The function of PlcR in Bacillus anthracis vaccine strain A16R.

Bacillus anthracis, B. thuringiensis and B. cereus are members of the B. cereus group. They share high genetic similarity. Whereas plcR (Phospholipase C regulator) usually encodes a functional pleiotropic activator protein in B. cereus and B. thuringiensis isolates, a characteristic nonsense mutation is found in all B. anthracis strains investigated, making the gene dysfunctional. To study the function of PlcR in B. anthracis, we used the B. cereus CMCC63301 genome as a template and constructed a recombinant expression plasmid pBE2A-plcR, and introduced it into the B. anthracis vaccine strain A16R, and then analyzed the activity of the hemolysin and sphingomyelinase. The results showed that transformation of B. anthracis with plasmid pBE2A-plcR carrying the native B. cereus plcR gene active the expression of sphingomyelinase gene, but did not activate expression of hemolysin genes of B. anthracis A16R.

Proteome analysis of Streptococcus suis serotype 2.

Outbreaks in humans, caused by Streptococcus suis serotype 2 (SS2), were reported in 1998 and 2005 in China. However, the mechanism of SS2-associated infection remains unclear. For the first time, a 2-D gel approach combined with MS was used to establish a comprehensive 2-D reference map for aiding our understanding of the pathogenicity of SS2. The identification of 694 out of 834 processed spots revealed 373 proteins. Most of the identified proteins were located in the cytoplasm and were involved in energy metabolism, protein synthesis, and cellular processes. Proteins that were abundant in the 2-DE gels could be linked mainly to housekeeping functions in carbohydrate metabolism, protein quality control and translation. 2-DE of secretory proteins was performed using IPG strips of pH 4-7. Among the 102 protein spots processed, 87 spots representing 77 proteins were successfully identified. Some virulence-associated proteins of SS2 were found, including arginine deiminase, ornithine carbamoyl-transferase, carbamate kinase, muramidase-released protein precursor, extracellular factor, and suilysin. Enolase and endopeptidase have been proposed as putative virulence-associated factors in this study. The 2-D reference map might provide a powerful tool for analyzing the virulence factor and the regulatory network involved in the pathogenicity of this microorganism.

Dynamic proteome changes of Shigella flexneri 2a during transition from exponential growth to stationary phase.

Shigella flexneri is an infectious pathogen that causes dysentery to human, which remains a serious threat to public health, particularly in developing countries. In this study, the global protein expression patterns of S. flexneri during transition from exponential growth to stationary phase in vitro were analyzed by using 2-D PAGE combined with MALDI-TOF MS. In a time-course experiment with five time points, the relative abundance of 49 protein spots varied significantly. Interestingly, a putative outer membrane protein YciD (OmpW) was almost not detected in the exponential growth phase but became one of the most abundant proteins in the whole stationary-phase proteome. Some proteins regulated by the global regulator FNR were also significantly induced (such as AnsB, AspA, FrdAB, and KatG) or repressed (such as AceEF, OmpX, SodA, and SucAB) during the growth phase transition. These proteins may be the key effectors of the bacterial cell cycle or play important roles in the cellular maintenance and stress responses. Our expression profile data provide valuable information for the study of bacterial physiology and form the basis for future proteomic analyses of this pathogen.