Diversity and composition of microbial communities in Jinsha earthen site under different degree of deterioration.

Earthen sites are the important cultural heritage that carriers of human civilization and contains abundant history information. Microorganisms are one of important factors causing the deterioration of cultural heritage. However, little attention has been paid to the role of biological factors on the deterioration of earthen sites at present. In this study, microbial communities of Jinsha earthen site soils with different deterioration types and degrees as well as related to environmental factors were analyzed. The results showed that the concentrations of Mg2+ and SO42- were higher in the severe deterioration degree soils than in the minor deterioration degree soils. The Chao1 richness and Shannon diversity indices of bacteria in different type deterioration were higher in the summer than in the winter; the Chao1 and Shannon indices of fungi were lower in the summer. The differences in bacterial and fungal communities were associated with differences in Na+, K+, Mg2+ and Ca2+ contents. Based on both the relative abundances in amplicon sequencing and isolated strains, the bacterial phyla Actinobacteria, Firmicutes and Proteobacteria, and the Ascomycota genera Aspergillus, Cladosporium and Penicillium were common in all soils. The OTUs enriched in the severe deterioration degree soils were mostly assigned to Actinobacteria and Proteobacteria, whereas the Firmicutes OTUs differentially abundant in the severe deterioration degree were all depleted. All bacterial isolates produced alkali, implying that the deterioration on Jinsha earthen site may be accelerated through alkali production. The fungal isolates included both alkali and acid producing strains. The fungi with strong ability to produce acid were mainly from the severe deterioration degree samples and were likely to contribute to the deterioration. Taken together, the interaction between soil microbial communities and environment may affect the soil deterioration, accelerate the deterioration process and threaten the long-term preservation of Jinsha earthen site.

Bacterial community in the buckwheat rhizosphere responds more sensitively to single microplastics in lead-contaminated soil compared to the arbuscular mycorrhizal fungi community.

Soil pollution by microplastics (MPs), defined as plastic particles <5 mm, and heavy metals is a significant environmental issue. However, studies on the co-contamination effects of MPs and heavy metals on buckwheat rhizosphere microorganisms, especially on the arbuscular mycorrhizal fungi (AMF) community, are limited. We introduced low (0.01 g kg-1) and high doses of lead (Pb) (2 g kg-1) along with polyethylene (PE) and polylactic acid (PLA) MPs, both individually and in combination, into soil and assessed soil properties, buckwheat growth, and rhizosphere bacterial and AMF communities in a 40-day pot experiment. Notable alterations were observed in soil properties such as pH, alkaline hydrolyzable nitrogen (AN), and the available Pb (APb). High-dose Pb combined with PLA-MPs hindered buckwheat growth. Compared to the control, bacterial Chao1 richness and Shannon diversity were lower in the high dose Pb with PLA treatment, and differentially abundant bacteria were mainly detected in the high Pb dose treatments. Variations in bacterial communities correlated with APb, pH and AN. Overall, the AMF community composition remained largely consistent across all treatments. This phenomenon may be due to fungi having lower nutritional demands than bacteria. Stochastic processes played a relatively important role in the assembly of both bacterial and AMF communities. In summary, MPs appeared to amplify both the positive and negative effects of high Pb doses on the buckwheat rhizosphere bacteria.

Bacterial community drives soil organic carbon transformation in vanadium titanium magnetite tailings through remediation using Pongamia pinnata.

With continuous mine exploitation, regional ecosystems have been damaged, resulting in a decline in the carbon sink capacity of mining areas. There is a global shortage of effective soil ecological restoration techniques for mining areas, especially for vanadium (V) and titanium (Ti) magnetite tailings, and the impact of phytoremediation techniques on the soil carbon cycle remains unclear. Therefore, this study aimed to explore the effects of long-term Pongamia pinnata remediation on soil organic carbon transformation of V-Ti magnetite tailing to reveal the bacterial community driving mechanism. In this study, it was found that four soil active organic carbon components (ROC, POC, DOC, and MBC) and three carbon transformation related enzymes (S-CL, S-SC, and S-PPO) in vanadium titanium magnetite tailings significantly (P < 0.05) increased with P. pinnata remediation. The abundance of carbon transformation functional genes such as carbon degradation, carbon fixation, and methane oxidation were also significantly (P < 0.05) enriched. The network nodes, links, and modularity of the microbial community, carbon components, and carbon transformation genes were enhanced, indicating stronger connections among the soil microbes, carbon components, and carbon transformation functional genes. Structural equation model (SEM) analysis revealed that the bacterial communities indirectly affected the soil organic carbon fraction and enzyme activity to regulate the soil total organic carbon after P. pinnata remediation. The soil active organic carbon fraction and free light fraction carbon also directly regulated the soil carbon and nitrogen ratio by directly affecting the soil total organic carbon content. These results provide a theoretical reference for the use of phytoremediation to drive soil carbon transformation for carbon sequestration enhancement through the remediation of degraded ecosystems in mining areas.

Chelativorans petroleitrophicus sp. nov., a paraffin oil-degrading bacterium isolated from a mixture of oil-based drill cuttings and paddy soil.

We isolated a paraffin oil-degrading bacterial strain from a mixture of oil-based drill cutting and paddy soil, and characterized the strain using a polyphasic approach. The Gram-positive, aerobic, rod-shaped and non-spore-forming strain (SCAU 2101T) grew optimally at 50 °C, pH 7.0 and 0.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that the strain represented a distinct clade in the genus Chelativorans, neighbouring Chelativorans intermedius LMG 28482T (97.1 %). The genome size and DNA G+C content of the strain were 3 969 430 bp and 63.1 mol%, respectively. Whole genome based phylogenomic analyses showed that the average nucleotide identity and digital DNA-DNA hybridization values between strain SCAU 2101T and C. intermedius LMG 28482T were 77.5 and 21.2 %, respectively. The major respiratory quinone was Q-10. The dominant fatty acids were C19 : 0 cyclo ω8c (50.6 %), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c; 22.5 %) and C18 : 0 (13.8 %). The polar lipids of the strain included phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, phosphatidylcholine and diphosphatidylglycerol. Based on the results, strain SCAU 2101T was considered to represent a novel species in the genus Chelativorans, for which the name Chelativorans petroleitrophicus sp. nov. is proposed. The type strain is SCAU 2101T (= CCTCC AB 2021125T=KCTC 92067T).

Response of soil microbial community structure and function to different altitudes in arid valley in Panzhihua, China.

BACKGROUND: Altitude affects biodiversity and physic-chemical properties of soil, providing natural sites for studying species distribution and the response of biota to environmental changes. We sampled soil at three altitudes in an arid valley, determined the physic-chemical characteristics and microbial community composition in the soils, identified differentially abundant taxa and the relationships between community composition and environmental factors. RESULTS: The low, medium and high altitudes were roughly separated based on the physic-chemical characteristics and clearly separated based on the microbial community composition. The differences in community composition were associated with differences in soil pH, temperature, and SOC, moisture, TN, TP, AN, AP and SMBC contents. The contents of organic and microbial biomass C, total and available N and available P, and the richness and diversity of the microbial communities were lowest in the medium altitude. The relative abundances of phyla Proteobacteria, Gemmatimonadetes, Actinobacteria and Acidobacteria were high at all altitudes. The differentially abundant amplified sequence variants (ASVs) were mostly assigned to Proteobacteria and Acidobacteria. The highest number of ASVs characterizing altitude were detected in the high altitude. However, the predicted functions of the communities were overlapping, suggesting that the contribution of the communities to soil processes changed relatively little along the altitude gradient. CONCLUSIONS: The low, medium and high altitudes were roughly separated based on the physicochemical characteristics and clearly separated based on the microbial community composition. The differences in community composition were associated with differences in soil pH, temperature, and SOC, moisture, TN, TP, AN, AP and SMBC contents.

Changes in the taxonomic and functional structures of microbial communities during vegetable waste mixed silage fermentation.

Silage fermentation, a sustainable method of using vegetable waste resources, is a complex process driven by a variety of microorganisms. We used lettuce waste as the main raw material for silage, analyzed changes in the physicochemical characteristics and bacterial community composition of silage over a 60-day fermentation period, identified differentially abundant taxa, predicted the functional profiles of bacterial communities, and determined the associated effects on the quality of silage. The largest changes occurred during the early stages of silage fermentation. Changes in the physicochemical characteristics included a decrease in pH and an increase in the ammonia nitrogen to total nitrogen ratio and lactic acid content. The number of lactic acid bacteria (LAB) increased, while molds, yeasts, and aerobic bacteria decreased. The bacterial communities and their predicted functions on day 0 were different from those on day 7 to day 60. The relative abundances of phylum Firmicutes and genus Lactobacillus increased. Nitrite and nitrate ammonification were more prevalent after day 0. The differences in the predicted functions were associated with differences in pH and amino acid, protein, carbohydrate, NH3-N, ether extract, and crude ash contents.

Role of rhizobia in promoting non-enzymatic antioxidants to mitigate nitrogen-deficiency and nickel stresses in Pongamia pinnata.

The contribution of rhizobia in the mitigation of non-enzymatic antioxidants against nitrogen deficiency and heavy metal toxicity for legume plant is not clear. Therefore, it is hypothesized that the inoculation of rhizobia could mitigate nitrogen deficiency and nickel (Ni) stresses in P. pinnata tissues by enhancing the formation of certain non-enzymatic antioxidants. The effect of symbiotic nitrogen-fixing rhizobia on the mitigation of nitrogen-deficiency and Ni stresses in P. pinnata was evaluated by inoculating two different rhizobia, i.e., Rhizobium pisi PZHK2 and Ochrobacterium pseudogrignonense PZHK4, around the rhizosphere of P. pinnata grown in soil containing 40 mg kg-1 Ni2+ and without nitrogen addition. The inoculation with both rhizobial strains promoted the growth of P. pinnata under nickel stress or nitrogen-deficiency condition, increased nitrogen content in all plant tissues and nickel content in shoots and leaves, but reduced nickel accumulation in roots. The four non-enzymatic antioxidants including glutathione (GSH), proanthocyanidin (OPC), ascorbic acid (ASA) and flavonoids (FLA) distributed in roots, shoots and leaves were followed in descending order: GSH > OPC > ASA > FLA. The four non-enzymatic antioxidants showed different levels of change under the nitrogen-deficiency and nickel stresses and in the non-stress control. The inoculation of PZHK2 and PZHK4 significantly (p < 0.05) increased the four non-enzymatic antioxidants in P. pinnata tissues, especially in roots. Some non-enzymatic antioxidants showed correlations with nickel or nitrogen in P. pinnata tissues, and the four non-enzymatic antioxidants also had correlations among each other. Therefore, this research revealed an excellent role of rhizobia in promoting non-enzymatic antioxidants to mitigate nitrogen-deficiency or nickel stress for P. pinnata.

Synergistic anti-oxidative effects of Pongamia pinnata against nickel mediated by Rhizobium pisi and Ochrobacterium pseudogrignonense.

Nickel is widely spread by different anthropogenic activities and shows toxicity for plant growth and development. Whether rhizobia symbiotically fix nitrogen can eliminate or reduce nickel toxic effect on plant or not is still unknown. This study was aimed to investigate the effect of different rhizobia genus inoculation on growth, nitrogen fixing ability, metal accumulation and enzymatic antioxidative balance of Pongamia pinnnaa. Inoculation with Rhizobium pisi and Ochrobacterium pseudogrignonense increased the all the growth parameters both in 0 and 40 mg/kg nickel as comparison with control. Only shoot length increased in presence of nitrogen as compared with no supply of nitrogen. Nitrogen content also increased both in rhizobia inoculation as compared to no nitrogen supply and non-inoculation control, respectively. Nickel uptake was higher in shoots and leaves but lower in roots in case of inoculation as compared to non-inoculation control. Rhizobia inoculation improved the plant antioxidant capacity by increasing the activity of enzymatic scavengers catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and ascorbate (GR). However, 40 mg/kg of nickel adding showed mostly effect on the activity CAT, SOD, POD in leaves. All the enzymatic activity showed a significant increase in absence of nitrogen supply as compared nitrogen supply. Our results suggested that rhizobia inoculation effectively mediated nickel stress for legume plants by increasing nitrogen supplement and inducing antioxidant capacity.

Changes in soil microbial communities at Jinsha earthen site are associated with earthen site deterioration.

BACKGROUND: Earthen sites are immobile cultural relics and an important part of cultural heritage with historical, artistic and scientific values. The deterioration of features in earthen sites result in permanent loss of cultural information, causing immeasurable damage to the study of history and culture. Most research on the deterioration of earthen sites has concentrated on physicochemical factors, and information on microbial communities in earthen sites and their relationship with the earthen site deterioration is scarce. We used high-throughput sequencing to analyze bacterial and fungal communities in soils from earthen walls with different degree of deterioration at Jinsha earthen site to characterize the microbial communities and their correlation with environmental factors, and to compare microbial community structures and the relative abundances of individual taxa associated with different degree of deterioration for identifying possible marker taxa. RESULTS: The relative abundances of Proteobacteria and Firmicutes were higher and that of Actinobacteria lower with higher degree of deterioration. At the genus level, the relative abundances of Rubrobacter were highest in all sample groups except in the most deteriorated samples where that of Bacteroides was highest. The relative abundance of the yeast genus Candida was highest in the severely deteriorated sample group. The bacterial phylum Bacteroidetes and genus Bacteroides, and fungal class Saccharomycetes that includes Candida sp. were specific for the most deteriorated samples. For both bacteria and fungi, the differences in community composition were associated with differences in EC, moisture, pH, and the concentrations of NH4+, K+, Mg2+, Ca2+ and SO42-. CONCLUSION: The microbial communities in soil with different degree of deterioration were distinctly different, and deterioration was accompanied with bigger changes in the bacterial than in the fungal community. In addition, the deteriorated soil contained higher concentrations of soluble salts. Potentially, the accumulation of Bacteroides and Candida plays an important role in the deterioration of earthen features. Further work is needed to conclude whether controlling the growth of the bacteria and fungi with high relative abundances in the deteriorated samples can be applied to alleviate deterioration.

The open reading frame 02797 from Candida tropicalis encodes a novel NADH-dependent aldehyde reductase.

Owing to its high-temperature tolerance, robustness, and wide use of carbon sources, Candida tropicalis is considered a good candidate microorganism for bioconversion of lignocellulose to ethanol. It also has the intrinsic ability to in situ detoxify aldehydes derived from lignocellulosic hydrolysis. However, the aldehyde reductases that catalyze this bioconversion in C. tropicalis remain unknown. Herein, we found that the uncharacterized open reading frame (ORF), CTRG_02797, from C. tropicalis encodes a novel and broad substrate-specificity aldehyde reductase that reduces at least seven aldehydes. This enzyme strictly depended on NADH rather than NADPH as the co-factor for catalyzing the reduction reaction. Its highest affinity (Km), maximum velocity (Vmax), catalytic rate constant (Kcat), and catalytic efficiency (Kcat/Km) were observed when reducing acetaldehyde (AA) and its enzyme activity was influenced by different concentrations of salts, metal ions, and chemical protective additives. Protein localization assay demonstrated that Ctrg_02797p was localized in the cytoplasm in C. tropicalis cells, which ensures an effective enzymatic reaction. Finally, Ctrg_02797p was grouped into the cinnamyl alcohol dehydrogenase (CADH) subfamily of the medium-chain dehydrogenase/reductase family. This research provides guidelines for exploring more uncharacterized genes with reduction activity for detoxifying aldehydes.

New insights into two yeast BDHs from the PDH subfamily as aldehyde reductases in context of detoxification of lignocellulosic aldehyde inhibitors.

At least 24 aldehyde reductases from Saccharomyces cerevisiae have been characterized and most function in in situ detoxification of lignocellulosic aldehyde inhibitors, but none is classified into the polyol dehydrogenase (PDH) subfamily of the medium-chain dehydrogenase/reductase (MDR) superfamily. This study confirmed that two (2R,3R)-2,3-butanediol dehydrogenases (BDHs) from industrial (denoted Y)/laboratory (denoted B) strains of S. cerevisiae, Bdh1p(Y)/Bdh1p(B) and Bdh2p(Y)/Bdh2p(B), were members of the PDH subfamily with an NAD(P)H binding domain and a catalytic zinc binding domain, and exhibited reductive activities towards lignocellulosic aldehyde inhibitors, such as acetaldehyde, glycolaldehyde, and furfural. Especially, the highest enzyme activity towards acetaldehyde by Bdh2p(Y) was 117.95 U/mg with cofactor nicotinamide adenine dinucleotide reduced (NADH). Based on the comparative kinetic property analysis, Bdh2p(Y)/Bdh2p(B) possessed higher specific activity, substrate affinity, and catalytic efficiency towards glycolaldehyde than Bdh1p(Y)/Bdh1p(B). This was speculated to be related to their 49% sequence differences and five nonsynonymous substitutions (Ser41Thr, Glu173Gln, Ile270Leu, Ile316Met, and Gly317Cys) occurred in their conserved NAD(P)H binding domains. Compared with BDHs from a laboratory strain, Bdh1p(Y) and Bdh2p(Y) from an industrial strain displayed five nonsynonymous mutations (Thr12, Asn61, Glu168, Val222, and Ala235) and three nonsynonymous mutations (Ala34, Ile96, and Ala369), respectively. From a first analysis with selected aldehydes, their reductase activities were different from BDHs of laboratory strain, and their catalytic efficiency was higher towards glycolaldehyde and lower towards acetaldehyde. Comparative investigation of kinetic properties of BDHs from S. cerevisiae as aldehyde reductases provides a guideline for their practical applications in in situ detoxification of aldehyde inhibitors during lignocellulose bioconversion.Key Points• Two yeast BDHs have enzyme activities for reduction of aldehydes.• Overexpression of BDHs slightly improves yeast tolerance to acetaldehyde and glycolaldehyde.• Bdh1p and Bdh2p differ in enzyme kinetic properties.• BDHs from strains with different genetic backgrounds differ in enzyme kinetic properties.

Effect of common bean seed exudates on growth, lipopolysaccharide production, and lipopolysaccharide transport gene expression of Rhizobium anhuiense.

Lipopolysaccharide (LPS) is essential for successful nodulation during the symbiosis of rhizobia and legumes. However, the detailed mechanism of the LPS in this process has not yet been clearly elucidated. In this study, the effects of common bean seed exudates on the growth, lipopolysaccharide production, and lipopolysaccharide transport genes expression (lpt) of Rhizobium anhuiense were investigated. Rhizobium anhuiense exposed to exudates showed changes in LPS electrophoretic profiles and content, whereby the LPS band was wider and the LPS content was higher in R. anhuiense treated with seed exudates. Exudates enhanced cell growth of R. anhuiense in a concentration-dependent manner; R. anhuiense exposed to higher doses of the exudate showed faster growth. Seven lpt genes of R. anhuiense were amplified and sequenced. Sequences of six lpt genes, except for lptE, were the same as those found in previously analyzed R. anhuiense strains, while lptE shared low sequence similarity with other strains. Exposure to the exudates strongly stimulated the expression of all lpt genes. Approximately 6.7- (lptG) to 301-fold (lptE) increases in the transcriptional levels were observed after only 15 min of exposure to exudates. These results indicate that seed exudates affect the LPS by making the cell wall structure more conducive to symbiotic nodulation.

Changes of root microbial populations of natively grown plants during natural attenuation of V-Ti magnetite tailings.

Mine tailings contain dangerously high levels of toxic metals which pose a constant threat to local ecosystems. Few naturally grown native plants can colonize tailings site and the existence of their root-associated microbial populations is poorly understood. The objective of this study was to give further insights into the interactions between native plants and their microbiota during natural attenuation of abandoned V-Ti magnetite mine tailings. In the present work, we first examined the native plants' potential for phytoremediation using plant/soil analytical methods and then investigated the root microbial communities and their inferred functions using 16 S rRNA-based metagenomics. It was found that in V-Ti magnetite mine tailings the two dominant plants Bothriochloa ischaemum and Typha angustifolia were able to increase available nitrogen in the rhizosphere soil by 23.3% and 53.7% respectively. The translocation factors (TF) for both plants indicated that B. ischaemum was able to accumulate Pb (TF = 1.212), while T. angustifolia was an accumulator of Mn (TF = 2.502). The microbial community structure was more complex in the soil associated with T. angustifolia than with B. ischaemum. The presence of both plants significantly reduced the population of Acinetobacter. Specifically, B. ischaemum enriched Massilia, Opitutus and Hydrogenophaga species while T. angustifolia significantly increased rhizobia species. Multivariate analyses revealed that among all tested soil variables Fe and total organic carbon (TOC) could be the key factors in shaping the microbial structure. The putative functional analysis indicated that soil sample of B. ischaemum was abundant with nitrate/nitrite reduction-related functions while that of T. angustifolia was rich in nitrogen fixing functions. The results indicate that these native plants host a diverse range of soil microbes, whose community structure can be shaped by plant types and soil variables. It is also possible that these plants can be used to improve soil nitrogen content and serve as bioaccumulators for Pb or Mn for phytoremediation purposes.

YKL107W from Saccharomyces cerevisiae encodes a novel aldehyde reductase for detoxification of acetaldehyde, glycolaldehyde, and furfural.

The aldehyde reductases from the short-chain dehydrogenase/reductase (SDR) family were identified as a series of critical enzymes for the improved tolerance of Saccharomyces cerevisiae to the aldehydes by catalyzing the detoxification reactions of aldehydes. Herein, we report that a novel aldehyde reductase Ykl107wp deduced from YKL107W from S. cerevisiae belongs to the classical SDR group and can catalyze the reduction reactions of acetaldehyde (AA), glycolaldehyde (GA), furfural (FF), formaldehyde (FA), and propionaldehyde (PA) but cannot reduce the six representative ketones. Ykl107wp displayed the best maximum velocity (Vmax), catalytic rate constant (Kcat), catalytic efficiency (Kcat/Km), and highest affinity (Km) to acetaldehyde. The optimum pH of Ykl107wp was 6.0 for the reduction of AA and 7.0 for the reduction of GA and FF, and the optimum temperatures were 40, 35, and 30 °C for the reduction of AA, GA, and FF, respectively. Ykl107wp for the reduction of AA was greatly affected by metal ions, chemical additives, and salts and showed poor thermal and pH stability, but its stability was slightly affected by a substrate. Ykl107wp was localized in endoplasmic reticulum and prevented the yeast cells from damage caused by furfural via the detoxification of furfural to furfural alcohol. This research provides guidelines for the study of uncharacterized classical SDR aldehyde reductases and exploration of their protective mechanisms on the corresponding organelles.

Optimization of Laccase from Ganoderma lucidum Decolorizing Remazol Brilliant Blue R and Glac1 as Main Laccase-Contributing Gene.

Many dyes and pigments are used in textile and printing industries, and their wastewater has been classed as a top source of pollution. Biodegradation of dyes by fungal laccase has great potential. In this work, the influence of reaction time, pH, temperature, dye concentration, metal ions, and mediators on laccase-catalyzed Remazol Brilliant Blue R dye (RBBR) decolorization were investigated in vitro using crude laccase from the white-rot fungus Ganoderma lucidum. The optimal decolorization percentage (50.3%) was achieved at 35 °C, pH 4.0, and 200 ppm RBBR in 30 min. The mediator effects from syringaldehyde, 1-hydroxybenzotriazole, and vanillin were compared, and 0.1 mM vanillin was found to obviously increase the decolorization percentage of RBBR to 98.7%. Laccase-mediated decolorization percentages significantly increased in the presence of 5 mM Na+ and Cu2+, and decolorization percentages reached 62.4% and 62.2%, respectively. Real-time fluorescence-quantitative PCR (RT-PCR) and protein mass spectrometry results showed that among the 15 laccase isoenzyme genes, Glac1 was the main laccase-contributing gene, contributing the most to the laccase enzyme activity and decolorization process. These results also indicate that under optimal conditions, G. lucidum laccases, especially Glac1, have a strong potential to remove RBBR from reactive dye effluent.

Genetic diversity and characterization of arsenic-resistant endophytic bacteria isolated from Pteris vittata, an arsenic hyperaccumulator.

BACKGROUND: Alleviating arsenic (As) contamination is a high-priority environmental issue. Hyperaccumulator plants may harbor endophytic bacteria able to detoxify As. Therefore, we investigated the distribution, diversity, As (III) resistance levels, and resistance-related functional genes of arsenite-resistant bacterial endophytes in Pteris vittata L. growing in a lead-zinc mining area with different As contamination levels. RESULTS: A total of 116 arsenite-resistant bacteria were isolated from roots of P. vittata with different As concentrations. Based on the 16S rRNA gene sequence analysis of representative isolates, the isolates belonged to Proteobacteria, Actinobacteria, and Firmicutes. Major genera found were Agrobacterium, Stenotrophomonas, Pseudomonas, Rhodococcus, and Bacillus. The most highly arsenite-resistant bacteria (minimum inhibitory concentration > 45 mM) were isolated from P. vittata with high As concentrations and belonged to the genera Agrobacterium and Bacillus. The strains with high As tolerance also showed high levels of indole-3-acetic acid (IAA) production and carried arsB/ACR3(2) genes. The arsB and ACR3(2) were most likely horizontally transferred among the strains. CONCLUSION: The results of this study suggest that P. vittata plants with high As concentrations may select diverse arsenite-resistant bacteria; this diversity might, at least partly, be a result of horizontal gene transfer. These diverse endophytic bacteria are potential candidates to enhance phytoremediation techniques.

Analysis of the oligopeptide transporter gene family in Ganoderma lucidum: structure, phylogeny, and expression patterns.

Oligopeptide transporters (OPTs) are believed to transport broad ranges of substrates across the plasma membrane from the extracellular environment into the cell and are thought to contribute to various biological processes. In the present study, 13 putative OPTs (Gl-OPT1 to Gl-OPT13) were identified through extensive search of Ganoderma lucidum genome database. Phylogenetic analysis with OPTs from other fungi and plants indicates that these genes can be further divided into five groups. Motif compositions of OPT members are highly conserved in each group, indicative of functional conservation. Expression profile analysis of the 13 Gl-OPT genes indicated that, with the exception of Gl-OPT7-Gl-OPT9, for which no transcripts were detected, all paralogues were differentially expressed, suggesting their potential involvement in stress response and functional development of fungi. Overall, the analyses in this study provide a starting point for elucidating the functions of OPT in G. lucidum, and for understanding the complexities of metabolic regulation.

Pongamia pinnata inoculated with Bradyrhizobium liaoningense PZHK1 shows potential for phytoremediation of mine tailings.

Mine tailings contain high concentrations of metal contaminants and only little nutrients, making the tailings barren for decades after the mining has been terminated. Effective phytoremediation of mine tailings calls for deep-rooted, metal accumulating, and soil fertility increasing plants with tolerance against harsh environmental conditions. We assessed the potential of the biofuel leguminous tree Pongamia pinnata inoculated with plant growth promoting rhizobia to remediate iron-vanadium-titanium oxide (V-Ti magnetite) mine tailing soil by pot experiment and in situ remediation test. A metal tolerant rhizobia strain PZHK1 was isolated from the tailing soil and identified as Bradyrhizobium liaoningense by phylogenetic analysis. Inoculation with PZHK1 increased the growth of P. pinnata both in V-Ti magnetite mine tailings and in Ni-contaminated soil. Furthermore, inoculation increased the metal accumulation capacity and superoxide dismutase activity of P. pinnata. The concentrations of Ni accumulated by inoculated plants were higher than the hyperaccumulator threshold. Inoculated P. pinnata accumulated high concentration of Fe, far exceeding the upper limit (1000 mg kg-1) of Fe in plant tissue. In summary, P. pinnata-B. liaoningense PZHK1 symbiosis showed potential to be applied as an effective phytoremediation technology for mine tailings and to produce biofuel feedstock on the marginal land.

YKL071W from Saccharomyces cerevisiae encodes a novel aldehyde reductase for detoxification of glycolaldehyde and furfural derived from lignocellulose.

Aldehydes generated as by-products during the pretreatment of lignocellulose are the key inhibitors to Saccharomyces cerevisiae, which is considered as the most promising microorganism for industrial production of biofuel, xylitol as well as other special chemicals from lignocellulose. S. cerevisiae has the inherent ability to in situ detoxify aldehydes to corresponding alcohols by multiple aldehyde reductases. Herein, we report that an uncharacterized open reading frame YKL071W from S. cerevisiae encodes a novel "classical" short-chain dehydrogenase/reductase (SDR) protein with NADH-dependent enzymatic activities for reduction of furfural (FF), glycolaldehyde (GA), formaldehyde (FA), and benzaldehyde (BZA). This enzyme showed much better specific activities for reduction of GA and FF than FA and BZA, and displayed much higher Km and Kcat/Km but lower Vmax and Kcat for reduction of GA than FF. For this enzyme, the optimum pH was 5.5 and 6.0 for reduction of GA and FF, and the optimum temperature was 30 °C for reduction of GA and FF. Both pH and temperature affected stability of this enzyme in a similar trend for reduction of GA and FF. Cu2+, Zn2+, Ni2+, and Fe3+ had severe inhibition effects on enzyme activities of Ykl071wp for reduction of GA and FF. Transcription of YKL071W in S. cerevisiae was significantly upregulated under GA and FF stress conditions, and its transcription is most probably regulated by transcription factor genes of YAP1, CAD1, PDR3, and STB5. This research provides guidelines to identify more uncharacterized genes with reductase activities for detoxification of aldehydes derived from lignocellulose in S. cerevisiae.

The Diversity, Growth Promoting Abilities and Anti-microbial Activities of Bacteria Isolated from the Fruiting Body of Agaricus bisporus.

Agaricus bisporus plays an important role in ecological processes and is one of the most widely cultivated mushrooms worldwide. Mushroom growth-promoting bacteria have been isolated from casing soil and compost, but microorganisms in the fruiting body have received only a little attention. To get an overview of phylogenetic diversity of microorganisms in the fruiting body of A. bisporus, as well as to screen antimicrobial and mushroom growth-promoting strains, and eventually intensify mushroom production, we isolated and characterized microorganisms from the fruiting body of A. bisporus. In total, 55 bacterial strains were isolated, among which nine isolates represented Actinomycetes. All the isolates were analyzed by 16S rRNA gene RFLP and sixteen representative strains by 16S rRNA gene sequencing. According to the phylogenetic analysis, eleven isolates represented the Gram-positive Bacillus, Lysinibacillus, Paenibacillus, Pandorea and Streptomyces genera, and five isolates belonged to the Gram-negative Alcaligenes and Pseudomonas genera. The bacteria isolated from the fruiting body of A. bisporus had broad-spectrum antimicrobial activities and potential mushroom growth-promoting abilities.