Characterization of copper-resistant bacteria and bacterial communities from copper-polluted agricultural soils of central Chile

Abstract

BackgroundCopper mining has led to Cu pollution in agricultural soils. In this report, the effects of Cu pollution on bacterial communities of agricultural soils from Valparaiso region, central Chile, were studied. Denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA genes was used for the characterization of bacterial communities from Cu-polluted and non-polluted soils. Cu-resistant bacterial strains were isolated from Cu-polluted soils and characterized.ResultsDGGE showed a similar high number of bands and banding pattern of the bacterial communities from Cu-polluted and non-polluted soils. The presence of copA genes encoding the multi-copper oxidase that confers Cu-resistance in bacteria was detected by PCR in metagenomic DNA from the three Cu-polluted soils, but not in the non-polluted soil. The number of Cu-tolerant heterotrophic cultivable bacteria was significantly higher in Cu-polluted soils than in the non-polluted soil. Ninety two Cu-resistant bacterial strains were isolated from three Cu-polluted agricultural soils. Five isolated strains showed high resistance to copper (MIC ranged from 3.1 to 4.7 mM) and also resistance to other heavy metals. 16S rRNA gene sequence analyses indicate that these isolates belong to the genera Sphingomonas, Stenotrophomonas and Arthrobacter. The Sphingomonas sp. strains O12, A32 and A55 and Stenotrophomonas sp. C21 possess plasmids containing the Cu-resistance copA genes. Arthrobacter sp. O4 possesses the copA gene, but plasmids were not detected in this strain. The amino acid sequences of CopA from Sphingomonas isolates (O12, A32 and A55), Stenotrophomonas strain (C21) and Arthrobacter strain (O4) are closely related to CopA from Sphingomonas, Stenotrophomonas and Arthrobacter strains, respectively.ConclusionsThis study suggests that bacterial communities of agricultural soils from central Chile exposed to long-term Cu-pollution have been adapted by acquiring Cu genetic determinants. Five bacterial isolates showed high copper resistance and additional resistance to other heavy metals. Detection of copA gene in plasmids of four Cu-resistant isolates indicates that mobile genetic elements are involved in the spreading of Cu genetic determinants in polluted environments.

The potential capability of bacteria and yeast strains isolated from Rungkut Industrial Sewage in Indonesia as a bioaccumulators and biosorbents of copper

“…Afterward, the three bacterial and two yeast strains were designated as C1, C2, C4, and ES 9.3, ES10.2 respectively. These bacteria were resistant to copper with the MIC ranged from 3.1 to 4.7 mM (Altimera et al 2012). The resistance of microbial isolates to copper might be due to the selective pressure of high pollutants in the industrial wastewater at Rungkut as the location of microorganism isolation.…”

Cultivable endophytic bacteria from heavy metal(loid)-tolerant plants

“…The identification of Bacillus sp. NM3E10, Brevibacterium NG no growth a The high MICs for the metals were identified according to Zhu et al (2014) for As(V) and As(III); Chen and Wang (2007), Hasnain et al (1993) and Wei et al (2009) for Pb(II); Wei et al (2009), Bhojiya andJoshi (2012) and Barzanti et al (2007) for Zn(II); Wei et al (2009), Altimira et al (2012 and Luo et al (2010) for Cu(II) (Table 2). Furthermore, B. endophyticus was originally isolated from cotton plants (Gossypium sp.)…”

Transcriptional response machineries of Bacillus subtilis conducive to plant growth promotion

“…Some of them have been subjected to study bacterial copper efflux systems. 65) In B. subtilis, when the copper ion is in excess in its cytoplasm, a specific efflux system encoded by the cop-ZA operon is induced.…”