Incidence and risk factors of acute kidney injury after transcatheter aortic valve replacement.

PURPOSE: Acute kidney injury (AKI) is a common early complication secondary to transcatheter aortic valve replacement (TAVR). Studies on the incidence and risk factors for AKI after TAVR surgery are limited to date. Here, we retrospectively analyzed the incidence and risk factors for AKI after TAVR surgery in our hospital. MATERIALS AND METHODS: Patients who underwent TAVR surgery at our hospital from November 2017 to February 2023 were selected. AKI was defined using the 2012 KDIGO definition and staging criteria. The relevant data and information between the AKI group and the non-AKI group were compared and analyzed, and a binary logistic regression model was used to analyze the risk factors for AKI. RESULTS: A total of 75 patients who underwent TAVR surgery were included in the retrospective analysis. After TAVR, the incidence of AKI was 17.3% (13/75), of which 8 (61.5%) had stage 1 AKI, 2 (15.4%) had stage 2 AKI, 3 (23.1%) had stage 3 AKI, and 3 needed renal replacement therapy. After multivariate logistic analysis, contrast volume (OR = 1.024 (1.001, 1.047)) was found to be an independent risk factor for AKI, while patients with high estimated glomerular filtration rate (eGFR) (OR = 0.903 (0.826, 0.986)) have a reduced risk of AKI. CONCLUSION: A retrospective study revealed a 17.3% incidence of AKI after TAVR surgery in our hospital, most of which were stage 1 AKI. A low preoperative eGFR and contrast volume were found to be independent risk factors for AKI.

Marinimicrobium alkaliphilum sp. nov., an alkaliphilic bacterium isolated from soil and emended description of the genus Marinimicrobium.

Two Gram-stain-negative, rod-shaped bacterial strains, designated SW121T and W12, were isolated from a soil sample collected from Shanxi Province, China. The two strains were strictly aerobic, catalase-positive and oxidase-positive. Both strains grew at 6-42 °C (optimum, 30 °C), at pH 5.5-11.0 (optimum, pH 9.0) and in the presence of 0-15.0 % (w/v) NaCl (optimum, 2.0-3.0 %). The predominant cellular fatty acids of strain SW121T were C16 : 0, C18 : 1ω7c and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c). Strain SW121T contained ubiquinone-8 as the sole respiratory quinone. Diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol were major polar lipids. The genomic DNA G+C content of strain SW121T was 58.5 mol%. Comparative analysis of 16S rRNA gene sequences revealed that strains SW121T and W12 showed the highest similarities to Marinimicrobium koreense DSM 16974T(95.7 and 95.5 %, respectively). On the basis of phylogenetic inference and phenotypic characteristics, it is proposed that the two strains represent a novel species of the genus Marinimicrobium, for which the name Marinimicrobiumalkaliphilum sp. nov. is proposed. The type strain is SW121T (=CGMCC 1.16166T=KCTC 62651T).

Alcanivorax indicus sp. nov., isolated from seawater.

A Gram-stain-negative, motile, rod-shaped bacterium, designated SW127T, was isolated from a seawater sample collected from the Indian Ocean. Strain SW127T was aerobic, catalase- and oxidase-positive, and grew at 8-42 °C (optimum, 30 °C), at pH 5.5-9.0 (optimum, pH 7.5) and in the presence of 0.5-11.0 % (w/v) NaCl (optimum, 3.0-4.0 %). Comparative analysis of 16S rRNA gene sequences indicated that strain SW127T belonged to the genus Alcanivorax, and closely related to Alcanivorax pacificus MCCC 1A00474T (96.7 % sequence similarity). The predominant cellular fatty acids of strain SW127T were C16 : 0 and summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c). Strain SW127T contained phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids. The genomic DNA G+C content of strain SW127T was 62.8 mol%. On the basis of its phenotypic characteristics and phylogenetic data, strain SW127T represents a novel species of the genus Alcanivorax, for which the name Alcanivorax indicus sp. nov. is proposed. The type strain is SW127T (=CGMCC 1.16233T=KCTC 62652T).

Transcriptome and Zymogram Analyses Reveal a Cellobiose-Dose Related Reciprocal Regulatory Effect on Cellulase Synthesis in Cellulosilyticum ruminicola H1.

The rumen bacterium Cellulosilyticum ruminicola H1 efficiently hydrolyzes cellulose. To gain insights into the regulatory mechanisms of cellulase synthesis, comparative transcriptome analysis was conducted for cultures grown on 2% filter paper, 0.5 and 0.05% cellobiose, and 0.5% birchwood xylan. It was found that cellulose induced a majority of (hemi)cellulases, including 33 cellulases and a cellulosomal scaffoldin (1.3- to 22.7-fold); seven endoxylanases, two mannanases, and two pectatelyases (2- to 16-fold); and pyruvate formate-lyase (PFL, 1.5- to 7-fold). Noticeably, 3- and 2.5-fold increased transcription of a cellobiohydrolase and the cellulosomal scaffoldin precursor were detected in 0.05% than in 0.5% cellobiose. Consistently, 9- and 4-fold higher specific cellobiohydrolase activities were detected in the filter paper and 0.05% cellobiose culture. SDS- and native-PAGE zymograms of cellulose-enriched proteins from the filter paper culture displayed cellulase activities, and cellulolytic "complexes" were enriched from the filter paper- and 0.05% cellobiose-cultures, but not from the 0.5% cellobiose culture. LC-MS/MS identified the cellulosomal scaffoldin precursor in the "complexes" in addition to cellulase, hemicellulase, and PFL proteins. The addition of 0.5% cellobiose, but not 0.05% cellobiose remarkably inhibited strain H1 to degrade filter paper. Therefore, this work reveals a cellobiose-dose related regulatory mechanism of cellulase synthesis by lower for induction and higher for repression, which has extended our understanding of the regulation of microbial cellulase synthesis.

Re-examination of the genotoxic activity of water taken from the Songhua River in P. R. China.

The Songhua River, in northeast China, has heavy organic contamination due to domestic sewage and industrial wastewater. Thus, it is important to further determine its genotoxic activity, which is a potential hazard for human health. Short-term genotoxic bioassays using Salmonella, the cytokinesis-block micronucleus cytome assay, and mouse liver cell comet assay were employed to further examine the genotoxic activity of diethyl ether extracts of water samples taken from the Songhua River. Ames test results showed that there were still frame-shift mutagens, both direct and indirect, in water samples at doses of 5.0 or 7.0 L water equivalent/plate. The mutagenicity seems to be less when compared with the results from 2002 to 2003. A dose-response relationship was also obtained between DNA damage in mouse liver cells by comet assay and micronuclei formation by CBMN assay. These results indicate that the water samples showed genotoxic activity with a mutagenic potency. 88 and 104 compounds, respectively, were identified in summer and winter water sample extracts by gas chromatography-mass spectrometry analysis. Four priority pollutants listed by the United States Environmental Protection Agency and six priority pollutants listed by the Chinese Environment Protection Agency were found in summer or winter water samples, respectively. The results indicate that the diethyl ether extracts of surface water samples taken from the Songhua River still show genotoxic activity (≥3.0 L water). The risks of potential carcinogenicity for human health in the Songhua River should be studied further.

Acyl homoserine lactone-based quorum sensing in a methanogenic archaeon.

Acyl homoserine lactone (AHL)-based quorum sensing commonly refers to cell density-dependent regulatory mechanisms found in bacteria. However, beyond bacteria, this cell-to-cell communication mechanism is poorly understood. Here we show that a methanogenic archaeon, Methanosaeta harundinacea 6Ac, encodes an active quorum sensing system that is used to regulate cell assembly and carbon metabolic flux. The methanogen 6Ac showed a cell density-dependent physiology transition, which was related to the AHL present in the spent culture and the filI gene-encoded AHL synthase. Through extensive chemical analyses, a new class of carboxylated AHLs synthesized by FilI protein was identified. These carboxylated AHLs facilitated the transition from a short cell to filamentous growth, with an altered carbon metabolic flux that favoured the conversion of acetate to methane and a reduced yield in cellular biomass. The transcriptomes of the filaments and the short cell forms differed with gene expression profiles consistent with the physiology. In the filaments, genes encoding the initial enzymes in the methanogenesis pathway were upregulated, whereas those for cellular carbon assimilation were downregulated. A luxI-luxR ortholog filI-filR was present in the genome of strain 6Ac. The carboxylated AHLs were also detected in other methanogen cultures and putative filI orthologs were identified in other methanogenic genomes as well. This discovery of AHL-based quorum sensing systems in methanogenic archaea implies that quorum sensing mechanisms are universal among prokaryotes.

CBM3d, a novel subfamily of family 3 carbohydrate-binding modules identified in Cel48A exoglucanase of Cellulosilyticum ruminicola.

Previously, we found that exoglucanase Cel48A from Cellulosilyticum ruminicola H1 bound intensively to Avicel; however, no known carbohydrate-binding module (CBM) was observed in the protein. Bioinformatics suggested that a C-terminal fragment of 127 amino acids, named the Cellulosilyticum-specific paralogous module (CPM), could function in binding. CPM-appended proteins are all putative (hemi)cellulases from Cellulosilyticum spp. In the present work, we demonstrated that Cel48A without the CPM retained only exoglucanase activity and lost the Avicel-binding ability, while the isolated CPM exhibited a high affinity for Avicel. In addition, the CPM bound to chitin, but not to soluble polysaccharides, making it a type A CBM, which binds only insoluble polysaccharides. Phylogenetic analysis clustered the CPM and its homologs as a separate branch that was distantly related to CBM subfamilies 3a (28% identity), 3b (24% identity), and 3c (21% identity). Sequence alignment revealed distinct secondary structures of the new CBM 3 group, in particular, a conserved Pro66-Trp67 insert preceding strand ß4', a deletion preceding strand ß6, and incomplete strands ß8 and ß9. An alanine scan for six aromatic and three nonaromatic amino acid residues (D66, P66, and R111) by site-directed mutagenesis determined that Phe62, Pro66, Trp67, Tyr68, Arg111, and Trp117 were the functional residues for binding. Among them, Phe62, Pro66, and Trp67 were the newly determined key sites in the CPM for binding. Three-dimensional homolog modeling revealed two types of substrate-binding sites, planar and groove, in the CPM. Thus, a new subfamily, CBM family 3d, is proposed.

Three feruloyl esterases in Cellulosilyticum ruminicola H1 act synergistically to hydrolyze esterified polysaccharides.

Feruloyl esterases (Faes) constitute a subclass of carboxyl esterases that specifically hydrolyze the ester linkages between ferulate and polysaccharides in plant cell walls. Until now, the described microbial Faes were mainly from fungi. In this study, we report that Cellulosilyticum ruminicola H1, a previously described fibrolytic rumen bacterium, possesses three different active feruloyl esterases, FaeI, FaeII, and FaeIII. Phylogenetic analysis classified the described bacterial Faes into two types, FaeI and FaeII in type I and FaeIII in type II. Substrate specificity assays indicated that FaeI is more active against the ester bonds in natural hemicelluloses and FaeIII preferentially attacks the ferulate esters with a small moiety, such as methyl groups, while FaeII is active on both types of substrates. Among the three feruloyl esterase genes, faeI was the only one induced significantly by xylose and xylan, while pectin appeared to moderately induce the three genes during the late log phase to stationary phase. Western blot analysis determined that FaeI and FaeIII were secreted and cytoplasmic proteins, respectively, whereas FaeII seemed to be cell associated. The addition of FaeI and FaeII but not FaeIII enhanced the activity of a xylanase on maize cob, suggesting a synergy of the former two with xylanase. Hence, we propose that the three feruloyl esterases work in concert to hydrolyze ferulate esters in natural hemicelluloses.

Cellulosilyticum ruminicola, a newly described rumen bacterium that possesses redundant fibrolytic-protein-encoding genes and degrades lignocellulose with multiple carbohydrate- borne fibrolytic enzymes.

Cellulosilyticum ruminicola H1 is a newly described bacterium isolated from yak (Bos grunniens) rumen and is characterized by its ability to grow on a variety of hemicelluloses and degrade cellulosic materials. In this study, we performed the whole-genome sequencing of C. ruminicola H1 and observed a comprehensive set of genes encoding the enzymes essential for hydrolyzing plant cell wall. The corresponding enzymatic activities were also determined in strain H1; these included endoglucanases, cellobiohydrolases, xylanases, mannanase, pectinases, and feruloyl esterases and acetyl esterases to break the interbridge cross-link, as well as the enzymes that degrade the glycosidic bonds. This bacterium appears to produce polymer hydrolases that act on both soluble and crystal celluloses. Approximately half of the cellulytic activities, including cellobiohydrolase (50%), feruloyl esterase (45%), and one third of xylanase (31%) and endoglucanase (36%) activities were bound to cellulosic fibers. However, only a minority of mannase (6.78%) and pectinase (1.76%) activities were fiber associated. Strain H1 seems to degrade the plant-derived polysaccharides by producing individual fibrolytic enzymes, whereas the majority of polysaccharide hydrolases contain carbohydrate-binding module. Cellulosome or cellulosomelike protein complex was never isolated from this bacterium. Thus, the fibrolytic enzyme production of strain H1 may represent a different strategy in cellulase organization used by most of other ruminal microbes, but it applies the fungal mode of cellulose production.

Cellulosilyticum ruminicola gen. nov., sp. nov., isolated from the rumen of yak, and reclassification of Clostridium lentocellum as Cellulosilyticum lentocellum comb. nov.

An obligate anaerobic, Gram-staining-negative, mesophilic, cellulolytic bacterium, strain H1(T), was isolated from the rumen content of yak. Cells were straight to slightly curved rods, 0.8-1.0 x 3.0-4.0 microm in size, non-motile and encapsulated with mucous materials. Elliptical and terminal spores that swelled the cells were produced occasionally. The strain grew at 25-45 degrees C (optimum, 38 degrees C) and pH 6.0-7.8 (optimum, pH 6.7). Cellulose, cellobiose, xylan, xylose and maltose were used as carbon and energy sources, but not glucose. Products from cellulose and cellobiose fermentation were formic acid, acetic acid, carbon dioxide and trace amounts of ethanol, lactic acid and succinic acid. The genomic DNA G+C content was 33.7+/-1.2 mol%. The predominant fatty acids were C(16 : 0) (27.1 %), C(14 : 0) (9.2 %) and iso-C( 16 : 0) (6.4%). Based on the 16S rRNA gene sequence analysis, strain H1(T) was affiliated to the clostridial rRNA cluster XIVb and showed the highest 16S rRNA gene sequence similarity to Clostridium lentocellum DSM 5427(T) (96.0 %). These two strains formed a distinct lineage of the family 'Lachnospiraceae '. Based on data from this polyphasic taxonomic study, a new genus, Cellulosilyticum gen. nov., is proposed. Cellulosilyticum ruminicola sp. nov. is proposed for strain H1(T). The type strain of Cellulosilyticum ruminicola sp. nov. is strain H1(T) (=CGMCC 1.5065(T)=JCM 14822(T)). Clostridium lentocellum was reclassified in the new genus as Cellulosilyticum lentocellum comb. nov. (type strain RHM5(T)=ATCC 49066( T)=DSM 5427(T)=NCIMB 11756(T)).

Actinomyces ruminicola sp. nov., isolated from cattle rumen.

Two obligate anaerobic bacterial strains, B71(T) and D471, were isolated from cattle rumen. The novel strains were Gram-positive and rod-shaped. The strains hydrolysed xylan and starch, fermented some mono-, di- and oligosaccharides and produced formic, acetic and lactic acids as end products from glucose. Growth of the isolates was observed at 20-55 degrees Celsius and pH 6.5-9.0. The DNA G+C contents of strains B71(T) and D471 were 68.06 and 68.26 mol%, respectively. Although the two novel strains met the genus description for Actinomyces, some phenotypic characteristics, such as optimum growth temperature, requirement for O(2) and the end products of fermentation, distinguished them from previously described members of the genus. Phylogenetic analysis based on 16S rRNA gene sequences demonstrated that the novel strains belonged to the genus Actinomyces (88.3-93.6 % sequence similarity) and formed a distinct line within the clade containing Actinomyces bovis. On the basis of these results, a novel species, Actinomyces ruminicola sp. nov., is proposed. The type strain is B71(T) (=JCM 13352(T)=CGMCC 1.5030(T)).