Article

Microbial biofilms and catabolic plasmid harbouring degradative fluorescent pseudomonads in Scots pine mycorrhizospheres developed on petroleum contaminated soil

Department of Biosciences, Division of General Microbiology, Viikki Biocenter, P.O. Box 56 (Viikinkaari 9), FIN-00014, University of Helsinki, Helsinki, Finland
FEMS Microbiology Ecology (Impact Factor: 3.56). 01/1998; 27(2):115 - 126. DOI: 10.1111/j.1574-6941.1998.tb00529.x

ABSTRACT Cellular interactions and catabolic activities of mycorrhizal root associated non-sporulating bacteria were investigated in a simplified phytoremediation simulation involving a woody plant species. Mycorrhizal Scots pine (Pinus sylvestris) seedlings pre-colonised by Suillus bovinus or Paxillus involutus were grown in forest humus containing microcosms amended with petroleum hydrocarbon (PHC) contaminated soil. Fungal hyphae of both species, emanating from mycorrhizal roots, colonised the PHC contaminated soil over a 16-week period and dense long-lived patches of S. bovinus hyphae formed on the PHC contaminated soil. Transmission electron microscopy revealed a microbial biofilm at the PHC soil-fungal interface composed of differentiated pseudoparenchymous patch hyphae supporting a morphologically diverse bacterial population. Certain non-sporulating bacterial isolates closely associated with the S. bovinus patch hyphae or P. involutus‘web’ hyphae from the PHC soil harboured similar sized mega-plasmids (approx. 150 kb). Isolates of Pseudomonas fluorescens from the ‘patch’ mycorrhizospheres represented different biovars, displayed similar REP-PCR genomic fingerprints, grew on e.g. m-toluate and m-xylene as sole carbon sources, cleaved catechol, and harboured plasmid-borne catabolic marker genes, xylE and xylMA, involved in degradation of mono-aromatics. The plasmids were transmissible in vitro, and Pseudomonas putida transconjugants retained a similar catabolic profile. The identification of microbial biofilms containing catabolic bacteria in the external mycorrhizosphere is discussed in relation to both phytoremediation mechanisms and normal efficient nutrient mobilisation from highly lignin-rich forest soils.

0 Bookmarks
 · 
58 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the microhabitat that surrounds fungal hyphae in soil, coined the mycosphere, carbonaceous compounds that are released from the hyphae stimulate the growth of heterotrophic bacteria, and thus activate them, stimulating organism-to-organism contacts including genetic interactions. Therefore, the mycosphere is postulated to constitute a gene transfer arena, in which a plethora of genes, including locally-adaptive ones, are swapped across the resident microbial communities. Such genetic transfers may have plasmids, in particular ones with broad host ranges, as the basis. Indeed, evidence is increasing for the contention that plasmids play crucial roles as accelerators of evolution in the mycosphere, serving as a horizontal gene pool and, therefore, providing competence factors to local bacteria as well as fungi. The evidence so far points at mycosphere roles for two major plasmid classes, i.e. the IncP-1 and PromA groups. Moreover, recent data indicate that bacterium-to-fungus gene transfers are detectable and have been evolutionarily important. The large gene pool present in the mycosphere, coupled with the chances for cell-to-cell contact between mycosphere dwellers allows enhanced recombination frequencies, and as such, organisms are selected locally for enhanced fitness. This article is protected by copyright. All rights reserved.
    FEMS Microbiology Ecology 06/2014; 89(3):516. · 3.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Petroleum hydrocarbon (PHC) contamination is becoming more common in boreal forest soils. However, linkages between PHC biodegradation and microbial community dynamics in the mycorrhizosphere of boreal forest soils are poorly understood. Seedlings (lodgepole pine, paper birch, lingonberry) were established in reconstructed soil systems, consisting of an organic layer (mor humus, coarse woody debris, or previously oil-contaminated mor humus) overlying mineral (Ae, Bf) horizons. Light crude oil was applied to the soil surface after 4 months; systems were destructively sampled at 1 and 16 weeks following treatment. Soil concentrations of four PHC fractions were determined using acetone–hexane extraction followed by gas chromatography – flame ionization detection analysis. Genotypic profiles of root-associated bacterial communities were generated using length heterogeneity-PCR of 16S rDNA. Most plant–soil treatments showed significant loss in the smaller fraction PHCs indicating an inherent capacity for biodegradation. Concentrations of total PHCs declined significantly only in planted (pine-woody debris and birch-humus) systems (averaging 59% and 82% loss between 1 and 16 weeks respectively), reinforcing the importance of the mycorrhizosphere for enhancing microbial catabolism. Bacterial community structure was correlated more with mycorrhizosphere type and complexity than with PHC contamination. However, results suggest that communities in PHC-contaminated and pristine soils may become distinct over time.
    Environmental Microbiology Reports 07/2010; 2(4):587 - 593. · 3.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arbuscular mycorrhizal (AM) symbioses are formed by approximately 80% of vascular plant species in all major terrestrial biomes. In consequence an understanding of their functions is critical in any study of sustainable agricultural or natural ecosystems. Here we discuss the implications of recent results and ideas on AM symbioses that are likely to be of particular significance for plants dealing with abiotic stresses such as nutrient deficiency and especially water stress. In order to ensure balanced coverage, we also include brief consideration of the ways in which AM fungi may influence soil structure, carbon deposition in soil and interactions with the soil microbial and animal populations, as well as plant-plant competition. These interlinked outcomes of AM symbioses go well beyond effects in increasing nutrient uptake that are commonly discussed and all require to be taken into consideration in future work designed to understand the complex and multifaceted responses of plants to abiotic and biotic stresses in agricultural and natural environments.
    Plant and Soil 01/2010; 326(1):3-20. · 3.24 Impact Factor

Full-text

View
0 Downloads