Heme A Synthase Deficiency Affects the Ability of Bacillus cereus to Adapt to a Nutrient-Limited Environment

Unveiling Microbial Diversity: Raman Spectroscopy's Discrimination of Clostridium and Related Genera

In the clinical environment, the identification of phylogenetic closely related genera and species like Clostridium and Bacillus spp. is challenging. Both genera contain representatives of pathogenic and nonpathogenic species that need to be distinguished for a proper diagnostic read-out. Therefore, reliable and accurate detection methods must be employed for the correct identification of these genera and species. Despite their high pathogenicity, clostridial infections and food contaminations present significant challenges due to their unique cultivation conditions and developmental needs. Therefore, in many diagnostic protocols, the toxins are used for microbiological documentation. However, the applied laboratory methods suffer in accuracy, sometimes require large bacterial loads to provide reliable results, and cannot differentiate pathogenic from nonpathogenic strains. Here, Raman spectroscopy was employed to create an extensive Raman database consisting of pathogenic and nonpathogenic Bacillus and Clostridium species. These genera, as well as representatives of Paraclostridium and Clostridioides were specifically selected for their phylogenetic relation, cultivation conditions, and metabolic activity. A chemometric evaluation of the Raman spectra of single vegetative cells revealed a high discriminating power at the genus level. However, bacilli are considerably easier to classify at the species level than clostridia. The discrimination between the genera and species was based on their phylogeny and not their aerobic and anaerobic cultivation conditions. These encouraging results demonstrated that Raman spectroscopy coupled with chemometrics is a robust and helpful method for differentiating Clostridium species from Bacillus, Clostridioides, and Paraclostridium species. This approach has the potential to be a valuable tool in clinical diagnostics.

Elucidating the pivotal role of TSPO in porphyrin-related cellular processes, in Bacillus cereus

A structural homolog of the mammalian TSPO has been identified in the human pathogen Bacillus cereus. BcTSPO, in its recombinant form, has previously been shown to bind and degrade porphyrins. In this study, we generated a ΔtspO mutant strain in B. cereus ATCC 14579 and assessed the impact of the absence of BcTSPO on cellular proteomics and physiological characteristics. The proteomic analysis revealed correlations between the lack of BcTSPO and the observed growth defects, increased oxygen consumption, ATP deficiency, heightened tryptophan catabolism, reduced motility, and impaired biofilm formation in the ΔtspO mutant strain. Our results also suggested that BcTSPO plays a crucial role in regulating intracellular levels of metabolites from the coproporphyrin-dependent branch of the heme biosynthetic pathway. This regulation potentially underlies alterations in the metabolic landscape, emphasizing the pivotal role of BcTSPO in B. cereus aerobic metabolism. Notably, our study unveils, for the first time, the involvement of TSPO in tryptophan metabolism. These findings underscore the multifaceted role of TSPO, not only in metabolic pathways but also potentially in the microorganism's virulence mechanisms.

Dynamic Profile of S-Layer Proteins Controls Surface Properties of Emetic Bacillus cereus AH187 Strain

Many prokaryotes are covered by a two-dimensional array of proteinaceous subunits. This surface layers (S-layer) is incompletely characterized for many microorganisms. Here, we studied Bacillus cereus AH187. A genome analysis identified two genes encoding the S-layer proteins SL2 and EA1, which we experimentally confirmed to encode the two protein components of the S-layer covering the surface of B. cereus. Shotgun proteomics analysis indicated that SL2 is the major component of the B. cereus S-layer at the beginning of exponential growth, whereas EA1 becomes more abundant than SL2 during later stages of stationary growth. Microscopy analysis revealed the spatial organization of SL2 and EA1 at the surface of B. cereus to depend on their temporal-dynamics during growth. Our results also show that a mutant strain lacking functional SL2 and EA1 proteins has distinct surface properties compared to its parental strain, in terms of stiffness and hydrophilicity during the stationary growth phase. Surface properties, self-aggregation capacity, and bacterial adhesion were observed to correlate. We conclude that the dynamics of SL2 and EA1 expression is a key determinant of the surface properties of B. cereus AH187, and that the S-layer could contribute to B. cereus survival in starvation conditions.

Proteomic Analysis of Microorganisms

At the early stage of the development of proteomic technologies, Escherichia coli or Saccharomyces cerevisiae were used as model microorganisms for high-throughput identification technologies, such as shotgun proteomics or 2D gel electrophoresis-based LC-MS/MS analysis [...]

Recent Advances in Structural Studies of Cytochrome bd and Its Potential Application as a Drug Target

Cytochrome bd is a triheme copper-free terminal oxidase in membrane respiratory chains of prokaryotes. This unique molecular machine couples electron transfer from quinol to O₂ with the generation of a proton motive force without proton pumping. Apart from energy conservation, the bd enzyme plays an additional key role in the microbial cell, being involved in the response to different environmental stressors. Cytochrome bd promotes virulence in a number of pathogenic species that makes it a suitable molecular drug target candidate. This review focuses on recent advances in understanding the structure of cytochrome bd and the development of its selective inhibitors.