Effects of dry heating on the cleavage of casein and whey protein into peptides under simulated infant digestion.

Glycation elicits diverse effects on the digestion of caseins and whey proteins in a goat protein model system (40 % casein,60 % whey proteins). Caseins generated longer peptides in the digesta of heated vs unheated samples. The further cleavage of casein peptides was hindered by dry heating, which might be induced by glycated modification.

Nano in Micro: Novel Concepts in Foodborne Pathogen Transmission and Pathogenesis.

In this article, we highlight novel components of foodborne pathogens that influence their response, physiology, adaptation, and survival in the face of diverse stresses, and consequently have implications for their transmission in the food chain and their pathogenesis. Recent insights into the role of bacteriophages/prophages, bacterial extracellular vesicles, and bacterial microcompartments, which make up the emerging field we coined as "nano in micro," are presented, together with the role of understudied food-relevant substrates in pathogen fitness and virulence. These new insights also lead to reflections on generally adopted laboratory conditions in the long-standing research field of adaptive stress response in foodborne pathogens.

Activation of a silent lactose utilization pathway in an evolved Listeria monocytogenes F2365 outbreak isolate.

Listeria monocytogenes, a widespread food-borne pathogen, utilizes diverse growth substrates including mono- and di-saccharides via PEP-phosphotransferase (PTS) systems. We evaluated a collection of L. monocytogenes isolates of different origins for their ability to utilize lactose, a disaccharide composed of galactose and glucose and the main carbon source in milk and dairy products.

Ribosomal mutations enable a switch between high fitness and high stress resistance in .

Multiple stress resistant variants of with mutations in encoding ribosomal protein RpsU have previously been isolated after a single exposure to acid stress. These variants, including LO28 variant V14 with a complete deletion of the gene, showed upregulation of the general stress sigma factor Sigma B-mediated stress resistance genes and had a lower maximum specific growth rate than the LO28 WT, signifying a trade-off between stress resistance and fitness. In the current work V14 has been subjected to an experimental evolution regime, selecting for higher fitness in two parallel evolving cultures.

A single point mutation in the ribosomal gene enables SigB activation independently of the stressosome and the anti-sigma factor antagonist RsbV.

Microbial population heterogeneity leads to different stress responses and growth behavior of individual cells in a population. Previously, a point mutation in the gene () encoding ribosomal protein S21 was identified in a LO28 variant, which leads to increased multi-stress resistance and a reduced maximum specific growth rate. However, the underlying mechanisms of these phenotypic changes remain unknown.

Stress resistant rpsU variants of Listeria monocytogenes can become underrepresented due to enrichment bias.

Population heterogeneity is an important component of the survival mechanism of Listeria monocytogenes, leading to cells in a population with diverse stress resistance levels. We previously demonstrated that several ribosomal gene rpsU mutations enhanced the stress resistance of L. monocytogenes and lowered the growth rate at 30 °C and lower temperatures.

Amino acid substitutions in ribosomal protein RpsU enable switching between high fitness and multiple-stress resistance in Listeria monocytogenes.

Microbial population heterogeneity contributes to differences in stress response between individual cells in a population, and can lead to the selection of genetically stable variants with increased stress resistance. We previously provided evidence that the multiple-stress resistant Listeria monocytogenes LO28 variant 15, carries a point mutation in the rpsU gene, resulting in an arginine-proline substitution in ribosomal protein RpsU (RpsU). Here, we investigated the trade-off between general stress sigma factor SigB-mediated stress resistance and fitness in variant 15 using experimental evolution.