Functional analysis of promoters involved in quorum sensing-based regulation of bacteriocin production in Lactobacillus

Bacteriocin production in Lactobacillus sake LTH673 involves at least four operons: a regulatory operon (sppIPKR); two operons encoding bacteriocins and their immunity proteins (sppAiA and orfX); and an operon needed for secretion (sppTE). We show here that the response regulator encoded by sppR in L. sake LTH673, as well as the homologous response regulators encoded by plnC and plnD in Lactobacillus plantarum C11, bind to characteristic repeats found in the -80 to -40 regions of spp operons. The promoters controlling bacteriocin operons are strictly regulated, and their activity is increased more than 1000-fold upon activation. Constitutive expression for the regulatory and transport operons is driven, at least in part, by promoters upstream of the -80 to -40 regions. Peak promoter activity of the regulatory and transporter operons precedes that of the two bacteriocin operons. The results reveal how promoters involved in quorum sensing-based regulation of bacteriocin production in Lactobacillus differ in strength, leakiness and timing of their activity.     

Quorum-sensing regulation of gene expression: Fundamental and applied aspects and the role in bacterial communication

Quorum sensing (QS) is a specific type of regulation of gene expression in bacteria; it is dependent on the population density. QS systems include two obligate components: a low-molecular-weight regulator (autoinducer), readily diffusible through the cytoplasmic membrane, and a regulatory receptor protein, which interacts with the regulator. As the bacterial population reaches a critical level of density, autoinducers accumulate to a necessary threshold value and abrupt activation (induction) of certain genes and operons occurs. By means of low-molecular-weight regulators, bacteria accomplish communication between cells belonging to the same or different species, genera, and even families. QS systems have been shown to play a key role in the regulation of various metabolic processes in bacteria and to function as global regulators of the expression of bacterial genes. Data are presented on different types of QS systems present in bacteria of various taxonomic groups, on the species specificity of these systems, and on communication of bacteria by means of QS systems. The possibility is considered of using QS regulation systems as targets while combating bacterial infections; other applied aspects of QS investigation are discussed.     

Quorum-sensing regulation of gene expression: fundamental and applied aspects and the role in bacterial communication

Quorum sensing (QS) is a specific type of regulation of gene expression in bacteria; it is dependent on the population density. QS systems include two obligate components: a low-molecular-weight regulator (autoinducer), readily diffusible through the cytoplasmic membrane, and a regulatory receptor protein, which interacts with the regulator. As the bacterial population reaches a critical level of density, autoinducers accumulate to a necessary threshold value and abrupt activation (induction) of certain genes and operons occurs. By means of low-molecular-weight regulators, bacteria accomplish communication between cells belonging to the same or different species, genera, and even families. QS systems have been shown to play a key role in the regulation of various metabolic processes in bacteria and to function as global regulators of the expression of bacterial genes. Data are presented on different types of QS systems present in bacteria of various taxonomic groups, on the species specificity of these systems, and on communication of bacteria by means of QS systems. The possibility is considered of using QS regulation systems as targets while combating bacterial infections; other applied aspects of QS investigation are discussed.     

Major gene‐regulatory mechanisms operating in ribosomally synthesized and post‐translationally modified peptide (RiPP) biosynthesis

Post‐translationally modified peptides commonly display antimicrobial activity, but can also aid the development of bacterial colonies, giving a competitive advantage in the ecological niche. The production of post‐translationally modified peptides by bacteria is a complex and energetically costly process that is strictly orchestrated in the cell. The onset of peptide production is linked to the different enzymes that take part during maturation, the transporters and the immunity determinants (if required). Thus, the population can make optimal use of available resources and obtain the benefits of production at an advantageous moment during growth, avoiding toxicity to itself. The timing and level of expression of the different operons is controlled by diverse (complex) regulatory pathways in response to environmental changes, stress or master regulators during specific growth transition phases. In this review, we highlight the basic principles and mechanisms of regulation of expression of post‐translationally modified peptides and the relationship with the overall culture developmental processes and/or cellular differentiation. We also discuss the biotechnological consequences derived from the understanding of regulatory networks involved in the biosynthesis of these natural products.     

Genetic mechanisms of bacilli adaptation

Adaptive strategies of bacilli involving genetic regulatory mechanisms are reviewed. The role of master regulators and signal transduction systems that coordinate the interaction of the extracellular signals and the genetic programs responsible for the metabolic state of bacteria are discussed. Most of the known regulatory pathways are directly or indirectly regulated by the DegU, Spo0A, AbrB, and CodY global regulators. The main factor affecting the development of cell phenotype is the concentration of the regulatory protein and its ability to bind with varying affinity to promoters of the genes and operons. The effect of the regulatory systems on the bistability of microbial populations is discussed.     

细菌DeoR家族转录调控因子的研究进展

细菌基因组中存在大量的转录调控家族,这些转录调控家族在细菌的生长、代谢、外界信号感知与传递等方面发挥着至关重要的作用.DeoR家族是一类广泛分布于原核生物中的转录调控因子,主要参与调控细胞中多个生理过程,包括核苷酸类代谢、糖类代谢、致病菌的毒力以及链霉菌的次级代谢等.DeoR蛋白C末端的配体结合结构域,通常能够以相关代...     

The Yersinia enterocolitica motility master regulatory operon, flhDC, is required for flagellin production, swimming motility, and swarming motility

The ability to move over and colonize surface substrata has been linked to the formation of biofilms and to the virulence of some bacterial pathogens. Results from this study show that the gastrointestinal pathogen Yersinia enterocolitica can migrate over and colonize surfaces by swarming motility, a form of cooperative multicellular behavior. Immunoblot analysis and electron microscopy indicated that swarming motility is dependent on the same flagellum organelle that is required for swimming motility, which occurs in fluid environments. Furthermore, motility genes such as flgEF, flgMN, flhBA, and fliA, known to be required for the production of flagella, are essential for swarming motility. To begin to investigate how environmental signals are processed and integrated by Y. enterocolitica to stimulate the production of flagella and regulate these two forms of cell migration, the motility master regulatory operon, flhDC, was cloned. Mutations within flhDC completely abolished swimming motility, swarming motility, and flagellin production. DNA sequence analysis revealed that this locus is similar to motility master regulatory operons of other gram-negative bacteria. Genetic complementation and functional analysis of flhDC indicated that it is required for the production of flagella. When flhDC was expressed from an inducible ptac promoter, flagellin production was shown to be dependent on levels of flhDC expression. Phenotypically, induction of the ptac-flhDC fusion also corresponded to increased levels of both swimming and swarming motility.     

Urea metabolism in the cyanobacterium Anabaena cycadeae: regulation of urea uptake and urease by ammonia

A total of 160 Escherichia coli positive for F165 fimbrial antigen and isolated from diarrheic and septicemic animals, were examined for the presence of the pap, afa, and sfa/foc operons or related nucleotide sequences using colony hybridization. Most isolates shared DNA sequences with the pap operon sequences alone or in association with afa or sfa. Thus, our results indicate that F165-positive E. coli from diseased animals share DNA sequences with operons coding for adhesins important in human extra-intestinal disease and that multiple adhesin systems are often found in single isolates. However, 20% of the F165-positive isolates did not show any homology with the probes representing the three adhesin systems, suggesting that one of the operons responsible for F165 production could be different from the pap, sfa/foc, and afa operons.     

Horizontal transfer of mercury resistance genes in natural bacterial populations

The results of studying the horizontal transfer of mercury resistance determinants in environmental bacterial populations are reviewed. Identical or highly homologous mercury resistance (mer) operons and transposons were found in bacteria of different taxonomic groups from geographically distant regions. Recombinant mer operons and transposons were revealed. The data suggest high frequencies of horizontal transfer and of recombination for mercury resistance determinants. The mechanisms of horizontal gene transfer were elucidated in Gram-negative and Gram-positive bacteria. New transposons were found and analyzed.