CesH Represses Cereulide Synthesis as an Alpha/Beta Fold Hydrolase in <i>Bacillus cereus</i>

Cereulide is notorious as a heat-stable emetic toxin produced by Bacillus cereus and glucose is supposed to be an ingredient supporting its formation. This study showed that glucose addition benefited on cell growth and the early transcription of genes involved in substrate accumulation and toxin synthesis, but it played a negative role in the final production of cereulide. Meanwhile, a lasting enhancement of cesH transcription was observed with the addition of glucose. Moreover, the cereulide production in &#916;cesH was obviously higher than that in the wild type. This indicates that CesH has a repression effect on cereulide production. Bioinformatics analysis revealed that CesH was an alpha/beta hydrolase that probably associated with the cell membrane, which was verified by subcellular localization. The esterase activity against para-nitrophenyl acetate (PNPC2) of the recombinant CesH was confirmed. Although no sign of ester bond cleavage in cereulide or valinomycin was demonstrated in in vitro assays, CesH could reverse the cereulide analogue sensitivity of Bacillus subtilis in vivo, by which toxin degradation was facilitated. Moreover, site directed mutations identified that the conserved catalytic triad of CesH might consist of Serine 86, Glutamate 199, and Histidine 227. These results help us to understand the regulation of cereulide production and provide clues for developing control measurements

Comparative efficacy and safety of sodium–glucose cotransporter 2 inhibitors for renal outcomes in patients with type 2 diabetes mellitus: a systematic review and network meta-analysis

AbstractIn this study, the summarized WMDs and RRs were calculated using a pairwise analysis and a network meta-analysis with a random effects model, to compare and rank the efficacy and safety of SGLT-2i for renal outcomes in patients with T2DM. Among 1894 identified articles, 30 trials including 50,244 patients with T2DM were evaluated. Network analysis revealed that the administration of canagliflozin was associated with a reduced risk of renal impairment (surface under the cumulative ranking: 90.8%). Further, although the administration of SGLT-2i was not associated with the risk of renal impairment (RR = 0.88, 95%CI = 0.68–1.15, p = 0.354), the administration of empagliflozin was associated with a reduced risk of renal impairment compared to that with the administration of placebo (RR = 0.74, 95%CI = 0.62–0.90, p = 0.002). Moreover, compared with the administration of a placebo, the administration of 50, 100, and 200 mg of canagliflozin was associated with lower serum creatinine levels. Furthermore, compared with the administration of a placebo, the administration of 100 mg canagliflozin, 2.5 mg dapagliflozin, and 25 mg empagliflozin was associated with a lower reduction in the estimated glomerular filtration rate. Except for 300 mg canagliflozin, all SGLT-2i were associated with greater increases in blood urea nitrogen levels (WMD = 1.39, 95%CI = 1.20–1.59, p < 0.001). Finally, the administration of all SGLT-2i significantly increased the ratio of urinary glucose to creatinine compared with the ratio upon administration of placebo (WMD = 36.21, 95%CI = 31.50–40.92, p < 0.001). Briefly, canagliflozin exerts the greatest therapeutic effect in terms of reducing the risk of renal impairment. Empagliflozin and canagliflozin may be more effective than other SGLT-2i in preventing renal impairment

Phylogenetic tree based on the tail fiber proteins of 36 <i>Bacillus</i> phages.

<p>Phylogenetic trees were constructed based on the amino acid sequences of the tail fiber proteins of 36 <i>Bacillus</i> phages using neighbor joining with a bootstrap of 1,000. Circles represent the phages derived from emetic isolates. Numbers on the lines indicate branch support. Corresponding clusters (A-C) are also shown on the right.</p

Identification and genomic comparison of temperate bacteriophages derived from emetic <i>Bacillus cereus</i>

<div><p>Cereulide-producing <i>Bacillus cereus</i> isolates can cause serious emetic (vomiting) syndrome and even acute lethality. As mobile genetic elements, the exploration of prophages derived from emetic <i>B</i>. <i>cereus</i> isolates will help in our understanding of the genetic diversity and evolution of these pathogens. In this study, five temperate phages derived from cereulide-producing <i>B</i>. <i>cereus</i> strains were induced, with four of them undergoing genomic sequencing. Sequencing revealed that they all belong to the <i>Siphoviridae</i> family, but presented in different forms in their hosts. PfNC7401 and PfIS075 have typical icosahedral heads, probably existing alone as phagemids in the host with self-replicating capability in the lysogenic state. PfEFR-4, PfEFR-5, and PfATCC7953 have elongated heads, with the genomes of the former two identified as linear dsDNA, which could be integrated into the host genome during the lysogenic state. Genomic comparison of the four phages with others also derived from emetic <i>B</i>. <i>cereus</i> isolates showed similar genome structures and core genes, thus displaying host spectrum specificity. In addition, phylogenic analysis based on the complete genome and conserved tail fiber proteins of 36 <i>Bacillus</i> species-derived phages confirmed that the phages derived from emetic <i>B</i>. <i>cereus</i> strains were highly similar. Furthermore, one endolysin LysPfEFR-4 was cloned and showed lytic activity against all tested emetic <i>B</i>. <i>cereus</i> strains and cross-lytic activity against some other pathogenic bacteria, implying a potential to control bacterial contamination in the food supply.</p></div

Lytic activity and antimicrobial spectrum of LysEFR-4.

<p>Lytic activity of LysEFR-4 was measured by (a) turbid reduction assay and (b) plate lysis assay. CK indicates the control with the same volume of dialysis buffer replacing LysEFR-4 in the assay. (c) Antimicrobial spectrum of LysEFR-4. All experiments were carried out in triplicate.</p

Transmission electron micrographs of phages isolated in this study.

<p>PfNC7401 (a), PfIS075 (b), PfEFR-4 (c), PfEFR-5 (d), and PfATCC7953 (e) were stained with 2% phosphotungstic acid and visualized. White arrow indicates the putative tail fiber. Scale bars are 50 nm.</p

Plaques of temperate bacteriophages.

<p>Various plaques were formed on soft agar (0.5%) by PfNC7401 (a), PfIS075 (b), PfEFR-4 (c), PfEFR-5 (d), and PfATCC7953 (e) with their propagation strains. Scale bars are 10 mm.</p

Host range patterns of isolated bacteriophages.

<p>Host range patterns of isolated bacteriophages.</p