Actinopolyspora saharensis sp. nov., a novel halophilic actinomycete isolated from a Saharan soil of Algeria

A novel halophilic actinomycete, strain H32^T, was isolated from a Saharan soil sample collected in El-Oued province, south Algeria. The isolate was characterized by means of polyphasic taxonomy. Optimal growth was determined to occur at 28–32 °C, pH 6.0–7.0 and in the presence of 15–25 % (w/v) NaCl. The strain was observed to produce abundant aerial mycelium, which formed long chains of rod-shaped spores at maturity, and fragmented substrate mycelium. The cell wall was determined to contain meso-diaminopimelic acid and the characteristic whole-cell sugars were arabinose and galactose. The predominant menaquinones were found to be MK-10(H₄) and MK-9(H₄). The predominant cellular fatty acids were determined to be anteiso C_17:0, iso-C_15:0 and iso-C_16:0. The diagnostic phospholipid detected was phosphatidylcholine. Phylogenetic analyses based on the 16S rRNA gene sequence showed that this strain formed a distinct phyletic line within the radiation of the genus Actinopolyspora. The 16S rRNA gene sequence similarity indicated that strain H32^T was most closely related to ‘Actinopolyspora algeriensis’ DSM 45476^T (98.8 %) and Actinopolyspora halophila DSM 43834^T (98.5 %). Furthermore, the result of DNA–DNA hybridization between strain H32^T and the type strains ‘A. algeriensis’ DSM 45476^T, A. halophila DSM 43834^T and Actinopolyspora mortivallis DSM 44261^T demonstrated that this isolate represents a different genomic species in the genus Actinopolyspora. Moreover, the physiological and biochemical data allowed the differentiation of strain H32^T from its closest phylogenetic neighbours. Therefore, it is proposed that strain H32^T represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora saharensis sp. nov. is proposed. The type strain is H32^T (=DSM 45459^T=CCUG 62966^T).     

Isolation,Classification and Antagonistic Properties of Alkalitolerant Actinobacteria from Algerian Saharan Soils

Abstract

The Sahara, one of the most extreme environments on Earth, constitutes an unexplored source of alkalitolerant actinobacteria. In this work, we studied the diversity of alkalitolerant actinobacteria in various soils collected from different regions of the Algerian Sahara. A total of 29 alkalitolerant actinobacterial strains were isolated by using a complex agar medium. The diversity of these actinobacteria was evaluated using a polyphasic approach, which included morphological, chemotaxonomic, physiological (numerical taxonomy) and 16S rRNA gene analyses. The isolates which were assigned to the genus Nocardiopsis, shared relatively low 16S rRNA gene sequences similarities compared to closely related species suggesting that they belonged to putatively new species. All of the strains were tested for antibiotic activity against a broad range of microorganisms and screened for genes encoding polyketide synthases and non-ribosomal peptide synthetases and found to have the potential to produce secondary metabolites. Consequently, the study supports the view that extreme environments contain many novel actinobacteria, which represent an unexplored source for the discovery of biologically active compounds.     

Cloning, gene expression and characterization of a novel bacterial NAD-dependent non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase from Neisseria meningitidis strain Z2491

Alignment of the amino acid sequence of some archaeal, bacterial and eukaryotic non-phosphorylating glyceraldehydes-3-phosphate dehydrogenases (GAPNs) and aldehyde dehydrogenases (ALDHs) with the sequence of a putative GAPN present in the genome of the Gram-negative bacterium Neisseria meningitidis strain Z2491 demonstrated the conservation of residues involved in the catalytic activity. The predicted coding sequence of the N. meningitidis gapN gene was cloned in Escherichia coli XL1-blue under the expression of an inducible promoter. The IPTG-induced GAPN was purified ca. 48-fold from E. coli cells using a procedure that sequentially employed conventional ammonium sulfate fractionation as well as anion-exchange and affinity chromatography. The purified recombinant enzyme was thoroughly characterized. The protein is a homotetramer with a 50-kDa subunit, exhibiting absolute specificity for NAD and a broad spectrum of aldehyde substrates. Isoelectric focusing analysis with the purified fraction showed the presence of an acidic polypeptide with an isoelectric point of 6.3. The optimum pH of the purified enzyme was between 9 and 10. Studies on the effect of increasing temperatures on the enzyme activity revealed an optimal value ca. 64 °C. Molecular phylogenetic data suggest that N. meningitidis GAPN has a closer relationship with archaeal GAPNs and glyceraldehyde dehydrogenases than with the typical NADP-specific GAPNs from Gram-positive bacteria and photosynthetic eukaryotes.     

The role of caldesmon and its phosphorylation by ERK on the binding force of unphosphorylated myosin to actin

Background

Studies conducted at the whole muscle level have shown that smooth muscle can maintain tension with low Adenosine triphosphate (ATP) consumption. Whereas it is generally accepted that this property (latch-state) is a consequence of the dephosphorylation of myosin during its attachment to actin, free dephosphorylated myosin can also bind to actin and contribute to force maintenance. We investigated the role of caldesmon (CaD) in regulating the binding force of unphosphorylated tonic smooth muscle myosin to actin.

Methods

To measure the effect of CaD on the binding of unphosphorylated myosin to actin (in the presence of ATP), we used a single beam laser trap assay to quantify the average unbinding force (F_unb) in the absence or presence of caldesmon, extracellular signal-regulated kinase (ERK)-phosphorylated CaD, or CaD plus tropomyosin.

Results

F_unb from unregulated actin (0.10 ± 0.01 pN) was significantly increased in the presence of CaD (0.17 ± 0.02 pN), tropomyosin (0.17 ± 0.02 pN) or both regulatory proteins (0.18 ± 0.02 pN). ERK phosphorylation of CaD significantly reduced the F_unb (0.06 ± 0.01 pN). Inspection of the traces of the F_unb as a function of time suggests that ERK phosphorylation of CaD decreases the binding force of myosin to actin or accelerates its detachment.

Conclusions

CaD enhances the binding force of unphosphorylated myosin to actin potentially contributing to the latch-state. ERK phosphorylation of CaD decreases this binding force to very low levels.

General significance

This study suggests a mechanism that likely contributes to the latch-state and that explains the muscle relaxation from the latch-state.     

Effects of fishing on parasitism in a sparid fish: contrasts between two areas of the Western Mediterranean

This study addressed the impacts of fishing on the rates of parasitism using the sparid Boops boops as a model fish species. Using a large suite of parasite species in B. boops, with different life histories, transmission pathways and host specificity, we compared parasite diversity, prevalence, abundance and community structure at two Mediterranean localities in the Balearic Sea, Santa Pola Bay and the Gulf of Oran, that are characterised by a contrasting pattern of fishing of B. boops. A total of 360 fish were examined comprising nine distinct samples collected during the warm and the cold weather months. A total of 29 parasite species were identified, with eight species in common for the two localities. Parasite component communities at Santa Pola Bay were more species rich and abundant than those at the Gulf of Oran and exhibited a different community structure. Of the eight common taxa used in the quantitative comparisons, five exhibited significant difference for prevalence between the two localities, four having substantially higher prevalence at Santa Pola and only one being more prevalent at the Gulf of Oran. Two specialist trematodes and the sparid generalist monogenean exhibited consistently higher prevalence and abundance at Santa Pola Bay than at the Gulf of Oran; the two specialists were also identified as key species for assigning individual fish to their locality of origin. The consistent differences in the richness, abundance and structure of parasite communities in B. boops from Santa Pola Bay and the Gulf of Oran may reflect the contrasting patterns of exploitation of the populations of this fish host at the two localities.     

Discovery of an Upper Miocene Vertebrate fauna near Tizi N’Tadderht,Skoura, Ouarzazate Basin (Central High Atlas,Morocco)

The discovery of Upper Miocene vertebrates at Tizi N’Tadderht in the Ouarzazate basin (Morocco) helps to fill a gap in our knowledge of Neogene faunas in North Africa. The new fauna includes an ostrich cf. Struthio sp, a turtle cf. Centrochelys sp., Crocodylus cf. niloticus, and a relatively diverse fauna of large mammals. The mammal assemblage probably includes three hipparion species, including a very small form not previously reported from Africa, aff. Cremohipparion periafricanum, two species of rhinoceros cf. Ceratotherium sp. and aff. Chilotherium sp., a Proboscidean cf. Tetralophodon sp., a large member of the Giraffidae similar to “Palaeotragus” germaini and two bovids of which one is likely related to Prostrepsiceros, while the other is a new medium-sized antelope with spiral horns, certainly a representative of the Caprinae, a group that is rare in Africa. A late Miocene age, corresponding to the European Turolian Mammal age, is most likely for this fauna.     

"Candidatus Cloacamonas acidaminovorans": genome sequence reconstruction provides a first glimpse of a new bacterial division

Many microorganisms live in anaerobic environments. Most of these microorganisms have not yet been cultivated. Here, we present, from a metagenomic analysis of an anaerobic digester of a municipal wastewater treatment plant, a reconstruction of the complete genome of a bacterium belonging to the WWE1 candidate division. In silico proteome analysis indicated that this bacterium might derive most of its carbon and energy from the fermentation of amino acids, and hence, it was provisionally classified as "Candidatus Cloacamonas acidaminovorans." "Candidatus Cloacamonas acidaminovorans" is probably a syntrophic bacterium that is present in many anaerobic digesters. This report highlights how environmental sequence data might provide genomic and functional information about a new bacterial clade whose members are involved in anaerobic digestion.     

Affinity for MgADP and force of unbinding from actin of myosin purified from tonic and phasic smooth muscle

Smooth muscle is unique in its ability to maintain force at low MgATP consumption. This property, called the latch state, is more prominent in tonic than phasic smooth muscle. Studies performed at the muscle strip level have suggested that myosin from tonic muscle has a greater affinity for MgADP and therefore remains attached to actin longer than myosin from phasic muscle, allowing for cross-bridge dephosphorylation and latch-bridge formation. An alternative hypothesis is that after dephosphorylation, myosin reattaches to actin and maintains force. We investigated these fundamental properties of smooth muscle at the molecular level. We used an in vitro motility assay to measure actin filament velocity (nu(max)) when propelled by myosin purified from phasic or tonic muscle at increasing [MgADP]. Myosin was 25% thiophosphorylated and 75% unphosphorylated to approximate in vivo conditions. The slope of nu(max) versus [MgADP] was significantly greater for tonic (-0.51 +/- 0.04) than phasic muscle myosin (-0.15 +/- 0.04), demonstrating the greater MgADP affinity of myosin from tonic muscle. We then used a laser trap assay to measure the unbinding force from actin of populations of unphosphorylated tonic and phasic muscle myosin. Both myosin types attached to actin, and their unbinding force (0.092 +/- 0.022 pN for phasic muscle and 0.084 +/- 0.017 pN for tonic muscle) was not statistically different. We conclude that the greater affinity for MgADP of tonic muscle myosin and the reattachment of dephosphorylated myosin to actin may both contribute to the latch state.