Antimicrobial actions of dual oxidases and lactoperoxidase

The NOX/DUOX family of NADPH oxidases are transmembrane proteins generating reactive oxygen species as their primary enzymatic products. NADPH oxidase (NOX) 1–5 and Dual oxidase (DUOX) 1 and 2 are members of this family. These enzymes have several biological functions including immune defense, hormone biosynthesis, fertilization, cell proliferation and differentiation, extracellular matrix formation and vascular regulation. They are found in a variety of tissues such as the airways, salivary glands, colon, thyroid gland and lymphoid organs. The discovery of NADPH oxidases has drastically transformed our view of the biology of reactive oxygen species and oxidative stress. Roles of several isoforms including DUOX1 and DUOX2 in host innate immune defense have been implicated and are still being uncovered. DUOX enzymes highly expressed in the respiratory and salivary gland epithelium have been proposed as the major sources of hydrogen peroxide supporting mucosal oxidative antimicrobial defenses. In this review, we shortly present data on DUOX discovery, structure and function, and provide a detailed, up-to-date summary of discoveries regarding antibacterial, antiviral, antifungal, and antiparasitic functions of DUOX enzymes. We also present all the literature describing the immune functions of lactoperoxidase, an enzyme working in partnership with DUOX to produce antimicrobial substances.     

Assessment of genome organization among diploid species (2n = 2x = 14) belonging to primary and tertiary gene pools of pearl millet using fluorescent in situ hybridization with rDNA probes.

Two contrasting forms of Pennisetum belonging to the primary and tertiary gene pools were assessed for genomic organization using in situ hybridization with rDNA probes (18S-5.8S-25S and 5S) on metaphase and interphase cell nuclei. The primary gene pool is represented by diploid (2n = 2x = 14) cultivated pearl millet (Pennisetum glaucum) and its close wild relatives (Pennisetum violaceum and Pennisetum mollissimum). Pennisetum schweinfurthii (2n = 2x = 14) was taken as representative of the tertiary gene pool, owing to its diploid status and its similarity to the accessions of the primary gene pool in chromosome number. Using the 18S-5.8S-25S probe, we observed two sites of distribution in the four species but at different locations. Within the primary gene pool, signals were detected on the telomeric part of the short arm of chromosome pair VI and at the nucleolar organizing region (NOR) of the satellited chromosome pair (VII). Signals were observed at the NOR of the two satellited chromosome pairs (I and IV) of P. schweinfurthii. The 5S probe was detected at the telomeric part of the short arm of metacentric chromosome pair IV of the three species of the primary gene pool, while it occured in an intercalary position on the short arm of chromosome pair II of P. schweinfurthii. These results showed a chromosomal similarity of rDNA sequence locations within the primary gene pool and are in agreement with the high genetic identity between wild and cultivated forms of pearl millet previously revealed by allozyme studies. Implications of genomic organization for genetic resource enhancement are discussed. Key words : Pennisetum, in situ hybridization, rDNA probes, genomic organization.     

From limb to fin: an Eocene protocetid forelimb from Senegal sheds new light on the early locomotor evolution of cetaceans

Cetaceans constitute a textbook example of the secondary adaptation of tetrapods to aquatic life. This major event in the evolutionary history of mammals is often linked in the literature to the limb-to-fin transition. Paradoxically, limb bones are scarce in the fossil record of early cetaceans, and the transition from a limb-adapted morphology for an amphibious life in shallow water to a fin-adapted morphology for a pelagic lifestyle remains poorly documented. Here, we describe new protocetid remains from the upper Lutetian of Senegal, including a nearly complete articulated forelimb. A cladistic analysis including 24 taxa and 137 morphological characters recovers the new African specimen close to Carolinacetus. It also confirms that cetacean dispersal to the New World was not the result of a single colonization event. A 3D model of the forelimb was reconstructed. Anatomical comparisons suggest that it is unlikely that the Senegalese forelimb was used as a rigid pectoral flipper for steering as in basilosaurids and modern cetaceans. Instead, we suggest that the hand was actively used during swimming. This challenges previous reconstructions of protocetids as mainly foot-powered swimmers, and suggests that swimming specializations of early cetaceans were probably more diverse than previously considered.     

Loss in microbial diversity affects nitrogen cycling in soil

Microbial communities have a central role in ecosystem processes by driving the Earth''s biogeochemical cycles. However, the importance of microbial diversity for ecosystem functioning is still debated. Here, we experimentally manipulated the soil microbial community using a dilution approach to analyze the functional consequences of diversity loss. A trait-centered approach was embraced using the denitrifiers as model guild due to their role in nitrogen cycling, a major ecosystem service. How various diversity metrics related to richness, eveness and phylogenetic diversity of the soil denitrifier community were affected by the removal experiment was assessed by 454 sequencing. As expected, the diversity metrics indicated a decrease in diversity in the 1/10³ and 1/10⁵ dilution treatments compared with the undiluted one. However, the extent of dilution and the corresponding reduction in diversity were not commensurate, as a dilution of five orders of magnitude resulted in a 75% decrease in estimated richness. This reduction in denitrifier diversity resulted in a significantly lower potential denitrification activity in soil of up to 4–5 folds. Addition of wheat residues significantly increased differences in potential denitrification between diversity levels, indicating that the resource level can influence the shape of the microbial diversity–functioning relationship. This study shows that microbial diversity loss can alter terrestrial ecosystem processes, which suggests that the importance of functional redundancy in soil microbial communities has been overstated.     

Ostracodes et incursions marines dans l’Holocène terminal du lac Retba (Cap Vert, Sénégal)

The study of marine incursions based on ostracods is carried out for the first time in the late Holocene, with core sediments of the Lac Retba edge. Twenty-four species are identified along the core; most of them are encountered in the Gulf of Guinea shelf and its adjacent lagoons. For the first time Buntonia olokundudui Reyment and Van Valen, Hermanites foveolata Omatsola and Soudanella africana Omatsola are recorded in Senegal. Four ostracods assemblages are evidenced along the core, corresponding to different stages of the lake evolution. Cyprideis nigeriensis Omatsola, Neomonoceratina iddoensis Omatsola and Aglaiocypris gambiensis Witte dominate the first assemblage; they indicate a lagoon slightly open to the sea and bordered with mangrove swamps under relatively humid climate conditions. The second association yields the most diversified ostracod fauna with C. nigeriensis, N. iddoensis and high proportion of reworked “marine species” which evidence a marine little gulf bordered by mangrove under a humid climate. The third, monospecific association (C. nigeriensis) is typical of a closed and hypersaline lagoon under dry climate conditions. An oligospecific association with C. nigeriensis, Pseudoconcha omatsolai Witte and very scarce reworked “marine species” occurs at the top of the core and characterises an open and hypersaline lagoon under arid climate conditions. Ostracods evidence two marine incursions. The first and the stronger one is dated here for the first time between 1420 and 1250 years B.P. The more recent is the weaker and is not yet dated. Evidence of the beginning of the Retba Lake closure towards 680 years B.P. appears at the top of the core, as indicated by high reduction of ostracods abundance, predominance of reticulate Cyprideis and disappearance of the “marine species”, while salts precipitated at the bottom of the lake.     

Chromosome assignments of the human TNF p55 and p75 receptor genes.

At least two different receptor molecules have been described that are capable of binding tumor necrosis factor alpha, a cytokine that plays an important role in inflammation and antitumor activity. Comparative analyses at the nucleotide sequence level suggest that these receptors are members of a newly defined protein family that also includes human and rat nerve growth factor receptors. In this study, we determine the chromosome assignments of the human TNF alpha receptor genes, one of which may have evolved as part of a conserved Hox locus-containing chromosome segment.     

Optimization and enhancement of soil bioremediation by composting using the experimental design technique

The objective of this study was the application of the experimental design technique to optimize the conditions for the bioremediation of contaminated soil by means of composting. A low-cost material such as compost from the Organic Fraction of Municipal Solid Waste as amendment and pyrene as model pollutant were used. The effect of three factors was considered: pollutant concentration (0.1–2 g/kg), soil:compost mixing ratio (1:0.5–1:2 w/w) and compost stability measured as respiration index (0.78, 2.69 and 4.52 mg O₂ g⁻¹ Organic Matter h⁻¹). Stable compost permitted to achieve an almost complete degradation of pyrene in a short time (10 days). Results indicated that compost stability is a key parameter to optimize PAHs biodegradation. A factor analysis indicated that the optimal conditions for bioremediation after 10, 20 and 30 days of process were (1.4, 0.78, 1:1.4), (1.4, 2.18. 1:1.3) and (1.3, 2.18, 1:1.3) for concentration (g/kg), compost stability (mg O₂ g⁻¹ Organic Matter h⁻¹) and soil:compost mixing ratio, respectively.     

Synthesis of protoporphyrin IX induced by 5-aminolevulinic acid in yeast cells in the presence of 2,2;-dipyridyl

5-Aminolevulinic acid (ALA), a precursor of porphyrin synthesis, increased the production of various porphyrin compounds in Candida guilliermondii cells. Metalloporphyrins and protoporphyrin IX (PPIX) were predominantly accumulated, respectively, at ALA concentrations of 0.2-0.4 mM and at those higher than 1.5 mM. 2,2;-Dipyridyl which complexed with bivalent metals significantly increased the content of endogenous PPIX even at ALA concentrations lower than 0.5 mM. Under these conditions, the yeast sensitivity to photodynamic effect of visible light (400-600 nm) dramatically increased due to photosensitization by endogenous PPIX.