RESUMEN
The propensity of bacterium to sporulate or retain the vegetative form depends on the amount of phosphorylated Spo0A (Spo0A(-P)), regulated by Spo0E multigene family of phosphatases (Spo0E, YisI and YnzD). Phylogenetic analysis revealed that Spo0E multigene family of phosphatases (SMFP) descends in two distinct clades of aerobic (Bacillus cluster) and anaerobic (Clostridia cluster) sporulating bacteria. High sequence conservation within species gives a notion that these members could have evolved through lineage and species-specific duplication event. Of the five genes in Bacillus cereus group, three are pathogen specific, and their synteny suggests that these paralogs could be involved in the regulation of amino acid metabolism and its transport. Overexpression of B. subtilis Spo0E, an ortholog of SMFP members in B. anthracis (BAS1251), resulted in sporulation deficient phenotype in B. anthracis. B. anthracis Spo0A(-P) binds to a consensus DNA sequence 5'-TGNCGAA-3' ('0A-like box') and loses its DNA binding ability following treatment with B. subtilis Spo0E. Thus, B. subtilis Spo0E acts on B. anthracis Spo0A(-P) and, therefore could complement the function of BAS1251. Further, since '0A-like box' are present in the promoter region of abrB gene, a known regulator of anthrax toxin gene expression, cross talk among SMFP members and Spo0A(-P)-AbrB could regulate the expression of anthrax toxin genes.
Asunto(s)
Bacillus anthracis/genética , Proteínas Bacterianas/genética , Evolución Molecular , Familia de Multigenes , Bacillus anthracis/enzimología , Secuencia Conservada , ADN Bacteriano/metabolismo , Proteínas de Unión al ADN/genética , Regulación Bacteriana de la Expresión Génica , Genes Bacterianos , Monoéster Fosfórico Hidrolasas/genética , Filogenia , Alineación de Secuencia , Especificidad de la EspecieRESUMEN
Bacillus anthracis makes highly stable, heat-resistant spores which remain viable for decades. Effect of various stress conditions on sporulation in B. anthracis was studied in nutrient-deprived and sporulation medium adjusted to various pH and temperatures. The results revealed that sporulation efficiency was dependent on conditions prevailing during sporulation. Sporulation occurred earlier in culture sporulating at alkaline pH or in PBS than control. Spores formed in PBS were highly sensitive towards spore denaturants whereas, those formed at 45 degrees C were highly resistant. The decimal reduction time (D-10 time) of the spores formed at 45 degrees C by wet heat, 2 M HCl, 2 M NaOH and 2 M H(2)O(2) was higher than the respective D-10 time for the spores formed in PBS. The dipicolinic acid (DPA) content and germination efficiency was highest in spores formed at 45 degrees C. Since DPA is related to spore sensitivity towards heat and chemicals, the increased DPA content of spores prepared at 45 degrees C may be responsible for increased resistance to wet heat and other denaturants. The size of spores formed at 45 degrees C was smallest amongst all. The study reveals that temperature, pH and nutrient availability during sporulation affect properties of B. anthracis spores.