April 21, 2020  |  

Genomics and Experimental Analysis Reveal a Novel Factor Contributing to the Virulence of Cronobacter sakazakii Strains Associated With Neonate Infection.

Cronobacter sakazakii causes meningitis and necrotizing enterocolitis in premature infants. However, its virulence determinants, especially those specific for strains associated with neonate infections, remain largely unknown.In this study, we performed a comparative genomic analysis of 209 C. sakazakii genomes, and 8 clonal groups (CGs) were revealed.CG1 and CG2 were found to be significantly associated with neonate infections, and significantly prevalent genes in these 2 CGs were identified. Of these, a gene encoding the LysR-type regulator, CklR, was shown to contribute to bacterial pathogenicity based on animal experiments. We found that CklR directly binds and activates the suf Fe-S cluster biosynthesis operon, and high expression of the suf operon increases bacterial resistance to oxidative stress, which increases survival within the host. This leads to a high degree of bacteremia, which contributes to the development of meningitis.Our work revealed a novel virulence factor specific to predominant pathogenic C. sakazakii strains. © The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

April 21, 2020  |  

Iron-associated protein interaction networks reveal the key functional modules related to survival and virulence of Pasteurella multocida.

Pasteurella multocida causes respiratory infectious diseases in a multitude of birds and mammals. A number of virulence-associated genes were reported across different strains of P. multocida, including those involved in the iron transport and metabolism. Comparative iron-associated genes of P. multocida among different animal hosts towards their interaction networks have not been fully revealed. Therefore, this study aimed to identify the iron-associated genes from core- and pan-genomes of fourteen P. multocida strains and to construct iron-associated protein interaction networks using genome-scale network analysis which might be associated with the virulence. Results showed that these fourteen strains had 1587 genes in the core-genome and 3400 genes constituting their pan-genome. Out of these, 2651 genes associated with iron transport and metabolism were selected to construct the protein interaction networks and 361 genes were incorporated into the iron-associated protein interaction network (iPIN) consisting of nine different iron-associated functional modules. After comparing with the virulence factor database (VFDB), 21 virulence-associated proteins were determined and 11 of these belonged to the heme biosynthesis module. From this study, the core heme biosynthesis module and the core outer membrane hemoglobin receptor HgbA were proposed as candidate targets to design novel antibiotics and vaccines for preventing pasteurellosis across the serotypes or animal hosts for enhanced precision agriculture to ensure sustainability in food security. Copyright © 2018. Published by Elsevier Ltd.

April 21, 2020  |  

A Pathovar of Xanthomonas oryzae Infecting Wild Grasses Provides Insight Into the Evolution of Pathogenicity in Rice Agroecosystems

Xanthomonas oryzae (Xo) are critical rice pathogens. Virulent lineages from Africa and Asia and less virulent strains from the US have been well characterized. X. campestris pv. leersiae (Xcl), first described in 1957, causes bacterial streak on the perennial grass, Leersia hexandra, and is a close relative of Xo. L. hexandra, a member of the Poaceae, is highly similar to rice phylogenetically, is globally ubiquitous around rice paddies, and is a reservoir of pathogenic Xo. We used long read, single molecule, real time (SMRT) genome sequences of five strains of Xcl from Burkina Faso, China, Mali and Uganda to determine the genetic relatedness of this organism with Xo. Novel Transcription Activator-Like Effectors (TALEs) were discovered in all five strains of Xcl. Predicted TALE target sequences were identified in the L. perrieri genome and compared to rice susceptibility gene homologs. Pathogenicity screening on L. hexandra and diverse rice cultivars confirmed that Xcl are able to colonize rice and produce weak but not progressive symptoms. Overall, based on average nucleotide identity, type III effector repertoires and disease phenotype, we propose to rename Xcl to X. oryzae pv. leersiae (Xol) and use this parallel system to improve understanding of the evolution of bacterial pathogenicity in rice agroecosystems.

April 21, 2020  |  

A First Study of the Virulence Potential of a Bacillus subtilis Isolate From Deep-Sea Hydrothermal Vent.

Bacillus subtilis is the best studied Gram-positive bacterium, primarily as a model of cell differentiation and industrial exploitation. To date, little is known about the virulence of B. subtilis. In this study, we examined the virulence potential of a B. subtilis strain (G7) isolated from the Iheya North hydrothermal field of Okinawa Trough. G7 is aerobic, motile, endospore-forming, and requires NaCl for growth. The genome of G7 is composed of one circular chromosome of 4,216,133 base pairs with an average GC content of 43.72%. G7 contains 4,416 coding genes, 27.5% of which could not be annotated, and the remaining 72.5% were annotated with known or predicted functions in 25 different COG categories. Ten sets of 23S, 5S, and 16S ribosomal RNA operons, 86 tRNA and 14 sRNA genes, 50 tandem repeats, 41 mini-satellites, one microsatellite, and 42 transposons were identified in G7. Comparing to the genome of the B. subtilis wild type strain NCIB 3610T, G7 genome contains many genomic translocations, inversions, and insertions, and twice the amount of genomic Islands (GIs), with 42.5% of GI genes encoding hypothetical proteins. G7 possesses abundant putative virulence genes associated with adhesion, invasion, dissemination, anti-phagocytosis, and intracellular survival. Experimental studies showed that G7 was able to cause mortality in fish and mice following intramuscular/intraperitoneal injection, resist the killing effect of serum complement, and replicate in mouse macrophages and fish peripheral blood leukocytes. Taken together, our study indicates that G7 is a B. subtilis isolate with unique genetic features and can be lethal to vertebrate animals once being introduced into the animals by artificial means. These results provide the first insight into the potential harmfulness of deep-sea B. subtilis.

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