Project description:To perform natural transformation, one of the three main Horizontal Gene Transfer mechanisms, bacteria need to enter a physiological differentiated state called genetic competence. Interestingly, new bacteria displaying such aptitude are often discovered, and one of the latest is the human pathogen Staphylococcus aureus. Here, we developed a new protocol, based on planktonic cells cultures, leading to a large percentage of the population activating competence development and a significant improvement of S. aureus natural transformation efficiencies. Taking advantage of these new conditions, we performed transcriptomics analyses to characterize each central competence regulators regulon. SigH and ComK1 were both found essential for activating natural transformation genes but also important for activation or repression of peripheral functions. Even though ComK2 was not found important for the control of transformation genes, its regulon showed an important overlap with that of SigH and ComK1. Finally, we showed how microaerobic conditions, sensed by the SrrAB two-component system, was key to activate competence in S. aureus.
Project description:Horizontal Gene Transfer, Fitness Costs and Mobility shape the spread of antibiotic resistance genes from Acinetobacter baumannii into experimental populations of Acinetobacter baylyi.
Project description:Lactococcus lactis is one of the most important lactic acid bacterium used in the dairy industry. Activation of natural DNA transformation in this species would greatly improve the selection of novel strains with desired industrial traits. Here, we investigate the activation of natural transformation in L. lactis ssp. cremoris KW2, a strain of plant origin whose genome encodes the master competence regulator ComX and the complete set of essential late gene products required for natural transformation under its potential control. In absence of any information on the competence signaling system in this species, activation of natural DNA transformation by the constitutive production of ComX was attempted. Using a reporter strain of late competence phase activation and transcriptomic analyses, we show that all key genes for natural transformation can be induced in strain KW2. Then, we demonstrate that natural DNA transformation is functional in this strain and that this process requires the DNA uptake machinery dedicated to competence. Various chromosomal modifications such as point mutations or gene deletion/insertion could be quickly and efficiently achieved. These results are the first to report the functionality of natural DNA transformation in L. lactis and pave the way for the identification of molecular mechanisms activating competence development in this species.