In bacterial populations, quorum sensing (QS) systems participate in the regulation of specialization processes and regulate collective behaviors that mediate interactions and allow survival of the species. In Gram-positive bacteria, QS systems of the RRNPP family (Rgg, Rap, NprR, PlcR, and PrgX) consist of intracellular receptors and their cognate signaling peptides. Two of these receptors, Rap and NprR, have regained attention in Bacillus subtilis and the Bacillus cereus group. Some Rap proteins, such as RapH and Rap60, are multifunctional and/or redundant in function, linking the specialization processes of sporulation and competence, as well as global expression changes in the transition phase in B. subtilis. NprR, an evolutionary intermediate between Rap and RRNPP transcriptional activators, is a bifunctional regulator that modulates sporulation initiation and activates nutrient scavenging genes. In this review, we discuss how these receptors switch between functions and connect distinct signaling pathways. Based on structural evidence, we propose that RapH and Rap60 should be considered moonlighting proteins. Additionally, we analyze an evolutionary and ecological perspective to understand the multifunctionality and functional redundancy of these regulators in both Bacillus spp. and non-Bacillus Firmicutes. Understanding the mechanistic, structural, ecological, and evolutionary basis for the multifunctionality and redundancy of these QS systems is a key step for achieving the development of innovative technologies for health and agriculture.
This study focuses on the prevalence of Listeria monocytogenes (Lm) in pork meat and on inert surfaces from slaughterhouses in Sonora, Mexico. A total of 21 Lm were obtained from 103 samples, giving a prevalence of 20.3%. The prevalence of Lm in pork loin was 15.9% and 20.8% for inert surfaces in Federal Inspection Type (FIT) slaughterhouses. For non-FIT slaughterhouses, the prevalence was 25.7%. PCR amplification of genomic DNA from the Lm isolates revealed the presence of the hlyA gene, suggesting a pathogenic nature for these isolates. The isolates obtained in this work all clustered with Lm, according to our phylogenetic analysis based on the 16S rDNA sequence. This Lm cluster indicates that Lm isolates 7-2, 4, 2-1, 10B, 8, 3, 3-3, and 9 share 16S rRNA identity with other Lm isolates that have been reported as foodborne pathogens (rR2-502, J1817, J1816, J1926) and that are involved in foodborne outbreaks. The most commonly detected serotypes were 1/2a and 1/2b. All isolates displayed differential responses to the assayed antibiotics, and most isolates were able to grow in the presence of penicillin G, or both penicillin and penicillin-derived (oxacillin) antibiotics.
Quorum sensing (QS) are intercellular communication mechanisms to coordinate bacterial gene expression in response to signaling molecules. In Bacillus thuringiensis the QS system NprR-NprRB (receptor protein-signaling peptide) regulates the expression of genes related to nutrient scavenging during necrotrophism and also modulates sporulation onset. However, the relevance of QS in free-living stages of B. thuringiensis is less known. In this work, we depict the contribution of this QS system to spreading in colony biofilms. Through a spreading assay in spotted colonies of B. thuringiensis Bt8741 Wt and derived mutants, we find that the spreading phenotype depends on the NprR regulator and on the extracellular signaling NprRB peptide. We also show that this phenotype is associated to an increased fitness of the bacterium in these experimental conditions. Exogenous addition of a lipopeptide surfactant was sufficient to recover spreading in the ΔnprR-nprRB mutant, indicating that the phenotype could be mediated by the lipopeptide kurstakin. Finally, we suggest that the spreading is relevant in nature, since it occurs in the sole presence of soil nutrients, and it is conserved in several species of Bacillus commonly found in soil. This novel function of NprR-NprRB highlights the relevance of this QS system on the evolution and on the free-lifestyle ecology of B. thuringiensis.
Las toxinas Cry de Bacillus thuringiensis (Bt) son utilizadas como bioinsecticidas en la agricultura. Se precisa de métodos confiables que permitan analizar las características que se confieren a las plantas genéticamente modificadas (GM) durante su desarrollo, antes de su comercialización. El objetivo del trabajo fue estandarizar metodologías para el análisis de la expresión de genes y proteínas conferidas al algodonero GM durante sus diferentes etapas fenológicas en campo. Como principal aplicación práctica del estudio realizado, las metodologías estandarizadas se podrán emplear en la caracterización de cultivos GM que se desarrollen y para los cuales sea necesario realizar su análisis de riesgo. Para ello se procesaron muestras de tejido vegetal en diferentes etapas fenológicas obtenidas de predios comerciales de algodonero GM en el Valle del Yaqui. En los diferentes tejidos se cuantificó la expresión génica y proteica mediante análisis RTq-PCR y Elisa, respectivamente. Los resultados obtenidos muestran variación en la expresión de los genes conferidos a lo largo del desarrollo de la misma variedad y entre los diferentes sitios donde se ubicaron los cultivos. Los mayores niveles de expresión se identificaron, como se esperaba, en las etapas tempranas del cultivo (valores medios de 8.5 μg g-1 para Cry1Ac y 63.1 μg g-1 para Cry2Ab) comparados con lo observado en etapas tardías o maduras (valores medios de 0.05 y 0.3 μg g-1 para Cry1Ac y Cry2Ab, respectivamente). Por lo tanto, se concluye que las técnicas de RTq-PCR y ELISA son adecuadas para evaluar la expresión espacial y temporal de genes que se confieran a plantas GM, información requerida para caracterizar la exposición al peligro y poder realizar el análisis de riesgo.
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