Novel Pathway for Vanadium(V) Bio-Detoxification by Gram-Positive Lactococcus raffinolactis

Abstract

Whereas prospects of bioremediation for a vanadium­(V) [V­(V)]-contaminated environment are widely recognized, reported functional species are extremely limited, with the vast majority of Gram-negative bacteria in Proteobacteria. Herein, the effectiveness of V­(V) reduction is proved for the first time by Lactococcus raffinolactis, a Gram-positive bacterium in Firmicutes. The V­(V) removal efficiency was 86.5 ± 2.17% during 10-d operation, with an average removal rate of 4.32 ± 0.28 mg/L·d in a citrate-fed system correspondingly. V­(V) was bio-reduced to insoluble vanadium­(IV) and distributed both inside and outside the cells. Nitrite reductase encoded by gene nirS mainly catalyzed intracellular V­(V) reduction, revealing a previously unrecognized pathway. Oxidative stress induced by reactive oxygen species from dissimilatory V­(V) reduction was alleviated through strengthened superoxide dismutase and catalase activities. Extracellular polymeric substances with chemically reactive hydroxyl (−OH) and carboxyl (−COO–) groups also contributed to V­(V) binding and reduction as well as ROS scavenging. This study can improve the understanding of Gram-positive bacteria for V­(V) bio-detoxification and offer microbial resources for bioremediation of a V­(V)-polluted environment.

Selective Adsorption of Amino Acids in Crystals of Monohydrocalcite Induced by the Facultative Anaerobic Enterobacter ludwigii SYB1

“…As one of the most extensive processes on the Earth’s surface, microbially induced carbonate precipitation (MICP) plays a key role in biogeochemical cycles of carbon, as well as influences global climate and seawater chemistry ( Lowenstam and Weiner, 1989 ; Li et al, 2019 ). In recent years, more attention has been draw to this topic in view of its potential biological and engineering applications, including: (1) pretreatment of seawater Ca–Mg desalination ( Arias et al, 2017 ; Ansari et al, 2020 ), (2) rust protection of underwater steel and self-repair of building materials ( Achal et al, 2015 ; Bundur et al, 2017 ; Guo et al, 2019 ), (3) bioremediation of heavy metal polluted soils ( Lian et al, 2006 ; Achal et al, 2012 ), (4) fixation of atmospheric CO 2 ( Sharma and Bhattacharya, 2010 ), and (5) bioprecipitation of free hazardous ions ( Zhang et al, 2015 ; Lu et al, 2020 ; Shi C. et al, 2020 ; Shi J. et al, 2020 ; Zhao et al, 2020a ; Wang et al, 2021 ; Zhang et al, 2021 ). Thus, an in-depth understanding of the bioprecipitation mechanism and the formation of the special structure of biominerals is of great importance for the biomimetic design and synthesis of functional materials.…”

Vanadate Bio-Detoxification Driven by Pyrrhotite with Secondary Mineral Formation

“…It reduced heavy metals such as V(V), Se(VI), and Cr(VI) through mediating electron transfer reactions on cell surfaces. ,, Cyt c also contributed to the electron transfer between Fe(II) and cell membranes to mediate the Fe(II) oxidation process . NADH is an intracellular coenzyme that functions as an electron donor to detoxify V(V) . The appearance of NADH although with lower contents suggested that V(V) reduction took place in cells.…”

Microbial selenate detoxification linked to elemental sulfur oxidation: Independent and synergic pathways

“…Real-time quantitative PCR (qPCR) was chosen to quantify the functional genes with previously reported primers (Table S1, Supporting Information) during the S(0)driven Se(VI) bioreduction process (Throbäck et al, 2004;Bru et al, 2007;Ma et al, 2007;Meyer et al, 2007;Wen et al, 2016). Electron transfer compounds, such as cytochrome c (Cyt c) on cell surfaces and intracellular nicotinamide adenine dinucleotide (NADH), were also examined, and their measurements normalized to volatile suspended solids (VSS) according to previously documented procedure Shi et al, 2020a;Zhang et al, 2021). Intermediate metabolites were also monitored.…”