From dormant to germinating spores of Streptomyces coelicolor A3(2): new perspectives from the crp null mutant

Effect of potato suberin on Streptomyces scabies proteome

Two-dimensional (2D) PAGE was used to detect proteins induced in Streptomyces scabies by potato suberin, a lipidic plant polymer. Nineteen up-regulated proteins were excised from 2D gels and analysed by N-terminal sequencing or tandem mass spectrometry (MS/MS). Four of the up-regulated proteins could be linked to the bacterial response to stress (AldH, GroES, TerD and LexA). Specific metabolic pathways seemed to be activated in the presence of suberin, as shown by the increased expression of specific transporters and of enzymes related not only to glycolysis, but also to nucleotide and amino acid metabolism. Suberin also appeared to influence secondary metabolism as it also caused the overproduction of the BldK proteins that are known to be involved in differentiation and secondary metabolism.

Evaluating the insecticidal genes and their expressed products in Bacillus thuringiensis strains by combining PCR with mass spectrometry

By a combination of PCR and mass spectrometry, a total of five cry genes (cry1Aa, cry1Ac, cry2Aa, cry2Ab, and cry1Ia) were detected in genomic DNA from the wild-type Bacillus thuringiensis strain 4.0718, and three protoxins (Cry1Aa, Cry1Ac, and Cry2Aa) were identified in the strain's parasporal crystals. These results indicated that this complementary method may be useful in evaluating B. thuringiensis strains at both the gene and protein levels.

The chitobiose-binding protein, DasA, acts as a link between chitin utilization and morphogenesis in Streptomyces coelicolor

Streptomycetes are mycelial soil bacteria that undergo a developmental programme that leads to sporulating aerial hyphae. As soil-dwelling bacteria, streptomycetes rely primarily on natural polymers such as cellulose, xylan and chitin for the colonization of their environmental niche and therefore these polysaccharides may play a critical role in monitoring the global nutritional status of the environment. In this work we analysed the role of DasA, the sugar-binding component of the chitobiose ATP-binding cassette transport system, in informing the cell of environmental conditions, and its role in the onset of development and in ensuring correct sporulation. The chromosomal interruption of dasA resulted in a carbon-source-dependent vegetative arrest phenotype, and we identified a second DasR-dependent sugar transporter, in addition to the N-acetylglucosamine phosphotransferase system (PTS(GlcNAc)), that relates primary metabolism to development. Under conditions that allowed sporulation, highly aberrant spores with many prematurely produced germ tubes were observed. While GlcNAc locks streptomycetes in the vegetative state, a high extracellular concentration of the GlcNAc polymer chitin has no effect on development. The striking distinction is due to a difference in the transporters responsible for the import of GlcNAc, which enters via the PTS, and of chitin, which enters as the hydrolytic product chitobiose (GlcNAc(2)) through the DasABC transporter. A model explaining the role of these two essentially different transport systems in the control of development is provided.

Effect of protein kinase inhibitors on protein phosphorylation and germination of aerial spores from Streptomyces coelicolor

In vitro phosphorylation reaction using extracts prepared from cells in the exponential phase of growth and aerial spores of Streptomyces coelicolor displayed the presence of multiply phosphorylated proteins. Effect of protein kinase inhibitors (PKIs) (geldanamycin, wortmannin, apigenin, genistein, roscovitine, methyl 2,5-dihydroxycinnamate, rapamycin, staurosporine) was determined on protein phosphorylation and on germination of spores. The in vitro experiments showed differences in phosphoprotein pattern due to the presence of PKIs. Cultivation of aerial spores with PKIs led to a significant delay in germ tube emergence and filament formation. However, none of the tested PKIs completely blocked the germination process. These results indicate that protein kinases of spores form complex networks sharing common modulating site that plays an important role in proper timing of early developmental events.

Sample preparation for two-dimensional blue native/SDS polyacrylamide gel electrophoresis in the identification of Streptomyces coelicolor cytoplasmic protein complexes

Ammonium sulfate precipitation was tested as a sample preparation step for BN-PAGE analyses of S. coelicolor cytoplasmic protein complexes. A procedure of sample preparation compatible with two-dimensional BN/SDS-PAGE was established and used to visualize protein complexes. To validate the sample preparation procedure, representative protein complexes were identified. Several previously characterized protein complexes were rediscovered and their reported oligomeric states reconfirmed. In addition, we identified new but plausible interactions that have never been reported before. Our work provides useful reference for the wide application of BN-PAGE in protein interaction study.

Transcription activation mediated by a cyclic AMP receptor protein from Thermus thermophilus HB8

The extremely thermophilic bacterium Thermus thermophilus HB8, which belongs to the phylum Deinococcus-Thermus, has an open reading frame encoding a protein belonging to the cyclic AMP (cAMP) receptor protein (CRP) family present in many bacteria. The protein named T. thermophilus CRP is highly homologous to the CRP family proteins from the phyla Firmicutes, Actinobacteria, and Cyanobacteria, and it forms a homodimer and interacts with cAMP. CRP mRNA and intracellular cAMP were detected in this strain, which did not drastically fluctuate during cultivation in a rich medium. The expression of several genes was altered upon disruption of the T. thermophilus CRP gene. We found six CRP-cAMP-dependent promoters in in vitro transcription assays involving DNA fragments containing the upstream regions of the genes exhibiting decreased expression in the CRP disruptant, indicating that the CRP is a transcriptional activator. The consensus T. thermophilus CRP-binding site predicted upon nucleotide sequence alignment is 5'-(C/T)NNG(G/T)(G/T)C(A/C)N(A/T)NNTCACAN(G/C)(G/C)-3'. This sequence is unique compared with the known consensus binding sequences of CRP family proteins. A putative -10 hexamer sequence resides at 18 to 19 bp downstream of the predicted T. thermophilus CRP-binding site. The CRP-regulated genes found in this study comprise clustered regularly interspaced short palindromic repeat (CRISPR)-associated (cas) ones, and the genes of a putative transcriptional regulator, a protein containing the exonuclease III-like domain of DNA polymerase, a GCN5-related acetyltransferase homolog, and T. thermophilus-specific proteins of unknown function. These results suggest a role for cAMP signal transduction in T. thermophilus and imply the T. thermophilus CRP is a cAMP-responsive regulator.

A proteomic analysis ofStreptomyces coelicolor programmed cell death

Programmed cell death (PCD) is an active cellular suicide that occurs in eukaryotes and bacteria in response to both abiotic and biotic stresses. In contrast to eukaryotic apoptosis, little is known about the molecular machinery that regulates bacterial PCD. In a previous work, we described the existence of PCD phenomena in Streptomyces (Manteca et al., Res. Microbiol. 2006, 157, 143-152). In the present study, we performed a proteomic analysis of PCD in Streptomyces coelicolor, for which we developed a system to obtain dead and live cell-enriched samples. PCD in this filamentous bacterium is accompanied by the appearance of enzymes involved in the degradation of cellular macromolecules, regulatory proteins, and stress-induced proteins. We argue that some of these proteins have specific functions in the PCD pathway and putative roles for the identified proteins have been proposed. The increased amounts of several antioxidant proteins suggest oxidative stress as either the cause or consequence of the cell death.

SsgA-like proteins determine the fate of peptidoglycan during sporulation ofStreptomyces coelicolor

During developmental cell division in sporulation-committed aerial hyphae of streptomycetes, up to a hundred septa are simultaneously produced, in close harmony with synchromous chromosome condensation and segregation. Several unique protein families are involved in the control of this process in actinomycetes, including that of the SsgA-like proteins (SALPs). Mutants for each of the individual SALP genes were obtained, and high-resolution and fluorescence imaging revealed that each plays an important and highly specific role in the control of the sporulation process, and their function relates to the build-up and degradation of septal and spore-wall peptidoglycan. While SsgA and SsgB are essential for sporulation-specific cell division in Streptomyces coelicolor, SsgC-G are responsible for correct DNA segregation/condensation (SsgC), spore wall synthesis (SsgD), autolytic spore separation (SsgE, SsgF) or exact septum localization (SsgG). Our experiments paint a picture of a novel protein family that acts through timing and localization of the activity of penicillin-binding proteins and autolysins, thus controlling important steps during the initiation and the completion of sporulation in actinomycetes.