BackgroundChromobacterium violaceum (C. violaceum) occurs abundantly in a variety of ecosystems, including ecosystems that place the bacterium under stress. This study assessed the adaptability of C. violaceum by submitting it to nutritional and pH stresses and then analyzing protein expression using bi-dimensional electrophoresis (2-DE) and Maldi mass spectrometry.ResultsChromobacterium violaceum grew best in pH neutral, nutrient-rich medium (reference conditions); however, the total protein mass recovered from stressed bacteria cultures was always higher than the total protein mass recovered from our reference culture. The diversity of proteins expressed (repressed by the number of identifiable 2-DE spots) was seen to be highest in the reference cultures, suggesting that stress reduces the overall range of proteins expressed by C. violaceum. Database comparisons allowed 43 of the 55 spots subjected to Maldi mass spectrometry to be characterized as containing a single identifiable protein. Stress-related expression changes were noted for C. violaceum proteins related to the previously characterized bacterial proteins: DnaK, GroEL-2, Rhs, EF-Tu, EF-P; MCP, homogentisate 1,2-dioxygenase, Arginine deiminase and the ATP synthase β-subunit protein as well as for the ribosomal protein subunits L1, L3, L5 and L6. The ability of C. violaceum to adapt its cellular mechanics to sub-optimal growth and protein production conditions was well illustrated by its regulation of ribosomal protein subunits. With the exception of the ribosomal subunit L3, which plays a role in protein folding and maybe therefore be more useful in stressful conditions, all the other ribosomal subunit proteins were seen to have reduced expression in stressed cultures. Curiously, C. violeaceum cultures were also observed to lose their violet color under stress, which suggests that the violacein pigment biosynthetic pathway is affected by stress.ConclusionsAnalysis of the proteomic signatures of stressed C. violaceum indicates that nutrient-starvation and pH stress can cause changes in the expression of the C. violaceum receptors, transporters, and proteins involved with biosynthetic pathways, molecule recycling, energy production. Our findings complement the recent publication of the C. violeaceum genome sequence and could help with the future commercial exploitation of C. violeaceum.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0606-2) contains supplementary material, which is available to authorized users.

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Background: Shigella is a Gram-negative bacterium and belongs to Enterobacteriaceae family. These bacteria have been described as responsible for many diarrheic infections around the world and affects children as 5 years old. As a striking feature of these bacteria, we can say about the invasive capacity and the severe damage in the intestine of the host. Epidemiological studies conducted during 2007 to 2009 by our research group, Diagnosis and Control of Infectious Diseases of the Amazon - DCDIA, identified Shigella as the 4th most frequent bacterial pathogen in children with diarrhea treated in public hospitals in Manaus - AM. To understand the mechanisms of pathogenesis of these clinical strains, and to describe the mechanisms of cellular invasion, this study proposes the identification of the proteome of two isolates, through the mass spectrometry coupled to liquid chromatography. The clinical strains were submitted to experimental conditions that mimic the epithelial cellular contact in the host, using the inductor Congo Red, in order to investigate which proteins are being produced by this pathogen. Results: The proteomic profile of Shigella strain 201 reveals 386 intracellular proteins cultivated in LB medium and 189 intracellular proteins cultivated using the Congo Red inductor. For the M90T strain, a total of 470 intracellular proteins were detected in LB medium and 383 intracellular proteins cultivated with Congo Red. The findings reveal that proteins exclusively induced by Congo Red in the clinical strain are related to virulence processes, such as IpaC and IpaD proteins, which have already been extensively investigated in the literature. Conclusions: However, new target proteins are pointed out, such as Hmp, YkfE, AepA, MobC, MetK, OsmY, LptA and LuxS which are classified as proteins predicted as pathogenic, based on our analyses. Although such proteins are involved in the virulence of enteric pathogens, their functions are still little explored or inexistent for the Shigella genus, mainly in the northern region of Brazil. We expected this work to reveal the mechanisms underlying the isolated clinical strains and elucidate new effectors and how they modulate the pathogenesis of these bacteria.