Molecular hydrogen as an energy source for Helicobacter pylori

The gastric pathogen Helicobacter pylori is known to be able to use molecular hydrogen as a respiratory substrate when grown in the laboratory. We found that hydrogen is available in the gastric mucosa of mice and that its use greatly increased the stomach colonization by H. pylori. Hydrogenase activity in H. pylori is constitutive but increased fivefold upon incubation with hydrogen. Hydrogen concentrations measured in the stomachs of live mice were found to be 10 to 50 times as high as the H. pylori affinity for hydrogen. A hydrogenase mutant strain is much less efficient in its colonization of mice. Therefore, hydrogen present in animals as a consequence of normal colonic flora is an energy-yielding substrate that can facilitate the maintenance of a pathogenic bacterium.     

Unidirectional spread of secondary sexual plumage traits across an avian hybrid zone

Theory predicts that traits under positive selection can rapidly cross a hybrid zone in spite of a substantial barrier to neutral gene flow between hybridizing taxa. An avian hybrid zone between Manacus candei (white-collared manakin) and M. vitellinus (golden-collared manakin) is reported here that displays an unusual pattern of noncoincident clines. Male secondary sexual traits of M. vitellinus have spread into populations that are genetically and morphometrically like M. candei. These birds have a lek breeding system in which male mating success is highly skewed, suggesting that sexual selection is driving male sexual traits across the zone.     

Biomedicine. Combating Parkinson's disease--step three

The degeneration of dopamine neurons in the nigrostriatal pathway of the brain results in the debilitating motor deficits of Parkinson's disease. In a Perspective, Olson discusses a new study (Kordower et al.) demonstrating that injection of a lentiviral vector containing the gene encoding GDNF (a trophic factor for dopamine neurons) into the nigrostriatal pathway of monkeys with PD prevents neuronal loss and reverses some of the motor deficits of this disease.