Laribacter hongkongensis anaerobic adaptation mediated by arginine metabolism is controlled by the cooperation of FNR and ArgR

Abstract

Laribacter hongkongensis is a fish-borne pathogen associated with invasive infections and gastroenteritis. Its adaptive mechanisms to oxygen-limiting conditions in various environmental niches remain unclear. In this study, we compared the transcriptional profiles of L. hongkongensis under aerobic and anaerobic conditions using RNA-sequencing. Expression of genes involved in arginine metabolism significantly increased under anoxic conditions. Arginine was exploited as the sole energy source in L. hongkongensis for anaerobic respiration via the arginine catabolism pathway: specifically via the arginine deiminase (ADI) pathway. A transcriptional regulator FNR was identified to coordinate anaerobic metabolism by tightly regulating the expression of arginine metabolism genes. FNR executed its regulatory function by binding to FNR boxes in arc operons promoters. Survival of isogenic fnr mutant in macrophages decreased significantly when compared with wild-type; and expression level of fnr increased 8 h post-infection. Remarkably, FNR directly interacted with ArgR, another regulator that influences the biological fitness and intracellular survival of L. hongkongensis by regulating arginine metabolism genes. Our results demonstrated that FNR and ArgR work in coordination to respond to oxygen changes in both extracellular and intracellular environments, by finely regulating the ADI pathway and arginine anabolism pathways, thereby optimizing bacterial fitness in various environmental niches.

Redox-Sensing Iron–Sulfur Cluster Regulators

“…In Salmonella enterica serovar Typhimurium, FNR was shown to be essential for infection in a mouse model and for survival in the macrophage (47), and this was associated with the inability of an fnr mutant to respond to the cytotoxic oxidative burst associated with the NADPH phagocyte oxidase. Similar observations have been made for Neisseria meningitidis and Laribacter hongkongensis (5,40,183). The type III secretion system critical to Shigella flexneri virulence is controlled by FNR-mediated regulation of Ipa secretion (111).…”

Receptor Usage of a Novel Bat Lineage C Betacoronavirus Reveals Evolution of Middle East Respiratory Syndrome-Related Coronavirus Spike Proteins for Human Dipeptidyl Peptidase 4 Binding

“…Knockdown efficiency was determined by quantitative RT-PCR analysis using primers specific for hDPP4 (5′-CCTGCTTCTATGTTGATA-3′; 5′-CGAATAGTTCTGAATCCT-3′) and Western blot analysis using anti-hDPP4 antibody (Abcam, Cambridge, United Kingdom). The messenger RNA (mRNA) levels of target genes were normalized to that of the glyceraldehyde 3-phosphate dehydrogenase (gapdh) gene [34].…”

Mutation Landscape of Base Substitutions, Duplications, and Deletions in the Representative Current Cholera Pandemic Strain

“…The resulting plasmid was transferred into N16961 by bacterial conjugation with the E. coli SM10 λpir strain. Selection of the allelic replacement was performed as described previously ( Xiong et al. 2017 ), and the mutant strain was confirmed by PCR using the primers LPW28811/28814 and inner primers LPW28815/28816, which are specific for the deleted sequence.…”