Heterologous Expression of the Mevalonic Acid Pathway in Cyanobacteria Enhances Endogenous Carbon Partitioning to Isoprene

Heterologous expression of the isoprene synthase gene in the cyanobacterium Synechocystis PCC 6803 conferred upon these microorganisms the property of photosynthetic isoprene （C5H8） hYdrocarbons production. Continuous production of isoprene from CO2 and H2O was achieved in the light, occurring via the endogenous methylerythritolphosphate （MEP） pathway, in tandem with the growth of Synechocystis. This work addressed the issue of photosynthetic carbon partitioning between isoprene and biomass in Synechocystis. Evidence is presented to show heterologous genomic integration and cellular expression of the mevalonic acid （MVA） pathway genes in Synechocystis endowing a non-native pathway for carbon flux amplification to isopentenyl-diphosphate （IPP） and dimethylallyl-diphosphate （DMAPP） precursors of isoprene. Heterologous expression of the isoprene synthase in combination with the MVA pathway enzymes resulted in photosynthetic isoprene yield improvement by approximately 2.5-fold, compared with that measured in cyanobacteria transformed with the isoprene synthase gene only. These results suggest that the MVA pathway introduces a bypass in the flux of endogenous cellular substrate in Synechocystis to IPP and DMAPP, overcoming flux limitations of the native MEP pathway. The work employed a novel chromosomal integration and expression of synthetic gene operons in Synechocystis, comprising up to four genes under the control of a single promoter, and expressing three operons simultaneously. This is the first time an entire biosynthetic pathway with seven recombinant enzymes has been heterologously expressed in a photosynthetic microorganism. It constitutes contribution to the genetic engineering toolkit of photosynthetic microorganisms and a paradigm in the pursuit of photosynthetic approaches for the renewable generation of high-impact products.     

Estimating lagoonal biodiversity in Greece: comparison of rapid assessment techniques

An attempt is made to compare the results of different rapid biodiversity assessment techniques at the pan-Mediterranean, sectorial and local levels. A uniform multivariate pattern exists at the pan-Mediterranean and national (sectorial) levels: lagoons can be different when they host only a few species, but as species numbers increase, lagoons become homogenous in composition. Multivariate techniques cannot distinguish anthropogenically-impacted lagoons from those, which are naturally disturbed. In the pan-Mediterranean context it is the higher taxonomic levels, but in the national and local context it is the most abundant macrobenthic groups (polychaetes, molluscs and crustaceans) and meiobenthos which provide patterns closest to that derived from the species level. Taxonomic distinctness indices applied to polychaete and mollusc inventories provide meaningful results at most levels and scales of observation. These indices seem to be robust enough to discriminate anthropogenically impacted from naturally disturbed lagoons.     

Genomics of green algal hydrogen research

This article summarizes knowledge on genes and their respective proteins in the field of green algal hydrogen research. Emphasis is placed on recently cloned genes from the unicellular green alga Chlamydomonas reinhardtii, including HydA1 and HydA2, which encode homologous [Fe]-hydrogenases, Tla1, which encodes a chlorophyll antenna size regulatory gene, SulP, which encodes a chloroplast sulfate permease, and Sta7, which encodes an isoamylase. Analysis of the structure and function of these genes and of their respective proteins in C. reinhardtii, and related unicellular green algae, is presented in light of the role they play in the hydrogen metabolism in these organisms. A discussion is offered as to the potential application of these genes in the field of hydrogen photoproduction.     

Trends of Mortality due to Septicemia in Greece: An 8-Year Analysis

Background

Infectious diseases are among the major causes of death worldwide. We evaluated the trends of mortality due to septicemia in Greece and compared it with mortality due to other infections.

Methods

Data on mortality stratified by cause of death during 2003–2010 was obtained from the Hellenic Statistical Authority. Deaths caused by infectious diseases were grouped by site of infection and analyzed using SPSS 17.0 software.

Results

45,451 deaths due to infections were recorded in Greece during the 8-year period of time, among which 12.2% were due to septicemia, 69.7% pneumonia, 1.5% pulmonary tuberculosis, 0.2% influenza, 0.5% other infections of the respiratory tract, 7.9% intra-abdominal infections (IAIs), 2.5% urinary tract infections (UTIs), 2.2% endocarditis or pericarditis or myocarditis, 1.6% hepatitis, 1% infections of the central nervous system, and 0.7% other infections. A percentage of 99.4% of deaths due to septicemia were caused by bacteria that were not reported on the death certificate (noted as indeterminate septicemia). More deaths due to indeterminate septicemia were observed during 2007–2010 compared to 2003–2006 (3,558 versus 1,966; p<0.05).

Conclusion

Despite the limitations related to the quality of death certificates, this study shows that the mortality rate due to septicemia has almost doubled after 2007 in Greece. Proportionally, septicemia accounted for a greater increase in the mortality rate within the infectious causes of death for the same period of time. The emergence of resistance could partially explain this alarming phenomenon. Therefore, stricter infection control measures should be urgently applied in all Greek healthcare facilities.     

A new methodology for rapid detection of Lactobacillus delbrueckii subsp. bulgaricus based on multiplex PCR

In this study we present a novel multiplex PCR assay for rapid and efficient detection of Lactobacillus delbrueckii subsp. bulgaricus. The accuracy of our method was confirmed by the successful identification of L. delbrueckii subsp. bulgaricus in commercial yoghurts and food supplements and it may be readily applied to the food industry.     

Som-based class discovery exploring the ICA-reduced features of microarray expression profiles

Gene expression datasets are large and complex, having many variables and unknown internal structure. We apply independent component analysis (ICA) to derive a less redundant representation of the expression data. The decomposition produces components with minimal statistical dependence and reveals biologically relevant information. Consequently, to the transformed data, we apply cluster analysis (an important and popular analysis tool for obtaining an initial understanding of the data, usually employed for class discovery). The proposed self-organizing map (SOM)-based clustering algorithm automatically determines the number of 'natural' subgroups of the data, being aided at this task by the available prior knowledge of the functional categories of genes. An entropy criterion allows each gene to be assigned to multiple classes, which is closer to the biological representation. These features, however, are not achieved at the cost of the simplicity of the algorithm, since the map grows on a simple grid structure and the learning algorithm remains equal to Kohonen's one.     

Generation of CD1 tetramers as a tool to monitor glycolipid-specific T cells

CD1 molecules are beta(2)m-associated HLA class-I-like glycoproteins which have the unique ability to present glycolipid and phospholipid antigens to specific T lymphocytes. To study the biology of CD1 and its role in human disease we developed novel techniques for generation of recombinant CD1/lipid complexes by in vitro refolding. Fluorescent tetrameric complexes made from soluble recombinant CD1d/alpha-galactosylceramide complexes allowed highly sensitive and specific ex vivo and in vitro detection and functional characterization of novel human T-lymphocyte populations. Furthermore, protein crystals were obtained from soluble recombinant CD1b/beta(2)m-proteins loaded either with phosphatidylinositol or ganglioside GM2, which led to the first atomic structure determination of a CD1/lipid complex. The analysis of these crystal structures clarified how CD1b molecules can bind lipid ligands of different size, and revealed a broader spectrum of potential CD1b ligands than previously predicted.     

Novel lipophilic amidate oxorhenium and oxotechnetium complexes as potential brain agents: synthesis, characterization and biological evaluation

Novel oxorhenium and oxotechnetium complexes based on the tetradentate 1-(2-hydroxybenzamido)-2-(pyridinecarboxamido)benzene, H3L, ligand have been synthesized and characterized herein. Thus, by reacting equimolar quantities of the triply deprotonated ligand L3- with the suitable MO3+ precursor, the following neutral MOL complexes could be easily produced following similar synthetic routes: M = Re (1), M = 99gTc (2), and M = 99mTc (3). Complexes 1 and 2, prepared in macroscopic amounts, were chemically characterized and their structure determined by single-crystal X-ray analysis. They are isostructural metal chelates, adopting a distorted square pyramidal geometry around the metal. The N3O donor atom set of the tetradentate ligand defines the basal plane and the oxygen atom of the M = O core occupies the apex of the pyramid. Complex 3 forms quantitatively at tracer level by mixing the H3L ligand with Na99mTcO4 generator eluate in aqueous alkaline media and using tin chloride as reductant in the presence of citrate. Its structure was established by chromatographic comparison with prototypic complexes 1 and 2 using high-performance liquid chromatographic techniques. When challenged with excess glutathione in vitro, complex 3 is rapidly converted to hydrophilic unidentified metal species. Tissue distribution data after administration of complex 3 in vivo revealed a significant uptake and retention of this compound in brain tissue.