phosphorus (P), and host abundant dark septate endophytes (DSE). Relationships between hosts and fungal symbionts may change during deposition of anthropogenic N and P. We studied the long-term effects of N and P addition on two ericaceous shrubs, Calluna vulgaris and Erica tetralix, at Whim Bog, Scotland by analyzing fungal colonization of roots, enzymatic activity, and fungal species composition. Unexpectedly, the frequency of typical ERM intracellular colonization did not change while the occurrence of ERM hyphae tended to increase and DSE hyphae to decrease. Our findings indicate that altered nutrient limitations shift root associated fungal colonization patterns as well as affecting ericaceous root enzyme activity and thereby decomposition potential. Reduction of recalcitrant fungal biomass in melanized DSE may have implications for peatland C sequestration under nutrient addition.

Ectomycorrhizal fungi were characterised by restriction fragment length polymorphism (RFLP) and sequencing from Tilia cordata Mill root tips collected from forest, street and nursery habitats. Fungal colonisation intensity of roots was 80–90% in forest and street habitats and 60–70% at the nursery. On the whole, more Basidiomycota than Ascomycota were encountered in Tilia mycorrhizas, and soil horizons at depth of 5–10 cm contained more root tips and had higher diversity of mycorrhizal fungi than soils at depth of 20–25 cm. Healthy street trees and forest trees had the highest number of ectomycorrhizal morphotypes. Street and nursery trees did not have any common mycorrhizal fungal genera, whereas Boletus , Inocybe and Russula spp. were found from roots of both street and forest trees and Tuber spp. from roots of nursery and forest trees. Most of the genera found in this study do not have an earlier record of including Tilia root symbiotic species in Finland, although several but not all have been reported from other countries.

The effects of the transformation of a 4-coumarate:coenzyme A ligase (4CL) gene involved in lignin biosynthesis on the interactions between transgenic plants and soil microbiota were studied in silver birch (Betula pendula Roth). Although the genetic transformation did not lead to expected changes in wood chemistry, it had significant influence on root biomass and morphology. The transgenic lines had less root biomass and lower numbers of root tips than the wild-type birch. However, the transgenic lines formed normal ectomycorrhizas with Paxillus involutus (Batsch) Fr. and no differences between the transgenic lines and the wild-type birch were detected in the colonization by mycorrhizas in vitro. In a field trial, the decomposition of the transgenic and wild-type birch litter was equally rapid, and no marked differences were found between the transgenic lines and wild-type birch in total microbial biomass (SIR) or activity (basal respiration). The effects of the genetic transformation on the ergosterol content of the leaf litter were contradictory; the litter from one transgenic line had significantly higher ergosterol content and the litters from two other transgenic lines had significantly lower ergosterol content than the litter from wild-type birch. This study shows that the 4CL antisense transformation and the pleiotropic effects of the transformation on growth characteristics of birch did not disturb the formation of ectomycorrhizas with P. involutus and had no clear influence on the biodegradability of the leaf litter.

This study assessed the effect of mycorrhizal colonization by Glomus intraradices (Gi) and G. versiforme (Gv) on the bacterial community composition in the rhizosphere of canola, clover and two tomato genotypes (wild type (76R) and its mutant with reduced mycorrhizal colonization (rmc)). Additionally, the effect of light intensity on the rhizosphere bacterial community composition of the tomato genotypes was studied. The bacterial community composition was assessed by denaturing gradient gel electrophoresis (DGGE). In canola, which is considered to be a non-mycorrhizal species, inoculation with Gi increased the shoot dw compared to Gv and the non-mycorrhizal control plants and also induced changes in the bacterial community composition in the rhizosphere. These fungal effects were observed although less than 8% of the root length of canola was colonized. On the other hand, about 50% of the root length of clover was colonized and inoculation with Gv resulted in a higher shoot dw compared to Gi or the control plants but the rhizosphere bacterial community composition was not affected by inoculation. Plant growth, mycorrhizal colonization and bacterial community composition of the two tomato genotypes were affected by a complex interaction between tomato genotype, AM fungal species and light intensity. Low light intensity (photosynthetic photon flux 200–250 μmol m −2 s −1 ) increased the shoot–root ratio in both genotypes and reduced colonization in the wild type. The differences in bacterial community composition between the two genotypes were more pronounced at low than at high light intensity (550–650 μmol m −2 s −1 ).

The distribution of heterotrophic flagellates, naked amoebae, testate amoebae and ciliates was investigated in habitats created by Scots pine-Paxillus involutus and -Suillus bovinus ectomycorrhizospheres. The protozoa living on plant and fungal surfaces preferred the non-mycorrhizal pine roots over mycorrhizal roots or external mycelium. The testate amoebae were more abundant on external mycelium than on mycorrhizae regardless of the mycorrhizal fungal species. Numbers of protozoa were higher in the different habitats provided by S. bovinus mycorrhizospheres when compared with P. involutus mycorrhizospheres. Interestingly, the quality of the bacterial flora as food for the protozoa was affected by the mycorrhizal fungi even in the soils adjacent to non-mycorrhizal root tips of pine. These results demonstrate that mycorrhizal fungi create habitats differently suitable for protozoa living in boreal forest soil.

Heterogeneous ethylene polymerization catalysts were prepared by supporting tetrakis(dimethylamino)titanium, Ti[N(CH 3 ) 2 ] 4 , on chemically modified silica surface. The modification of silica was made using a silane coupling agent, Cp(CH 2 ) 3 Si(OCH 2 CH 3 ) 3 and atomic layer chemical vapor deposition (ALCVD). Titanium amide was also immobilized straight on the silica and on a methyllithium-treated modified silica. The aim of methyllithium treatment was to alkylate the unreacted ethoxy groups of the silane coupling agent on the silica. Methyllithium methylates, besides ethoxy groups, also silica surface and surface cyclopentadienyl groups. A model compound for these heterogeneous catalysts was prepared using a reaction of Ti[N(CH 3 ) 2 ] 4 with trimethylsilylcyclopentadienyl yielding a monocyclopentadienyl titanium compound, Me 3 SiCpTi[N(CH 3 ) 2 ] 3 . The preliminary results of ethylene polymerization using the prepared heterogeneous and homogeneous titanocene amide complexes and the effect of amount of MAO are presented.

Heterogeneous ethylene polymerization catalysts were prepared by supporting tetrakis(dimethylamino)zirconium on chemically modified silica surface. The silica was modified with a silane coupling agent, Cp(CH 2 ) 3 Si(OEt) 3 , using ALCVD-technique. On the resulting cyclopentadienyl surface zirconium amide, Zr(NMe 2 ) 4 , was immobilized with and without using methyllithium. Depending on the use of methyllithium the immobilization resulted in either mono- or bis-cyclopentadienyl zirconium complexes, which were characterized using chemical analysis, FT-IR, 13 C- and 29 Si-NMR results. Moreover, a homogeneous model compound, (Me 3 SiCp) 2 Zr(NMe 2 ) 2 , was synthesized with a reaction between Zr(NMe 2 ) 4 and Me 3 SiCp. The preliminary results of ethylene polymerization with these supported and unsupported organometallic complexes are presented.

A novel heterogeneous α-olefin polymerization catalyst is prepared by the immobilization of CpZrCl 3 on a chemically modified silica support. The surface modification of silica was carried out by utilizing the saturated gas-solid reactions of a silane coupling agent with a hydrocarbon spacer, Cp(CH 2 ) 3 Si(OCH 2 CH 3 ) 3, and a partially dehydroxylated silica. In gas-solid reactions all reactive surface hydroxyl groups were utilized in bonding the silane coupling agent on silica. The immobilization of CpZrCl 3 on the cyclopentadienyl surface formed on the silica was done using liquid-phase reactions. The prepared materials were characterized by FT-IR spectroscopy. The supported catalyst system has a high activity in ethylene polymerization and can be used to produce polyethylene with a narrow molecular weight distribution in the presence of methylaluminoxane. The catalytic activity was doubled when CpZrCl 3 was immobilized on the cyclopentadienyl surface of SiO 2 compared with the activity of CpZrCl 3 in homogeneous catalysis. However, the direct heterogenization of CpZrCl 3 onto unmodified silica produced a catalyst with a very low activity. The effect of surface modification reactions and the surface structure of a support on the catalyst performance is presented and discussed.

In filamentous fungi a well-preserved hyphal cytoskeleton was obtained for indirect immunofluorescence (IIF) microscopy by quick-freezing in Freon 22 cooled with liquid nitrogen, followed by fixation with glutaraldehyde in ethanol or formaldehyde in methanol at −75°C. Several factors previously claimed to alter the structure of the cytoskeleton during the fixation process were totally or partially avoided. No microtubule stabilizing buffers were used, detergent treatment of hyphae was unnecessary when the fixative was formaldehyde in methanol, and the visualization of the microtubule cytoskeleton was possible without enzymatic treatment of hyphal walls. The procedure confirmed the picture of the structure of the microtubule cytoskeleton in the hyphae earlier achieved by more conventional fixation methods, and made possible the resolution of some new details. The visualization of actin was also improved.

The widespread use of motor oil makes it a notable risk factor to cause scattered contamination in soil. The monitoring of microbial community dynamics can serve as a comprehensive tool to assess the ecological impact of contaminants and their disappearance in the ecosystem. Hence, a field study was conducted to monitor the ecological impact of used motor oil under different perennial cropping systems (fodder galega, brome grass, galega-brome grass mixture and bare fallow) in a boreal climate zone. Length heterogeneity PCR characterized a successional pattern in bacterial community following oil contamination over a four-year bioremediation period. Soil pH and electrical conductivity were associated with the shifts in bacterial community composition. Crops had no detectable effect on bacterial community composition or complexity. However, the legume fodder galega increased soil microbial biomass, expressed as soil total DNA. Oil contamination induced an abrupt change in bacterial community composition at the early stage, yet the effect did not last as long as the oil in soil. The successional variation in bacterial community composition can serve as a sensitive ecological indicator of oil contamination and remediation in situ. (C) 2015 Elsevier B.V. All rights reserved.