Overview on the bacterial Iron-Riboflavin metabolic axis

Redox reactions are ubiquitous in biological processes. Enzymes involved in redox metabolism often use cofactors in order to facilitate electron-transfer reactions. Common redox cofactors include micronutrients such as vitamins and metals. By far, while iron is the main metal cofactor, riboflavin is the most important organic cofactor. Notably, the metabolism of iron and riboflavin seem to be intrinsically related across life kingdoms. In bacteria, iron availability influences expression of riboflavin biosynthetic genes. There is documented evidence for riboflavin involvement in surpassing ironrestrictive conditions in some species. This is probably achieved through increase in iron bioavailability by reduction of extracellular iron, improvement of iron uptake pathways and boosting hemolytic activity. In some cases, riboflavin may also work as replacement of iron as enzyme cofactor. In addition, riboflavin is involved in dissimilatory iron reduction during extracellular respiration by some species. The main direct metabolic relationships between riboflavin and iron in bacterial physiology are reviewed here.This work was funded by CONICYT/Fondecyt (Chile) Grant Number 1150818

Differential regulation of riboflavin supply genes in Vibrio cholerae

© 2017 The Author(s). Background: Riboflavin is the precursor of important redox cofactors such as flavin mononucleotide (FMN) and flavin adenine dinucleotide, required for several biological processes. Vibrio cholerae, a pathogenic bacterium responsible for the cholera disease, possesses the ability to biosynthesize de novo as well as to uptake riboflavin through the riboflavin biosynthetic pathway (RBP) and the RibN importer, respectively. The intra-organism relationship between riboflavin biosynthesis and uptake functions has not been studied. Results: This work determined the transcriptional organization of RBP genes and ribN in V. cholerae through reverse transcription polymerase chain reaction and analyzed their expression when growing with or without extracellular riboflavin using real time PCR. The RBP is organized in three transcriptional units, the major one containing ribD, ribE, ribA and ribH together with genes involved in functions not directly related to riboflavin bios

Contribution of riboflavin supply pathways to Vibrio cholerae in different environments

Background: The waterborne diarrheagenic bacterium Vibrio cholerae, cause of the pandemic cholera disease, thrives in a variety of environments ranging from estuarine waters to the human intestinal tract. This species has two ways to obtain the essential micronutrient riboflavin, de novo biosynthesis and environmental uptake through the RibN importer. The way these functions interrelate to fulfill riboflavin needs in different conditions in this species is unknown. Results: This study analyzed the contributions of riboflavin biosynthesis and transport to the culturability of Vibrio cholerae in river and seawater in vitro and in the Caenorhabditis elegans nematode host model. Elimination of the ribD riboflavin biosynthetic gene renders the bacteria riboflavin-auxotrophic, while a ribN mutant strain has no growth defect in minimal media. When growing in river water, deletion of ribD causes an impairment in culturability. In this condition, the Delta ribN strain has a defect to compete against a wild type strain but outcompetes the Delta ribD strain. The latter effect is inverted by the addition of riboflavin to the water. In contrast, growth in seawater causes a loss in culturability independent of riboflavin biosynthesis or transport. In the C. elegans model, only the Delta ribD strain is attenuated. Conclusion: Results indicate that while riboflavin biosynthesis seems to outweigh riboflavin uptake, the latter may still provide a selective advantage to V. cholerae in some environments.CONICYT FONDECYT Regular (Chile) 115081

Transcriptomics reveals a crossmodulatory effect between riboflavin and iron and outlines responses to riboflavin biosynthesis and uptake in Vibrio cholerae

CONICYT-FONDECYT (Chile) 1150818Vibrio cholerae, a pandemic diarrheagenic bacterium, is able to synthesize the essential vitamin riboflavin through the riboflavin biosynthetic pathway (RBP) and also to internalize it through the RibN importer. In bacteria, the way riboflavin biosynthesis and uptake functions correlate is unclear. To gain insights into the role of the riboflavin provision pathways in the physiology of V. cholerae, we analyzed the transcriptomics response to extracellular riboflavin and to deletions of ribD (RBP-deficient strain) or ribN. Many riboflavin-responsive genes were previously reported to belong to the iron regulon, including various iron uptake genes. Real time PCR analysis confirmed this effect and further documented that reciprocally, iron regulates RBP and ribN genes in a riboflavin-dependent way. A subset of genes were responding to both ribD and ribN deletions. However, in the subset of genes specifically affected in the Delta ribD strain, the functional terms protein folding and oxidation reduction process were enriched, as determined by a Gene Ontology analysis. In the gene subset specifically affected in the Delta ribN strain, the cytochrome complex assembly functional term was enriched. Results suggest that iron and riboflavin interrelate to regulate its respective provision genes and that both common and specific effects of biosynthesized and internalized riboflavin exist

MOESM2 of Contribution of riboflavin supply pathways to Vibrio cholerae in different environments

Additional file 2. River water does not changes the ribN/ribD expression ratio compared to growth in T minimal media. Relative expression of ribN compared to expression of ribD in T minimal media and river water as determined by RT-PCR. Media and standard deviation of three independent experiments are shown

High proportion of potential candidates for immunotherapy in a Chilean cohort of gastric cancer patients: results of the FORCE1 study

Gastric cancer (GC) is a heterogeneous disease. This heterogeneity applies not only to morphological and phenotypic features but also to geographical variations in incidence and mortality rates. As Chile has one of the highest mortality rates within South America, we sought to define a molecular profile of Chilean GCs (ClinicalTrials.gov identifier: NCT03158571/(FORCE1)). Solid tumor samples and clinical data were obtained from 224 patients, with subsets analyzed by tissue microarray (TMA; n = 90) and next generation sequencing (NGS; n = 101). Most demographic and clinical data were in line with previous reports. TMA data indicated that 60% of patients displayed potentially actionable alterations. Furthermore, 20.5% were categorized as having a high tumor mutational burden, and 13% possessed micro-satellite instability (MSI). Results also confirmed previous studies reporting high Epstein-Barr virus (EBV) positivity (13%) in Chilean-derived GC samples suggesting a high proportion of patients could benefit from immunotherapy. As expected, TP53 and PIK3CA were the most frequently altered genes. However, NGS demonstrated the presence of TP53, NRAS, and BRAF variants previously unreported in current GC databases. Finally, using the Kendall method, we report a significant correlation between EBV+ status and programmed death ligand-1 (PDL1)+ and an inverse correlation between p53 mutational status and MSI. Our results suggest that in this Chilean cohort, a high proportion of patients are potential candidates for immunotherapy treatment. To the best of our knowledge, this study is the first in South America to assess the prevalence of actionable targets and to examine a molecular profile of GC patients