Characterization of mleR, a positive regulator of malolactic fermentation and part of the acid tolerance response in Streptococcus mutans

BACKGROUND: One of the key virulence determinants of Streptococcus mutans, the primary etiological agent of human dental caries, is its strong acid tolerance. The acid tolerance response (ATR) of S. mutans comprises several mechanisms that are induced at low pH and allow the cells to quickly adapt to a lethal pH environment. Malolactic fermentation (MLF) converts L-malate to L-lactate and carbon dioxide and furthermore regenerates ATP, which is used to translocate protons across the membrane. Thus, MLF may contribute to the aciduricity of S. mutans but has not been associated with the ATR so far. RESULTS: Here we show that the malolactic fermentation (mle) genes are under the control of acid inducible promoters which are induced within the first 30 minutes upon acid shock in the absence of malate. Thus, MLF is part of the early acid tolerance response of S. mutans. However, acidic conditions, the presence of the regulator MleR and L-malate were required to achieve maximal expression of all genes, including mleR itself. Deletion of mleR resulted in a decreased capacity to carry out MLF and impaired survival at lethal pH in the presence of L-malate. Gel retardation assays indicated the presence of multiple binding sites for MleR. Differences in the retardation patterns occurred in the presence of L-malate, thus demonstrating its role as co-inducer for transcriptional regulation. CONCLUSION: This study shows that the MLF gene cluster is part of the early acid tolerance response in S. mutans and is induced by both low pH and L-malate

Nineteenth-Century Mathematics in the Mirror of Its Literature: A Quantitative Approach

AbstractThe point of departure of this paper is the idea that the development of mathematics is reflected in its publications. Hence, the existence of a nearly complete database renders possible general statistical accounts of the development of mathematical activities. To this end, the authors utilize the mathematical index of theCatalogue of Scientific Papersof the Royal Society of London dealing with the mathematical journal literature of the 19th century. The relation between the journal and book literature of that century is discussed, with the result that the size of the journal literature is presumably a valid indicator of the intensity of mathematical activities in particular areas. On the basis of thisCatalogue,graphs of the publication activity of all of 19th-century mathematics and of 34 of its most important subareas are displayed; both the number of active contributors in each area and its share of 19th-century mathematics publications are exhibited. Furthermore, the share of mathematics of the total scientific journal literature of the 19th-century is estimated. Frequency distributions of publication activity and the specialization of 19th-century mathematicians conform to patterns well known in modern scientometrics.In dieser Arbeit wird davon ausgegangen, daß sich die Entwicklung der Mathematik in ihren Publikationen widerspiegelt. Eine annähernd vollständige bibliographische Datengrundlage gestattet daher globale statistische Beschreibungen der Entwicklung mathematischer Aktivitäten. Die Autoren werteten zu diesem Zweck den mathematischen Index desCatalogue of Scientific Papersder Royal Society of London aus, der die mathematische Zeitschriftenliteratur des 19. Jahrhunderts berücksichtigt. Sie diskutieren das Verhältnis von Zeitschriften- zu Buchliteratur in diesem Jahrhundert mit dem Ergebnis, daß der Umfang der Zeitschriftenliteratur vermutlich als Indikator der Intensität mathematischer Aktivitäten auf einzelnen Gebieten gelten kann. Auf der Grundlage des Catalogue werden zur gesamten Mathematik sowie zu 34 der wichtigsten Teilgebiete Verlaufskurven der Publikationsaktivitäten gezeigt, zum einen als Publikationsanteile am Gesamtgebiet, zum anderen als absolute Zahl der auf einem Teilgebiet überhaupt aktiven Mathematiker. Ferner wird der Anteil der Mathematik an der gesamten naturwissenschaftlichen Zeitschriftenliteratur des 19. Jahrhunderts geschätzt. Häufigkeitsverteilungen der Publikationsaktivität und der Spezialisierung der mathematischen Autoren des 19. Jahrhunderts ergaben in der zeitgenössischen Szientometrie bekannte Verteilungsmuster.Utgångspunkten för denna artikel är föreställningen, att matematikens utveckling återspeglas i dess publikationer. Existensen av en så gott som fullständig databas möjliggör därför allmänna statistiska beskrivningar av utvecklingen av matematiska aktiviteter. För detta ändamål utnyttjade författarna det matematiska indexet till denCatalogue of Scientific Papers,som utgivits av Royal Society of London och som behandler 1800-talets matematiska tidskriftslitteratur. Förhållandet mellan det åhundradets tidskrifts- och boklitteratur diskuteras med resultatet, att tidskriftslitteraturens omfång förmodligen gör, att den kan gälla som indikator på itensiteten hos matematiska aktiviteter på ensklida områden. Utgående från dennaCataloguevisas kurvor på 34 av dess viktigaste delområden; i det senare fallet anges dels varje delområdes andel i publikationer av hela mathematiken, dels antalet aktiva matematiker på området. Vidare uppskattas matematikens andel av hela den naturvetenskapliga tidskriftslitteraturen under 1800-talet. Frekvensfördelningar av publikationsaktiviteten och specialiseringen hos 1800-talets matematiker följer mönster, som är bekanta i den moderna scientometrin

Is autoinducer-2 a universal signal for interspecies communication: a comparative genomic and phylogenetic analysis of the synthesis and signal transduction pathways

BACKGROUND: Quorum sensing is a process of bacterial cell-to-cell communication involving the production and detection of extracellular signaling molecules called autoinducers. Recently, it has been proposed that autoinducer-2 (AI-2), a furanosyl borate diester derived from the recycling of S-adenosyl-homocysteine (SAH) to homocysteine, serves as a universal signal for interspecies communication. RESULTS: In this study, 138 completed genomes were examined for the genes involved in the synthesis and detection of AI-2. Except for some symbionts and parasites, all organisms have a pathway to recycle SAH, either using a two-step enzymatic conversion by the Pfs and LuxS enzymes or a one-step conversion using SAH-hydrolase (SahH). 51 organisms including most Gamma-, Beta-, and Epsilonproteobacteria, and Firmicutes possess the Pfs-LuxS pathway, while Archaea, Eukarya, Alphaproteobacteria, Actinobacteria and Cyanobacteria prefer the SahH pathway. In all 138 organisms, only the three Vibrio strains had strong, bidirectional matches to the periplasmic AI-2 binding protein LuxP and the central signal relay protein LuxU. The initial two-component sensor kinase protein LuxQ, and the terminal response regulator luxO are found in most Proteobacteria, as well as in some Firmicutes, often in several copies. CONCLUSIONS: The genomic analysis indicates that the LuxS enzyme required for AI-2 synthesis is widespread in bacteria, while the periplasmic binding protein LuxP is only present in Vibrio strains. Thus, other organisms may either use components different from the AI-2 signal transduction system of Vibrio strains to sense the signal of AI-2, or they do not have such a quorum sensing system at all

Bacterial strains resistant to inorganic and organic forms of mercury isolated from polluted sediments of the Orbetello Lagoon, Italy, and their possible use in bioremediation processes

Bacteria are able to adapt to heavy metals in contaminated environments, by developing specific mechanisms of resistance. A mercury (Hg)-resistant bacterial community was isolated from polluted sediments of the Orbetello Lagoon, Italy. The members of the Hg-resistant bacterial community showed high levels of resistance both to the inorganic and to the organic forms of Hg. 16S rRNA gene sequencing showed the presence of different genera, and a bacterial strain resistant to Hg belonging to the genus Luteimonas was evidenced for the first time. The merA gene coding for mercury-reductase conferring resistance to inorganic Hg, and the merB gene coding for mercury-lyase enzymes, for resistance to the organic forms of Hg, were detected in the tested bacterial strains. The community showed the presence of bacteria belonging to the genera Pseudomonas and Psychrobacter that highlighted the capability to reduce Hg2+ to the volatile form of Hg0. Experiments carried out with immobilized cells of the Hg-resistant strains removed 96% of Hg in sediments leachates in a bioremediation laboratory scale pilot plant. A methylating activity of the sulphate-reducing bacteria of the same polluted sediments was moreover evidenced. These results evidenced the presence of microbial communities highly adapted to the presence of Hg into the sediments of the lagoon. The use of the isolated autochthonous bacterial strains for bioremediation of the native sediments contaminated by Hg is suggested

Metabolic fluxes in the central carbon metabolism of Dinoroseobacter shibae and Phaeobacter gallaeciensis, two members of the marine Roseobacter clade

<p>Abstract</p> <p>Background</p> <p>In the present work the central carbon metabolism of <it>Dinoroseobacter shibae </it>and <it>Phaeobacter gallaeciensis </it>was studied at the level of metabolic fluxes. These two strains belong to the marine <it>Roseobacter </it>clade, a dominant bacterial group in various marine habitats, and represent surface-associated, biofilm-forming growth (<it>P. gallaeciensis</it>) and symbiotic growth with eukaryotic algae (<it>D. shibae</it>). Based on information from recently sequenced genomes, a rich repertoire of pathways has been identified in the carbon core metabolism of these organisms, but little is known about the actual contribution of the various reactions <it>in vivo</it>.</p> <p>Results</p> <p>Using ¹³C labelling techniques in specifically designed experiments, it could be shown that glucose-grown cells of <it>D. shibae </it>catabolise the carbon source exclusively via the Entner-Doudoroff pathway, whereas alternative routes of glycolysis and the pentose phosphate pathway are obviously utilised for anabolic purposes only. Enzyme assays confirmed this flux pattern and link the lack of glycolytic flux to the absence of phosphofructokinase activity. The previously suggested formation of phosphoenolpyruvate from pyruvate during mixotrophic CO₂assimilation was found to be inactive under the conditions studied. Moreover, it could be shown that pyruvate carboxylase is involved in CO₂assimilation and that the <it>cyclic </it>respiratory mode of the TCA cycle is utilised. Interestingly, the use of intracellular pathways was highly similar for <it>P. gallaeciensis</it>.</p> <p>Conclusion</p> <p>The present study reveals the first insight into pathway utilisation within the <it>Roseobacter </it>group. Fluxes through major intracellular pathways of the central carbon metabolism, which are closely linked to the various important traits found for the <it>Roseobacter </it>clade, could be determined. The close similarity of fluxes between the two physiologically rather different species might provide the first indication of more general key properties among members of the <it>Roseobacter </it>clade which may explain their enormous success in the marine realm.</p

Functional profiling of mercuric reductase (mer A) genes in biofilm communities of a technical scale biocatalyzer

BACKGROUND: Bacterial mercury resistance is based on enzymatic reduction of ionic mercury to elemental mercury and has recently been demonstrated to be applicable for industrial wastewater clean-up. The long-term monitoring of such biocatalyser systems requires a cultivation independent functional community profiling method targeting the key enzyme of the process, the merA gene coding for the mercuric reductase. We report on the development of a profiling method for merA and its application to monitor changes in the functional diversity of the biofilm community of a technical scale biocatalyzer over 8 months of on-site operation. RESULTS: Based on an alignment of 30 merA sequences from Gram negative bacteria, conserved primers were designed for amplification of merA fragments with an optimized PCR protocol. The resulting amplicons of approximately 280 bp were separated by thermogradient gelelectrophoresis (TGGE), resulting in strain specific fingerprints for mercury resistant Gram negative isolates with different merA sequences. The merA profiling of the biofilm community from a technical biocatalyzer showed persistence of some and loss of other inoculum strains as well as the appearance of new bands, resulting in an overall increase of the functional diversity of the biofilm community. One predominant new band of the merA community profile was also detected in a biocatalyzer effluent isolate, which was identified as Pseudomonas aeruginosa. The isolated strain showed lower mercury reduction rates in liquid culture than the inoculum strains but was apparently highly competitive in the biofilm environment of the biocatalyzer where moderate mercury levels were prevailing. CONCLUSIONS: The merA profiling technique allowed to monitor the ongoing selection for better adapted strains during the operation of a biocatalyzer and to direct their subsequent isolation. In such a way, a predominant mercury reducing Ps. aeruginosa strain was identified by its unique mercuric reductase gene

A genome-wide study of two-component signal transduction systems in eight newly sequenced mutans streptococci strains

<p>Abstract</p> <p>Background</p> <p>Mutans streptococci are a group of gram-positive bacteria including the primary cariogenic dental pathogen <it>Streptococcus mutans </it>and closely related species. Two component systems (TCSs) composed of a signal sensing histidine kinase (HK) and a response regulator (RR) play key roles in pathogenicity, but have not been comparatively studied for these oral bacterial pathogens.</p> <p>Results</p> <p>HKs and RRs of 8 newly sequenced mutans streptococci strains, including <it>S. sobrinus </it>DSM20742, <it>S. ratti </it>DSM20564 and six <it>S. mutans </it>strains, were identified and compared to the TCSs of <it>S. mutans </it>UA159 and NN2025, two previously genome sequenced <it>S. mutans </it>strains. Ortholog analysis revealed 18 TCS clusters (HK-RR pairs), 2 orphan HKs and 2 orphan RRs, of which 8 TCS clusters were common to all 10 strains, 6 were absent in one or more strains, and the other 4 were exclusive to individual strains. Further classification of the predicted HKs and RRs revealed interesting aspects of their putative functions. While TCS complements were comparable within the six <it>S. mutans </it>strains, <it>S. sobrinus </it>DSM20742 lacked TCSs possibly involved in acid tolerance and fructan catabolism, and <it>S. ratti </it>DSM20564 possessed 3 unique TCSs but lacked the quorum-sensing related TCS (ComDE). Selected computational predictions were verified by PCR experiments.</p> <p>Conclusions</p> <p>Differences in the TCS repertoires of mutans streptococci strains, especially those of <it>S. sobrinus </it>and <it>S. ratti </it>in comparison to <it>S. mutans</it>, imply differences in their response mechanisms for survival in the dynamic oral environment. This genomic level study of TCSs should help in understanding the pathogenicity of these mutans streptococci strains.</p

Fatal affairs - conjugational transfer of a dinoflagellate-killing plasmid between marine Rhodobacterales

The roseobacter group of marine bacteria is characterized by a mosaic distribution of ecologically important phenotypes. These are often encoded on mobile extrachromosomal replicons. So far, conjugation had only been experimentally proven between the two model organisms Phaeobacter inhibens and Dinoroseobacter shibae. Here, we show that two large natural RepABC-type plasmids from D. shibae can be transferred into representatives of all known major Rhodobacterales lineages. Complete genome sequencing of the newly established Phaeobacter inhibens transconjugants confirmed their genomic integrity. The conjugated plasmids were stably maintained as single copy number replicons in the genuine as well as the new host. Co-cultivation of Phaeobacter inhibens and the transconjugants with the dinoflagellate Prorocentrum minimum demonstrated that Phaeobacter inhibens is a probiotic strain that improves the yield and stability of the dinoflagellate culture. The transconjugant carrying the 191 kb plasmid, but not the 126 kb sister plasmid, killed the dinoflagellate in co-culture

Strategi Pembangunan Pariwisata melalui Sinergitas Dinas Pariwisata dengan Desa Adat ( Studi Kasus pada Pengelolaan Obyek Wisata Pantai Labuan Sait dalam Meningkatkan Retribusi Daerah di Kabupaten Badung)

A gradual Tourism development is very important to improve the quality of tourism each year to compete with other tourist attraction. The synergy between the Central Government with local government plays an important role to the development of tourism. The background to this research is the development of tourism which is still insufficient in Labuan Sait both in terms of means and infrastructure, promotion, as well as structuring tourism. This study measures how does tourism development strategy through the synergy with the customary village tourism office on the management of Beach Tourism Labuan Sait in increasing the levy County in Badung Regency with the theory of development that uses the concept of planning development by Sjahrizal in the regional development planning in the era of autonomy. The indicator consists of planning, implementation, monitoring and evaluation. In addition also use the concept of synergy from Najiyati and Rahmat which consists of indicators communication and coordination as well as indicators of the SWOT by Freddy Rangkuti. Method used in this study is a qualitative method with descriptive approach with data collection techniques in the form of in-depth interviews to several informants associated with this research. The results of the research showed that the development strategy of tourism through the synergy with the customary village Tourism Office on the management of Beach Tourism Labuan Sait in improving regional levies in Badung Regency are still insufficient. That is because the is still lacking from the indicator monitoring and implementation and evaluation of the impact against the decline of levy of admission attractions Labuan Sait in the 2017. &nbsp; &nbsp; Keywords: Development, Tourism, Synergy, and Strateg

Integrated Transcriptional Regulatory Network of Quorum Sensing, Replication Control, and SOS Response in Dinoroseobacter shibae

Quorum sensing (QS) coordinates population wide gene expression of bacterial species. Highly adaptive traits like gene transfer agents (GTA), morphological heterogeneity, type 4 secretion systems (T4SS), and flagella are QS controlled in Dinoroseobacter shibae, a Roseobacter model organism. Its QS regulatory network is integrated with the CtrA phosphorelay that controls cell division in alphaproteobacteria. To elucidate the network topology, we analyzed the transcriptional response of the QS-negative D. shibae strain ΔluxI1 toward externally added autoinducer (AI) over a time period of 3 h. The signaling cascade is initiated by the CtrA phosphorelay, followed by the QS genes and other target genes, including the second messenger c-di-GMP, competence, flagella and pili. Identification of transcription factor binding sites in promoters of QS induced genes revealed the integration of QS, CtrA phosphorelay and the SOS stress response mediated by LexA. The concentration of regulatory genes located close to the origin or terminus of replication suggests that gene regulation and replication are tightly coupled. Indeed, addition of AI first stimulates and then represses replication. The restart of replication comes along with increased c-di-GMP levels. We propose a model in which QS induces replication followed by differentiation into GTA producing and non-producing cells. CtrA-activity is controlled by the c-di-GMP level, allowing some of the daughter cells to replicate again. The size of the GTA producing subpopulation is tightly controlled by QS via the AI Synthase LuxI2. Finally, induction of the SOS response allows for integration of GTA DNA into the host chromosome