A mathematical model of quorum sensing regulated EPS production in biofilm communities

Background  

Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based on population densities.     

Prolactin signaling through the short isoform of the mouse prolactin receptor regulates DNA binding of specific transcription factors, often with opposite effects in different reproductive issues

Background  

Externalization of phosphatidylserine (EPS) occurs in apoptotic-like spermatozoa and could be used to remove them from sperm preparations to enhance sperm quality for assisted medical procreation. We first characterized EPS in sperms from infertile patients in terms of frequency of EPS spermatozoa as well as localization of phosphatidylserine (PS) on spermatozoa. Subsequently, we determined the impact of depleting EPS spermatozoa on sperm quality.     

Partial characterization of an exopolysaccharide secreted by a marine bacterium,Vibrio neocaledonicus sp. nov., from New Caledonia

Aims

Exopolysaccharides (EPS) are industrially valuable molecules with numerous useful properties. This study describes the techniques used for the identification of a novel Vibrio bacterium and preliminary characterization of its EPS.

Methods and Results

Bioprospection in marine intertidal areas of New Caledonia followed by screening for EPS producing brought to selection of the isolate NC470. Phylogenetic analysis (biochemical tests, gene sequencing and DNA–DNA relatedness) permitted to identify NC470 as a new member of the Vibrio genus. The EPS was produced in batch fermentation, purified using the ultrafiltration process and analysed by colorimetry, Fourier Transform Infrared spectroscopy, gas chromatography, Nuclear Magnetic Resonance and HPLC‐size exclusion chromatography. This EPS exhibits a high N‐acetyl‐hexosamines and uronic acid content with a low amount of neutral sugar. The molecular mass was 672 × 10³ Da. These data are relevant for possible technological exploitation.

Conclusions

We propose the name Vibrio neocaledonicus sp. nov for this isolate NC470, producing an EPS with an unusual sugar composition. Comparison with other known polymers permitted to select applications for this polymer.

Significance and Impact of the Study

This study contributes to evaluate the marine biodiversity of New Caledonia. It also highlights the biotechnological potential of New Caledonia marine bacteria.     

Combined effects of biochar addition and nitrogen fertilizer reduction on the rhizosphere metabolomics of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) seedlings

Background

Extracellular polymeric matrix (EPM) is a complex component of the organo-mineral assemblages created by biological soil crusts (BSCs). Mainly of polysaccharidic origin, it embeds soil and sediments and provides key benefits to the crust community. Services provided include: sediment cohesion and resistance to erosion, moisture provision, protection from external harmful factors, as well as support to plant establishment and growth. EPM is the product of BSC microbial community, and it is constituted by exopolysaccharides (EPS) associated to other substances, organized in a three-dimensional structure having different levels of gelation, and degrees of condensation.

Scope

This review aims at focusing scientific attention, for the first time, on the characteristics and the roles of three operationally defined EPM fractions, one water soluble, one more adherent to cells and sediments, and one firmly attached to microbial cells. The latest results obtained by analyzing EPM of natural and induced (i.e, the result of cyanobacteria inoculation) BSCs are outlined, and the optimized extraction methodology is described in details.

Conclusions

The review underlines the complexity of investigating the characteristics and the role of microbial EPS, and its supra-structure (EPM), in natural conditions (as opposed to cultures in laboratory conditions), where the matrix is subjected to continuous microbial rearrangement due to biosynthetic, self- and cross-feeding processes, and where microbial activity affected by environmental parameters.

     

Structure,substrate recognition and reactivity of <Emphasis Type="Italic">Leishmania major</Emphasis> mevalonate kinase

Background  

Isoprenoid precursor synthesis via the mevalonate route in humans and pathogenic trypanosomatids is an important metabolic pathway. There is however, only limited information available on the structure and reactivity of the component enzymes in trypanosomatids. Since isoprenoid biosynthesis is essential for trypanosomatid viability and may provide new targets for therapeutic intervention it is important to characterize the pathway components.     

Effects of phytohormones on mycelial growth and exopolysaccharide biosynthesis of medicinal mushroom <Emphasis Type="Italic">Pellinus linteus</Emphasis>

Effects of phytohormones including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and 1-naphthalentacetic acid (NAA) on mycelial growth of medicinal mushroom Phellinus linteus were investigated. Under the optimal IAA, IBA and NAA concentration of 1.0, 1.5 and 5.0 mg/l, the maximal mycelial diameter reached 8.6 ± 0.4, 7.3 ± 2.6 and 9.0 ± 1.0 mm, respectively. The mycelial biomass and exopolysaccharide (EPS) production with addition of 5.0 mg/l NAA in a shake flask were 6.24 ± 0.18 g/l at 168 h and 0.86 ±0.01 g/l at 192 h, which were enhanced by 15.98 and 56.36% compared to the control, respectively. However, the molecular weight and infrared spectrum of EPS were coincident with the control. Results indicated that NAA at the proper concentration was beneficial in stimulating mycelial growth and EPS biosynthesis, whereas it could not alter the molecular structure of EPS. An erratum to this article can be found at     

Comparative secretome analyses of two <Emphasis Type="Italic">Trichoderma reesei</Emphasis> RUT-C30 and CL847 hypersecretory strains

Background  

Due to its capacity to produce large amounts of cellulases, Trichoderma reesei is increasingly been researched in various fields of white biotechnology, especially in biofuel production from lignocellulosic biomass. The commercial enzyme mixtures produced at industrial scales are not well characterized, and their proteinaceous components are poorly identified and quantified. The development of proteomic methods has made it possible to comprehensively overview the enzymes involved in lignocellulosic biomass degradation which are secreted under various environmental conditions.     

Influences of naturally occurring agents in combination with fluoride on gene expression and structural organization of Streptococcus mutans in biofilms

Background  

The association of specific bioactive flavonoids and terpenoids with fluoride can modulate the development of cariogenic biofilms by simultaneously affecting the synthesis of exopolysaccharides (EPS) and acid production by Streptococcus mutans, which enhanced the cariostatic effectiveness of fluoride in vivo. In the present study, we further investigated whether the biological actions of combinations of myricetin (flavonoid), tt-farnesol (terpenoid) and fluoride can influence the expression of specific genes of S. mutans within biofilms and their structural organization using real-time PCR and confocal fluorescence microscopy.     

Environmental assessment of cod (<Emphasis Type="BoldItalic">Gadus morhua</Emphasis>) from autoline fisheries

Purpose  

The main purpose of this study has been to document the environmental performance of products based on autoline-caught cod and the distribution of environmental impacts in the value chain from fishing to retail. Another aim has been to document the performed environmental improvement analyses.     

Rice bacterial blight pathogen <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzae</Emphasis> produces multiple DSF-family signals in regulation of virulence factor production

Background  

Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice bacterial blight disease. Xoo produces a range of virulence factors, including EPS, extracellular enzyme, iron-chelating siderophores, and type III-secretion dependent effectors, which are collectively essential for virulence. Genetic and genomics evidence suggest that Xoo might use the diffusible signal factor (DSF) type quorum sensing (QS) system to regulate the virulence factor production. However, little is known about the chemical structure of the DSF-like signal(s) produced by Xoo and the factors influencing the signal production.     

Differential regulation of insulin-like growth factor binding protein-1 and -2 by insulin in the baboon (<Emphasis Type="Italic">Papio anubis</Emphasis>) endometrium

Background  

The purpose of this study was to examine the effect of insulin on expression and synthesis of IGFBP-1 and IGFBP-2 in the baboon endometrium in vitro.     

Environmental amoebae do not support the long‐term survival of virulent mycobacteria

Aims

To test the hypothesis that Mycobacterium bovis can persist in the environment within protozoa.

Methods and Results

In this study, we used a novel approach to detect internalized mycobacteria in environmental protozoa from badger latrines. Acid‐fast micro‐organisms were visualized in isolated amoebae, although we were unable to identify them to species level as no mycobacteria were grown from these samples nor was M. bovis detected by IS6110 PCR. Co‐incubation of Acanthamoeba castellanii with virulent M. bovis substantially reduced levels of bacilli, indicating that the amoebae have a negative effect on the persistence of M. bovis.

Conclusions

The internalization of mycobacteria in protozoa might be a rare event under environmental conditions. The results suggest that amoebae might contribute to the inactivation of M. bovis rather than representing a potential environmental reservoir.

Significance and Impact of the Study

Protozoa have been suggested to act as an environmental reservoir for M. bovis. The current study suggests that environmental amoebae play at most a minor role as potential reservoirs of M. bovis and that protozoa might inhibit persistence of M. bovis in the environment.     

Conservation between higher plants and the moss <Emphasis Type="Italic">Physcomitrella patens</Emphasis>in response to the phytohormone abscisic acid: a proteomics analysis

Background  

The plant hormone abscisic acid (ABA) is ubiquitous among land plants where it plays an important role in plant growth and development. In seeds, ABA induces embryogenesis and seed maturation as well as seed dormancy and germination. In vegetative tissues, ABA is a necessary mediator in the triggering of many of the physiological and molecular adaptive responses of the plant to adverse environmental conditions, such as desiccation, salt and cold.     

A comparative study of protein synthesis in <Emphasis Type="Italic">in vitro</Emphasis> systems: from the prokaryotic reconstituted to the eukaryotic extract-based

Background  

Cell-free protein synthesis is not only a rapid and high throughput technology to obtain proteins from their genes, but also provides an in vitro platform to study protein translation and folding. A detailed comparison of in vitro protein synthesis in different cell-free systems may provide insights to their biological differences and guidelines for their applications.     

Global transcriptional responses of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> DC3000 to changes in iron bioavailability <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Pseudomonas syringae pv tomato DC3000 (DC3000) is a Gram-negative model plant pathogen that is found in a wide variety of environments. To survive in these diverse conditions it must sense and respond to various environmental cues. One micronutrient required for most forms of life is iron. Bioavailable iron has been shown to be an important global regulator for many bacteria where it not only regulates a wide variety of genes involved in general cell physiology but also virulence determinants. In this study we used microarrays to study differential gene regulation in DC3000 in response to changes in levels of cell-associated iron.     

Optimisation of transgene action at the post-transcriptional level: high quality parthenocarpic fruits in industrial tomatoes

Background  

Genetic engineering of parthenocarpy confers to horticultural plants the ability to produce fruits under environmental conditions that curtail fruit productivity and quality. The DefH9-iaaM transgene, whose predicted action is to confer auxin synthesis specifically in the placenta, ovules and derived tissues, has been shown to confer parthenocarpy to several plant species (tobacco, eggplant, tomato) and varieties.     

The photosensor protein Ppr of <Emphasis Type="Italic">Rhodocista centenaria</Emphasis> is linked to the chemotaxis signalling pathway

Background  

Rhodocista centenaria is a phototrophic α-proteobacterium exhibiting a phototactic behaviour visible as colony movement on agar plates directed to red light. As many phototrophic purple bacteria R. centenaria possesses a soluble photoactive yellow protein (Pyp). It exists as a long fusion protein, designated Ppr, consisting of three domains, the Pyp domain, a putative bilin binding domain (Bbd) and a histidine kinase domain (Pph). The Ppr protein is involved in the regulation of polyketide synthesis but it is still unclear, how this is connected to phototaxis and chemotaxis.     

Viable nonsense mutants for the essential gene <Emphasis Type="Italic">SUP45</Emphasis> of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Background  

Termination of protein synthesis in eukaryotes involves at least two polypeptide release factors (eRFs) – eRF1 and eRF3. The highly conserved translation termination factor eRF1 in Saccharomyces cerevisiae is encoded by the essential gene SUP45.