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Quantitative lacZ reporter gene analysis of aioBA::lacZ expression in strains HAL1, HAL1-phoR931, HAL1-ΔphoB, and HAL1-ΔphoB-C. β-galactosidase activity is presented as Miller units. Data are shown as the mean of three replicates, with the error bars represent ± 1 SD. (A) Bacteria were cultured in MMNH4 medium containing 0.1 mM Pi and 0.8 M NaCl, with or without the addition of 1 mM As(III). With the addition of As(III), the mean values of strain HAL1 and HAL1-▵phoB-C were significantly different from the ones with the absence of As(III) (*p < 0.05). (B) Bacteria were cultured in MMNH4 medium containing 1 mM Pi and 0.8 M NaCl, with or without the addition of 1 mM As(III). With the addition of As(III), the mean values of all the four strains were significantly different from the ones with the absence of As(III) (*p < 0.05).
Source publication
Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HA...
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Citations
... Links between As(III) and PhoPR have been described in other bacteria, revealing other metabolic connections between As and phosphate metabolism. In Halomonas sp., the TCS PhoBR (homolog to PhoPR) regulates the expression of the aioBA genes coding for As(III) oxidases, which promote As(III) to As(V) conversion depending on phosphate availability [36]. In Agrobacterium tumefaciens, an antimonite [Sb(III)]-detoxifying mechanism that promotes Sb(III) oxidation to antimonate [Sb(V)] has also been described, mediated by the Sb(III) oxidase AnoA, which shows cross-reactivity with As(III), and whose expression is also controlled by phosphate through PhoB (PhoP) [37]. ...
The use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated with exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally low. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the transcriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention, plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP.
... Links between As(III) and PhoPR have been described in other bacteria, revealing other metabolic connections between As and phosphate metabolism. In Halomonas sp., the TCS PhoBR (equivalent to PhoPR) regulates the expression of the aioBA genes coding for As(III) oxidases which promote As(III) to As(V) conversion depending on phosphate availability [35]. In Agrobacterium tumefaciens an antimonite [Sb(III)] detoxifying mechanism that promotes Sb(III) oxidation to antimonate [Sb(V)] has also been described, mediated by the Sb(III) oxidase AnoA, which shows cross reactivity with As(III), and whose expression is also controlled by phosphate through PhoB (PhoP) [36]. ...
Use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated to exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally lower. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the tran-scriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP.
... To date, many As(III) oxidation bacteria have been isolated, such as Halomonas sp. HAL1 (Chen et al., 2015), Agrobacterium tumefaciens GW4 (Shi et al., 2018) and Bosea sp. AS-1 (Lu et al., 2018). ...
... than that of some As(III)-oxidizers, such as Halomonas sp. HAL1 (0.31 mg/l/h, OD 600 > 1.0) (Chen et al., 2015), A. tumefaciens GW4 (3.75 mg/l/h, OD 600 > 0.5) and Bosea sp. AS-1 (6.25 mg/l/h, OD 600 > 0.5) (Lu et al., 2018). ...
Introduction:
Nitrogen and arsenic contaminants often coexist in groundwater, and microbes show the potential for simultaneous removal of nitrogen and arsenic. Here, we reported that Hydrogenophaga sp. H7 was heterotrophic nitrification and aerobic denitrification (HNAD) and arsenite [As(III)] oxidation bacterium.
Methods:
The appearance of nitrogen removal and As(III) oxidation of Hydrogenophaga sp. H7 in liquid culture medium was studied. The effect of carbon source, C/N ratio, temperature, pH values, and shaking speeds were analyzed. The impact of strains H7 treatment with FeCl3 on nitrogen and As(III) in wastewater was assessed. The key pathways that participate in simultaneous nitrogen removal and As(III) oxidation was analyzed by genome and proteomic analysis.
Results and discussion:
Strain H7 presented efficient capacities for simultaneous NH4 +-N, NO3 --N, or NO2 --N removal with As(III) oxidation during aerobic cultivation. Strikingly, the bacterial ability to remove nitrogen and oxidize As(III) has remained high across a wide range of pH values, and shaking speeds, exceeding that of the most commonly reported HNAD bacteria. Additionally, the previous HNAD strains exhibited a high denitrification efficiency, but a suboptimal concentration of nitrogen remained in the wastewater. Here, strain H7 combined with FeCl3 efficiently removed 96.14% of NH4 +-N, 99.08% of NO3 --N, and 94.68% of total nitrogen (TN), and it oxidized 100% of As(III), even at a low nitrogen concentration (35 mg/L). The residues in the wastewater still met the V of Surface Water Environmental Quality Standard of China after five continuous wastewater treatment cycles. Furthermore, genome and proteomic analyses led us to propose that the shortcut nitrification-denitrification pathway and As(III) oxidase AioBA are the key pathways that participate in simultaneous nitrogen removal and As(III) oxidation.
... This was because the TCA cycle (Fig. S4) (as indicated by M00009, M00011, and ko00020) was pivotal to the complete oxidation of carbohydrates, proteins, and lipids to carbon dioxide and water in aerobic respiration (Bulusu et al. 2011) that could supply energy for ATP synthesis. Besides, the function of ko02020 could also be responsible for phosphate assimilation (Fig. S5) during the denitrification process (Chen et al. 2015). ...
Generally, the purification performance of bioreactors could be influenced by temperature variation via shaping different microbial communities. However, the underlying mechanisms remain largely unknown. Here, the variation trends of microbial communities in three sequencing batch biofilm reactors (SBBRs) under four different temperatures (15, 20, 25, 30 °C) were compared. It was found that temperature increment led to an obvious enhancement in nutrient removal which was mainly occurred in the aerobic section. Meanwhile, distinct differences in dominant microbial communities or autotrophic nitrifiers were also observed. The performance of the SBBR reactors was closely associated with nitrifier communities since the treated wastewater was characterized by a severe lack of carbon sources (mean effluent COD ≤ 14.4 mg/L). Spearman correlation unraveled that: most of the differentiated microbes as well as the dominant potential functions were strongly associated with nutrient removal, indicating the temperature-induced difference in microbial community well explained the distinction in purification performance.
... By the top 30 genera shown in Fig. S1B, we detected several DPAOs, such as Zoogloea , unclassified f Rhodocyclaceae , and Brevundimonas (Li et al., 2016a), which were responsible for denitrifying phosphorus removal from the SBBR systems. This was consistent with the significant positive correlation between IP removal and the function of [K02483] (Fig. 4F) as this function could be responsible for phosphate assimilation during the denitrification process (Chen et al., 2015). ...
In this study, a set of novel double-layer-packed sequencing batch biofilm reactors (SBBRs) were constructed to treat secondary effluent with a low carbon-to-nitrogen ratio (C/N = 3.0). All the reactors were operated under identical conditions except dissolved oxygen (DO) in the aerobic section, which was controlled at seven different levels (0.5, 1.0, 1.5, 2.0, 2.5, 3.5 and 4.5 mg/L). It was found that the aerobic section contributed most to performance at an optimal DO of 2.0 mg/L. The change in DO accounted for the varied bacterial communities, which resulted in different performances. Both bacterial community structure and potential functions displayed close associations with performance implying nutrients were mainly removed by simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) process. Moreover, the proliferation of nonfunctional nitrifiers/denitrifiers led to the inhibition of denitrification resulting in a lower removal of total dissolved nitrogen and phosphorus.
... HAL1 [75] and so on, provides plentiful genomic information for boosting the developments of endogenous genetic parts mining, valuable pathways identification, metabolic networks modeling [73,76] etc., which offers fundamental insights into rational microbial cell factory engineering based on Halomonas sp. [35,[76][77][78]. Genome editing tools including homologous recombination and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 have been commonly used for site-specific mutagenesis in many microorganisms [79]. ...
With the rapid development of systems and synthetic biology, the non-model bacteria, Halomonas spp., have been developed recently to become a cost-competitive platform for producing a variety of products including polyesters, chemicals and proteins owing to their contamination resistance and ability of high cell density growth at alkaline pH and high salt concentration. These salt-loving microbes can partially solve the challenges of current industrial biotechnology (CIB) which requires high energy-consuming sterilization to prevent contamination as CIB is based on traditional chassis, typically, Escherichia coli, Bacillus subtilis, Pseudomonas putida and Corynebacterium glutamicum. The advantages and current status of Halomonas spp. including their molecular biology and metabolic engineering approaches as well as their applications are reviewed here. Moreover, a systematic strain engineering streamline, including product-based host development, genetic parts mining, static and dynamic optimization of modularized pathways and bioprocess-inspired cell engineering are summarized. All of these developments result in the term called next-generation industrial biotechnology (NGIB). Increasing efforts are made to develop their versatile cell factories powered by synthetic biology to demonstrate a new biomanufacturing strategy under open and continuous processes with significant cost-reduction on process complexity, energy, substrates and fresh water consumption.
... Type II (aioXSR) is adjacent to aioBA but has the opposite transcriptional direction. Type III has no aioXSR system in the bacterial genome (Cai et al., 2009b;Li et al., 2012;Li H. et al., 2013;Moinier et al., 2014;Chen F. et al., 2015;Wang et al., 2015a). ...
... Interestingly, genomic surveys have revealed that the two pst/pho systems often occur in As(III)-oxidizing bacteria (Figure 1; Li H. et al., 2013). The pst1/pho1 system is adjacent to aioBA genes (Figure 1), and the pst2/pho2 system is located elsewhere in the genome (Kang et al., 2012b;Li H. et al., 2013;Chen F. et al., 2015). The Pst/Pho system, including a Pi transport complex PstSABC and a two-component system PhoR/PhoB, is involved in Pi uptake under low Pi concentration (Qiao et al., 2019). ...
... In nature, there are another type of As(III) oxidation strains (Type III) which have no aioXSR regulation system in the genomes (Figure 1). The bacterial As(III) oxidation regulatory mechanism in Type III strains is unique compared to those of Type I and Type II (Lin et al., 2012;Chen F. et al., 2015). In the Type III As(III)-oxidizing Halomonas sp. ...
Arsenic (As) is a metalloid that occurs widely in the environment. The biological oxidation of arsenite [As(III)] to arsenate [As(V)] is considered a strategy to reduce arsenic toxicity and provide energy. In recent years, research interests in microbial As(III) oxidation have been growing, and related new achievements have been revealed. This review focuses on the highlighting of the novel regulatory mechanisms of bacterial As(III) oxidation, the physiological relevance of different arsenic sensing systems and functional relationship between microbial As(III) oxidation and those of chemotaxis, phosphate uptake, carbon metabolism and energy generation. The implication to environmental bioremediation applications of As(III)-oxidizing strains, the knowledge gaps and perspectives are also discussed.
... The phosphate (Pi) related genes such as phoB, pstS, and phoR were also identified in Bacillus sp. S3, which have been proved to be co-regulated with As (III) oxidation and could be induced by Sb(III) in previous report [26]. ...
AimsAntimony (Sb)-oxidizing bacteria play an important role in Sb biogeochemical cycle in soil, but the benefits of microbial oxidation for plants have not been well documented. The aim of this study was to explore the contribution of Sb(III)-oxidizing bacteria to alleviate the Sb toxicity in plants.Methods
The plant growth-promoting (PGP) characteristics of Sb(III)-oxidizing bacterium Bacillus sp. S3 and the effects of bacterial inoculation on Arabidopsis plants were evaluated under controlled and Sb stressed conditions.ResultsIndole acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate-deaminase (ACC-deaminase) activity were the only two PGP strategies that Bacillus sp. S3 possessed, despite the production level of IAA and the activity of ACC deaminase sharply decreased under Sb stress. Bacillus sp. S3 inoculation significantly increased the plant biomass and chlorophyll content, alleviated the peroxidation of membrane lipids, decreased the activities of the antioxidant enzymes, and reduced the transcription of Sb transporters and reactive oxygen species (ROS)-related enzymes in Arabidopsis. Noteworthily, inoculation of Bacillus sp. S3 not only significantly decreased the Sb accumulation but also reduced the percentage of Sb(III) of total Sb in Arabidopsis.Conclusions
This study indicates that the Sb(III)-oxidizing strain of Bacillus sp. S3 is a promising inoculant used for bacteria-assisted phytoremediation on Sb-contaminated sites.
... The phosphate (Pi) related genes such as phoB, pstS, and phoR were also identified in Bacillus sp. S3, which have been proved to be co-regulated with As (III) oxidation and could be induced by Sb(III) in previous report [26]. ...
Background:
Antimonite [Sb(III)]-oxidizing bacterium has great potential in the environmental bioremediation of Sb-polluted sites. Bacillus sp. S3 that was previously isolated from antimony-contaminated soil displayed high Sb(III) resistance and Sb(III) oxidation efficiency. However, the genomic information and evolutionary feature of Bacillus sp. S3 are very scarce.
Results:
Here, we identified a 5,436,472 bp chromosome with 40.30% GC content and a 241,339 bp plasmid with 36.74% GC content in the complete genome of Bacillus sp. S3. Genomic annotation showed that Bacillus sp. S3 contained a key aioB gene potentially encoding As (III)/Sb(III) oxidase, which was not shared with other Bacillus strains. Furthermore, a wide variety of genes associated with Sb(III) and other heavy metal (loid) s were also ascertained in Bacillus sp. S3, reflecting its adaptive advantage for growth in the harsh eco-environment. Based on the analysis of phylogenetic relationship and the average nucleotide identities (ANI), Bacillus sp. S3 was proved to a novel species within the Bacillus genus. The majority of mobile genetic elements (MGEs) mainly distributed on chromosomes within the Bacillus genus. Pan-genome analysis showed that the 45 genomes contained 554 core genes and many unique genes were dissected in analyzed genomes. Whole genomic alignment showed that Bacillus genus underwent frequently large-scale evolutionary events. In addition, the origin and evolution analysis of Sb(III)-resistance genes revealed the evolutionary relationships and horizontal gene transfer (HGT) events among the Bacillus genus. The assessment of functionality of heavy metal (loid) s resistance genes emphasized its indispensable role in the harsh eco-environment of Bacillus genus. Real-time quantitative PCR (RT-qPCR) analysis indicated that Sb(III)-related genes were all induced under the Sb(III) stress, while arsC gene was down-regulated.
Conclusions:
The results in this study shed light on the molecular mechanisms of Bacillus sp. S3 coping with Sb(III), extended our understanding on the evolutionary relationships between Bacillus sp. S3 and other closely related species, and further enriched the Sb(III) resistance genetic data sources.
... The phosphate (Pi) related genes, such as phoB, pstS, and phoR, were also identi ed in Bacillus sp. S3, which have been proved to be co-regulated with As(III) oxidation and could be induced by Sb(III) in previous report [44]. ...
Background: Antimonite [Sb(III)]-oxidizing bacterium has great potential in the environmental bioremediation of Sb-polluted sites. Bacillus sp. S3 that was previously isolated from antimony-contaminated soil displayed high Sb(III) resistance and Sb(III) oxidation efficiency. However, the genomic information and evolutionary feature of Bacillus sp. S3 are very scarce.
Results: Here, we identified a 5,579,638 bp chromosome with 40.30% GC content and a 241,339 bp plasmid with 36.74% GC content in the complete genome of Bacillus sp. S3. Genomic annotation showed that Bacillus sp. S3 contained a key aioB gene potentially encoding As(III)/Sb(III) oxidase, which was not shared with other Bacillus strains. Further, a series of genes associated with Sb(III) and other heavy metal(loid)s were also ascertained in Bacillus sp. S3, reflecting its adaptive advantage for growth in the harsh eco-environment. Based on the analysis of phylogenetic relationship and the average nucleotide identities (ANI), we found that Bacillus sp. S3 was a novel species within the Bacillus genus. The majority of mobile genetic elements (MGEs) mainly distributed on chromosomes within the Bacillus genus. Pan-genome analysis showed that the 45 genomes contained 554 core genes and many unique genes were dissected in analyzed genomes. Whole genomic alignment showed that Bacillus genus underwent frequently large-scale evolutionary events. In addition, the origin and evolution analysis of Sb(III)-resistance genes revealed that evolutionary relationships and horizontal gene transfer (HGT) events among the Bacillus genus. The assessment of functionality of heavy metal(loid)s resistance genes emphasized its indispensable roles in the harsh eco-environment of Bacillus genus. The real-time Quantitative PCR (RT-qPCR) results of Sb(III)-related genes indicated that the Sb(III) resistance was constantly increased under the Sb(III) stress.
Conclusions: The results in this study shed light on the molecular mechanisms of Bacillus sp. S3 coping with Sb(III), extended our understanding on the evolutionary relationship between Bacillus sp. S3 and other closely related species, and further enriched the Sb(III) resistance genetic data sources.
