UNRAVEL THE WHOLE-GENOME, TRANSCRIPTOME AND ECO-PHYSIOLOGICAL INSIGHTS ON ARSENIC-RESISTANT AND REDOX-ACTIVE GROUNDWATER ISOLATE LYSINIBACILLUS SP. B2A1 INTERACTING WITH ARSENIC-SOURCE MINERAL

The microbes-arsenic source mineral interactions are considered as the primary source of biogenic soluble arsenic in the sub-surface systems. Our knowledge about bacterial eco-physiology and interactions with the As-source mineral is obscure. Although multiple arsenic transport, redox and resistance genes have been elucidated, their genome-wide abundance and organization are still poorly understood due to a prerequisite of a well-resolved genome-mapping and characterization. Additionally, unique bacterial physiology and transcriptome profiles under the arsenic species-specific stress and mineral-interacting state have not been completely lucid.

Recently, we have underpinned on bacteria-mineral molecular interactions and their As-redox activity with genetic markers. The present study highlights the whole-genome mapping of a facultative anaerobe Lysinibacillus sp. B2A1 isolated from the Beimen groundwater in southwestern Taiwan wherein we have extensively studied the groundwater geochemistry and recently identified the arsenic source mineral as As-pyrite. Furthermore, we studied the transcriptome of this arsenic hyper-resistant strain under relevant arsenic exposures. We have mapped the arsenic resistance and metabolic genes present on two distinct syntenies both containing a unique copy of arsenite S-adenosylmethyltransferase (arsM) which could convert highly toxic inorganic As(III) to less toxic organic form. Our RNA-Seq studies underpinned the transcriptome profiles related to the As(III) & As(V) exposure and arsenopyrite(FeAsS) interaction condition by identifying the specifically up-regulated As-associated genes. Adapting to niche, during the FeAsS interaction, Lysinibacillus sp. B2A1 was found to be up-regulated in sulfide assimilation and siderophore biosynthesis allowing mineral-derived iron and sulfur utilization for growth. We strongly believe that spore-forming physiology supports this strain to thrive in the groundwater with high arsenic concentrations. Furthermore, Synchrotron-FTIR studies also underpinned the arsenite lethality by affecting the α-helices of protein structures. Ultimately, we strongly propose that biogenic arsenic mobilization in groundwater could be associated with such As-resistant redox-active firmicutes having the capacity to weather arsenic-source mineral.