Streptomyces Genetics and Development
Centre for Protein Engineering, University of Liège, Belgium
Programmed cell death and Streptomyces development
The life cycle of streptomycetes is very complex. Streptomyces development includes a morphological differentiation (sporulation) and a physiological differentiation process (secondary metabolite production). Upon nutrient limitation and/or physico-chemical stresses, the vegetative mycelium perishes and surviving cells will form aerial hyphae that will, in turn, differentiate into chains of spores for species preservation and dissemination. Several rounds of a programmed cell death (PCD) process are required for this complex metamorphosis. Our objective is to understand the molecular mechanisms that trigger PCD and those that are induced by PCD in order for Streptomyces to produce antibiotics and to initiate cell differentiation.
Role of secondary metabolite for the producing microorganism
‘Are antibiotics naturally antibiotics?’ is an important question raised in 2006 by Prof. Julian Davies. Microorganisms ‘offered’ us thousands of natural compounds that we now use for their therapeutic properties but the real function of these molecules in their natural environment is nowadays intensively debated. The initial hypothesis that these compounds are used as weapons in the inter-cellular warfare is frequently questioned. Although still very little is known about the significance of antibiotics and other secondary metabolites in nature, there is a growing body of evidence that they are involved in a plethora of cellular processes such as cell-cell communication, redox modulation, and gene regulation.
Carbon catabolite control in actinomycetes
Streptomycetes and many other actinomycetes are soil-dwelling bacteria. They thus live in a rich carbon and poor nitrogen environment. Their success in colonizing the most diverse type of soils is in part due to their ability to exploit many different carbon sources, from the simplest ones such as glucose, to the more complex biopolymers such as xylan, chitin, and cellulose.
The utilization of different carbon sources is tightly regulated by a process called carbon catabolite control. Mono-, oligo-, and polysaccharides occupy different hierarchical levels in terms of utilization preference. In the presence of a complex mixture of carbohydrates, bacteria will privilege the use of the simplest sources as they require less energy for their degradation, transport and catabolism. Understanding how these bacteria dictate their choices amongst different carbon sources could lead to the discovery of important molecular mechanisms responsible for the evolutionary success of the Streptomyces genus.
MM agar plate with glucose and xylan. S. lividans (on the right) does not produce xylanases (no halo) and feeds on glucose. The mutant on the left is impaired in carbon catabolite repression as it uses the complex polysaccharide xylan (see the halo due to xylanases production) even if the simple sugar glucose is present.
Computational prediction of transcription factors regulons
PREDetector : Prokaryotic Regulatory Elements Detector
PREDetector is a tool developed to predict regulons of DNA-binding proteins in bacterial genomes. In addition to the automatic prediction, this bioinformatical tool provides a score and position of potential binding sites and their respective target genes in annotated bacterial genomes. It also provides an easy way to estimate the thresholds within which reliable possible new target genes are found.
There are over 500 PREDetector users. You are the next one ! http://www.montefiore.ulg.ac.be/~hiard/PreDetector/
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