Differential fungal colonization and physiological defense responses of new olive cultivars infected by the necrotrophic fungus <Emphasis Type="Italic">Verticillium dahliae</Emphasis>

New olive cultivars adapted to Tunisia’s growing conditions were examined for their resistance to verticillium wilt (VWO) to determine whether differences in susceptibility among currently grown cultivars might contribute to the management of this disease. Based on the evaluation of 14 cultivars, 10 were classified as susceptible or extremely susceptible (Chetoui, Chemlali, Rkhami, Jarboui, Zalmati, Jarboui, Oueslati, Manzanille, Picholine and Frangivento), 2 as moderately susceptible (Koroneiki and Coratina), and 2 as resistant (Meski and Sayali) to VWO. Three cultivars with different susceptibility levels were selected to examine the levels of hydrogen peroxide (H₂O₂), soluble sugars (SS), soluble proteins (SP), total polyphenols (TP), lipid peroxidation, activities of antioxidant enzymes, and fungal biomass in planta. V. dahliae DNA occurred early in the roots at 15 dpi and reached a maximum of 3.507 and 2.52 ng/100 ng of plant DNA, respectively, in the extremely susceptible and resistant cultivars. Fungal DNA in the stems occurred at 30 dpi and increased slowly to reach a maximum of 0.23 ng/100 ng of total DNA in the extremely susceptible cultivars. We showed that the amount of fungal DNA in planta was roughly correlated with the susceptibility to VWO (P < 0.0001; r = 0.95). The comparison of cultivars at the physiological level indicated that olive resistance is roughly correlated with the antioxidant enzymes activity, H₂O₂ concentration, and TP and SP contents. The results of this study open new perspectives for olive genetic improvement programs aiming at developing new cultivars resistant to this wilt.     

Interproximal wear facets and tooth associations in the Paşalar hominoid sample

Interproximal wear facets were examined on hominoid teeth from the middle Miocene site at Pa?alar, Turkey. The aim was to find matches between adjacent premolar and molar teeth from single individuals that were collected in the field as isolated teeth and use them to reconstruct tooth rows. These were then used to investigate: (1) the wear gradient on the molar teeth; (2) the dispersal of teeth from single mandibles and maxillae; (3) the size ratios among the molars; and (4) the number of individuals represented by the hominoid sample. Facets were scored for size and shape and were assessed visually using photographs and superimposed outline drawings on acetate transparencies. Out of a sample of approximately 1,500 teeth collected between 1983 and 1996, 532 molars and 258 premolars produced apparent matches making up 160 tooth rows. These were then examined rigorously for morphological consistency and state of wear, and, employing the criterion that only the most unequivocal associations should be used, the final number was reduced to 48 tooth rows-31 mandibular and 17 maxillary. The tooth associations represent a minimum of 21 individuals and probably as many as 34. Molar wear was rapid, with M1s having almost twice as much wear as M3s, as measured by a wear-gradient index. The M2s are intermediate but generally closer to M1s in degree of wear, as are P4s. This wear pattern suggests either delayed eruption of M3s or extremely abrasive diets causing rapid, heavy wear. There is some indication that the wear patterns in Griphopithecus alpani and Kenyapithecus kizili are different, with the latter perhaps having a lower wear gradient, but the K. kizili sample is very small. In both species, the M2 is the largest molar and the M1 is the smallest. Separation of individual teeth in the 48 tooth associations varied from widely separated-up to 8.5m apart-to within a few centimeters of each other. One tooth row (D922) was found with the teeth in contact but the maxillary bone had dissolved away. Two dispersal mechanisms have been identified from earlier taphonomic work: transport of disarticulated elements to the fossil site and reworking of sediments by spring action.     

Effects of Dietary Supplementation with Bacillus amyloliquefaciens US573 on Intestinal Morphology and Gut Microbiota of European Sea Bass

Probiotics and Antimicrobial Proteins - Probiotics or direct-fed microbials (DFM) have proven strong potential for improving aquaculture sustainability. This study aims to evaluate the effects of...     

Induced-fit upon ligand binding revealed by crystal structures of the hot-dog fold thioesterase in dynemicin biosynthesis

Dynemicins are structurally related 10-membered enediyne natural products isolated from Micromonospora chernisa with potent antitumor and antibiotic activity. The early biosynthetic steps of the enediyne moiety of dynemicins are catalyzed by an iterative polyketide synthase (DynE8) and a thioesterase (DynE7). Recent studies indicate that the function of DynE7 is to off-load the linear biosynthetic intermediate assembled on DynE8. Here, we report crystal structures of DynE7 in its free form at 2.7 Å resolution and of DynE7 in complex with the DynE8-produced all-trans pentadecen-2-one at 2.1 Å resolution. These crystal structures reveal that upon ligand binding, significant conformational changes throughout the substrate-binding tunnel result in an expanded tunnel that traverses an entire monomer of the tetrameric DynE7 protein. The enlarged inner segment of the channel binds the carbonyl-conjugated polyene mainly through hydrophobic interactions, whereas the putative catalytic residues are located in the outer segment of the channel. The crystallographic information reinforces an unusual catalytic mechanism that involves a strictly conserved arginine residue for this subfamily of hot-dog fold thioesterases, distinct from the typical mechanism for hot-dog fold thioesterases that utilizes an acidic residue for catalysis.     

Homology modeling of human serum paraoxonase1 and its molecular interaction studies with aspirin and cefazolin

Human serum paraoxonase1 (HuPON1) belongs to the family of A-esterases (EC.3.1.8.1). It is associated with HDL particle and prevents atherosclerosis by cleaving lipid hydroperoxides and other proatherogenic molecules of oxidized low density lipoproteins (LDL). Since the precise structure of HuPON1 is not yet available, the structure-function relationship between HuPON1 and activators/inhibitors is still unknown. Therefore, a theoretical model of HuPON1 was generated using homology modelling and precise molecular interactions of an activator aspirin and an inhibitor cefazolin with PON1 were studied using Autodock software. The ligand binding residues were found to be similar to the predicted active site residues. Both cefazolin and aspirin were found to dock in the vicinity of the predicted active sites of PON1; cefazolin bound at residues N166, S193 and Y71, while aspirin at residues N309, I310 and L311. Binding region in the PON1 by prediction (3D2GO server) and docking studies provide useful insight into mechanism of substrate and inhibitor binding to the enzyme active site.     

Streptomyces tunisiensis sp. nov., a novel Streptomyces species with antibacterial activity

A novel actinomycete strain designated CN-207^T was isolated from northern Tunisian soil. This strain exhibited potent broad spectrum antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus species and several other Gram-positive and Gram-negative bacteria. Strain CN-207^T developed greyish aerial mycelium and pale grey substrate mycelium on yeast extract/malt agar. The isolate produced branching vegetative mycelia with sporangiophores bearing sporangia developing at a late stage of growth. The sporangia contained smooth, non-motile spores. Chemotaxonomic characteristics of strain CN-207^T were typical of the Streptomyces genus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CN-207^T belonged to the genus Streptomyces, and was most closely related to Streptomyces griseoincarnatus DSM 40274^T, Streptomyces variabilis DSM 40179^T, Streptomyces labedae DSM 41446^T and Streptomyces erythrogriseus DSM 40116^T. Low DNA–DNA relatedness values were recorded between strain CN-207^T and its closest phylogenetic neighbours. Strain CN-207^T was also distinguished from the nearest phylogenetic neighbours using a combination of morphological and phenotypic characteristics. On the basis of its phenotypic and molecular properties, strain CN-207^T is considered as a novel species of the Streptomyces genus, for which the name Streptomyces tunisiensis sp. nov. is proposed. The type strain is CN-207^T (=JCM 17589^T = DSM 42037^T).     

Metabolic capacities and toxigenic potential as key drivers of Bacillus cereus ubiquity and adaptation

Bacillus cereus is ubiquitous and is commonly found in a wide range of environments, including food. In this study, we analyzed 114 foodborne B. cereus strains isolated mainly from starchy and dairy products in order to investigate their phenotypic diversity (API system), antimicrobial resistance and toxigenic profiles (hblA, nheA, hlyII, cereolysin O, cytK2, cytK1 and EM1 genes). All isolates were confirmed as B. cereus using their 16–23S ribosomal DNA intergenic transcribed spacer (ITS) signature, and were shown to be Gram-positive, catalase and caseinase positive, hemolytic (97 %), and positive for lecithin hydrolysis and motility (97 and 87 %, respectively). PCR detection of B. cereus-specific toxin genes revealed occurrence rates of 100 % for cereolysin O, 98 % for nheA, 74 % for cytk2, 52 % for hblA, 28 % for hlyII, and the absence of cytK1. Only two strains (2 %), isolated from intestine of boar and pheasant, carried the emetic toxin genetic determinants (ces). The antimicrobial susceptibility of isolates was tested towards 15 different antimicrobial agents. We detected susceptibility of all strains to most antibiotics, intermediate resistance to clindamycin, and resistance to β-lactam antibiotics with 83 % of the resistant isolates producing β-lactamase enzyme. This large phenotypic diversity, combined with the toxigenic traits and antibiotic resistance, emphasize the high potential risk of food poisoning of B. cereus isolates. Additionally, a clear correlation between the metabolic features and the origin of isolation was shown. Most starchy isolates were able to hydrolyze starch while dairy strains were not able to produce amylases. Overall, our results reveal that metabolic flexibility and toxigenic potential represent the main drivers for B. cereus ubiquity and adaptation in a given ecological niche.     

Isolation and characterization of a lectin gene from seeds of chickpea (Cicer arietinum L.).

A cDNA library was constructed in lambda TriplEx2 vector using poly (A(+)) RNA from immature seeds of Cicer arietinum. The lectin gene was isolated from seeds of chickpea through library screening and RACE-PCR. The full-length cDNA of Chichpea seed lectin(CpGL)is 972 bp and contains a 807 bp open reading frame encoding a 268 amino acid protein. Analysis shows that CpSL gene has strong homology with other legume lectin genes. Phylogenetic analysis showed the existence of two main clusters and clearly indicated that CpSL belonged to mannose-specific family of lectins. RT-PCR revealed that CAA gene expressed constitutively in various plant tissues including flower, leaf, root and stem. When chickpea lectin mRNA level was checked in developing seeds, it was higher in 10 DAF seeds and decreased throughout seed development.     

Independent introduction of two lactase-persistence alleles into human populations reflects different history of adaptation to milk culture

The T₋₁₃₉₁₀ variant located in the enhancer element of the lactase (LCT) gene correlates perfectly with lactase persistence (LP) in Eurasian populations whereas the variant is almost nonexistent among Sub-Saharan African populations, showing high prevalence of LP. Here, we report identification of two new mutations among Saudis, also known for the high prevalence of LP. We confirmed the absence of the European T₋₁₃₉₁₀ and established two new mutations found as a compound allele: T/G₋₁₃₉₁₅ within the −13910 enhancer region and a synonymous SNP in the exon 17 of the MCM6 gene T/C₋₃₇₁₂, −3712 bp from the LCT gene. The compound allele is driven to a high prevalence among Middle East population(s). Our functional analyses in vitro showed that both SNPs of the compound allele, located 10 kb apart, are required for the enhancer effect, most probably mediated through the binding of the hepatic nuclear factor 1 α (HNF1α). High selection coefficient (s) ~0.04 for LP phenotype was found for both T₋₁₃₉₁₀ and the compound allele. The European T₋₁₃₉₁₀ and the earlier identified East African G₋₁₃₉₀₇ LP allele share the same ancestral background and most likely the same history, probably related to the same cattle domestication event. In contrast, the compound Arab allele shows a different, highly divergent ancestral haplotype, suggesting that these two major global LP alleles have arisen independently, the latter perhaps in response to camel milk consumption. These results support the convergent evolution of the LP in diverse populations, most probably reflecting different histories of adaptation to milk culture.