The microbial profile of rivers and lagoons three years after the impact of the world's largest mining disaster (Fundão dam, Brazil).

The collapse of the Fundão tailings dam (Minas Gerais, Brazil) was the largest environmental disaster in Brazil's history and in the world mining industry. This disaster carried approximately 55 million m3 of iron ore tailings along the rivers and the lagoons of the Doce river basin. Although multiple studies assessed the impact on microbial communities in those rivers and lagoons right after the dam rupture, it is not known whether the microbiome in those environments remains impacted years after the disaster. Assessing the microbiome is very important to evaluate impacts and evaluate the health of the environment, due to the several ecological roles played by microorganisms. Here, we evaluated the impact of the dam failure on water and sediment bacteriome and archaeome by high-throughput next-generation sequencing. Samples were taken from two rivers and six lagoons during the dry and rainy seasons approximately three years post disturbance. The results showed a large number and abundance of microbial groups associated with the presence of heavy metals and mine tailings sediments. Some of these microorganisms were also reported in large abundance in the impacted rivers shortly after the Fundão dam rupture. Among the most abundant microorganisms in the Doce River, we can highlight the bacteria hgcI clade and the archaea Nitrososphera sp. in the water, and the bacteria Anaerolineaceae sp. in the sediment. These results suggest that the microbiome of the rivers and the lagoons in the Doce river basin remains severely impacted by the Fundão tailings dam failure even three years after the disaster. The presence of those microorganisms can also help to assess the occurrence of the Fundão dam sediment in other environments.

Beach sand plastispheres are hotspots for antibiotic resistance genes and potentially pathogenic bacteria even in beaches with good water quality.

Massive amounts of microplastics are transported daily from the oceans and rivers onto beaches. The ocean plastisphere is a hotspot and a vector for antibiotic resistance genes (ARGs) and potentially pathogenic bacteria. However, very little is known about the plastisphere in beach sand. Thus, to describe whether the microplastics from beach sand represent a risk to human health, we evaluated the bacteriome and abundance of ARGs on microplastic and sand sampled at the drift line and supralittoral zones of four beaches of poor and good water quality. The bacteriome was evaluated by sequencing of 16S rRNA gene, and the ARGs and bacterial abundances were evaluated by high-throughput real-time PCR. The results revealed that the microplastic harbored a bacterial community that is more abundant and distinct from that of beach sand, as well as a greater abundance of potential human and marine pathogens, especially the microplastics deposited closer to seawater. Microplastics also harbored a greater number and abundance of ARGs. All antibiotic classes evaluated were found in the microplastic samples, but not in the beach sand ones. Additionally, 16 ARGs were found on the microplastic alone, including genes related to multidrug resistance (blaKPC, blaCTX-M, tetM, mdtE and acrB_1), genes that have the potential to rapidly and horizontally spread (blaKPC, blaCTX-M, and tetM), and the gene that confers resistance to antibiotics that are typically regarded as the ultimate line of defense against severe multi-resistant bacterial infections (blaKPC). Lastly, microplastic harbored a similar bacterial community and ARGs regardless of beach water quality. Our findings suggest that the accumulation of microplastics in beach sand worldwide may constitute a potential threat to human health, even in beaches where the water quality is deemed satisfactory. This phenomenon may facilitate the emergence and dissemination of bacteria that are resistant to multiple drugs.