Biology subjects

Knop, R.

Publications and source records attributed to Knop, R..

3 recordsLinked to original sources

bioRxiv2024

A rubrerythrin locus of Clostridioides difficile efficiently detoxifies reactive oxygen species

As an intestinal human pathogen, Clostridioides difficile is the main cause of antibiotic-associated diarrhoea. Endospores of this gram-positive bacterium enter the intestinal tract via faecal-oral transmission, germinate into vegetative and toxin-producing cells and can trigger a Clostridioides difficile infection. The microaerophilic conditions (0.1 to 0.4 % O2) of the large intestine represent a challenge for the strictly anaerobic organism, which protects itself by a variety of oxidative stress proteins. Four of these are encoded in an operon that is assumed to be involved in the detoxification of H2O2 and O2[bullet]-. This operon encodes a rubrerythrin (rbr), its own transcriptional repressor PerR (perR), a desulfoferrodoxin (rbo) and a putative glutamate dehydrogenase (CD630_08280) with an N-terminal rubredoxin domain, which is only expressed under high oxidative stress conditions. In this study, the enzyme activity of Rbr, Rbo and CD630_08280 was tested in-vitro. Recombinant proteins were overexpressed in C. difficile and purified anaerobically by affinity chromatography. A H2O2 reduction potential was demonstrated for Rbr, Rbo and glutamate dehydrogenase. Rbr and glutamate dehydrogenase proved to synergistically detoxify H2O2 very efficiently. Furthermore, Rbo was verified as a O2[bullet]- reductase and its activity compared to the superoxide dismutase of E. coli. The investigated gene locus codes for an oxidative stress operon whose members are able to completely neutralize O2[bullet]- and H2O2 to water and could thus be vital for C. difficile to establish an infection in the host.

microbiology↗

bioRxiv2024

Dietary restriction reveals sex-specific expression of the mTOR pathway genes in Japanese quails

Limited resources affect an organisms physiology through the conserved metabolic pathway, the mechanistic target of rapamycin (mTOR). Males and females often react differently to nutritional limitation, but whether it leads to differential mTOR pathway expression remains unknown. Recently, we found that dietary restriction (DR) induced significant changes in the expression of mTOR pathway genes in female Japanese quails (Coturnix japonica). We simultaneously exposed 32 male and female Japanese quails to either 20%, 30%, 40% restriction or ad libitum feeding for 14 days and determined the expression of six key genes of the mTOR pathway in the liver to investigate sex differences in the expression patterns. We found that DR significantly reduced body mass, albeit the effect was milder in males compared to females. We observed sex-specific liver gene expression. DR downregulated mTOR expression more in females than in males. Under moderate DR, ATG9A and RPS6K1 were increased more in males than in females. Like females, body mass in males was correlated positively with mTOR and IGF1, but negatively with ATG9A and RS6K1. Our findings highlight that sexes may cope with nutritional deficits differently and emphasise the importance of considering sexual differences in studies of dietary restriction.

molecular biology↗

bioRxiv2023

Dietary restriction and life-history trade-offs: insights into mTOR pathway regulation and reproductive investment in birds

Resources are needed for growth, reproduction and survival, and organisms must trade-off limited resources among competing processes. Nutritional availability in organisms is sensed and monitored by nutrient-sensing pathways that can trigger physiological changes or alter gene expression. Previous studies have proposed that one such signalling pathway, the mechanistic target of rapamycin (mTOR), underpins a form of adaptive plasticity when individuals encounter constraints in their energy budget. Despite the fundamental importance of this process in evolutionary biology, how nutritional limitation is regulated through the expression of genes governing this pathway and its consequential effects on fitness remains understudied, particularly in birds. We used dietary restriction to simulate resource depletion and examined its effects on body mass, reproduction and gene expression in Japanese quails (Coturnix japonica). Quails were subjected to ad libitum (ADL) feeding or 20%, 30%, and 40% restriction levels for two weeks. All restricted groups exhibited reduced body mass, whereas reductions in the number and mass of eggs were observed only under more severe restrictions. Dietary restriction led to decreased expression of mTOR and insulin-like growth factor 1 (IGF1), whereas the ribosomal protein S6 kinase 1 (RPS6K1) and autophagy-related genes (ATG9A and ATG5) were upregulated. The pattern in which mTOR respond to restriction was similar to what has been seen in body mass. Regardless of the treatment, proportionally higher reproductive investment was associated with individual variation in mTOR expression. These findings reveal the connection between dietary intake and the expression of mTOR and related genes in this pathway.

molecular biology↗