Carbon-dependent chromate toxicity mechanism in an environmental Arthrobacter isolate

Abstract

Arthrobacter spp. are widespread in soil systems and well-known for their Cr(VI) reduction capabilities making them attractive candidates for in situ bioremediation efforts. Cellulose drives carbon flow in soil systems; yet, most laboratory studies evaluate Arthrobacter-Cr(VI) interactions solely with nutrient-rich media or glucose. This study aims to determine how various cellulose degradation products and biostimulation substrates influence Cr(VI) toxicity, reduction, and microbial growth of an environmental Arthrobacter sp. isolate. Laboratory culture-based studies suggest there is a carbon-dependent Cr(VI) toxicity mechanism that affects subsequent Cr(VI) reduction by strain LLW01. Strain LLW01 could only grow in the presence of, and reduce, 50 μM Cr(VI) when glucose or lactate were provided. Compared to lactate, Cr(VI) was at least 30-fold and 10-fold more toxic when ethanol or butyrate was the sole carbon source, respectively. The addition of sulfate mitigated toxicity somewhat, but had no effect on the extent of Cr(VI) reduction. Cell viability studies indicated that a small fraction of cells were viable after 8 days suggesting cell growth and subsequent Cr(VI) reduction may resume. These results suggest when designing bioremediation strategies with Arthrobacter spp. such as strain LLW01, carbon sources such as glucose and lactate should be considered over ethanol and butyrate.

Three-Stage Single-Chambered Microbial Fuel Cell Biosensor Inoculated with Exiguobacterium aestuarii YC211 for Continuous Chromium (VI) Measurement

“…in addition to the four strains that existed in MFC 1. The Cr(VI)-reducing capability of these three strains has been reported [32,33,34]. In MFC2, the dominant strain remained E. aestuarii (95.12%), and other strains were represented at <1.5%.…”

Chemical-Assisted Microbially Mediated Chromium (Cr) (VI) Reduction Under the Influence of Various Electron Donors, Redox Mediators, and Other Additives: An Outlook on Enhanced Cr(VI) Removal

“…However, if the available electron donors are not suitable for any microorganism, adverse impacts on both growth and reduction process are noticeable. For example, Cr(VI) can be more toxic to microbes, when ethanol or butyrate is the sole electron donor as compared to more favorable glucose or lactate (Field et al, 2018). The cells in aerobic systems cannot gain enough energy from butyrate or ethanol for growth.…”

“…Abundant natural substances such as cellulose, hemicellulose, pectin, starch, and xylose can be the bulk sources of reducing equivalents like NADH and reduced ferredoxin during the metabolic route of glucose fermentation (Bai et al, 2018). Cellulosic waste that can be biodegraded to other carbon sources such as sugars, organic acids, and alcohols can readily stimulate bacterial growth and the subsequent reduction of Cr(VI) (Thomas et al, 2016;Field et al, 2018). This was also supported by an observation where Cr stress situation enhanced production of cellulase enzyme for the hydrolysis of cellulose (Aslam et al, 2019).…”

The Roles of Plant-Growth-Promoting Rhizobacteria (PGPR)-Based Biostimulants for Agricultural Production Systems

“…Arthrobacter species are obligate aerobes and Gram-positive chemoorganotrophs that are often found among soil bacteria [ 13 ], which is a major aerobic bacterium under the class of Actinobacteria and the family Micrococcaceae [ 14 ]. The most well-known and important in situ bioremediation of them is Cr(VI) reduction abilities [ 15 ]. The biomass of Arthrobacter protophormiae was used to detach Cd(II) from an aqueous solution [ 16 ].…”