Biology subjects

Ricca, E.

Publications and source records attributed to Ricca, E..

3 recordsLinked to original sources

bioRxiv2022

Sporulation efficiency and spore quality in a human intestinal isolate of Bacillus cereus

The Bacillus cereus group is a species complex of the Bacillus genus that includes several closely related species. Within this group, bacteria indicated as B. cereus sensu stricto (B. cereus) are the causative agent of two different types of gastrointestinal diseases associated with food poisoning. Outbreaks of this opportunistic pathogen are generally due to the resistance of its spores to heat, pH and desiccation that makes hard their complete inactivation from food products. B. cereus is commonly isolated from a variety of environments, including intestinal samples of infected and healthy people. We report the genomic and physiological characterization of MV19, a human intestinal strain closely related (ANI value of 98.81%) to the reference strain B. cereus ATCC 14579. MV19 cells were able to grow in a range of temperatures between 20 and 44{degrees}C. At the optimal temperature the sporulation process was induced very rapidly and mature spores efficiently released, however these appeared structurally and morphologically defective. At the sub-optimal growth temperature of 25{degrees}C sporulation was slow and less efficient but a high total number of fully functional spores was produced. Altogether, results reported here indicate that the reduced rapidity and efficiency of sporulation at 25{degrees}C are compensated by a high quality and quantity of released spores, suggesting the relevance of different performances at different growth conditions for the adaptation of this bacterium to diverse environmental niches.

microbiology↗

bioRxiv2020

Nasal immunization with the C-terminal domain of BclA3 induced specific IgG production and attenuated disease symptoms in mice infected with Clostridioides difficile spores

Clostridioides difficile is a Gram-positive, spore-forming bacterium that causes a severe intestinal infection. Spores of this pathogen enter in the human body through the oral route, interact with intestinal epithelial cells and persist in the gut. Once germinated, the vegetative cells colonize the intestine and produce toxins that enhance a strong immune response that perpetuate the disease. Therefore, spores are major players of the infection and ideal targets of new therapeutic treatments. In this context, spore surface proteins of C. difficile, are potential antigens for the development of vaccines targeting C. difficile spores. Here we report that the C-terminal domain of the spore surface protein BclA3, BclA3CTD, was identified as an antigenic epitope, over-produced in Escherichia coli and tested as an immunogen in mice. To increase antigen stability and efficiency, BclA3CTD was also exposed on the surface of B. subtilis spores, a well-established mucosal vaccine delivery system. In the experimental conditions used in this study, free BclA3CTD induced antibody production in mice and attenuated some CDI symptoms after a challenge with the pathogen, while the spore-displayed antigen resulted less effective. Although dose regimen and immunization route need to be optimized, our results suggest BclA3CTD as a potentially effective antigen to develop a new vaccination strategy targeting C. difficile spores.

microbiology↗

bioRxiv2018

A protein phosphorylation module patterns the Bacillus subtilis spore outer coat

Assembly of the Bacillus subtilis spore coat involves over 80 protein components, which self-organize into a basal layer, a lamellar inner coat, a striated electrondense outer coat and a more external crust. CotB is an abundant component of the outer coat. Its C-terminal moiety contains a region, termed SKRB, formed by a series of serine-rich repeats, which we show is phosphorylated by the coat-associated Ser/Thr kinase CotH at multiple Ser residues. Another coat protein, CotG, which contains a central repeat region, SKRG, interacts with the C-terminal moiety of CotB and promotes its phosphorylation by CotH in vivo and in a heterologous system. CotG itself is phosphorylated by CotH but phosphorylation is enhanced in the absence of CotB. Spores of a cotHD288A strain, producing an inactive form of the kinase, like those formed by a cotG deletion mutant, lack the characteristic pattern of electrondense outer coat striations, while retaining the crust. Specifically, in the absence of CotG or CotH activity, most of the outer coat proteins are assembled but form a layer of amorphous material that peels-off the spore if crust formation is genetically ablated. In contrast, deletion of the SKRB region, has no major impact on the structure of the outer coat. Thus, phosphorylation of CotG by CotH is the principal factor establishing the structural pattern of the spore outer coat. The presence of the cotB/cotH/cotG cluster in several species closely related to B. subtilis and of cotG-like proteins in nearly all spore-formers that also code for a CotH homologue hints at the importance of this protein phosphorylation module in the morphogenesis of the spore outer layers.

microbiology↗