1 research outputs found
Transcriptional Activity of Arsenic-Reducing Bacteria and Genes Regulated by Lactate and Biochar during Arsenic Transformation in Flooded Paddy Soil
Organic
substrates and biochar are important in controlling arsenic
release from sediments and soils; however, little is known about their
impact on arsenic-reducing bacteria and genes during arsenic transformation
in flooded paddy soils. In this study, microcosm experiments were
established to profile transcriptional activity of AsĀ(V)-respiring
gene (<i>arrA</i>) and arsenic resistance gene (<i>arsC</i>) as well as the associated bacteria regulated by lactate
and/or biochar in anaerobic arsenic-contaminated paddy soils. Chemical
analyses revealed that lactate as the organic substrate stimulated
microbial reduction of AsĀ(V) and FeĀ(III), which was simultaneously
promoted by lactate+biochar, due to biocharās electron shuttle
function that facilitates electron transfer from bacteria to AsĀ(V)/FeĀ(III).
Sequencing and phylogenetic analyses demonstrated that both <i>arrA</i> closely associated with <i>Geobacter</i> (>60%,
number of identical sequences/number of the total sequences) and <i>arsC</i> related to <i>Enterobacteriaceae</i> (>99%)
were selected by lactate and lactate+biochar. Compared with the lactate
microcosms, transcriptions of the bacterial 16S rRNA gene, <i>Geobacter</i> spp., and <i>Geobacter</i> <i>arrA</i> and <i>arsC</i> genes were increased in the lactate+biochar
microcosms, where transcript abundances of <i>Geobacter</i> and <i>Geobacter</i> <i>arrA</i> closely tracked
with dissolved AsĀ(V) concentrations. Our findings indicated that lactate
and biochar in flooded paddy soils can stimulate the active AsĀ(V)-respiring
bacteria <i>Geobacter</i> species for arsenic reduction
and release, which probably increases arsenic bioavailability to rice
plants