Detection of Bacillus Species with Arsenic Resistance and Plant Growth Promoting Efficacy from Agricultural Soils of Nepal

Abstract

Arsenic contamination in soil and water is one of the major environmental problems in multiple countries including Nepal imposing a serious threat to the ecosystem and public health. Many soil bacteria can detoxify arsenic, including genus Bacillus. With an objective to gauge the plant growth-promoting activities of arsenic-resistant Bacillus species, 36 samples (soil, rice, cauliflower, and beans) were collected from the Terai region of Nepal. For selective isolation of Bacillus species, each sample was heated at 80°C for 15 min before the inoculation into nutrient agar (NA). Following the standard protocol, arsenic-resistant Bacillus species were screened using NA supplemented with 100 ppm sodium arsenate and sodium arsenite. Among 158 randomly selected isolates, only five isolates were able to tolerate sodium arsenite concentration up to 600 ppm. Notably, all five isolates were able to produce indole acetic acid (IAA), a plant hormone, and solubilize phosphate. Based on biochemical analysis and 16S rRNA gene sequencing, isolates N4-1, RW, KR7-12, Bhw1-4, and BW2-2 were identified as B. subtilis subsp. stercosis, B. flexus, B. licheniformis, B. cereus, and B. flexus, respectively. To the best of our knowledge, this is the first study showing the presence of arsenic-resistant B. flexus in Nepalese soil with plant growth-promoting traits. Possible utilization of these Bacillus strains could facilitate the novel bioremediation pathway to reduce the toxic effect of arsenic from the soil and water in the Terai region of Nepal.

An analysis of arsenic toxicity's origins, manifestations, and remediation

“…Arsenic-resistant bacteria (Acidithiobacillus Pseudomonas) can play a notable role in reducing As from fertile soil as well as increasing plant growth. In a recent study conducted in the Terai region of Nepal, Arsenic Bacillus species were isolated and ch found to possess some astounding properties such as high As tolerance and the ability to transform toxic form of arsenic: As(V) to less toxic form As(III) (Magar et al, 2022). As(III) in comparison to As(V) is less toxic and is considered to be able to readily be removed by forming precipitates along with the oxides and hydroxides of aluminium and iron (Burton et al, 2014).…”

“…Flowchart showing the circulation of arsenic in the ecosystem (Photos source: www.flickr.com) Acidithiobacillus, Bacillus, Deinococcus, Desulfitobacterium, can play a notable role in reducing As from fertile soil as well as increasing plant growth. In a recent study conducted in the Terai region of Nepal, Arsenic species were isolated and characterised from 36 different samples collected and were found to possess some astounding properties such as high As tolerance and the ability to transform toxic form of arsenic: As(V) to less toxic form As(III) (Magar et al, 2022). As (III) to As(V) is less toxic and is considered to be able to readily be removed by forming precipitates along with the oxides and hydroxides of aluminium and iron (Burton et Arsenate reductase, first reported in Staphylococcus aureus plasmid pl258, is responsible for Escherichia coli, five genes (arsA, arsB, arsC, arsD, arsR) were responsible for the As detoxification, compared to three genes (arsB, arsC, arsR) in (Ji & Silver, 1992).…”

Arsenic pollution and arsenic-resistant bacteria of drying Urmia Salt Lake

“…Bacillus members are usually found in arsenic-contaminated environments (Magar et al, 2022). They have recently attracted much interest due to their role in arsenic bioremediation and have been shown to carry chromosomal or plasmid-borne arsC genes, and these genes may remove arsenic from contaminated environments.…”