Coping with arsenic stress: Adaptations of arsenite‐oxidizing bacterial membrane lipids to increasing arsenic levels

Abstract

Elevated levels of arsenic (As) in aquifers of South East Asia have caused diverse health problems affecting millions of people who drink As‐rich groundwater and consume various contaminated agriculture products. The biogeochemical cycling and mobilization/immobilization of As from its mineral‐bound phase is controlled by pH, oxic/anoxic conditions, and different microbial processes. The increased As flux generated from ongoing biogeochemical processes in the subsurface in turn affects the in situ microbial communities. This study analyzes how the indigenous arsenite‐oxidizing bacteria combat As stress by various biophysical alterations and self‐adaptation mechanisms. Fifteen arsenite‐oxidizing bacterial strains were isolated and identified using a polyphasic approach. The bacterial strains isolated from these aquifers belong predominantly to arsenite‐oxidizing bacterial groups. Of these, the membrane‐bound phospholipid fatty acids (PLFA) were characterized in seven selected bacterial isolates grown at different concentrations of As(III) in the medium. One of the significant findings of this study is how the increase in external stress can induce alteration of membrane PLFAs. The change in fatty acid saturation and alteration of their steric conformation suggests alteration of membrane fluidity due to change in As‐related stress. However, different bacterial groups can have different degrees of alteration that can affect sustainability in As‐rich aquifers of the Bengal Delta Plain.

Diversity of Betaproteobacteria revealed by novel primers suggests their role in arsenic cycling

“…Acidovorax and Dechloromonas) have previously been observed in these wells. Moreover, recent cultured studies from BDP wells (204 and 28) have reported the presence of several strains of Acidovorax, many of which are potentially new species [12]. These results suggest that potential of Gallionellaceae in trapping arsenic indirectly through the production of biogenic iron oxides.…”

“…The specificity of the newly designed primers was investigated by targeting genomic DNA extracted from 3 Betaproteobacteria strains (Hydrogenophaga atypica strain BDP10, Hydrogenophaga bisanensis strain BDP20 and Acidovorax facilis strain BDP24) isolated previously in our laboratory from groundwater of our study site [12]. Successful amplification of a ca.…”

“…On the other hand, arsenic can be microbially immobilized by arsenic-and iron-oxidizing bacteria through direct enzymatic oxidation [5] or adsorption onto biogenic iron oxides [6]. A number of environmental parameters such as biodegradable organic matter [7], iron [8], phosphate [9] and other electron acceptors [10,11] have been shown to influence microbial arsenic cycling as well as groundwater microbial community composition and functions [12]. Therefore, an in-depth understanding of the composition and distribution of indigenous microbial communities in BDP aquifers is crucial, particularly in the context of developing cost-effective long-term arsenic mitigation strategies and for supply of arsenic free potable water.…”

Prenatal arsenic exposure interferes in postnatal immunocompetence despite an absence of ongoing arsenic exposure

“…each can differ in how they are assembled in lymphocyte membrane bi-layers. Although we have not yet studied the potential impact of in utero As exposure on membrane fluidity, it is known that As-induced "stress" can cause changes in cell membrane fluidity (Ghosh et al 2018).…”

Novel arsenic hyper-resistant bacteria from an extreme environment, Crven Dol mine, Allchar, North Macedonia

“…and Stenotrophomonas sp. are well known (Ben Fekih et al, 2018;Ghosh et al, 2018). Many studies revealed that microorganisms have evolved a variety of strategies to survive toxic effects of As compounds.…”