Laboratory experiments were conducted with the millipede Harpaphe haydeniana haydeniana Wood (Polydesmida: Xystodesmidae) to determine (i) its litter feeding preferences, (ii) rates of leaf litter consumption, (iii) feeding effects on available nitrogen, and (iv) functional microbial diversity. The millipede exhibited a preference for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and, to a lesser extent, Sitka spruce (Picea sitchensis (Bong.) Carrière) litter compared with western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) litter when given a choice. When only one litter type was provided, millipedes consumed considerably more western redcedar than Douglas-fir, Sitka spruce, or western hemlock. Among the six broadleaf species tested, paper birch (Betula papyrifera Marsh.), bigleaf maple (Acer macrophyllum Pursh), vine maple (Acer circinatum Pursh), and red alder (Alnus rubra Bong.) were consumed at much higher rates than swordfern (Polystichum munitum (Kaulf.) Presl.) or salal (Gaultheria shallon Pursh). Daily rates of conifer litter consumption ranged between 10 and 20% of the millipede's fresh biomass and may translate to 36% of the annual litter fall. Our results suggest that transformation of conifer litter into millipede frass can increase rates of litter decomposition and N mineralization, as well as influence microbial activity and diversity in coastal forests.Résumé : Des expériences en laboratoire ont été réalisées avec des millipèdes (Harpaphe haydeniana haydeniana Wood, Polydesmida : Xystodesmidae) en vue de déterminer (i) la litière qu'ils préfèrent comme source de nourriture, (ii) leur taux de consommation de litière de feuilles, (iii) les effets de leur consommation sur l'azote disponible et (iv) la diversité microbienne fonctionnelle. Lorsqu'ils avaient le choix, les millipèdes ont manifesté une préférence pour la litière du douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) et, dans une moindre mesure, pour celle de l'épinette de Sitka (Picea sitchensis (Bong.) Carrière), comparativement à la litière de la pruche de l'Ouest (Tsuga heterophylla (Raf.) Sarg.) et du thuya géant (Thuja plicata Donn ex D. Don). Lorsqu'on leur fournissait seulement un type de litière, les millipèdes consommaient beaucoup plus de thuya géant que de douglas de Menzies, d'épinette de Sitka ou de pruche de l'Ouest. Parmi les six espèces feuillues testées, le bouleau blanc (Betula papyrifera Marsh.), l'érable à grandes feuilles (Acer macrophyllum Pursh), l'érable circiné (Acer circinatum Pursh) et l'aulne rouge (Alnus rubra Bong.) étaient consommés à un taux beaucoup plus élevé que le polystic épée (Polystichum munitum (Kaulf.) Presl) ou la gaulthérie salal (Gaultheria shallon Pursh). Les taux journaliers de consommation de litière de conifères se situaient entre 10 et 20% de la biomasse fraîche des millipèdes et pouvaient représenter 36% de la chute annuelle de litière. Les résultats obtenus suggèrent que, dans les forêts côtières, la transformation de la litièr...

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Twenty-two Bacillus spp. isolates from the rhizosphere of Phaseolus vulgaris 'Contender' were identified using Biolog™, gas chromatographic fatty acid methyl ester, and 23S rDNA analyses. Some of the Bacillus isolates produced significant amounts of the phytohormone indoleacetic acid (IAA) when grown in a liquid culture medium supplemented with 100 μg L-tryptophan/L; less IAA was produced in culture medium not supplemented with L-tryptophan. Thin-layer chromatography, high-performance liquid chromatography, gas chromatography – mass spectrometry, and the avena coleoptile bioassay were used to identify and quantify IAA produced by Bacillus isolates. Significant differences were observed in the amounts of IAA produced by different strains of Bacillus, with amounts varying from 0.40 to 4.88 μg/mL. α-Methyltryptophan-resistant mutants of Bacillus exhibited altered IAA production and excreted tryptophan into the growing medium. The IAA-producing Bacillus isolates promoted root growth and (or) nodulation when coinoculated with Rhizobium etli (TAL 182) on Phaseolus vulgaris 'Contender' under gnotobiotic conditions in growth chambers. Coinoculation resulted in increased nodule number, nodule fresh weight, nitrogenase activity, leghemoglobin content, and total soluble protein content in the root nodules of Phaseolus vulgaris. In contrast, coinoculation with α-methyltryptophan mutants resulted in decreased nodulation, indicating that Bacillus isolates have a direct effect on either the Rhizobium or the plant and the effect may not be singularly attributed to their ability to produce IAA in vitro.Key words: Bacillus, indoleacetic acid production, nodulation enhancement.