Function of arsATorf7orf8 of Bacillus sp. CDB3 in arsenic resistance

Abstract

Bacillus sp. CDB3 isolated from an arsenic contaminated cattle dip site possesses an uncommon arsenic resistance (ars) operon bearing eight genes in the order of arsRYCDATorf7orf8. We investigated the functions of arsA, arsT, orf7 and orf8 in arsenic resistance using a plasmid-based gene knockout approach in the ars gene deficient Escherichia coli strain AW3110. The CDB3 arsA gene was shown to play a significant role in resistance, suggesting that the encoded ArsA may couple with the arsenite transporter, forming an ArsAY complex that can enhance arsenite extrusion efficiency. The disruption of either arsT or orf7 was not observed to affect arsenic resistance in the heterologous E. coli host, but their involvement in arsenic resistance can not be excluded. The orf8 gene is predicted to encode a putative dual-specificity protein phosphatase which also shares certain homology to arsenate reductases. The function loss of orf8 resulted in a remarkable decrease in resistance to arsenate, though not arsenite. To examine if this effect was due to the reduction of arsenate by orf8, the arsC gene within the 8-gene operon was disrupted. The resulting abolishment of arsenate resistance suggests that the involvement of orf8 in arsenic resistance is not via reductase activity. AbstractBacillus sp. CDB3 isolated from an arsenic contaminated cattle dip site possesses an uncommon arsenic resistance (ars) operon bearing eight genes in the order of arsRYCDATorf7orf8. We investigated the functions of arsA, arsT, orf7 and orf8 in arsenic resistance using a plasmid-based gene knockout approach in the ars gene deficientEscherichia coli strain AW3110. The CDB3 arsA gene was shown to play a significant role in resistance, suggesting that the encoded ArsA may couple with the arsenite transporter,forming an ArsAY complex that can enhance arsenite extrusion efficiency. The disruption of either arsT or orf7 was not observed to affect arsenic resistance in the heterologous E. coli host, but their involvement in arsenic resistance can not be excluded. The orf8 gene is predicted to encode a putative dual-specificity protein phosphatase which also shares certain homology to arsenate reductases. The function loss of orf8 resulted in a remarkable decrease in resistance to arsenate, though not arsenite. To examine if this effect was due to the reduction of arsenate by Orf8, the arsC gene within the 8-gene operon was disrupted. The resulting abolishment of arsenate resistance suggests that the involvement of orf8 in arsenic resistance is not via reductase activity.

Effect of phosphorus on arsenic uptake and metabolism in rice cultivars differing in phosphorus use efficiency and response

“…Significant differences in nutrient concentrations among different cultivars could be the result of differences in the removal of As from the system among these genotypes, as well as development of As tolerance and adaptations to other stressful conditions (Tu and Ma 2003, Panda et al 2010, Zheng et al 2013, Otero et al 2016.…”

Transcriptional and posttranscriptional regulation ofBacillussp. CDB3 arsenic-resistance operonars1

“…However, switch control function of the terminator was only speculated under some specific physiological circumstances with no experimental evidence obtained ( Murakawa et al, 1991 ). Since ArsY and ArsC produced from the short transcript arsRYC can provide quite significant resistance, along with the downstream gene products conferring additional tolerance ( Zheng et al, 2013 ), it is reasonable to assume that employing a switch to regulate the two alternative transcription processes would benefit the host bacteria in terms of energy consumption. Further investigation is warranted.…”

“…The orf7 gene encodes a putative HesB-like protein and orf8 a putative dual-specificity protein phosphatase (DSP). Assessed in E. coli host, orf8 exhibited a significant resistance to arsenate but it could not complement the function-loss of arsC gene, indicating its role not as an arsenate reductase ( Zheng et al, 2013 ). In addition to these new genes, ars1 also displays features consistent with a novel regulation mechanism ( Bhat et al, 2011 ).…”

Draft Genome Sequence of Bacillus sp. Strain CDB3, an Arsenic-Resistant Soil Bacterium Isolated from Cattle Dip Sites

“…Genome analysis of CDB3 confirmed the 2 ars gene clusters found in our previous study ( 2 ). The long 8-gene operon, ars1 ( arsRYCDATorf7orf8 ), possesses an interesting posttranscriptional regulation mechanism ( 5 ) and 2 novel genes, orf7 and orf8 , coding for proteins homologous to HesB and dual-specificity protein phosphatase, respectively ( 6 ). The second operon, ars2, is highly homologous to other arsRorf2YC operons which are present in the skin element ( 7 ).…”