ABSTRACT
BACKGROUND The Amazon Region hosts invaluable and unique biodiversity as well as mineral resources. Consequently, large illegal and artisanal gold mining areas exist in indigenous territories. Mercury has been used in gold mining, and some has been released into the environment and atmosphere, primarily affecting indigenous people such as the Yanomami. In addition, other heavy metals have been associated with gold mining and other metal-dispersing activities in the region. OBJECTIVE Investigate the gut microbiome of two semi-isolated groups from the Amazon, focusing on metal resistance. METHODS Metagenomic data from the Yanomami and Tunapuco gut microbiome were assembled into contigs, and their putative proteins were searched against a database of metal resistance proteins. FINDINGS Proteins associated with mercury resistance were exclusive in the Yanomami, while proteins associated with silver resistance were exclusive in the Tunapuco. Both groups share 77 non-redundant metal resistance (MR) proteins, mostly associated with multi-MR and operons with potential resistance to arsenic, nickel, zinc, copper, copper/silver, and cobalt/nickel. Although both groups harbour operons related to copper resistance, only the Tunapuco group had the pco operon. CONCLUSION The Yanomami and Tunapuco gut microbiome shows that these people have been exposed directly or indirectly to distinct scenarios concerning heavy metals.
ABSTRACT
Bacteria colonizing heavily polluted tailing ponds in Southern Venezuela exhibit multiple resistances against mercurial compounds and antibiotics. The corresponding genetic determinants, mainly acquired through horizontal gene transfer, might also be transferred to pathogenic bacteria, an issue which represents an important risk to public health. In this work we show that indigenous, mercury-resistant bacterial strains isolated from a model tailing pond, located in El Callao (Bolivar State, Venezuela) and exhibiting a high concentration of soluble Hg, were able to transfer in vitro both heavy metal- and antibiotic resistance markers to potential human- and animal- pathogens (i.e. Escherichia coli and Pseudomonas aeruginosa). The frequencies of transfer ranged between 1.2x10-6 and 5.5x10-7 transconjugants per recipient. Transconjugants were also detected in the field, in model biofilms previously grown in natural sponges (Luffa cylindrica) and submersed in the ponds, at frequencies ranging from 1x10-4 to 5x10-3 transconjugants per recipient. These results are of particular relevance from the public health viewpoint, especially in light of the potential risk of horizontal flow of antibiotic resistance genes between indigenous bacteria and potential human pathogens.
Las bacterias que colonizan lagunas de cola altamente contaminadas en el sur de Venezuela, presentan resistencia a compuestos mercuriales y múltiples antibióticos. Los determinantes genéticos responsables de estas resistencias, adquiridos principalmente a través de transferencia horizontal de genes, pueden ser transferidos a bacterias patógenas. En este trabajo mostramos que cepas bacterianas indígenas, resistentes al mercurio y aisladas a partir de una laguna de cola modelo, localizada en El Callao (Estado Bolívar, Venezuela) conteniendo una alta concentración de Hg soluble, fueron capaces de transferir in vitro marcadores de resistencia a metales y antibióticos a cepas potencialmente patógenas para el hombre y animales (ej. Escherichia coli y Pseudomonas aeruginosa). Las frecuencias de transferencia variaron entre 1,2x10-6 y 5,5x10-7 transconjugantes por receptora. Los transconjugantes también fueron detectados en el campo, utilizando un modelo de biopelículas desarrollado en esponjas naturales (Luffa cylindrica) sumergidas en lagunas contaminadas, con frecuencias que variaron entre 1x10-4 y 5x10-3 transconjugantes por receptora. Estos resultados presentan una relevancia particular desde el punto de vista de salud pública, especialmente en vista del riesgo potencial de transferencia horizontal de genes de resistencia a antibióticos entre las bacterias indígenas y bacterias potencialmente patógenas para el hombre.
ABSTRACT
Mercury-resistant Aeromonas strains isolated from diarrhea were studied. Resistance occurs via mercuric ion reduction but merA and merR genes were only detected in some strains using PCR and dot hybridization. Results indicate a high variability in mer operons in Aeromonas. To our knowledge, this is the first report of mercury-resistant clinical Aeromonas strains.