|
Adaptation of rhizobia to non-growing conditions Transition from fast-growing to non-growing conditions is pivotal in the life cycle of bacteria and essential for successful adaptation to diverse environments. In many bacteria, the alarmone (p)ppGpp is an important trigger regulating cellular adaptation through modulation of gene expression upon nutritional and other stresses. Our group analyses genetic pathways, putatively linked to ppGpp production, contributing to survival of Rhizobium etli in free-living and symbiotic conditions. |
 |
 |
Peptide uptake affects stress resistance and symbiosis Peptides are well known for their signaling role in quorum sensing amongst Gram-positive bacteria. In R. etli, peptide uptake contributes to nitrogen fixation and free-living survival in the presence of diverse stresses. Our research analyses the molecular mechanisms and signal transduction pathways coupling peptide uptake with symbiosis and stress resistance in R. etli. |
|
Swarming behavior of Rhizobium etli and Pseudomonas aeruginosa Swarming is the fastest known mode of surface translocation, allowing rapid colonization of a nutrient-rich environment and host tissues. This complex multicellular behavior requires integration of chemical and physical signals, leading to physiological and morphological differentiation of the bacteria into swarmer cells. Our research focuses on genetic pathways leading to swarmer cell differentiation and on the interaction between biological and physico-chemical processes leading to swarming migration and pattern formation in Pseudomonas aeruginosa and R. etli. |
 |
 |
Persistence in Pseudomonas aeruginosa and Escherichia coli Since persister cells present in bacterial populations are capable of surviving very high doses of antibiotics, they are held responsible for recurring outbreaks of infections when the antibiotic pressure decreases. While bacterial resistance and tolerance to antimicrobials have been thoroughly studied in the past, the exact cause of persistence remains elusive. We recently identified a number of genes involved in persistence by selecting strains from a P. aeruginosa plasposon mutant library using a high throughput screening procedure for persister mutants. Further characterization of these persistence genes will aid in unraveling the persistence phenomenon, possibly leading to the development of new drugs to treat chronic infections. |
|
Bacterial protein secretion in the bean - Rhizobium etli symbiosis Protein secretion is an important bacterial factor contributing to the generally narrow specificity of the symbiotic interaction between rhizobia and their host plants. We have identified a calmodulin-like protein that is expressed and secreted specifically during symbiosis between R. etli and P. vulgaris, named calsymin. Furthermore, we study the function and regulation of the type III secretion system that allows direct injection of effector proteins into the host cell cytoplasm. Such specialized secretion systems are used by pathogenic bacteria of both animals and plants to modulate the host's defence responses by interfering with signaling pathways or by affecting expression of host genes. |
 |
 |
Symbiotic nitrogen fixation in climbing beans Climbing beans have among the highest symbiotic nitrogen fixation (SNF) capacity of all known beans and are therefore excellent material to study SNF in beans. By studying a population of climbing beans showing variations in SNF efficiency, we aim to pinpoint sites in the bean genome (quantitative trait loci, QTL) affecting SNF. In addition, this will give an idea about how SNF efficiency is inherited over generations of climbing beans, providing assistance to improve SNF in common bean through breeding. We also look at the social, cultural and economic consequences of growing climbing beans and using SNF for farmers in the East African Central Highlands. |