Novel arsenic-transforming bacteria and the diversity of their arsenic-related genes and enzymes arising from arsenic-polluted freshwater sediment

Abstract

Bacteria are essential in arsenic cycling. However, few studies have addressed 16S rRNA and arsenic-related functional gene diversity in long-term arsenic-contaminated tropical sediment. Here, using culture-based, metagenomic and computational approaches, we describe the diversity of bacteria, genes and enzymes involved in AsIII and AsV transformation in freshwater sediment and in anaerobic AsIII- and AsV-enrichment cultures (ECs). The taxonomic profile reveals significant differences among the communities. Arcobacter, Dechloromonas, Sedimentibacter and Clostridium thermopalmarium were exclusively found in ECs, whereas Anaerobacillus was restricted to AsV-EC. Novel taxa that are both AsV-reducers and AsIII-oxidizers were identified: Dechloromonas, Acidovorax facilis, A. delafieldii, Aquabacterium, Shewanella, C. thermopalmarium and Macellibacteroides fermentans. Phylogenic discrepancies were revealed among the aioA, arsC and arrA genes and those of other species, indicating horizontal gene transfer. ArsC and AioA have sets of amino acids that can be used to assess their functional and structural integrity and familial subgroups. The positions required for AsV reduction are conserved, suggesting strong selective pressure for maintaining the functionality of ArsC. Altogether, these findings highlight the role of freshwater sediment bacteria in arsenic mobility, and the untapped diversity of dissimilatory arsenate-reducing and arsenate-resistant bacteria, which might contribute to arsenic toxicity in aquatic environments.

Adaptions of Lichen Microbiota Functioning Under Persistent Exposure to Arsenic Contamination

“…In general, the results obtained with metagenomic analyses indicate that a high diversity is maintained in the lichen microbiome irrespective of the presence of arsenicals in the environment. Previous metagenomics-based analyses support this findings and also showed that As-contamination in the environment is not restrictive for microbial diversity ( Suhadolnik et al, 2017 ). Complex microbial communities can support functional diversity related to As transformation and contribute to the mobility of arsenicals in sediments.…”

Use of in-field bioreactors demonstrate groundwater filtration influences planktonic bacterial community assembly, but not biofilm composition

“…Furthermore, order BD7-3 was not significant within the biofilm community at the end of the experiment. There is limited information regarding order BD7-3 [ 67 ], although they have been identified in activated sludge [ 68 , 69 ], and contaminated soils [ 70 ], including their role in hydrocarbon degradation. Overall, the bacterial communities were sensitive to both the incoming groundwater and particles greater than 0.2 μm, consistent with previous findings [ 48 , 49 ].…”

Arsenic Uptake, Toxicity, Detoxification, and Speciation in Plants: Physiological, Biochemical, and Molecular Aspects

“…Soil microbial activity can affect As adsorption/desorption, solubility, bioavailability, mobility, and soil-plant transfer by altering the chemical speciation of As in soil [ 106 , 107 ]. Microorganisms can interconvert As(III) and As(VI) and thus are capable of either solubilizing or immobilizing As in the soil-plant system [ 2 , 108 ]. These microbially induced biotransformations of As play important roles in the biogeochemical behavior of As and is key in risk assessment and remediation studies [ 109 ].…”

“…Different studies have isolated and reported various species of strict aerobic As(III)-oxidizing and facultative anaerobic As(V)-reducing bacteria from As-contaminated sites [ 108 ]. Bacterial species such as Thermus thermophiles , Thermus Aquaticus , P. arsenitoxidans , Crysiogenes arsenates , Bacillus arsenic oselenatis , Desulfutomaculum auripigmentu , Geospirillum barnesi , and Geospirillum arsenophilus are capable of synthesizing arsenite oxidase and oxidize As(III) into As(V) [ 110 , 111 ].…”

“…Microbially induced transformations of As from one from to another occurs via different processes/mechanisms such as methylation and demethylation (conversions of inorganic to organic forms and vice versa) [ 2 , 104 , 108 , 109 ]. It is reported that microorganisms can biomethylate inorganic As species to organic forms of As [ 116 ].…”