Characterization of Halorubrum sfaxense sp. nov., a New Halophilic Archaeon Isolated from the Solar Saltern of Sfax in Tunisia

An extremely halophilic archaeon, strain ETD6, was isolated from a marine solar saltern in Sfax, Tunisia. Analysis of the 16S rRNA gene sequence showed that the isolate was phylogenetically related to species of the genus Halorubrum among the family Halobacteriaceae, with a close relationship to Hrr. xinjiangense (99.77% of identity). However, value for DNA-DNA hybridization between strain ETD6 and Hrr.xinjiangense were about 24.5%. The G+C content of the genomic DNA was 65.1 mol% (T(m)). Strain ETD6 grew in 15–35% (w/v) NaCl. The temperature and pH ranges for growth were 20–55°C and 6–9, respectively. Optimal growth occurred at 25% NaCl, 37°C, and pH 7.4. The results of the DNA hybridization against Hrr. xinjiangense and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain ETD6 from other Hrr. species. Therefore, strain ETD6 represents a novel species of the genus Halorubrum, for which the name Hrr. sfaxense sp. nov. is proposed. The Genbank EMBL-EBI accession number is GU724599

Characterization of heterotrophic prokaryote subgroups in the Sfax coastal solar salterns by combining flow cytometry cell sorting and phylogenetic analysis

Here, we combined flow cytometry (FCM) and phylogenetic analyses after cell sorting to characterize the dominant groups of the prokaryotic assemblages inhabiting two ponds of increasing salinity: a crystallizer pond (TS) with a salinity of 390 g/L, and the non-crystallizer pond (M1) with a salinity of 200 g/L retrieved from the solar saltern of Sfax in Tunisia. As expected, FCM analysis enabled the resolution of high nucleic acid content (HNA) and low nucleic acid content (LNA) prokaryotes. Next, we performed a taxonomic analysis of the bacterial and archaeal communities comprising the two most populated clusters by phylogenetic analyses of 16S rRNA gene clone library. We show for the first time that the presence of HNA and LNA content cells could also be extended to the archaeal populations. Archaea were detected in all M1 and TS samples, whereas representatives of Bacteria were detected only in LNA for M1 and HNA for TS. Although most of the archaeal sequences remained undetermined, other clones were most frequently affiliated to Haloquadratum and Halorubrum. In contrast, most bacterial clones belonged to the Alphaproteobacteria class (Phyllobacterium genus) in M1 samples and to the Bacteroidetes phylum (Sphingobacteria and Salinibacter genus) in TS samples

Antagonistic properties of some halophilic thermoactinomycetes isolated from superficial sediment of a solar saltern and production of cyclic antimicrobial peptides by the novel isolate paludifilum halophilum

This study has focused on the isolation of twenty-three halophilic actinomycetes from two ponds of different salinity and the evaluation of their ability to exert an antimicrobial activity against both their competitors and several other pathogens. From the 23 isolates, 18 strains showed antagonistic activity, while 19 showed activities against one or more of the seven pathogen strains tested. Six strains exhibited consistent antibacterial activity against Gram-negative and Gram-positive pathogens characterized at the physiological and molecular levels. These strains shared only 94-95% 16S rRNA sequence identity with the closely related species of the Thermoactinomycetaceae family. Among them, the potent strain SMBg3 was further characterized and assigned to a new genus in the family for which the name Paludifilum halophilum (DSM 102817T) is proposed. Sequential extraction of the antimicrobial compounds with ethyl acetate revealed that the crude extract from SMBg3 strain had inhibitory effect on the growth of the plant pathogen Agrobacterium tumefaciens and the human pathogens Staphylococcus aureus, Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa. Based on the HRESI-MS spectral data, the cyclic lipopeptide Gramicidin S and four cyclic dipeptides (CDPs) named cyclo(L-4-OH-Pro-L-Leu), cyclo(L-Tyr-L-Pro), cyclo(L-Phe-L-Pro), and cyclo(L-Leu-L-Pro) were detected in the fermentation broth of Paludifilum halophilum. To our knowledge, this is the first report on the isolation of these compounds from members of the Thermoactinomycetaceae family

201: Are QT intervals correlated to apnea-hypopnea index in obstructive sleep apnea?

IntroductionSeveral studies proved that obstructive sleep apnea (OSA) is associated with cardio-vascular diseases such as cardiac arrhythmia. QT duration and dispersion reflect the heterogeinity of ventricular repolarization and are considered as precursors of ventricular arrhythmiaAimThe aim of this study is to assess the relation between the severity of OSA parameters as apnea hypopnea index and QT intervals.MethodsForty patients (18 men and 22 women) who were diagnosed with OSA by overnight polysomnography were included in this prospective study. The mean age was 56±10 years old. They were all in sinus rhythm. Before initiating continuous positive airway pressure therapy, we calculated on a 12 lead ECG : QT duration (QTend) corrected to Bazett formula and QT dispersion (QT end max -QT end min).ResultsTwenty four patients had severe OSA (AHI >30), 4 had moderate OSA (AHI between 15 and 30) and 12 had a mild OSA (AHI between 5 and 15). There was a significant positive correlation between QT dispersion and AHI (r=0.48, p=0.001)ConclusionThe severity of OSA seems to be correlated with ventricular repolarization heterogeinity These results suggest that the higher is the AHI the higher is the risk of ventricular arrhythmia occurence. Further studies are needed to validate these results

Contribution a l'etude d'un procede de production en continu d'acide L-aspartique par cellules de Pseudomonas putida immobilisees

SIGLECNRS TD Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Inactivation of the gene katA or sodA affects the transient entry into the viable but non-culturable response of Staphylococcus aureus in natural seawater at low temperature

International audienc

Spatial and seasonal variability of pico-, nano- and microphytoplankton at the bottom seawater in the north coast of Sfax, Eastern Mediterranean Sea

In the frame of the Taparura Project, we studied thedistribution of pico-, nano- and microphytoplankton communitiesin relation to environmental variables at 18 stationssampled during four coastal cruises conducted betweenOctober 2009 and July 2010 at the bottom, on the north coastof Sfax (Tunisia, Eastern Mediterranean Sea). The restorationeffect on coastal ultraphytoplankton (<10 μm) andmicrophytoplankton (<200 μm) was investigated using conventionalflow cytometry and inverted microscopy. Flow cytometryanalysis of ultraphytoplankton resolved six groups(Prochlorococcus, Synechococcus, nanoeukaryotes and threedistinct subgroups within picoeukaryotes). In addition to theseautotrophic groups, two unknown groups were characterisedon the north coast. Picophytoplankton abundance shifted froma summer dominance of Synechococcus to a dominance ofpicoeukaryotes and Prochlorococcus during spring.Nanoeukaryotes were the most abundant in spring.Microphytoplankton was resolved into five groups, labelledBacillariophyceae, Dinophyceae, Cyanobacteriae,Euglenophyceae and Chlorophyceae. A total of 90microphytoplankton species were identified in all stations,with an overwhelming abundance of large diatoms, a typicaltrait of benthic communities (Coscinodiscus sp.,Grammatophora sp., Navicula sp., Pleurosigma sp.,Striatella unipunctata …). Results collected in this study arefavouring a beneficial impact on the ecosystem of the Sfaxnorth coast restoration achieved by the Taparura Project

Restoration impact of an uncontrolled phosphogypsum dump site on the seasonal distribution of abiotic variables, phytoplankton and zooplankton along the near shore of the south-western Mediterranean coast

International audienceIn connection with the Taparura Project, we studied the distribution of phytoplankton and zooplankton communities in relation to environmental variables at 18 stations sampled during four coastal cruises conducted between October 2009 and July 2010 on the north coast of Sfax (Tunisia, western Mediterranean Sea). The inshore location was largely dominated by diatoms (66 %) represented essentially by members of the genera Navicula, Grammatophora, and Licmophora. Dinophyceae were numerically the second largest group and showed an enhanced species richness. Cyanobacteriae developed in association with an important proliferation of colonial Trichodesmium erythraeum, contributing 39.4 % of total phytoplankton abundances. The results suggest that phytoplankters are generally adapted to specific environmental conditions. Copepods were the most abundant zooplankton group (82 %) of total zooplankton. A total of 21 copepod species were identified in all stations, with an overwhelming abundance of Oithona similis in autumn and summer, Euterpina acutifrons in winter, and Oncaea conifera in spring. The phosphogypsum restoration had been acutely necessary allowing dominant zooplankton species to exploit a wide range of food resources including phytoplankton and thus improving water quality

Diversity of cultivable halophilic archaea and bacteria from superficial hypersaline sediments of Tunisian solar salterns

Prokaryotes in the superficial sediments are ecologically important microorganisms that are responsible for the decomposition, mineralization and subsequent recycling of organic matter. The aim of this study was to explore the phylogenetic and functional diversity of halophilic archaea and bacteria isolated from the superficial sediments of solar salterns at Sfax, Tunisia. Sixty four strains were isolated from crystallizer (TS18) and non-crystallizer (M1) ponds and submitted to genotypic characterization and evaluation by amplified ribosomal RNA restriction analysis (ARDRA) techniques. Our findings revealed that the archaeal diversity observed for 29 isolates generated five distinct patterns from the non-crystallizer M1 pond, with Halorubrum chaoviator as the most prevalent cultivable species. However, in the TS18 crystallizer pond, ten restriction patterns were observed, with the prevalence of haloarchaea EB27K, a not yet identified genotype. The construction of a neighbour-joining tree of 16S rRNA gene sequences resulted in the division of the potential new species into two major groups, with four strains closely related to the sequence of the unculturable haloarchaeon EB27K and one strain to the recently described Halovenus aranensis strain. The 35 bacterial strains observed in this work were present only in the non-crystallizer pond (M1) and presented two distinct ARDRA patterns. These strains belonged to the γ-proteobacteria subdivision, with members of Salicola marasensis (83 %) being the most predominant species among the isolates. 16S rRNA gene sequencing revealed that Salicola strains displayed different degrees of homogeneity. The results from pulsed field gel electrophoresis assays showed that the Salicola isolates could be clustered in two distinct groups with different genome sizes