mRNA Interferase Bacillus cereus BC0266 Shows MazF-Like Characteristics Through Structural and Functional Study

Bacteriophages benefit from mobilizing pathogenicity islands encoding immune systems against competitors

Bacteria encode sophisticated anti-phage systems that are diverse and versatile and display high genetic mobility. How this variability and mobility occurs remains largely unknown. Here, we demonstrate that a widespread family of pathogenicity islands, the phage-inducible chromosomal islands (PICIs), carry an impressive arsenal of defense mechanisms, which can be disseminated intra- and inter-generically by helper phages. These defense systems provide broad immunity, blocking not only phage reproduction, but also plasmid and non-cognate PICI transfer. Our results demonstrate that phages can mobilize PICI-encoded immunity systems to use them against other mobile genetic elements, which compete with the phages for the same bacterial hosts. Therefore, despite the cost, mobilization of PICIs may be beneficial for phages, PICIs, and bacteria in nature. Our results suggest that PICIs are important players controlling horizontal gene transfer and that PICIs and phages establish mutualistic interactions that drive bacterial ecology and evolution.

The association between platelet-lymphocyte ratio and the risk of all-cause mortality in chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

Chronic kidney disease (CKD) patients have high levels of inflammatory mediators. These inflammatory mediators contribute to the increased risk of cardiovascular events and all-cause mortality. Platelet-lymphocyte ratio (PLR) has recently been recognized as a novel inflammatory marker and has been shown to be associated with the prognosis in CKD patients. However, the quality of these studies varies and their results are controversial. The purpose of this meta-analysis was to investigate the relationship between PLR and all-cause mortality in CKD patients.

METHODS

A systematic literature search of PubMed, EMBASE, CENTRAL and ISI Web of Science was conducted. The databases were searched from their inception dates up to the latest issue (31 October 2021). Two reviewers independently searched the databases and screened studies. Data were extracted using a standardized collection form. Meta-analysis was performed to compare PLR values between CKD and non-CKD patients, and to investigate the association between PLR and all-cause mortality in CKD patients. This meta-analysis is reported in adherence to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

A total of 11 studies involving 4244 participants were selected. The pooled data indicated that PLR values were significantly higher in CKD patients than non-CKD controls (weighted mean difference = 21.6, 95% CI 17.39-25.81, p < 0.01), and PLR is associated with an increased risk of all-cause mortality in CKD patients (hazard ratio = 2.49, 95% CI 1.78-3.49, p < 0.01).

CONCLUSIONS

Patients with CKD have higher PLR values compared to non-CKD patients. Meanwhile, PLR values were highly associated with all-cause mortality in CKD patients. PLR is a valid predictor as a clinically accessible indicator for patients with CKD.

Functional Characterization of the mazEF Toxin-Antitoxin System in the Pathogenic Bacterium Agrobacterium tumefaciens

Agrobacterium tumefaciens is a pathogen of various plants which transfers its own DNA (T-DNA) to the host plants. It is used for producing genetically modified plants with this ability. To control T-DNA transfer to the right place, toxin-antitoxin (TA) systems of A. tumefaciens were used to control the target site of transfer without any unintentional targeting. Here, we describe a toxin-antitoxin system, Atu0939 (mazE-at) and Atu0940 (mazF-at), in the chromosome of Agrobacterium tumefaciens. The toxin in the TA system has 33.3% identity and 45.5% similarity with MazF in Escherichia coli. The expression of MazF-at caused cell growth inhibition, while cells with MazF-at co-expressed with MazE-at grew normally. In vivo and in vitro assays revealed that MazF-at inhibited protein synthesis by decreasing the cellular mRNA stability. Moreover, the catalytic residue of MazF-at was determined to be the 24th glutamic acid using site-directed mutagenesis. From the results, we concluded that MazF-at is a type II toxin-antitoxin system and a ribosome-independent endoribonuclease. Here, we characterized a TA system in A. tumefaciens whose understanding might help to find its physiological function and to develop further applications.