Geoalkalibacter halelectricus SAP‐1 sp. nov. possessing extracellular electron transfer and mineral‐reducing capabilities from a haloalkaline environment

Abstract

The extracellular electron transfer (EET)-capable electroactive microorganisms (EAMs) play crucial roles in mineral cycling and interspecies electron transfer in different environments and are used as biocatalysts in microbial electrochemical technologies. Studying EAMs from extreme environments is desired to advance the electromicrobiology discipline, understanding their unique metabolic traits with implications to extreme microbiology, and develop specific bioelectrochemical applications. Here, we present a novel haloalkaliphilic bacterium named Geoalkalibacter halelectricus SAP-1, isolated from a microbial electroactive biofilm enriched from the haloalkaline lake sediments. It is a rod-shaped Gram-negative heterotrophic anaerobe that uses various carbon and energy sources and respires on soluble and insoluble terminal electron acceptors. Besides 16S-rRNA and wholegenome sequence-based phylogeny, the GGDC values of 21.7%, ANI of 78.5%, and 2.77% genomic DNA GC content difference with the closest validly named species Geoalkalibacter ferrihydriticus (DSM 17813 T ) confirmed its novelty. When grown with the solid-state electrode as the only electron acceptor, it produced 460 AE 23 μA/cm 2 bioelectrocatalytic current, thereby confirming its electroactivity. Further electrochemical analysis revealed the presence of membrane redox components with a high formal potential, putatively involved in the direct mode of EET. These are distinct from EET components reported for any known electroactive microorganisms, including well-studied Geobacter spp., Shewanella spp., and Desulfuromonas acetexigens. The capabilities of G. halelectricus SAP-1 to respire on soluble and insoluble electron acceptors including fumarate, SO 4 2À , Fe 3+ , and Mn 4+ suggests its role in cycling these elements in haloalkaline environments.

The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition

“…All experiments, including media preparation and incubations, were conducted under aseptic and anoxic conditions and at a controlled temperature of 30C, if not stated otherwise. A modified M9 medium with pH 9.5 and salinity 20 gNaCl/L and containing (per L of distilled water) 4.33 g Na 2 HPO 4 , 2.69 g NaH 2 PO 4 , 20 g NaCl, 4.3 g Na 2 CO 3 , 0.13 g KCl, 0.31 g NH 4 Cl, 12.5 ml vitamins, 12.5 ml trace elements, and suitable electron donor or acceptor according to the tested experimental conditions, was used for culturing and maintaining G. halelectricus (Yadav and Patil, 2020;Yadav et al, 2022). All chemicals and reagents were of analytical or molecular grade and obtained from Merck and Sigma-Aldrich.…”

“…To this end, the present work pertains to studying iron cycling by a recently reported haloalkaliphilic Geoalkalibacter halelectricus SAP-1 via bi-directional EET under highly saline-alkaline (pH 9.5 and salinity 20 g/L) conditions. It is an anaerobic, non-spore-forming, rod-shaped, Gramnegative, and heterotrophic EET-capable bacterium isolated from the electroactive biofilm enriched from haloalkaline lake sediments (Yadav et al, 2022). The bi-directional EET capabilities were checked with Fe 3+ -oxide and Fe 0 as the sole insoluble electron acceptor and donor under strictly anoxic conditions in biochemical experiments.…”

The outlooks and key challenges in renewable biomass feedstock utilization for value-added platform chemical via bioprocesses

“…An example of a microbe screened under harsh conditions is an uncultured electroactive microorganism (EAM) that possesses an extracellular electron transfer process for biosensing and bioelectronics applications and the valorization of liquid and gaseous wastes. It can be screened from extreme environments with high salinity, alkalinity, pressure, and temperature [ 59 ]. Compared with EAM screened from mild environments, extremophilic EAM can be used in broader microbial electrochemical technologies.…”

A Survey of theDesulfuromonadiacytochromome provides a glimpse of the unexplored diversity of multiheme cytochromes in nature

“…(28)(29)(30), Desulfuromonas acetoxidans (31)(32)(33) and Geoalkalibacter spp. (34,35). In this study, we focused on the 'cytochromome' of the Desulfuromadia class and obtained a comprehensive overview of the diversity of MHC in these organisms and conservation patterns of their number of heme-binding motifs.…”