Biology subjects

Friz, S.

Publications and source records attributed to Friz, S..

3 recordsLinked to original sources

bioRxiv2023

Metabolization of alpha-D-carba-glucosamine in vivo generates antimetabolites of cell wall precursors

-D-Carba-glucosamine (CGlcN) is a carbocyclic analog of -D-glucosamine that inhibits growth of Bacillus subtilis and Staphylococcus aureus. CGlcN is internalized and concomitantly phosphorylated via the phosphotransferase system yielding -D-carba-glucosamine-6-phosphate (CGlcN6P), which interferes with expression of the glutamine-fructose-6-phosphate amidotransferase (GlmS; glucosamine synthase) by activating the glmS riboswitch. Herein, we report that CGlcN6P is efficiently metabolized to carbasugar nucleotides along the peptidoglycan biosynthetic route. Mass spectrometric analysis confirmed the occurrence of carbocyclic peptidoglycan nucleotides UDP-carba-D-N-acetyl-glucosamine (UDP-CGlcNAc) and UDP-carba-D-N-acetylmuramic acid-pentapeptide (UDP-CMurNAc-5P) in the presence of CGlcN and revealed accumulation of these carba-metabolites upon antibiotic treatment interfering with biosynthetic enzyme functions. Thus, carbocyclic carbohydrates and nucleotide analogs are generated by the promiscuous bacterial cell wall biosynthetic enzymes and act as antimetabolites, causing bacterial growth inhibition by interference with cell wall synthesis. Our findings reveal CGlcN not only as putative antibiotic molecule with previously unknown antimetabolite mode of action, but also as tool to study the bacterial cell wall metabolism, e.g., in synergy with other antibiotics.

microbiology↗

bioRxiv2022

The TonB dependent uptake of pyrroloquinoline-quinone (PQQ) and secretion of gluconate by Escherichia coli K-12.

Glucose is taken up by Escherichia coli through the phosphotransferase system (PTS) as the preferred carbon source. PTS mutants grow with glucose as a carbon source only in the presence of pyrroloquinoline quinone (PQQ), which is needed as a redox cofactor for the glucose dehydrogenase Gcd. The membrane-anchored Gcd enzyme oxidizes glucose to gluconolactone in the periplasm. For this reaction to occur, external supply of PQQ is required as E. coli is unable to produce PQQ de novo. Growth experiments show that PqqU (YncD) is the TonB-ExbBD dependent transporter for PQQ through the outer membrane. PQQ protected the cells from the PqqU dependent phage IsaakIselin (Bas10) by competition for the receptor protein. As a high affinity uptake system PqqU allows E. coli to activate Gcd even at surrounding PQQ concentrations of about 1 nmol/l. At about 30 fold higher PQQ concentrations the activation of Gcd gets PqqU independent. Due to its small size Pqq may also pass the outer membrane through porins. The PQQ dependent production of gluconate has been demonstrated in many plant growth promoting bacteria that solubilise phosphate minerals in the soil by secreting this acid. Under Pi limiting conditions also E. coli induces the glucose dehydrogenase and secretes gluconate, even in absence of PTS, that is, even when the bacterium is unable to grow on glucose without PQQ.

microbiology↗

bioRxiv2021

Glucose-1,6-bisphosphate, a key metabolic regulator, is synthesized by a distinct family of α-D-phosphohexomutases widely distributed in prokaryotes

The reactions of -D-phosphohexomutases (PHM) are ubiquitous, key to primary metabolism and essential for several processes in all domains of life. The functionality of these enzymes relies on an initial auto-phosphorylation step which requires the presence of -D-glucose-1,6-bisphosphate (Glc-1,6-BP). While well investigated in vertebrates, the origin of this activator compound in bacteria is unknown. Here we show that the Slr1334 protein from the unicellular cyanobacterium Synechocysitis sp. PCC 6803 is a Glc-1,6-BP-synthase. Biochemical analysis revealed that Slr1334 efficiently converts fructose-1,6-bisphosphate (Frc-1,6-BP) and -D-glucose-1-phosphate/-D-glucose-6-phosphate into Glc-1,6-BP and also catalyzes the reverse reaction. As inferred from phylogenetic analysis, the slr1334 product belongs to a primordial subfamily of PHMs that is present especially in deeply branching bacteria and also includes human commensals and pathogens. Remarkably, the homologue of Slr1334 in the human gut bacterium Bacteroides salyersiae catalyzes the same reaction, suggesting a conserved and essential role for the members of this PHM subfamily.

microbiology↗