Resumo

ROJAS PIRELA, Maura Lina; BOTELLO SUAREZ, Wilmar Alirio  e  BALL VARGAS, María Mercedes. Antibiotic- and heavy-metal resistance in bacteria isolated from deep subsurface in El Callao region, Venezuela. Rev. colomb. biotecnol [online]. 2014, vol.16, n.2, pp.141-149. ISSN 0123-3475.  https://doi.org/10.15446/rev.colomb.biote.v16n2.41004.

The effect of contamination with mercury (Hg) in the deep subsurface bacterial communities in the region of El Callao (Bolívar State, Venezuela) was investigated. Bacterial communities from two deep levels (-288 m and -388 m) in a gold mine were studied with the aim of describe the most relevant features of their colonizing indigenous culturable bacteria. Antibiotic and heavy metals resistance patterns, presence of the merA gene and plasmids in resistant isolates were evaluated. A high frequency of resistant indigenous bacteria to Hg and other heavy metals was found. From 76 Hg-resistant isolates tested 73.7 % were, in addition, resistant to ampicillin, 86.8% to chloramphenicol, 67.1 % for tetracycline, 56.6 % streptomycin, and 51.3 % kanamycin. Furthermore, it was found that 40.74 % (-328 mm) and 26.53 % (-388 m) of Hg-resistant bacteria were simultaneously resistant to both four and five of these antibiotics. The presence of low and high molecular weight plasmids was detected and, despite that isolated showed resistance to mercurial compounds, the presence of the gene merA was detected only in 71.05 % of strains. These results suggest that exposure to Hg could be a selective pressure on the proliferation of antibiotic-resistant bacteria and promote the preservation and propagation of these resistance genes. However, the existence of such resistances to these depths could also support the idea that antibiotic resistance in these bacteria is natural and has a more ancient origin than their exposure to Hg.

Palavras-chave : subsurface bacteria; resistance; mercury; antibiotic; plasmid.

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