Nécessité d’une gestion des résidus agricoles et agro-industriels à Kinshasa

La pression humaine sur les ressources naturelles et la pollution environnementale, notamment par les résidus végétaux, constituent deux importantes conséquences du manque de politique structurée d’urbanisation et de traitement des déchets à Kinshasa. Une des pistes de solution à ce problème consiste à intégrer les acteurs qui sont à la base de ce problème. Dans les cas des résidus végétaux, il s’agit des producteurs agricoles et agroindustriels. Dans ce travail, une investigation a été menée auprès de trente producteurs agricoles et cinq agroindustriels localisés dans cinq communes de Kinshasa, dans le but d’évaluer le mode de gestion des résidus lignocellulosiques qu’ils génèrent par leurs activités. Aucun producteur agricole ni agro-industriel, ne dispose des outils d’estimation de la quantité des résidus qu’il génère ; les producteurs maraîchers utilisent presque tous les résidus de récolte pour la fertilisation des plates-bandes en vue de nouvelles cultures, tandis que les producteurs de riz ont un surplus de résidus. Les producteurs agro-industriels connaissent tous un problème d’élimination des résidus végétaux que leurs activités produisent.© 2015 International Formulae Group. All rights reserved.Mots clés: Environnement, pollution, lignocellulosiques, producteursEnglish AbstractThe human strong need in natural resources and the environmental pollution, in particular by vegetable residues, represent two main consequences of the lack of structured urbanization policy and of the material waste processing in Kinshasa. One way of solutions to this problem consists in involving the persons who are on the basis of it. In the framework of vegetable residues, this concerns agricultural and agro-industrial producers. In this study, we aimed at evaluating the lignocellulosic residues management generated by thirty agricultural producers and five agro-industrials located in five municipalities of Kinshasa. Among agricultural and agro-industrials none have the use of tools necessary to estimate the amount of residues generated in their activities. Market gardeners use almost all residues of harvesting to fertilize plate bands for new cultivations while rice producers have surplus residues. All the agro-industrials experience a problem of elimination of vegetables residues generated by their activities.© 2015 International Formulae Group. All rights reserved.Keywords: Environment, pollution, lignocellulosic, producer

Preservation and Evolution of Organic Matter During Experimental Fossilisation of the Hyperthermophilic Archaea Methanocaldococcus jannaschii

International audienceIdentification of the earliest traces of life is made difficult by the scarcity of the preserved microbial remains and by the alteration and potential contamination of the organic matter (OM) content of rocks. These factors can confuse interpretations of the biogenicity and syngenicity of fossilised structures and organic molecules found in ancient rocks. In order to improve our knowledge of the fossilisation processes and their effects at the molecular level, we made a preliminary study of the fate of OM during experimental fossilisation. Changes in the composition and quantity of amino acids, monosaccharides and fatty acids were followed with HPLC, GC and GC-MS analyses during 1 year of silicification of the hyperthermophilic Archaea Methanocaldococcus jannaschii. Although the cells themselves did not fossilise and the accompanying extracellular polymeric substances (EPS) did, our analyses showed that the OM initially present in both cells and EPS was uniformly preserved in the precipitated silica, with amino acids and fatty acids being the best preserved compounds. This study thus completes previous data obtained by electron microscopy investigations of simulated microbial fossilisation and can help better identification and interpretation of microbial biosignatures in both ancient rocks and in recent hydrothermal formations and sediments

TPV1, the first virus isolated from the hyperthermophilic genus Thermococcus.

International audienceWe describe a novel virus, TPV1 (Thermococcus prieurii virus 1), which was discovered in a hyperthermophilic euryarchaeote isolated from a deep-sea hydrothermal chimney sample collected at a depth of 2700 m at the East Pacific Rise. TPV1 is the first virus isolated and characterized from the hyperthermophilic euryarchaeal genus Thermococcus. TPV1 particles have a lemon-shaped morphology (140 nm × 80 nm) similar to the structures previously reported for Fuselloviruses and for the unclassified virus-like particle PAV1 (Pyrococcus abyssi virus 1). The infection with TPV1 does not cause host lysis and viral replication can be induced by UV irradiation. TPV1 contains a double-stranded circular DNA of 21.5 kb, which is also present in high copy number in a free form in the host cell. The TPV1 genome encompasses 28 predicted genes; the protein sequences encoded in 16 of these genes show no significant similarity to proteins in public databases. Proteins predicted to be involved in genome replication were identified as well as transcriptional regulators. TPV1 encodes also a predicted integrase of the tyrosine recombinase family. The only two genes that are homologous between TPV1 and PAV1 are TPV1-22 and TPV1-23, which encode proteins containing a concanavalin A-like lectin/glucanase domain that might be involved in virus-host recognition

Effect of variation of environmental conditions on the microbial communities of deep-sea vent chimneys, cultured in a bioreactor

The original publication is available at www.springerlink.comInternational audienceBoth cultivation and molecular techniques were used to investigate the microbial diversity and dynamic of a deep-sea vent chimney. The enrichment cultures performed in a gas-lift bioreactor were inoculated with a black smoker chimney sample collected on TAG site on the mid-Atlantic ridge. To mimic as close as possible environmental conditions, the cultures were performed in oligotrophic medium with nitrogen, hydrogen and carbon dioxide (N(2)/H(2)/CO(2)) gas sweeping. Also, the temperature was first settled at a temperature of 85 degrees C and colloidal sulphur was added. Then, the temperature was lowered to 60 degrees C and sulphur was omitted. Archaeal and bacterial diversity was studied in both culture and natural samples. Through 16S rRNA gene sequences analysis of the enrichment cultures microorganisms affiliated to Archeoglobales, Thermococcales were detected in both conditions while, Deferribacterales and Thermales were detected only at 65 degrees C in the absence of sulphur. Single-stranded conformational polymorphism and quantitative PCR permit to study the microbial community dynamic during the two enrichment cultures. The effect of environmental changes (modification of culture conditions), i.e. temperature, medium composition, electron donors and acceptors availability were shown to affect the microbial community in culture, as this would happen in their environment. The effect of environmental changes, i.e. temperature and medium composition was shown to affect the microbial community in culture, as this could happen in their environment. The modification of culture conditions, such as temperature, organic matter concentration, electron donors and acceptors availability allowed to enrich different population of prokaryotes inhabiting hydrothermal chimneys

Marinitoga litoralis sp. nov., a thermophilic, heterotrophic bacterium isolated from a coastal thermal spring on Ile Saint-Paul, Southern Indian Ocean.

International audienceA novel thermophilic, anaerobic and organotrophic bacterium, designated strain MC3T, was isolated from a coastal thermal spring on Ile Saint-Paul in the Southern Indian Ocean. Cells of strain MC3T were motile rods, 0.8-1.0 microm wide and 1.0-2.4 microm long during exponential phase and up to 7.0 microm long during stationary phase. Strain MC3T was an anaerobic organotroph able to use diverse organic compounds. It was also able to reduce sulfur to sulfide. Growth was observed at temperatures ranging from 45 to 70 degrees C (optimum at 60 degrees C), between pH 5.5 and 7.5 (optimum at pH 6) and from 8 to 46 g NaCl l(-1) (optimum at 26 g l(-1)). The total G+C content of the genomic DNA was 26.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequence comparisons indicated that strain MC3T was affiliated with the genus Marinitoga within the order Thermotogales. It shared 94.4-95.7% 16S rRNA gene sequence similarity with strains of other Marinitoga species; Marinitoga hydrogenitolerans was found to be the most closely related organism. Based on the data from the phylogenetic analysis and the physiological properties of the novel isolate, strain MC3T should be classified as a representative of a novel species, for which the name Marinitoga litoralis sp. nov. is proposed; the type strain is MC3T (=DSM 21709T =JCM 15581T)

Complete Genome Sequence of Hyperthermophilic Archaeon Thermococcus sp. EXT12c, Isolated from the East Pacific Rise 9°N

We report the genome sequence of Thermococcus sp. EXT12c isolated from a deep-sea hydrothermal vent at the East Pacific Rise 9°N. Microbes in the genus Thermococcus are able to grow anaerobically at high temperature, around neutral pH, and some of them under high hydrostatic pressure

Experimental fossilisation of the thermophilic Gram-positive bacterium Geobacillus SP7A: a long duration preservation study.

International audienceRecent experiments to fossilise microorganisms using silica have shown that the fossilisation process is far more complex than originally thought; microorganisms not only play an active role in silica precipitation but may also remain alive while silica is precipitating on their cell wall. In order to better understand the mechanisms that lead to the preservation of fossilised microbes in recent and ancient rocks, we experimentally silicified a Gram-positive bacterium, Geobacillus SP7A, over a period of five years. The microbial response to experimental fossilisation was monitored with the use of LIVE/DEAD staining to assess the structural integrity of the cells during fossilisation. It documented the crucial role of silicification on the preservation of the cells and of their structural integrity after several years. Electron microscopy observations showed that initial fossilisation of Gram-positive bacteria was extremely rapid, thus allowing very good preservation of Geobacillus SP7A cells. A thick layer of silica was deposited on the outer surface of cell walls in the earliest phase of silicification before invading the cytoplasmic space. Eventually, the cell wall was the only recognisable feature. Heavily mineralised cells thus showed morphological similarities with natural microfossils found in the rock record

Draft Genome Sequences of Two Marinitoga camini Isolates Producing Bacterioviruses

Here, we present the draft genome sequences of two thermophilic Marinitoga strain members of the Thermotogales order, Marinitoga camini DV1155 and Marinitoga camini DV1197. These strains were isolated from deep-sea hydrothermal vents of the Mid-Atlantic Ridge

Newly identified proviruses in Thermotogota suggest that viruses are the vehicles on the highways of interphylum gene sharing

Phylogenomic analyses of bacteria from the phylum Thermotogota have shown extensive lateral gene transfer with distantly related organisms, particularly with Firmicutes. One likely mechanism of such DNA transfer is viruses. However, to date, only three temperate viruses have been characterized in this phylum, all infecting bacteria from the Marinitoga genus. Here we report 17 proviruses integrated into genomes of bacteria belonging to eight Thermotogota genera and induce viral particle production from one of the proviruses. All except an incomplete provirus from Mesotoga fall into two groups based on sequence similarity, gene synteny and taxonomic classification. Proviruses of Group 1 are found in the genera Geotoga, Kosmotoga, Marinitoga, Thermosipho and Mesoaciditoga and are similar to the previously characterized Marinitoga viruses, while proviruses from Group 2 are distantly related to the Group 1 proviruses, have different genome organization and are found in Petrotoga and Defluviitoga. Genes carried by both groups are closely related to Firmicutes and Firmicutes (pro)viruses in phylogenetic analyses. Moreover, one of the groups show evidence of recent gene exchange and may be capable of infecting cells from both phyla. We hypothesize that viruses are responsible for a large portion of the observed gene flow between Firmicutes and Thermotogota