Cd-resistant Bacteria Research Articles

Comprehensive Analysis of Microbiomes and Metabolomics Reveals the Mechanism of Adaptation to Cadmium Stress in Rhizosphere Soil of Rhododendron decorum subsp. Diaprepes

The toxicity of cadmium (Cd) not only affects the growth and development of plants but also has an impact on human health. In this study, high-throughput sequencing and LC-MS were conducted to analyze the effect of CdCl2 treatment on the microbial community and soil metabolomics of rhizosphere soil in Rhododendron decorum subsp. diaprepes. The results showed that CdCl2 treatment reduced the quality of the rhizosphere soil by significantly decreasing the soil organic carbon (SOC) content, urease, and invertase activities, increasing the percentage of the exchangeable Cd fraction. CdCl2 treatment did not significantly change the Chao1 and Shannon indices of bacterial and fungal communities in the rhizosphere soil. R. decorum was more likely to recruit Cd-resistant bacteria (e.g., Proteobacteria, Chloroflexi) and increase the abundance of Cd-resistant fungi (e.g., Basidiomycota, Rozellomycota). Moreover, CdCl2 treatment decreased the content of secondary metabolites associated with plants’ resistance to Cd. Rhizosphere soil urease, invertase activities, alkaline phosphatase (ALP), SOC, total potassium (TK), Cd, and nitrate nitrogen (NN) were the main drivers of the composition of rhizosphere bacterial and fungal communities. CdCl2 treatment weakened the relationships among bacterial/fungi, differential metabolites, and physicochemical properties in rhizosphere soil.

Optimization of bacterial consortia for enhanced cadmium removal from contaminated environments: a case study near the Cochin Backwater System, Kerala, India

Heavy metal contamination is a major environmental and ecological threat worldwide, posing significant challenges. Excessive accumulation of heavy metal like cadmium in the environment poses significant risks to both the environment and human health, particularly in regions with industrial activities and insufficient waste management practices. In this study, we focused on optimizing bacterial consortia composed of Aeromonas hydrophila and Psychrobacter nivimaris for efficient removal of cadmium from contaminated environments, with specific emphasis on areas near the Cochin backwater system in Kerala, India. Sampling conducted at Sreebhoothapuram and Eloor Ferry Kadavu stations near Fertilizers and Chemicals Travancore (FACT) revealed these sites as having significant cadmium accumulation. Bacterial strains isolated from these stations exhibited notable resistance to cadmium, with levels reaching up to 40 mg/l and these strains maintained similar growth conditions, making them good candidates for constructing a bacterial consortium. The Cd-resistant bacteria were characterized and identified as Aeromonas hydrophila and Psychrobacter nivimaris. Through a synergetic approach, a consortium comprising two bacterial strains from different combinations obtained from these stations demonstrated promising cadmium resistance, reaching up to 60 mg/l. Mixture design optimization facilitated the determination of an optimal ratio (Aeromonas hydrophila: Psychrobacter nivimaris) = (0.329:0.671) for maximum removal efficiency. The scanning electron microscopy (SEM) analysis of both individuals and the consortium revealed morphological changes, such as modifications in the cell wall, shape, and size of the bacteria, that occur during the absorption of Cd (II). The efficiency of the optimized consortium was validated through Atomic Absorption Spectroscopy, achieving an impressive removal percentage of 96.5% for a real wastewater sample with a Relative Standard Deviation (RSD) less than 10%. This study underscores the potential of tailored bacterial consortia as effective bioremediation agents for Cd-contaminated environments, particularly in regions with elevated cadmium levels like the Cochin backwater system in Kerala.

The role and mechanism of Bacillus megaterium strain A14 in inhibiting the cadmium uptake by peanut plants in acidic red soil.

This study explores the potential of cadmium (Cd)-resistant bacteria, specifically Bacillus megaterium A14, to decrease Cd accumulation in peanuts, a crop susceptible to metal uptake from contaminated soils, by understanding the bacterium's impact on plant Cd absorption mechanisms. Through pot experiments, we observed that A14 inoculation significantly increased peanut biomass under Cd stress conditions, primarily by immobilizing the metal and reducing its bioavailability. The bacterium effectively changed the distribution of Cd, with a notable 46.53% reduction in the exchangeable fraction, which in turn limited the expression of genes related to Cd transport in peanuts. Additionally, A14 enhanced the plant's antioxidant response, improving its tolerance to stress. Microbial analysis through 16S sequencing demonstrated that A14 inoculation altered the peanut rhizosphere, particularly by increasing populations of Firmicutes and Proteobacteria, which play crucial roles in soil remediation from heavy metals. The A14 strain effectively counters Cd toxicity in peanuts, promoting growth through soil Cd sequestration, root barrier biofilm formation, antioxidant system enhancement, suppression of Cd transport genes, and facilitation of Cd-remediating microorganisms.

Cadmium-resistant bacterium Ralstonia sp. YDR alleviated Cd toxicity in rice seedlings by enhancing antioxidant defense and inhibiting Cd2+ influx and H+ efflux

Cadmium (Cd) accumulation in rice (Oryza sativa L.) and its potential risks for human health have attracted great attention. Several Cd-resistant bacteria can promote plant growth and alleviate Cd toxicity to rice, but how they regulate Cd2+ flux in rice roots is still poorly understood. Here, a new Cd-resistant endophytic bacterium Ralstonia sp. YDR was isolated and used to evaluate its role in reducing rice Cd accumulation. Ralstonia sp. YDR tolerated 80 mg L−1 Cd and removed amounts of Cd via bio-adsorption and bio-absorption. Ralstonia sp. YDR also harbored good alkalizing ability and exhibited typical plant growth-promoting characteristics. Hydroponic experiment showed that inoculation with Ralstonia sp. YDR not only significantly promoted rice growth but also decreased rice Cd by 14.4–41.3%. Further analyses verified the involvement of Ralstonia sp. YDR in increasing the activities of catalase, glutathione, peroxidase, and superoxide dismutase by 27.7–77.3%, 1.7–57.6%, 57.4–100.8%, and 5.31–60.2%, and decreasing the activity of malonaldehyde by up to 56% in rice seedlings as compared with control. Moreover, a significant reduction in Cd2+ influx and H+ efflux occurred in rice roots after inoculating with Ralstonia sp. YDR. Collectively, bacterial adsorption and absorption of Cd, bacteria-aided antioxidation, and bacterial regulation of Cd2+ and H+ fluxes all contributed to a low Cd accumulation in rice. Our study provides new clues to better understand microbial mechanisms underlying the low Cd accumulation in rice plants, which helps to enhance the production of low Cd rice in agricultural practice.

Cadmium biosorption and mechanism investigation using two cadmium-tolerant microorganisms isolated from rhizosphere soil of rice

Microbial remediation of cadmium-contaminated soil offers advantages like environmental friendliness, cost-effectiveness, and simple operation. However, the efficacy of this remediation process relies on obtaining dominant strains and a comprehensive understanding of their Cd adsorption mechanisms. This study identified two Cd-resistant bacteria, Burkholderia sp. 1–22 and Bacillus sp. 6–6, with significant growth-promoting effects from rice rhizosphere soil. The strains showed remarkable Cd resistance up to ∼200 mg/L and alleviated Cd toxicity by regulating pH and facilitating bacterial adsorption of Cd. FTIR analysis showed crucial surface functional groups, like carboxyl and amino groups, on bacteria played significant roles in Cd adsorption. The strains could induce CdCO3 formation via a microbially induced calcium precipitation (MICP) mechanism, confirmed by SEM-EDS, X-ray analysis, and elemental mapping. Pot experiments showed these strains significantly increased organic matter and enzyme activity (e.g., urease, sucrase, peroxidase) in the rhizosphere soil versus the control group. These changes are crucial for restricting Cd mobility. Furthermore, strains 6–6 and 1–22 significantly enhance plant root detoxification of Cd, alleviating toxicity. Notably, increased pH likely plays a vital role in enhancing Cd precipitation and adsorption by strains, converting free Cd into non-bioavailable forms.

Stenotrophomonas strain CD2 reduces cadmium accumulation in Brassica rapa L.

IntroductionCadmium (Cd) is a highly toxic heavy metal which contaminates agricultural soils and is easily absorbed by plants. Brassica rapa L. is one of the most popular vegetables in China and is known to accumulate Cd in its roots and aerial tissues.MethodsA highly Cd-resistant bacterium (‘CD2’) was isolated and identified. Its ability to immobilize Cd(II) in medium was studied. Strain CD2 were added into Cd-polluted soil to ameliorate Cd accumulation in B. rapa. The underlying mechanisms of ‘CD2’ to reduce Cd accumulation in B. rapa. were analyzed by transcriptomics.Results and discussionStrain CD2 was classified as belonging to the genus Stenotrophomonas. Strain CD2 was found to be able to remove 0.1 mmol/L Cd(II) after 36 h by intracellular sequestration and by producing biofilm, exopolysaccharide, and H2S. When applied to Cd-contaminated soil, ‘CD2’ significantly increased the content of nonbioavailable Cd by 212.70%. Furthermore, ‘CD2’-inoculated B. rapa exhibited a 51.16% decrease in the Cd content of roots and a 55.56% decrease in the Cd content of aerial tissues. Transcriptome analysis identified 424 differentially expressed genes (DEGs) in the roots and 501 DEGs in the aerial tissues of uninoculated Cd-exposed plants. By comparison, 1107 DEGs were identified in the roots and 1721 DEGs were identified in the aerial tissues of ‘CD2’-inoculated Cd-exposed plants. In both treatment groups, genes related to vacuolar sequestration were upregulated, resulting in inhibited Cd transport. In addition, both catalase and glutathione transferase were induced in uninoculated plants, while the oxidative stress-related genes CPK and RBOH belonged to ‘plant-pathogen interactions’ were upregulated in ‘CD2’-inoculated plants. Moreover, inoculation with ‘CD2’ resulted in the enrichment of phenylpropane metabolism; cutin, suberine, and wax biosynthesis; and the AP2, Dof, WOX, Trihelix, B3, EIL, and M-type_MADS transcription factors; as well as the downregulation of zinc transporters and blue copper proteins. All of these changes likely contributed to the reduced Cd accumulation in ‘CD2’-inoculated B. rapa. The results of this study suggest that Stenotrophomonas sp. CD2 may prove to be a useful inoculant to prevent Cd accumulation in B. rapa.

Screening of Cadmium-Resistant Microbes to Improve the Tolerance of Sorghum bicolor (L.) Moench Against Cadmium

To improve the cadmium (Cd) resistance and the remediation ability of Sorghum bicolor (L.) Moench, fourteen Cd-resistant bacteria were screened from cadmium-contaminated soil, together with two strains preserved in the laboratory. It was found that 3 strains (ZR451, ZR452, and ZJSH1) significantly promoted the growth of Cd-stressed S. bicolor in hydroponics and mitigated Cd toxicity to plants, and SR8, ZRK1, and ZR211 promoted sorghum growth lightly. Further studies indicated that strains SR8, ZR211, and ZJSH1 were Cd-resistant and acid-resistant strains. Strains ZR211and ZR121 significantly produced two hormones (SA and GA), ZJSH1 significantly produced IAA and SA, and strains SR8, ZR451 and ZR452 produced one hormone. Strains SR8, ZR451, ZR452, and ZJSH1 produced siderophores. In addition, strain ZJSH1fixed nitrogen and produced ACC deaminase, while ZR451 and ZJSH1 solubilized phosphorus Correlation analysis showed that the Cd resistance of the strains was significantly and positively correlated with their IAA and GA production. The screening of the three cadmium resistant strains ZJSH1 (Sphingomonas paucimobilis), ZR451 (Bacillus cereus) and ZR452 (Bacillus cereus) provided bacterial resources for the efficient remediation of Cd-contaminated soils by bacterial - S. bicolor combination.

Enhanced Cd activation by Coprinus comatus endophyte Bacillus thuringiensis and the molecular mechanism

Fungal endophytes not only tolerate and activate Cd in soil but also promote host growth, yet its Cd activation capacity and mechanism remain unrevealed. Our previous study isolated a robust endophyte Bacillus thuringiensis L1 from Coprinus comatus fruiting body with splendid Cd resistance and activation abilities under laboratory conditions. In this study, those peculiarities were investigated in the actual soil environment. L1 could significantly increase the soil bioavailable Cd content and effectively compensate for alkali-hydro nitrogen losses and microbial inhibition caused by Cd. Furthermore, L1 inoculation improved the soil's bacterial community structure and increased the relative abundance of Cd-resistant bacteria, such as Actinobacteria, Chloroflexi, Acidobacter, and Firmicutes, closely associated with the soil enzyme activity shift. The genome sequencing analysis revealed the presence of genes related to growth promotion, resistance to Cd stress, and Cd activation, which were significantly up-regulated under Cd stress. Notably, L1 mainly activates Cd in soil by secreting citric acid, succinic acid, siderophore, and soluble phosphorus substances to chelate with Cd or dissolve bounded Cd. Meanwhile, the metal-responsive transcription repressor (CadC) and the Cd-translocating protein P-type ATPase (CadA) can help the L1 to suppress the toxicity of Cd. Those results help to unveil the possible mechanism of L1 in Cd-contaminated soil remediation, providing a clear strategy for Cd bio-extraction from soil.

Biosorption of Cd by an indigenous Cd-resistant bacterium isolated from soil contaminated with Cd

Biosorption of Cd by an indigenous Cd-resistant bacterium isolated from soil contaminated with Cd

Shifts in bacterial diversity, interactions and microbial elemental cycling genes under cadmium contamination in paddy soil: Implications for altered ecological function

Cadmium (Cd) contamination has become an emergent environmental issue in agroecosystems worldwide. The impacts of Cd on microbial community and their ecological functional remain unrevealed. This study investigated the response of bacterial community and microbial ecological functions to Cd contamination in paddy soil of East China. Bacterial diversity and community structure significantly changed under Cd contamination. Proteobacteria and Acidobacteria were identified as biomarkers to indicate Cd contamination. The overall elemental cycling genes abundance was negatively correlated to soil Cd content. Acetyl-CoA synthesis, organic N mineralization, N fixation and nitrous reduction genes were especially sensitive to elevated Cd stress, resulting in loss of microbial derived soil C and N pool and increase in N2O emission potential. Bacteria interactions were sparser yet more competitive under Cd contamination. Cd resistant genera Massilia, Burkholderia, Streptomyces and Methylobacterium were essential to bacterial interactions via building connections with non-resistant species. Microbial Cd immobilization potential by urea hydrolysis was enhanced under Cd contamination, with Massilia being the keystone functional taxa involved in this process. Our study elucidated the ecological risks of altered microbial functions under Cd contamination in paddy soil, as well as the significance of Cd resistant bacteria to microbial community and ecological functionality.

Effect of cadmium stress on the bacterial community in the rhizosphere of mulberry (Morus alba L.).

Mulberry has a good tolerance to cadmium (Cd) and is considered a candidate plant for phytoremediation. The rhizosphere microbial community plays an important role in phytoremediation. Nevertheless, little information on the rhizosphere microbial community mechanisms in mulberry during the phytoremediation of Cd-contaminated soil is available. In this study, the remediation efficiency of mulberry in pots subjected to three simulated Cd pollution levels and their rhizosphere bacterial communities during the remediation process were analyzed. "Yuesang 11" was used as the test mulberry variety, and three simulated Cd pollution levels were set by adding three concentrations of Cd (Cd5, 5 mg kg-1; Cd3, 3 mg kg-1; Cd2, 2 mg kg-1). The results showed that the elimination rates of Cd in the rhizosphere soil were 81.7%, 85.3%, and 57.9% under the stress of the Cd2, Cd3, and Cd5 conditions, respectively. Meanwhile, 3,082,583 high-quality sequence reads and 976 operational taxonomic units were successfully obtained from the mulberry rhizosphere soil by high-throughput absolute quantification sequencing and further assigned to 11 bacterial phyla and 26 families. Of these, decreased abundances of 19 bacteria at the family level and increased abundances of seven bacteria under Cd stress were revealed by comparative analysis. Based on the alpha diversity indices (Chaol, Shannon and Simpson) and principal component analysis, the rhizosphere bacterial diversity of the Cd5 condition was significantly decreased, but that of the Cd2 and Cd3 conditions was not different from that of soil without Cd (CK). Likewise, redundancy analysis showed that the abundances of Acidobacteria Gp2, Acidobacteria Gp13, and Sphingobacteria were significantly positively associated with the elimination rates of Cd. This study suggested that the mulberry rhizosphere contains a relatively stable bacterial community consisting of diverse Cd-resistant bacteria, providing a scientific basis for remediating heavy-metal polluted soils using mulberry.

ISOLASI DAN KARAKTERISASI BAKTERI RESISTEN CD DARI KAWASAN PENAMBANGAN TIMAH

Bangka Belitung Province is one of the largest tin producing area in Indonesia. One of the mining sites located on the Sampur Beach, Kebintik Village, Central Bangka Regency. Tin mining activities can increase heavy metals harmful to the environment, such as Cadmium (Cd). This research aimed to measure Cd levels in sediment and seawater, to isolate and identify Cd resistant bacteria from sediment. Cd metal was analyzed using Atomic Absorption Spectrophotometer (AAS). The average Cd metal level in seawater is 0,0080 ppm and in sediment is 0,0086 ppm. Bacteria were isolated using Zobell 2216E media with the spread plate method. The isolated Bacteria were tested for resistance to Cd with concentration of 20 ppm, 50 ppm, 80 ppm, 100 ppm, and 120 ppm. From 16 bacterial isolates that have been obtained, 7 isolates were resistant to all concentrations, 1 isolate was resistant to 50 ppm, 1 isolate was only resistant to 20 ppm, and 7 isolates were not resistant. Based on the results of the analyzed, the seven isolates of resistant bacteria have similarity with Halomonas sp. (R2 and R3), Neisseria sp. (R4), Cupriviadus sp. (R5), Bacillus sp. (R11), Alcaligenes sp. (R12), and Roseobacter sp. (R13).

Characterization of a cadmium-resistant functional bacteria (Burkholderia sp. SRB-1) and mechanism analysis at physiochemical and genetic level.

In this study, the capacity of cadmium (Cd)-resistant plant growth-promoting bacteria (PGPB) Burkholderia sp. SRB-1 (SRB-1) and its mechanisms were explored through morphological characterizations, biochemical response, plant growth-promoting traits, and functional gene expression patterns. The results showed that SRB-1 was an excellent Cd-resistant bacteria (MIC was 420mg L-1), and its maximum Cd removal rate reached 72.25%. Biosorption was the main removal method of Cd for SRB-1, preventing intracellular Cd accumulation and maintaining cellular metabolism. Various functional groups on the cell wall were involved in Cd binding, which deposited as CdS and CdCO3 on the cell surface according to XPS analysis and might be critical for reducing Cd physiochemical toxicity. Furthermore, metals exporting (zntA, czcA, czcB, czcC), detoxification (dsbA, cysM), and antioxidation (katE, katG, SOD1) related genes were annotated in the SRB-1 genome. The results of Cd distribution and antioxidative enzyme activity in SRB-1 also illustrated that Cd2+ efflux and antioxidative response were the main intracellular Cd-resistant mechanisms. These conclusions were further verified by qRT-PCR analysis. Overall, the strategies of extracellular biosorption, cation efflux, and intracellular detoxification jointly build the Cd-resistant system, which invested Burkholderia sp. SRB-1 with potential for bioremediation in heavily Cd-contaminated environmental sites.

Cadmium (Cd) Resistant Bacteria

Anthropogenic sources of toxic cadmium (Cd) have significantly risen during the past few decades. Currently several physical and chemical techniques are used in the Cd decontamination methods. But these techniques are expensive and even causes secondary pollution. Therefore, it is crucial to investigate eco-friendly, effective, and affordable strategies that can eliminate the Cd threat from the environment. The biological methods are far suitable than other methods in recent years. A bunch of bacteria (Bacillus cereus, Aeromonas caviae) are able to tolerate this heavy metal. Cadmium tolarent bacteria (CdtB) are numerous and unrelated phylogenetically. They contain cadA and cadB gene systems which is responsible for their Cd-resistant capacity. The objective of this review is to demonstrate the importance, culturable diversity, metabolic purification mechanisms, and contemporary applications of CdtB bacteria in soil bioremediation processes.

Effects of Pb-, Cd-resistant bacterium Pantoea sp. on growth, heavy metal uptake and bacterial communities in oligotrophic growth substrates of Lolium multiflorum Lam.

Phosphate-solubilizing bacteria (PSB) can accelerate phytoremediation, especially in those fertilized soils. However, PSB function in oligotrophic growth substrates remains poorly studied. In this study, we isolated lead (Pb)- and cadmium (Cd)-resistant PSB from contaminated sandy soil at an abandoned lubricant plant. The isolated Pantoea sp. PP4 (PP4 hereafter) can produce organic acid and IAA (Indole-3-acetic acid) and dissolve up to 238mg/L of inorganic phosphate Ca2(PO4)3, exhibiting biosorption capability for Pb and bioprecipitation for Pb and Cd. In the sand pot experiment, inoculation of PP4 increased the accumulation of Pb and Cd in Lolium multiflorum Lam. by 28.9% and 95.5%, respectively, and increased the available phosphorous in oligotrophic river sand by 30.8% (P < 0.05). Meanwhile, the growth of Lolium multiflorum Lam. was also stimulated, resulting in 89.2%, 57.1%, 184.6%, and 28.5% increase in fresh weight, dry weight, root length, and shoot length, respectively. NMDS analysis showed that the bacterial communities in river sand were more clustered after inoculation with PP4. These results indicated that the application of Pantoea sp. PP4 can facilitate the phytoremediation of Pb and Cd in oligotrophic growth substrates, forming a convergent bacterial community. Our findings highlighted the importance of identifying ideal PSB to improve phytoremediation efficiency in oligotrophic environments.

两种镉积累型小麦根际微生物群落结构及功能多样性

PDF HTML阅读 XML下载 导出引用 引用提醒 两种镉积累型小麦根际微生物群落结构及功能多样性 DOI: 10.5846/stxb202104170997 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 安徽省自然科学基金项目（2008085MD120）；北京市农林科学院创新能力建设专项（KJCX20210439） Rhizosphere microbial community structure and functional diversity in two Cd-accumulating wheat cultivars Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究不同积累型小麦品种对根际微生物群落结构及功能多样性的影响，以镉低积累型小麦济麦22和镉高积累型小麦冀5265为研究材料，采用分离培养法和Biolog-Eco微平板法分析根际细菌数量、可培养优势群落结构以及微生物群落功能多样性。结果表明：污染土壤济麦22根际总细菌数量和抗Cd细菌数量均显著高于冀5265，而非污染土壤中两品种间无差异。污染土济麦22根际发现较多产脲酶和高镉抗性菌株（200 mg/L）。污染土济麦22根际优势菌多为Arthrobacter sp.和Bacillus sp.，冀5265根际优势菌主要为Streptomyces sp.；非污染土济麦22与冀5265根际优势菌群相似，均以Bacillus sp.为主。Biolog试验结果表明，两个小麦品种根际微生物群落对碳源的利用能力存在差异，济麦22根际微生物AWCD值、Mc Intosh指数、Shannon-Wiener指数、Simpson指数在污染土和无污染土中均显著高于冀5265。因此，污染土壤中不同积累型小麦品种根际微生物群落结构及功能多样性均存在差异，该研究结果对于揭示高低积累型小麦根际微生物机制提供了重要参考依据。 Abstract:In order to investigate the effects of the different accumulating wheat cultivars on rhizosphere microorganism community structure and functional diversity, low Cd-accumulating wheat Jimai 22 (JM22) and high Cd-accumulating wheat Ji 5265 (JI5265) were planted in pots filled with contaminated soil and non-contaminated soil and collected at the tillering stage of wheat. In total, four experimental treatments were set up, containing JM22 grown in contaminated soil (CJM), JI5265 grown in contaminated soil (CJI), JM22 grown in non-contaminated soil (NJM) and JI5265 grown in non-contaminated soil (NJI). The number of rhizosphere bacteria, community structure of culturable dominant bacteria and microbial community functional diversity were analyzed by traditional dilution plate culture method and Biolog-Eco microplate method. The results from the standard spread-plate method showed that the population of total bacteria and Cd-resistant bacteria in rhizosphere soil of JM22 were significantly higher than those of JI5265 in contaminated soil, but there was no significant difference in the population of total bacteria and Cd-resistant bacteria of rhizosphere soil between the two different accumulating wheat cultivars in non-contaminated soil. Studies on the biological characteristics of the isolated strains showed that more urease producing bacterial strains and Cd-resistant bacterial strains (200 mg/L) in rhizosphere soil of JM22 grown in contaminated soil were isolated than those of JI5265 grown in contaminated soil. Based on 16S rRNA gene sequences analysis, bacterial community composition was different in rhizosphere soil between cultivar JM22 and cultivar JI5265 in contaminated soil. Most of the dominant rhizosphere bacteria in JM22 were identified as Arthrobacter sp. and Bacillus sp., while Streptomyces sp. predominated in rhizosphere soil of wheat JI5265 in contaminated soil. The dominant rhizosphere bacteria in JM22 and JI5265 grown in non-contaminated soil were similar, and they were mainly Bacillus sp. The Biolog-Eco plate experiment results showed that there were differences in the utilization of carbon sources between the two wheat cultivars, and the average well color development (AWCD) values, Mc Intosh index, Shannon-Wiener index and Simpson index of rhizosphere microbes of wheat cultivar JM22 were significantly higher than those of cultivar JI5265 in both contaminated soil and non-contaminated soil after 120 h of incubation. Taken together, the community structure and functional diversity of rhizosphere microorganisms in the two Cd-accumulating wheat cultivars grown in contaminated soil were different. The results provide an important reference for understanding the rhizosphere microbial mechanism in high and low accumulating wheats. 参考文献 相似文献 引证文献

Pseudomonas sp. TCd-1 significantly alters the rhizosphere bacterial community of rice in Cd contaminated paddy field

Cadmium (Cd) pollution of paddy soils is one of the main concerns causing food security and environmental problems. Microbial bioremediation is an effective and eco-friendly measure that uses microbes to reduce Cd accumulation in crops. Additionally, rhizosphere bacterial communities also act essential roles in crop tolerance of heavy metals. However, the effects of inoculations with Cd resistant bacteria on crop rhizosphere bacterial communities under Cd exposure are largely unknown. In this study, we used high-throughput 16S rRNA gene sequencing technologies to explore the community structure and co-occurrence network of the rhizosphere bacterial communities associated with the rice crop under different Cd treatments and the application of Cd-tolerant strain Pseudomonas sp. TCd-1. We found that the strain TCd-1 both significantly reduced the rhizobacterial alpha diversity and changed the beta diversity. PERMANOVA and NMDS analysis showed that Cd stress and TCd-1 strain could act as strong environmental filters resulting in observable differentiation of rhizobacterial community composition among different groups. In addition, RDA results indicated that the rhizosphere pH, root Cd content, catalase (CAT), urease (URE), gibberellic acid (GA3) exert significant association with rhizosphere bacterial assembly. PICRUSt analysis revealed that the TCd-1 strain improved the metabolic capacity of rhizosphere bacteria under Cd stress. Furthermore, co-occurrence network topological features and keystone taxa also varied among different groups. This study could provide necessary insights into developing an efficient bioremediation and safe production of rice crops in Cd contaminated paddy fields with the application of Pseudomonas sp. TCd-1 strain, as well as advance our understanding of the principles of rhizosphere bacterial community assembly under Cd stress.

Heavy metal ATPase genes (HMAs) expression induced by endophytic bacteria, “AI001, and AI002” mediate cadmium translocation and phytoremediation

Contamination of heavy metals is a serious threat, which causes threats to the environment. Our study aimed to determine the role of endophytic bacteria in Cd phytoremediation and heavy metal ATPase gene expression. Cadmium (Cd) resistant endophytic bacteria were isolated from Solanum nigrum on LB agar plates, contaminated with 0–30 mg/L Cd. The phosphate solubilization and indole-3-acetic acid (IAA) production of endophytes were estimated by growing them on Pikovskaya agar medium and GC-MS analysis, respectively. An experiment in a pot was performed to evaluate the effects of bacteria on rice plants contaminated with 5–25 mg/L of Cd. Expression of Cd response genes was quantified through qRT–PCR and Cd translocation from one part to another part of the plant was measured through the ICP. BLAST alignment of 16 S-rDNA gene sequences confirmed the bacterial isolates as Serratia sp. AI001 and Klebsiella sp. Strain AI002. Both strains tolerated Cd up to 25 mg/L and produced 27–30 μg/mL of IAA. Inoculation of AI001 and AI002 improved plant growth dynamics (i.e., plant length, biomass, chlorophyll contents), relieved electrolyte leakage, and improved reduced glutathione significantly (P < 0.05). The inoculation of AI001 and AI002 significantly (P < 0.05) induced the expression of heavy metal ATPase genes ie., “HMA2, HMA3, and HMA4” and Cd translocation compared to uninoculated plants. Both AI001 and AI002 exhibited very prominent plant-growth-promoting and Cd phytoremediation properties. The results revealed that isolates also contributed a lot to the expression of rice plant heavy metal ATPase genes and in the Cd translocation in the plant.

Interactions of chlorpyrifos degradation and Cd removal in iron-carbon-based constructed wetlands for treating synthetic farmland wastewater

Pesticide and heavy metal contaminants, such as chlorpyrifos (CP) and cadmium (Cd) in farmland drainage had caused the water pollution and attracted extensive concerns around the world. The incorporation of zeolite-based iron-carbon (ZB-IC) into constructed wetlands (CWs) was prepared to simultaneously remove chlorpyrifos (CP) and cadmium (Cd) in farmland drainage, and the interaction of CP degradation and Cd removal was investigated. Laboratory simulated experiments were carried out in this study, and the results presented that the removal efficiencies of CP and Cd by ZB-IC coupled CWs (ZB–IC–CW) were 99.55% and 98.59%, respectively, which were much higher than that of the zeolite-based (ZB) CWs (CP = 92.99%; Cd = 63.54%). The removal mechanism of CP and Cd by ZB-IC substrate was mainly attributed to electron transfer, which occurred from iron corrosion and hydrogen generation process. In addition, CP could act as carbon source to promote denitrification process. Microbial analysis revealed that the relative abundances of CP-resistant bacteria (Firmicutes, Clostridia and Acetobacterium), Cd-resistant bacteria (Bacteroidetes) and denitrifying bacteria (Proteobacteria and Patescibacteria) were dramatically increased due to the addition of ZB-IC. The higher czcA gene and opd gene in ZB–IC–CW demonstrated that the addition of CP played a positive role in Cd removal, while Cd showed slightly affect to CP removal.

Cadmium Pollution Impact on the Bacterial Community Structure of Arable Soil and the Isolation of the Cadmium Resistant Bacteria.

Microorganisms play an important role in the remediation of cadmium pollution in the soil and their diversity can be affected by cadmium. In this study, the bacterial community in arable soil samples collected from two near geographical sites, with different degrees of cadmium pollution at three different seasons, were characterized using Illumina MiSeq sequencing. The result showed that cadmium is an important factor to affect the bacterial diversity and the microbial communities in the high cadmium polluted area (the site H) had significant differences compared with low cadmium polluted area (the site L). Especially, higher concentrations of Cd significantly increased the abundance of Proteobacteria and Gemmatimonas whereas decreased the abundance of Nitrospirae. Moreover, 42 Cd-resistant bacteria were isolated from six soil samples and evaluated for potential application in Cd bioremediation. Based on their Cd-MIC [minimum inhibitory concentration (MIC) of Cd2+], Cd2+ removal rate and 16S rDNA gene sequence analyses, three Burkholderia sp. strains (ha-1, hj-2, and ho-3) showed very high tolerance to Cd (5, 5, and 6 mM) and exhibited high Cd2+ removal rate (81.78, 79.37, and 63.05%), six Bacillus sp. strains (151-5,151-6,151-13, 151-20, and 151-21) showed moderate tolerance to Cd (0.8, 0.4, 0.8, 0.4, 0.6, and 0.4 mM) but high Cd2+ removal rate (84.78, 90.14, 82.82, 82.39, 81.79, and 84.17%). Those results indicated that Burkholderia sp. belonging to the phylum Proteobacteria and Bacillus sp. belonging to the phylum Firmicutes have developed a resistance for cadmium and may play an important role in Cd-contaminated soils. Our study provided baseline data for bacterial communities in cadmium polluted soils and concluded that Cd-resistant bacteria have potential for bioremediation of Cd-contaminated soils.