The effect of quorum sensing on cadmium- and lead-containing wastewater treatment using activated sludge: Removal efficiency, enzyme activity, and microbial community.

Quorum sensing (QS) is prevalent in activated sludge processes; however, its essential role in the treatment of heavy metal wastewater has rarely been studied. Therefore, in this study, acyl homoserine lactone (AHL)-mediated QS was used to regulate the removal performance, enzyme activity, and microbial community of Cd- and Pb-containing wastewater in a sequencing batch reactor (SBR) over 30 cycles. The results showed that exogenous AHL strengthened the removal of Cd(II) and Pb(II) in their coexistence wastewater during the entire period. The removal of NH4+-N, total phosphorus, and chemical oxygen demand (COD) was also enhanced by the addition of AHL despite the coexistence of Cd(II) and Pb(II). Meanwhile, the protein content of extracellular polymeric substances was elevated and the microbial metabolism and antioxidative response were stimulated by the addition of AHL, which was beneficial for resistance to heavy metal stress and promoted pollutant removal by activated sludge. Microbial sequencing indicated that AHL optimized the microbial community structure, with the abundance of dominant taxa Proteobacteria and Unclassified_f_Enterobacteriaceae increasing by 73.9% and 59.2% maximally, respectively. This study offers valuable insights into the mechanisms underlying Cd(II) and Pb(II) removal as well as microbial community succession under AHL availability in industrial wastewater.

Effects of biochar layer position on treatment performance and microbial community in subsurface flow constructed wetlands for removal of cadmium and lead.

Levels of cadmium (Cd) and lead (Pb) correspond to common composition in acid mine wastewater of Hunan Province of China. The removal path of Cd and Pb and the structure of microbial community were investigated by developing constructed wetlands (CWs) with different layer positions of biochar. The biochar as a layer at the bottom of CW (BCW) system exhibited maximum Cd and Pb removal efficiencies of 96.6-98.6% and 97.2-98.9%, respectively. Compared with original soil, BCW increased the relative proportions of Proteobacteria, Firmicutes, Acidobacteriota, Verrucomicrobiota, Desulfobacterota, Armatimonadota, Bacteroidota, Patescibacteria, Basidiomycota (phylum level) and Burkholderia-Caballeronia-Paraburkholderia, Citrifermentans, Chthonomonadales, Cellulomonas, Geothrix, Terracidiphilus, Gallionellaceae, Microbacterium, Vanrija, Apiotrichum, Saitozyma, Fusarium (genus level). The concentrations of Cd and Pb were positively correlated with the abundance of Verrucomicrobiota, Basidiomycota (phylum level), and Methylacidiphilaceae, Meyerozyma, Vanrija (genus level). This study demonstrates that BCW system can improve removal performance toward Cd and Pb, as well as alter microbial community.

Nesterenkonia endophytica sp. nov., isolated from roots of Glycyrrhiza uralensis.

A Gram-positive and non-motile actinobacterium, designated strain EGI 60016T, was isolated from healthy roots of Glycyrrhiza uralensis F. collected from Xinyuan County, Xinjiang Province, China. The 16S rRNA gene sequence of strain EGI 60016T was found to show 97.5 and 97.3 % sequence similarities to Nesterenkonia rhizosphaerae EGI 80099T and Nesternkonia massiliensis NP1T, respectively. The neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain EGI 60016T formed a distinct clade with N. rhizosphaerae EGI 80099T and N. massiliensis NP1T. The polar lipids detected for strain EGI 60016T were diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol, an unidentified glycolipid, an unidentified lipid and an unidentified phospholipid. The DNA G+C content was determined to be 64.1 mol%. Other chemotaxonomic features of strain EGI 60016T included MK-7, MK-8 and MK-9 as the respiratory quinones, and anteiso-C15 : 0 and anteiso-C17 : 0 as the major fatty acids. Based on the results of the phylogenetic analysis supported by morphological, physiological, chemotaxonomic and other differentiating phenotypic characteristics, strain EGI 60016T is considered to represent a novel species of the genus Nesterenkonia, for which the name Nesterenkonia endophytica sp. nov. is proposed. The type strain is EGI 60016T (=CCTCC AB 2017176T=NBRC 112398T).

Sphingobacteriumsoli sp. nov., isolated from soil.

A Gram-stain-negative, strictly aerobic, rod-shaped, non-motile, non-spore-forming bacterial strain, designated YIM X0211T, was isolated from a soil sample of Shiling County, Yunnan Province, south-west China. The new isolate was characterized taxonomically by using a polyphasic approach. The strain grew optimally at 30 °C, at pH 7.0 and with 0-3 % (w/v) NaCl. It was positive for catalase and oxidase but negative for H2S production. Comparative 16S rRNA gene sequence analysis showed that strain YIM X0211T fell within the cluster comprising Sphingobacterium species and clustered with Sphingobacterium mizutaii DSM 11724T (97.93 % similarity). The G+C content of the genomic DNA was 41.2 mol%. The predominant respiratory quinone was menaquinone MK-7. The major fatty acids were iso-C15 : 0 2-OH, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1ω7c/C16 : 1ω6c). The polar lipids consisted of phosphatidylethanolamine, sphingolipid, and several unknown phospholipids or lipids. The DNA-DNA hybridization value between strain YIM X0211T and S. mizutaii DSM 11724T was 42.3±0.4 %, which is below the 70 % limit for species delineation. These chemotaxonomic data supported the affiliation of strain YIM X0211T to the genus Sphingobacterium. Based on the recorded phenotypic and genotypic characteristics, it is determined that the isolate represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium soli sp. nov. is proposed. The type strain is YIM X0211T (=KCTC 42696T=CGMCC 1.15966T).

Pseudoclavibacter endophyticus sp. nov., isolated from roots of Glycyrrhiza uralensis.

A Gram-stain-positive, aerobic, rod-shaped, non-motile actinomycete strain, designated EGI 60007T, was isolated from healthy roots of Glycyrrhiza uralensis F. collected from Yili County, Xinjiang Province, north-west China. A polyphasic approach was applied to study the taxonomic position of the new isolate. The 16S rRNA gene sequence of strain EGI 60007T had highest similarities with members of the genus Pseudoclavibacter, including Pseudoclavibacter chungangensis CAU 59T (96.98 % 16S rRNA gene sequence similarity), Pseudoclavibacter helvolus DSM 20419T (96.43 %) and Pseudoclavibacter terrae THG-MD12T (96.14 %). The neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain EGI 60007T clustered with members of the genus Pseudoclavibacter, and formed a distinct clade with P. chungangensis CAU 59T. The polar lipids detected for strain EGI 60007T were phosphatidylglycerol, diphosphatidylglycerol, one unidentified glycolipid and one unidentified lipid. The DNA G+C content was determined to be 63.3 mol%. The chemotaxonomic features of strain EGI 60007T showed typical characteristics of the genus Pseudoclavibacter, with MK-9 as the respiratory quinone, 2,4-diaminobutyric acid as the diamino acid in the peptidoglycan, and anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0 as the major fatty acids. The sugars of whole-cell hydrolysates were mainly mannose, rhamnose, ribose and glucose, and a minor amount of xylose. Based on the results of the phylogentic analysis supported by morphological, physiological, chemotaxonomic and other differentiating phenotypic characteristics, strain EGI 60007T is considered to represent a novel species of the genus Pseudoclavibacter, for which the name Pseudoclavibacter endophyticus sp. nov. is proposed. The type strain is EGI 60007T ( = CGMCC 1.15081T = KCTC 39112T = DSM 29943T).