Assessment of bacterial community structure in a long-term copper-polluted ex-vineyard soil

Abstract

The influence of long-term copper contamination on the diversity of bacterial communities was investigated in an ex-vineyard soil. Two sites of the same area but exhibiting different 3-fold exchangeable copper (Ex-Cu) concentrations were analysed. Culturable bacterial community structure was assessed using a variety of approaches: determination of culturable bacteria number, analyses of 132 isolates, and denaturing gradient gel lectrophoresis (DGGE) patterns of bacterial biomass grown on agar plates and of soil DNA. There was no significant difference in the number of total heterotrophs at the two sites, whereas the percentage of fast-growing bacteria growing in 1 day, was lower at the site with the higher Ex-Cu content. A high percentage of Cu-tolerant bacteria was found in both sites (63-70%) and it was relatively independent of the Cu content. Shifts in species composition of the culturable bacterial community were detected by analysing isolates from the two soils, Gram-positive bacteria prevailed in the less-polluted soil while Gram-negative bacteria in the more-polluted soil. Each sample site had a community with a different metal resistance pattern. Our study seems to indicate that in this soil ecosystem, copper influenced the culturable bacterial communities, affecting the structural diversity and altering some of the metal resistance of the microorganisms. The Sorensen similarity index calculated on DGGE profiles of 16S rDNA of total and culturable bacterial communities indicated a different species composition at the two sites, although both sites had the same biodiversity degree and different dominance.

Isolation and characterization of heavy metals resistant Rhizobium isolates from different governorates in Egypt

“…Furthermore, the tested isolates exhibited more sensitive against Cu than the other heavy metals Pb and Zn. These observations are in agreement with previous studies showed that the high concentrations of Cu are toxic to soil microorganisms by affecting their structural diversity and metal tolerance (Cervantes and GutierrezCorona, 1994;Dell'Amico et al, 2008). The appearance of resistance levels in isolates as RL 3 and R6 against some heavy metals as Pb is due to these isolates contain the pb-resistant gene pbrA ( Figure 1A).…”

Selection for Cu-Tolerant Bacterial Communities with Altered Composition, but Unaltered Richness, via Long-Term Cu Exposure

“…Members of a number of relatively high-abundance classes of the Actinobacteria and Proteobacteria were negatively influenced by increasing Cu levels, as were those of the less-abundant phyla and candidate phyla Bacteroidetes, Verrucomicrobia, Chloroflexi, WS3, and Planctomycetes. Several previous studies relying on cultivation-independent community fingerprinting methods such as automated ribosomal intergenic spacer analysis (ARISA), terminal restriction fragment length polymorphism (T-RFLP) analysis, and denaturing gradient gel electrophoresis (DGGE) have reported changes in community composition caused by short-term or long-term Cu pollution (7,11,12,26,43). However, only one previous study reported significant impacts of Cu on the abundance of specific taxonomic groups (46).…”

“…The use of rRNA gene-based fingerprinting techniques has revealed that Cu can influence the structure of bacterial communities in soil (7,12,26,43). In those studies, however, Cu caused only small differences in community fingerprints.…”

Seasonal and Interannual Fluctuation of the Microbial Soil Community in a Maize Field under Long-Term Conservation Agriculture Management

“…Aslam et al [59] found 27 and 38 genera in a subtropical soil managed under conventional and no-tillage practices, respectively. However, in a Mediterranean soil contaminated with copper, with organic carbon and nitrogen contents similar to the soil analyzed in our study, 16 genera and 32 species were recovered using culture-dependent methods [60], and another study described eight phylogenetic groups in an extremely low-moisture silt soil [61]. These differences could be due to the intrinsic properties of the different soils considered, and to the environmental conditions at each location, especially the climate.…”