NnrA is required for full virulence and regulates several Brucella melitensis denitrification genes

We identified two regulators of denitrification genes in Brucella melitensis 16M: NarR, which regulates the nitrate reductase (nar) operon, and NnrA, which is involved in the expression of the last three reductases of the denitrification pathway (nirK, norB, and nosZ). NnrA is required for virulence in mice and for intracellular resistance to nitric oxide.     

Spectral gradients of downwelling light in a fluvial lake (Lake Saint-Pierre, St-Lawrence River)

Large fluvial lakes are understudied with respect to their underwaterlight climates. Fluvial lakes pose unique challenges for photobiologistsinterested in the interactions amongst light climate, nutrients and microbialcommunity structure and biodiversity. This is because fluvial lakes are typifiedby highly dynamic flow regimes often incorporating different inflows anddischarges each characterized by their own unique physico-chemical composition.These compositional characteristics include the concentrations of chromophoricdissolved organic matter (CDOM), suspended solids, and pigments such aschlorophyll. Together these factors contribute to the distribution andcomposition of the water masses that make up fluvial lakes. These water masses,in turn, flow over lakebeds that are typically complex in their morphometry andfeature extensive macrophyte beds, further enhancing the habitat heterogeneityof these ecosystems. We here report on the spectral attenuation of ultravioletradiation (UVR = 280–400 nm) and photosyntheticallyactive radiation (PAR = 400–700 nm) in the three mainwater masses of Lake Saint-Pierre and evaluate the relative contribution ofCDOM, and particulate organic material to UVR attenuation. We demonstrate thatUVR penetrates 18 to 30% of the water column (1% penetration depth) in the LakeSaint-Pierre ecosystem, and show how the underwater spectral UVR varies withinthe three water masses.     

Eosialis, a new alderfly genus in French Lowermost Eocene amber (Insecta, Megaloptera, Sialidae)

A new genus and species of Sialidae, Eosialis dorisi nov. gen., nov. sp. is described from the Lowermost Eocene amber of Oise (France). Its phylogenetic affinities within this family remain uncertain.     

Intestinal absorption in the mechanically obstructed rat intestine: Protection by prostaglandins

Intestinal obstruction inhibits amino acid absorption. The inhibition, being dependent on the pathological changes of the absorptive epithelium, was considered as an index of injury and measured after varying periods of obstruction and after pretreatment with clindamycin, indomethacin, 16, 16-dimethyl-PGE2 or arachidonic acid. A reduction in amino acid uptake was apparent after 2h of obstruction and was increasingly evident after 4, 6 and 18h. During the late phase (after 6h), inhibition was partly prevented by pretreatment with clindamycin, but the antibiotic was ineffective during the early phase (within the first 2h). Bacterial colony counts of luminal contents of rats obstructed for 2h, were not different from counts obtained in controls, but significantly lower than counts in rats that have been obstructed for 6h. Pretreatment of rats with 16,16-dimethyl-PEG2 or with arachidonic acid prevented the early inhibitory effects of the obstruction. The findings suggest that the early inhibition in amino acid uptake may be related to metabolic changes that are correctable by the administration of 16,16-dimethyl-PGE2 or of arachidonic acid. The inhibition, during the late phase, is mainly related to an overgrowth of the enteric bacteria.     

Detection of bacterial and mycoplasma contamination in cell cultures by polymerase chain reaction

A fast and simple method to detect bacterial and especially mycoplasma contamination in tissue culture by means of polymerase chain reaction (PCR) amplification is described. In a first step the universal primer pairs P1/P2 (190-bp fragment) and P3/P4 (120-bp fragment) directed to different conserved parts of the prokaryotic 16S rRNA gene are used. A positive signal after amplification on cell culture DNA with these primers provides an indication of bacterial infection. Using the internal primers IP1, IP3 and IP'3 complementary to a part of the V4 and V8 variable regions of the 16S rRNA gene, in combination with a universal primer, cultures contaminated with mycoplasma could be identified. Six mycoplasma species, typical contaminants in tissue cultures, were investigated: Mycoplasma orale, M. fermentans, M. arginini, M. hyorhinis, M. hominis and Aeromonas laidlawii. This mycoplasma test is an easy, specific and sensitive assay which should be extremely useful in any tissue culture setting.     

New remains of primitive ruminants from Thailand: evidence of the early evolution of the Ruminantia in Asia

A new tragulid, Archaeotragulus krabiensis , gen. n. et sp. n., is described from the late Eocene Krabi Basin (south Thailand). It represents the oldest occurrence of the family which was previously unknown prior to the Miocene. Archaeotragulus displays a mixture of primitive and derived characters, together with the M structure on the trigonid, which appears to be the main dental autapomorphy of the family. We also report the occurrence at Krabi of a new Lophiomerycid, Krabimeryx primitivus , gen. n. et sp. n., which displays affinities with Chinese representatives of the family, particularly Lophiomeryx . The familial status of Iberomeryx is discussed and a set of characters is proposed to define both Tragulidae and Lophiomerycidae. Results of phylogenetic analysis show that tragulids are monophyletic and appear nested within the lophiomerycids. The occurrence of Tragulidae and Lophiomerycidae in the upper Eocene of south-east Asia enhances the hypothesis that ruminants originated in Asia, but it also challenges the taxonomic status of traguloids within the Ruminantia.     

Does agonistic dominance imply feeding priority in lemurs? a study inEulemur fulvus mayottensis

We studied agonistic dominance and priority of access to a limited drinking resource in two captive groups of Eulemur fulvus mayottensis.Gender is not systematically related to agonistic dominance or to drinking priority. The dominance hierarchy obtained in the drinking competition test is correlated with the baseline hierarchy in the absence of induced competition, but not with drinking priority. We analyze results within the framework of recent dicussions on female dominance in Malagasy prosimians.