Genome Sequencing Analysis of a Rare Case of Blood Infection Caused by Flavonifractor plautii.

BACKGROUND Flavonifractor plautii belongs to the clostridium family, which can lead to local infections as well as the bloodstream infections. Flavonifractor plautii caused infection is rarely few in the clinic. To understand better Flavonifractor plautii, we investigated the drug sensitivity and perform genome sequencing of Flavonifractor plautii isolated from blood samples in China and explored the drug resistance and pathogenic mechanism of the bacteria. CASE REPORT The Epsilometer test method was used to detect the sensitivity of flavonoid bacteria to antimicrobial agents. PacBio sequencing technology was employed to sequence the whole genome of Flavonifractor plautii, and gene prediction and functional annotation were also analyzed. Flavonifractor plautii displayed sensitivity to most drugs but resistance to fluoroquinolones and tetracycline, potentially mediated by tet (W/N/W). The total genome size of Flavonifractor plautii was 4,573,303 bp, and the GC content was 59.78%. Genome prediction identified 4,506 open reading frames, including 9 ribosomal RNAs and 66 transfer RNAs. It was detected that the main virulence factor-coding genes of the bacteria were the capsule, polar flagella and FbpABC, which may be associated with bacterial movement, adhesion, and biofilm formation. CONCLUSIONS The results of whole-genome sequencing could provide relevant information about the drug resistance mechanism and pathogenic mechanism of bacteria and offer a basis for clinical diagnosis and treatment.

Advanced oxidation of recalcitrant chromophores in full-scale MBR effluent for non-potable reuse of leachate co-treated municipal wastewater.

Wastewater non-potable reuse involves further processing of secondary effluent to a quality level acceptable for reuse and is a promising solution to combating water scarcity. Recalcitrant chromophores in landfill leachate challenge the water quality for non-potable reuse when leachate is co-treated with municipal wastewater. In this study, we first use multivariate statistical analysis to reveal that leachate is an important source (with a Pearson's coefficient of 0.82) of recalcitrant chromophores in the full-scale membrane bioreactor (MBR) effluent. We then evaluate the removal efficacies of chromophores by chlorination, breakpoint chlorination, and the chlorination-UV/chlorine advanced oxidation treatment. Conventional chlorination and breakpoint chlorination only partially remove chromophores, leaving a colour level exceeding the standards for non-potable reuse (>20 Hazen units). We demonstrate that pre-chlorination (with an initial chlorine dosing of 20 mg/L as Cl2) followed by UV radiation (with a UV fluence of 500 mJ/cm2) effectively degraded recalcitrant chromophores (>90%). By quantifying the electron donating capacity (EDC) and radical scavenging capacity (RSC) of the reclaimed water, we demonstrate that pre-chlorination reduces EDC and RSC by up to 64%, increases UV transmittance by 32%, and increases radical yields from UV photolysis of chlorine by 1.7-2.2 times. The findings advance fundamental understanding of the alteration of dissolved coloured substances by (photo)chlorination treatment and provide implications for applying advanced oxidation processes in treating wastewater effluents towards sustainable non-potable reuse.

Ap-2ß regulates cranial osteogenic potential via the activation of Wnt/ß-catenin signaling pathway.

The skull is a fundamental bone that protects the development of brain and consists of several bony elements, such as the frontal and parietal bones. Frontal bone exhibited superior in osteogenic potential and regeneration of cranial defects compared to parietal bone. However, how this regional difference is regulated remains largely unknown. In this study, we identified an Ap-2ß transcriptional factor with a higher expression in frontal bone, but its molecular function in osteoblasts needs to be elucidated. We found that Ap-2ß knockdown in preosteoblasts leads to reduced proliferation, increased cell death and impaired differentiation. Through RNA-seq analysis, we found that Ap-2ß influences multiple signaling pathways including the Wnt pathway, and overexpression of Ap-2ß showed increased nuclear ß-catenin and its target genes expressions in osteoblasts. Pharmacological activation of Wnt/ß-catenin signaling using LiCl treatment cannot rescue the reduced luciferase activities of the ß-catenin/TCF/LEF reporter in Ap-2ß knockdown preosteoblasts. Besides, transient expression of Ap-2ß via the lentivirus system could sufficiently rescue the inferior osteogenic potential in parietal osteoblasts, while Ap-2ß knockdown in frontal osteoblasts resulted in reduced osteoblast activity, reduced active ß-catenin and target genes expressions. Taken together, our data demonstrated that Ap-2ß modulates osteoblast proliferation and differentiation through the regulation of Wnt/ß-catenin signaling pathway and plays an important role in regulating regional osteogenic potential in frontal and parietal bone.

Regulation of las and rhl Quorum Sensing on Aerobic Denitrification in Pseudomonas aeruginosa PAO1.

The bacterium Pseudomonas aeruginosa negatively regulates denitrification under anerobic conditions by two acyl-homoserine lactone quorum-sensing (QS) systems called las and rhl. However, it is unknown whether these systems have the same effect on denitrification in aerobic conditions. In this study, we investigated the regulation of las and rhl systems on aerobic denitrification. We showed that the removal of nitrate in P. aeruginosa PAO1 was repressed by both the las and rhl systems. The las and rhl systems had negative effects on activities of denitrifying enzymes NAP, NIR, NOR, and NOS. At the level of transcription, both QS systems inhibited the expression of target genes napA, nirS, norB, norC, and nosZ. Furthermore, the addition of an acylase, which degrades the acyl-homoserine lactone signals (AHLs), to wild type resulted in an increase in the removal of nitrate. Additionally, in aerobic denitrification process, the transcription factor DNR, which controls denitrification, was repressed by both QS systems. The results implied that modulation of QS in denitrifying bacteria, possibly through quorum quenching or QS inhibition, could help to improve the reduction of nitrate in wastewater treatment.

Bioaugmentation and quorum sensing disruption as solutions to increase nitrate removal in sequencing batch reactors treating nitrate-rich wastewater.

Bioaugmentation of denitrifying bacteria can serve as a promising technique to improve nutrient removal during wastewater treatment. While denitrification inhibition by bacterial quorum sensing (QS) in Pseudomonas aeruginosa has been indicated, the application of bacterial QS disruption to improve nitrate removal from wastewater has not been investigated. In this study, the effect of bioaugmentation of P. aeruginosa SD-1 on nitrate removal in sequencing batch reactors that treat nitrate rich wastewater was assessed. Additionally, the potential of a quorum sensing inhibitor (QSI) to improve denitrification following bacterial bioaugmentation was evaluated. Curcumin, a natural plant extract, was used as a QSI. The chemical oxygen demand (COD) and initial nitrate concentration of the influent were 700±20 mg/L and 200±10 mg/L respectively, and their respective concentrations in the effluent were 56.9±3.2 mg/L and 9.0±3.2 mg/L. Thus, the results revealed that bioaugmentation of P. aeruginosa SD-1 resulted in an increased nitrate removal to 82%±1%. Further, nitrate was almost completely removed following the addition of the QSI, and activities of nitrate reductase and nitrite reductase increased by 88%±2% and 74%±2% respectively. The nitrogen mass balance indicated that aerobic denitrification was employed as the main pathway for nitrogen removal in the reactors. The results imply that bioaugmentation and modulation of QS in denitrifying bacteria, through the use of a QSI, can enhance nitrate removal during wastewater treatment.

Composting swine carcasses with nitrogen transformation microbial strains: Succession of microbial community and nitrogen functional genes.

In this study, nitrogen transformation strains, including three ammonium transformation strains, one nitrite strain and one nitrogen fixer, were inoculated at different swine carcass composting stages to regulate the nitrogen transformation and control the nitrogen loss. The final total nitrogen content was significantly increased (p < 0.01). The bacterial communities were assessed by amplicon sequencing and association analysis. Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes were the four most dominant phyla.,Brevibacterium, Streptomyces and Ochrobactrum had a significant (p < 0.05) and positive correlation with total nitrogen and ammonium nitrogen content in both groups. The quantitative results of nitrogen transformation genes showed that ammonification, nitrification, denitrification and nitrogen fixation were simultaneously present in the composting process of swine carcasses, with the latter two accounting for a higher proportion. The ammonium transformation strains significantly (p < 0.05) strengthened nitrogen fixation and remarkably (p < 0.01) weakened nitrification and denitrification, which, however, were notably (p < 0.05) enhanced by the nitrite strain and nitrogen fixer. In this research, the inoculated strains changed the bacterial structure by regulating the abundance and activity of the highly connected taxa, which facilitated the growth of nitrogen transformation bacteria and regulated the balance/symbiosis of nitrogen transformation processes to accelerate the accumulation of nitrogen.

Effects of exogenous microbial inoculum on the structure and dynamics of bacterial communities in swine carcass composting.

Composting is a widely accepted method for the disposal of deceased livestock. It is a biological self-heating process during which animal carcasses are converted to fertilizer products. Additional inoculants can facilitate the composting progress. This study investigated how the addition of microbial inoculants could improve the composting effectiveness and could change the structure and dynamics of bacterial communities in the carcass composting process. Four strains of Bacillus were inoculated into the swine carcass composting piles. The groups with the additional inoculants showed a higher temperature in the thermophilic phase and higher germination indices in the composted products. The sequencing results showed that the dominant phyla were Proteobacteria, Firmicutes, and Actinobacteria, and the dominant classified genera were Brevibacterium and Bacillus. Canonical correlation analysis showed that temperature and moisture exerted a stronger influence on the bacterial community diversity. The interaction network of dominant genera and the abundance variation of the bacterial community demonstrated that the inoculated bacterial agent changed the structure of bacterial communities and enriched the diversity of the species due to antagonism and symbiosis among the dominant bacterial communities.