Efficient cadmium-resistant plant growth-promoting bacteria loaded on pig bone biochar has higher efficiency in reducing cadmium phytoavailability and improving maize performance than on rice husk biochar.

Green agriculture faced challenges due to the shortage of efficient cadmium (Cd)-resistant plant growth-promoting bacteria (CdR-PGPB) and their low survival rate and activity during application. In this study, a diverse range of efficient CdR-PGPB were isolated from the rhizosphere soil of Desmodium elegans, especially those with high phosphate-solubilizing capabilities (272.87-450.45 mg L-1). Two highly efficient CdR-PGPB namely, XH1 and XH3 were loaded on to rice husk biochar (RHB) and pig bone biochar (PBB), labelled as RHBM and PBBM respectively. This study aimed to explore their effectiveness and mechanisms in promoting maize growth in a Cd-contaminated planting system. Results showed that PBBM performed best among all treatments. It significantly decreased soil phytoavailable Cd by 53.19 % and Cd content in maize shoot by 85.89 %. It also increased soil available phosphorus by 145.72 %, soil alkaline phosphatase activity by 76.34 %, maize shoot/root biomass by 47.06 %/67.98 %, Chlorophyll (a/b) content by 66.80 %/134.13 % and peroxidase activity by 171.96 %. These results were achieved through the synergistic action of efficient CdR-PGPB and PBB. Therefore, PBBM proved to be a promising and innovative application technique for sustainable agricultural development in Cd-contaminated farmland ecosystems.

Screening and diversity of culturable HNAD bacteria in the MBR sewage treatment system.

The activated sludge was collected from the Membrane BioReactor (MBR) pool of the sewage treatment system of Sanxing Town, Jintang County, Chengdu, to obtain a good population of heterotrophic nitrifying/aerobic denitrifying (HNAD) bacteria. After undergoing enrichment, isolation, and purification, the HNAD bacteria were selected using the pure culture method. The 16S rDNA molecular technology was used to determine the taxonomy of bacteria. The heterophic nitrifying ability and denitrification capacity of HNAD strains was ascertained through their growth characteristics in heterotrophic nitrification and denitrification media. The results showed that 53 HNAD strains selected from the MBR pool belonged to 2 phyla, 3 classes, 6 orders, 6 families, and 7 genera, with 26 species. Acinetobacter was the largest and dominant genus. Among these, strains numbered (bacterial strain) SW21HD14, SW21HD17, and SW21HD18 were potentially new species in the Acinetobacter genus. Each HNAD strain showed a significant heterotrophic nitrifying and aerobic denitrifying efficiency compared with the control strain (P < 0.05). Specifically, 10 strains demonstrated ammonia nitrogen degradation of greater than 70 mg·L-1 and 9 strains demonstrated nitrate nitrogen degradation above 150 mg·L-1. The HNAD bacteria, which were selected from the MBR pool of sewage treatment system of the Sanxing Town sewage treatment plant, exhibited rich diversity and strong nitrogen removal ability. These findings offered an effective strain source and theoretical basis for implementing biological denitrification technology that involves synchronous nitrification and denitrification.

Screening and biodiversity analysis of cultivable inorganic phosphate-solubilizing bacteria in the rhizosphere of Hydrilla verticillata.

The inorganic phosphate-solubilizing bacteria (IPB) in the rhizosphere of Hydrilla verticillata can convert insoluble inorganic phosphorus in the environment into soluble phosphorus that can be directly absorbed and utilized by Hydrilla verticillata. In this research, the roots and rhizosphere sediments of Hydrilla verticillata were collected from high-organic matter urban landscape water. The National Botanical Research Institute's Phosphate growth medium (NBRIP medium) was used to screen for efficient cultivable IPB. The 16S rRNA gene sequence analysis was used to determine the taxonomic affiliation of the strains, and ammonium molybdate spectrophotometry was used to detect the phosphate-solubilizing ability of the strains. The results show that a total of 28 IPB strains with good phosphate-solubilizing effect are obtained from the roots and rhizosphere sediments of Hydrilla verticillata. These IPB strains belong to two phyla, four orders, seven classes, nine families, and nine genera. Among these, Bacillus and Acinetobacter are the dominant genera, and the strains SWIH-7, SWIP-6, SWIP-7, SWIP-13, SWIP-15 and SWIP-16 are potential new species. The IPB strains isolated and screened in this research are rich in diversity, with potential new species and stable phosphate-solubilizing characteristic. These IPB strains are suitable for further development as microbial bacterial agents, which can be applied to promote the recovery of submerged plants in polluted water with high-organic matter, treatment of polluted water and ecological restoration of water.

The spatio-temporal distribution of alkaline phosphatase activity and phoD gene abundance and diversity in sediment of Sancha Lake.

The bacterial phoD gene encoding alkaline phosphatase (ALP) plays an important role in the release of soluble reactive phosphorus (SRP) from organic phosphorus in ecosystems. However, phoD gene diversity and abundance in ecosystems is poorly understood. In the present study, we sampled the surface sediments and the overlying water of Sancha Lake at 9 different sampling sites, a typical eutrophic sub-deep freshwater lake in China, in April 15 (spring) and November 3 (autumn), 2017. High-throughput sequencing and qPCR were performed to analyze the diversity and abundance of the bacterial phoD gene in the sediments. We further discussed the relationships between the diversity and abundance of the phoD gene and environmental factors and ALP activity. A total of 881,717 valid sequences were obtained from 18 samples and were classified into 41 genera, 31 families, 23 orders, 12 classes, and 9 phyla and grouped into 477 OTUs. The dominant phyla were Proteobacteria and Actinobacteria. The phylogenetic tree based on the sequences of the phoD gene was plotted and composed of three branches. The genetic sequences were aligned predominantly with genera Pseudomonas, Streptomyces, Cupriavidus, and Paludisphaer. The phoD-harboring bacterial community structure showed a significant difference in spring and autumn, but no apparent spatial heterogeneity. The phoD gene abundances at different sampling points were significantly higher in autumn than in spring. In autumn and spring, the phoD gene abundance was significantly higher in the tail of lake and where cage culture used to be intensive. pH value, dissolved oxygen (DO), total organic carbon (TOC), ALP, and phosphorus were important environmental factors affecting the diversity of the phoD gene and the phoD-harboring bacterial community structure. Changes in phoD-harboring bacterial community structure, phoD gene abundance, and ALP activity were negatively correlated with SRP in overlying water. Our study indicated phoD-harboring bacteria in the sediments of Sancha Lake with the characteristics of high diversity and significant spatial and temporal heterogeneity in abundance and community structure, which played a important role in the release of SRP.

Shinella lacus sp. nov., a novel microcystin-degrading alphaproteobacterium containing the bla carbapenemase gene.

A Gram-stain-negative, rod-shaped, microcystin-degrading bacterium, designated as CPCC 100929T, was isolated from a fresh water reservoir in Sichuan Province, PR China. This isolate grew well at 4-37 °C and pH 6.0-8.0, with optimal growth at 28-32 °C and pH 7.0, respectively. The major cellular fatty acids were C18:1 ω7c/C18:1 ω6c, C16:0, C18:1 ω7c 11-methyl and C19:0 cyclo ω8c. The predominant respiratory quinone was Q-10. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine and phosphatidylcholine were detected in the polar lipids extraction. The 16S rRNA gene sequence of strain CPCC 100929T was closely related to those of members of the genus Shinella, with the highest similarity of 98.6 % to Shinella zoogloeoides DSM 287T and 97.4-98.4 % with other identified Shinella members. In the phylogenetic trees based on 16S rRNA gene sequences and the core-genes analysis, strain CPCC 100929T was included within the clade of the genus Shinella. The values of average nucleotide identity (81.4-86.7 %) and digital DNA-DNA hybridization (25.4-44.6 %) between strain CPCC 100929T and other Shinella species were all below the thresholds for bacterial species delineation, respectively. The genomic DNA G+C content of strain CPCC 100929T was 63.6 %. The genomic sequence analysis indicated that this species contained genes encoding peroxidase, bla carbapenemase and the key enzyme for microcystin bio degradation, as well as rich carbohydrate-active enzyme coding genes, which might endow the micro-organism with properties to adapt to diverse environments. Based on its phenotypic and genetic properties, we propose that strain CPCC 100929T (=T1A350T=KCTC 72957T) is the type strain of a novel species with the name Shinella lacus sp. nov.

Great Facilitation of Thirty Years of Reforestation with Mixed Species to Ecosystem Nitrogen Accumulation in Dry-Hot Valley in the Jinsha River.

Nitrogen is a key factor influencing ecosystem structure and function in reforestation, but knowledge of ecosystem nitrogen accumulation through reforestation with mixed species is limited. Especially in the dry-hot valley of the Jinsha River, no studies cover total ecosystem nitrogen accumulation in mature plantations and its allocation for difficulty in collecting tree roots and deep soil from dry red soil. In this study, nitrogen accumulation of seven mixed plantations in the dry-hot valley in the Jinsha River was studied after thirty years of reforestation with an analogous sites method. The results were as follows: (1) Soil nitrogen stocks decreased with depth in the soil profile. Deep soil nitrogen storage (20-80 cm) was significantly correlated with stand age (R2 = 0.752, p = 0.000; n = 7), accounting for 56-63% of total soil nitrogen storage and 43-47% of soil nitrogen accumulation in the dry-hot valley. (2) Total biomass nitrogen stock of the 30-year-old plantation was 1.22 t ha-1, 61 times that of degraded wasteland and 7.6 times that of natural recovery shrub grassland, and it recovered to the reference level of natural forest following 30 years of reforestation. (3) Total ecosystem nitrogen stock in the 30-year-old plantation was 12.72 t ha-1, 1.4 times the reference wasteland and 1.19 times the natural recovery shrub grassland. The contribution of soil nitrogen to ecosystem nitrogen storage and accumulation was 90% and 67%, respectively. Litter nitrogen accounted for 1.6% ecosystem nitrogen storage. It indicated that reforestation with mixed plantation of Leucaena leucocephala and other species greatly facilitated more ecosystem nitrogen accumulation, especially soil nitrogen (including deep compartment). Secondary biomass nitrogen, especially litter, could not be overlooked. This study filled the gap of ecosystem nitrogen storage and distribution during reforestation in the dry-hot valley. Mixed plantation with legume species such as L. leucocephala and other species and an important role of secondary biomass, especially litter in nitrogen accumulation, provided a reference for the strategy formulation of reforestation and forest nitrogen management in the dry-hot valley and other semi-arid or arid regions.

Diversity and Phosphate Solubilizing Characteristics of Cultivable Organophosphorus-Mineralizing Bacteria in the Sediments of Sancha Lake.

The organophosphate-mineralizing bacteria (OPB) convert environmental organic phosphorus (P) into soluble P that can be directly absorbed and utilized by organisms. OPB is an important group of microorganisms in lake sediments. The P decomposed and released from the sediments by OPB is an important P-source in eutrophic water bodies. In this study, the egg-yolk organophosphate medium was used to isolate and screen OPB strains from the sediments of Sancha Lake. Furthermore, the obtained OPB strains were classified based on their 16S rDNA sequence. Both the solid and liquid lecithin hydrolyzing experiments were conducted to investigate the P-solubilizing characteristics of the obtained OPB strains. Microcosm experimentsiwere performed to study the P-release ability of OPB strains from sediments. A total of 39 OPB strains were isolated from the sediments of Sancha Lake. They belonged to three phyla, five families, and five genera, and contained two potentially new species. Bacillus and Pseudomonas were the dominant genera. On the solid lecithin plate, 35 of the 39 OPB strains produced visible phosphate halos, and 24 strains showed a high ratio of P halo diameter (HD)/colony diameter (CD). In the liquid lecithin medium, all 39 OPB strains demonstrated P-solubilizing ability, but with significant differences. The Pseudomonas strain demonstrated the strongest P-solubilizing ability, at 70.91 mg·L-1. There was no significant correlation between the amount of released phosphorus by OPB strains and pH. The P-solubilizing characteristics of OPB were affected by the interaction of dissolved inorganic phosphate and alkaline phosphatase. In the microcosm experiments, the added OPB strains significantly promoted the decomposition and release of organic phosphorus (OP) in the sediments. OPB in the sediments of Sancha Lake is rich in diversity and had a strong ability to release OP in the sediments.

Rapid Sequestration of Ecosystem Carbon in 30-year Reforestation with Mixed Species in Dry Hot Valley of the Jinsha River.

Reforestation plays an important role in the carbon cycle and climate change. However, knowledge of ecosystem carbon sequestration through reforestation with mixed species is limited. Especially in dry hot valley of the Jinsha River, no studies cover total ecosystem carbon sequestration level in mature mixed plantations for a limited area of mixed plantations and difficulty in the sampling of plant roots and deep soil. In this study, carbon sequestration of seven mixed plantations of different ages in dry hot valley of the Jinsha River was investigated with analogous sites method. The results are as follows: 1) Deep soil organic carbon (SOC) storage significantly increased with stand age (p = 0.025), possibly due to fine root exudates and dissolved organic carbon transportation into deep soil and retention. 2) Total biomass carbon storage in the 30-year-old mixed plantation was 77.78 t C ha-1, 54 times reference wasteland and 9 times reference natural recovery shrub-grassland. However, total biomass carbon storage of 30-year-old mixed plantation was insignificantly lower than that of reference natural forest (p = 0.429). After 30 years of reforestation, plantation biomass carbon storage recovered to reference level, and its sequestration rate was 2.54 t C ha-1 yr-1. 3) The total ecosystem carbon storage of 30-year-old mixed plantation was 185.50 t C ha-1, 2.38 times reference wasteland, 2.29 times reference natural recovery shrub grassland, and 29% lower than reference natural forest. It indicated that niche complementary, good stand structure, and characteristics of dominant species Leucaena leucocephala in mixed plantations facilitate more rapid carbon sequestration, especially biomass carbon in the dry hot valley.

Jatrophihabitans huperziae sp. nov., an endophytic actinobacterium isolated from surface-sterilized tissue of the medicinal plant Huperzia serrata (Thunb.).

A novel endophytic actinobacterium, designated strain CPCC 204076T, was isolated from surface-sterilized tissue of the medicinal plant Huperzia serrata (Thunb.) collected from Sichuan Province, south-west China. The taxonomic position of the isolate was investigated by a polyphasic approach. The strainwas aerobic, Gram-stain-positive, non-motile, non-spore-forming and rod-shaped. Growth was observed at 10-37 °C, at pH 5.0-10.0 and with 0-3.0 % (w/v) NaCl. The polar lipid fraction consisted of diphosphatidylglycerol, a phospholipid, an aminolipid, a glycolipid, an aminophospholipid and phosphatidylinositol. The cell wall contained meso-diaminopimelic acid as the diagnostic diamino acid and the peptidoglycan was of type A4γ. The menaquinone system consisted of MK-9(H4) and MK-8(H4). The major cellular fatty acids (>10 %) were iso-C16 : 0 and anteiso-C17 : 0. The genomic DNA G+C content of strain CPCC 204076T was found to be 71.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that CPCC 204076T belongs to the genus Jatrophihabitans with highest sequence similarity to Jatrophihabitans endophyticus DSM 45627T (96.5 %), Jatrophihabitans soli DSM 45908T (96.5 %) and Jatrophihabitans fulvus JCM 30448T (96.1 %), and much lower similarities (<95.0 %) to other available 16S rRNA gene sequences from validly described pure cultures. However, DNA-DNA hybridyzation values between strain CPCC 204076T and the three recognized Jatrophihabitans species were 31±3.1 % (J. endophyticus DSM 45627T), 33±2.9 % (J. soli DSM 45908T) and 37±1.7 % (J. fulvus JCM 30448T), which were all far below the recommended cut-off value of 70 %. The phenotypic and genomic characteristics distinctly indicated that strain CPCC 204076T represents a novel species of the genus Jatrophihabitans, for which the name Jatrophihabitans huperziae sp. nov. is proposed. The type strain is CPCC 204076T (I13A-01604) (=DSM 46866T=NBRC 110718T).

Steroidobacter flavus sp. nov., a microcystin-degrading Gammaproteobacterium isolated from soil.

A microcystin-degrading strain, designated CPCC 100154(T), was isolated from a forest soil sample collected from Hainan Island, South China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CPCC 100154(T) is affiliated to the family Sinobacteraceae in Gammaproteobacteria, with high 16S rRNA gene sequence similarities of 98.1, 96.6 and 96.6 % to Steroidobacter agariperforans JCM 18477(T), S. denitrificansis DSM 18526(T), and Povalibacter uvarum JCM 18749(T), respectively. In the phylogenetic tree based on 16S rRNA gene sequences, strain CPCC 100154(T) formed a stable phylogenetic subclade with S. agariperforans JCM 18477(T), which indicated that strain CPCC 100154(T) should be identified as a member of the genus Steroidobacter. The phylogenetic analysis based on partial gyrB gene sequences confirmed the affiliation of strain CPCC 100154(T) to the genus Steroidobacter. While the DNA-DNA hybridization value (47.0 ± 1.7 %) between the new isolate and its near phylogenetic neighbor S. agariperforans JCM 18477(T) was far below 70 %, which demonstrated that strain CPCC 100154(T) represents a different genomic species from S. agariperforans. The strain CPCC 100154(T) was found to be a Gram-stain negative, rod-shaped, motile with a polar flagellum, non-endospore-forming bacterium. Good growth was observed at 28-32 °C and pH 7.0-7.5. Polar lipids were identified to be diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, a unidentified phospholipid, an aminophospholipid and an unidentified aminolipid. The polyamine pattern was determined to contain spermidine as the predominant polyamine, moderate amounts of putrescine as well as traces of sym-homospermidine and spermine. The respiratory quinone was identified as ubiquinone-8. The major cellular fatty acids were found to include summed feature 3 (C16: 1 ω7C/C16: 1 ω6C) (46.1 %) and C16: 0 (29.6 %). The genomic DNA G+C content was determined to be 64.4 mol%. On the basis of the above polyphasic taxonomy evidence, a novel species, Steroidobacter flavus sp. nov. is proposed. The type strain is CPCC 100154(T) (=DSM 23339(T) =CGMCC 1.10759(T)).

Jonesia luteola sp. nov., a bacterium isolated from Xinjiang Province, China.

A Gram-positive, facultative anaerobe microorganism, designated YIM 93067(T), was isolated from a salt lake in Xinjiang Province of China and subjected to a polyphasic taxonomic study. Strain YIM 93067(T) grew at 5-40 °C, 0-8.0 % (w/v) NaCl and pH 7.0-9.0. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the organism belongs to the genus Jonesia and exhibited a sequence similarity of 98.8 % to the closely related type strain Jonesia quinghaiensis DSM 15701(T). The predominant menaquinone was MK-9 and the major fatty acids were anteiso-C15:0 and C16:0. The polar lipids consisted of diphosphatidylglycerol, glycolipid, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside and one unidentified phospholipid. The G+C content of the genomic DNA was 57.4 mol%. Based on the results of phylogenetic, physiological and chemotaxonomic comparative analyses, the isolate is assigned to a novel species of the genus Jonesia, for which the name Jonesia luteola sp. nov. is proposed, with the type strain YIM 93067(T) (=DSM 21367(T) = CCTCC AB 2014350(T)).