New data on the diversity of tolerance genes to major historical and contemporary metal pollutants arsenic, mercury and copper among Enterococcus spp. from anthropogenic sources and recovered from the last 120 years was published in the Journal Science of the Total Environment by UCIBIO researchers of the BacT-Drugs Lab at UCIBIO-University of Porto. This research work was done in collaboration with researchers from LAQV-REQUIMTE and Hospital Ramón y Cajal (Madrid, Spain).
Enterococcus have been considered indicators of fecal pollution and antibiotic resistance for years, but their metal gene content was largely underexplored precluding to understand their role as metal pollution bioindicators. In this unique and deep study on Enterococcus spp. metal tolerance, 381 field isolates from diverse backgrounds and 3547 enterococcal genomes available in genomic databases representing a time span during 1900-2019 were used. “By phenotypic and comparative genomic approaches, this study unveiled that Enterococcus spp. carry diverse functional Hg, As and Cu tolerant proteins showing variable levels of evolution and being shared with other 49 bacterial taxa of Gram-positive and Gram-negative bacteria living in the same ecosystems”, explain the authors of the article. Metal tolerance genes were identified in the older strains studied (1900´s) reflecting an old pollution. However, especially since the 1960’s, when antibiotics start to be massively used for infections treatment and in the agriculture, antibiotic resistance genes were increasingly identified in metal tolerant Enterococcus spp., widening the panoply of stresses favoring the selection of such strains.
“Although further studies are still needed, this work positions E. faecalis and E. faecium as good candidates to be used as model organisms in future projects aiming at the identification and quantification of bioindicators of metal polluted environments by anthropogenic activities”, ends Carla Novais.
Science of the Total Environment, 30 April 2021
Andreia Rebelo, Joana Mourão, Ana R. Freitas, Bárbara Duarte, Eduarda Silveira, Antonio Sanchez-Valenzuela, Agostinho Almeida, Fernando Baquero, Teresa M. Coque, Luísa Peixe, Patrícia Antunes, Carla Novais.