Dwight Baker - Academia.edu (original) (raw)

Papers by Dwight Baker

Soil Biology and Biochemistry, 1994

Biomass productivity and nitrogen fixation were studied for combinations of four Casuurina cultiv... more Biomass productivity and nitrogen fixation were studied for combinations of four Casuurina cultivars and four Frunkia strains. Seedlings were planted in pots containing a Frankia-free, low-nutrient soil. To evaluate nitrogen fixation over the duration of the experiment, a small amount of 'sN-enriched KNO, was supplied to the pots on a weekly basis. After 56 weeks, all of the plants were harvested and dry weights determined. Plant tissue was analyzed for N concentration and "N (atom % excess). Significant differences were observed in biomass productivity among the various host-strain concentrations. Differences were also observed in the proportion of N derived from nitrogen fixation (pNdfa) among the various host&strain combinations, and these were correlated with biomass productivity. From the results of our experiment, it is clear that performance and nitrogen fixation are related to the interaction between the host plant and the Frankia strain. If Casuarina-Frankia strain combinations are to be used, it is appropriate to conduct trials of symbiont compatibility to improve yield.

Journal of Visualized Experiments

Standards in Genomic Sciences, 2009

Against this background, we were commissioned to provide a detailed report that could inform the ... more Against this background, we were commissioned to provide a detailed report that could inform the negotiation process on these issues. The studies we prepared were aimed at the negotiators of the international regime, and are written for an audience with a mixture of technical, legal, and policy backgrounds. However, the topics we discuss are also relevant to the genomics community and we welcome any comments the readers of SIGS might like to share.

Plant and Soil, 2003

The extent of transfer of fixed N between N 2-fixing and non-N 2-fixing plant species is largely ... more The extent of transfer of fixed N between N 2-fixing and non-N 2-fixing plant species is largely unknown in successional studies. In order to redress this deficiency at a locale intensively studied ecologically, leaf tissue samples were collected from actinorhizal N 2-fixing (Alnus, Shepherdia, and Dryas) and two non-N 2-fixing (Salix) woody species within research plots located along a chronosequence of deglaciated fjord in Glacier Bay National Park, Alaska. The tissue samples were analyzed for δ 15 N content, and the resulting data analyzed for trends in plant tissue N. Among the non-N 2-fixing Salix species, δ 15 N values increased from the most recently deglaciated sites to converge with the temporally more-stable values for the symbiotic N 2-fixing species on sites at about 40 years after deglaciation. The lower δ 15 N values of sequestered N in plant tissues suggested that N derived from N 2-fixing plants accounts for the major portion of N in associated plants up to 40 years after deglaciation. The 15 N isotopic data also suggested that Shepherdia canadensis depends least on soil N, D. drummondii the most, and A. viridis ssp. sinuata somewhere between those two species. The presence of a sere dominated by dense thickets of A. viridis ssp. sinuata at the convergence of δ 15 N values for the N 2-fixing and non-N 2-fixing species indicated that this species is most responsible for accumulation of fixed N in soil at Glacier Bay.

The current state and future of the Tropical Resources Institute (TRI) in our School and Universi... more The current state and future of the Tropical Resources Institute (TRI) in our School and University is enviable in this era of academic retrenchment and uncertainty. Endowment now provides funds for internships, the Directorship, and related scholarships. We have an excellent leader; Dr. Florencia Montagnini, John M. Musser Director of the Tropical Resources Institute, is building a dynamic program on the solid and pioneering foundation built by Dr. William Burch, the founding director, and Dr. William Bentley, TRI's second director.

Plant and Soil - PLANT SOIL, 1999

Actinorhizal plants form a nodular, nitrogen-fixing root symbiosis with the actinomycete Frankia ... more Actinorhizal plants form a nodular, nitrogen-fixing root symbiosis with the actinomycete Frankia and are economically and ecologically important due to their ability to improve the nitrogen fertility of disturbed and infertile substrates. In this study, water-retentive polymer inoculum carriers were applied as a root dip. This treatment significantly increased nodulation and in some cases early growth of Alnus glutinosa (L.) Gaertn. and Casuarina equisetifolia var. equisetifolia Forst. & Forst. in a controlled environment and also of A. glutinosa under field conditions. Nodule number and nodule dry weight per plant were at least two to three times greater after 56 to 140 days for plants inoculated with Frankia carried in a water-retentive polymer base compared with plants inoculated with Frankia in water. Nodules on the roots of the plants that were inoculated with Frankia in a polymer slurry were distributed throughout the entire root system, rather than concentrated near the root ...

Natural Product Reports, 2007

The Journal of Antibiotics, 1997

Protein tyrosine kinase activity (PTK) is associated with the activity of many cellular and viral... more Protein tyrosine kinase activity (PTK) is associated with the activity of many cellular and viral oncogene products1'2) as well as signal transduction events for several growth factor receptors such as epidermal growth factor (EGF), platelet derived growth factor (PDGF) and insulin3'4). Activation of specific PTK mediated processes have been associated with proliferative diseases such as cancer5), artherosclerosis6) and probably pso-riasis6'7). This has led to the general concept that PTK inhibition may combat hyperproliferative conditions

The Journal of Antibiotics, 2000

Current Opinion in Biotechnology, 2004

A wide variety of novel small-molecule natural products has recently been reported. These compoun... more A wide variety of novel small-molecule natural products has recently been reported. These compounds were isolated from marine and terrestrial sources, and from a variety of animals, plants and microorganisms. With the breadth of diversity represented in these bioactive small molecules, the future of natural product drug discovery looks bright.

Canadian Journal of Microbiology, 1980

The actinomycete, Frankia sp. AvcI1, isolated from root nodules of Alnus viridis ssp. crispa was ... more The actinomycete, Frankia sp. AvcI1, isolated from root nodules of Alnus viridis ssp. crispa was grown in axenic culture and used to inoculate host seedlings. This bacterium has been shown to be an infective and effective nitrogen-fixing microsymbiont which can be distinguished from other frankiae, in vitro, on the basis of size, distinctive morphology, and growth characteristics. Cross-inoculation studies indicated that the host range of this symbiont encompasses all of the members of the genera Alnus, Myrica, and Comptonia tested. In all cases, the symbioses developed were effective in fixing atmospheric dinitrogen.

The Journal of …, 2000

1. J Antibiot (Tokyo). 2000 May;53(5):496-501. Identification of inhibitors of inducible nitric o... more 1. J Antibiot (Tokyo). 2000 May;53(5):496-501. Identification of inhibitors of inducible nitric oxide synthase from microbial extracts. Alvi KA, Baker DD, Stienecker V, Hosken M, Nair BG. MDS PANLABS, South, Bothell, WA 98011, USA. ...

Frontiers in Physiology

The success of the acaricide amitraz, a ligand of the tick tyramine/octopamine receptor (a G prot... more The success of the acaricide amitraz, a ligand of the tick tyramine/octopamine receptor (a G protein-coupled receptor; GPCR), stimulated interest on arthropod-specific GPCRs as targets to control tick populations. This search advances tick physiology because little is known about the pharmacology of tick GPCRs, their endogenous ligands or their physiological functions. Here we explored the tick kinin receptor, a neuropeptide GPCR, and its ligands. Kinins are pleiotropic insect neuropeptides but their function in ticks is unknown. The endogenous tick kinins are unknown and their cDNAs have not been cloned in any species. In contrast, more than 271 insect kinin sequences are available in the DINeR database. To fill this gap, we cloned the kinin cDNA from the cattle fever tick, Rhipicephalus microplus, which encodes 17 predicted kinins, and verified the kinin gene structure. We predicted the kinin precursor sequences from additional seven tick species, including Ixodes scapularis. All species showed an expansion of kinin paracopies. The "kinin core" (minimal active sequence) of tick kinins FX 1 X 2 WGamide is similar to those in insects. Pro was predominant at the X 2 position in tick kinins. Toward accelerating the discovery of kinin function in ticks we searched for novel synthetic receptor ligands. We developed a dual-addition assay for functional screens of small molecules and/or peptidomimetics that uses a fluorescent calcium reporter. A commercial library of fourteen small molecules antagonists of mammalian neurokinin (NK) receptors was screened using this endpoint assay. One acted as full antagonist (TKSM02) with inhibitory concentration fifty (IC 50) of ∼45 µM, and three were partial antagonists. A subsequent calcium bioluminescence assay tested these four antagonists through kinetic curves and confirmed TKSM02 as full antagonist and one as partial antagonist (TKSM14). Antagonists of NK receptors displayed selectivity (>10,000-fold) on the tick kinin receptor. Three peptidomimetic ligands of the mammalian NK receptors (hemokinin 1, antagonist G, and spantide I) were tested in the bioluminescence assay but none were active. Forward approaches may accelerate discovery of kinin ligands, either as reagents for tick physiological research or as lead molecules for acaricide development, and they demonstrate that selectivity is achievable between mammalian and tick neuropeptide systems.

International Journal of Systematic Bacteriology

INTERNATIONAL JOURNAL OF SYSTEMATIC BACTERIOLOGY, Apr. 1981, p. 148-151 0020-771 3/8 1 /020148-O4... more INTERNATIONAL JOURNAL OF SYSTEMATIC BACTERIOLOGY, Apr. 1981, p. 148-151 0020-771 3/8 1 /020148-O4$02.OO/O ... Immunochemical Analysis of Relationships Among Isolated Frankiae ( ActinomycetaZes) ... DWIGHT BAKER,? WILLIAM L. PENGELLY,$ ...

Journal of biomolecular screening, Jan 4, 2016

New and improved drugs against tuberculosis are urgently needed as multi-drug-resistant forms of ... more New and improved drugs against tuberculosis are urgently needed as multi-drug-resistant forms of the disease become more prevalent. Mycobacterium tuberculosis cytidylate kinase is an attractive target for screening due to its essentiality and different substrate specificity to the human orthologue. However, we selected the Mycobacterium smegmatis cytidylate kinase for screening because of the availability of high-resolution X-ray crystallographic data defining its structure and the high likelihood of active site structural similarity to the M. tuberculosis orthologue. We report the development and implementation of a high-throughput luciferase-based activity assay and screening of 19,920 compounds derived from small-molecule libraries and an in silico screen predicting likely inhibitors of the cytidylate kinase enzyme. Hit validation included a counterscreen for luciferase inhibitors that would result in false positives in the initial screen. Results of this counterscreen ruled out ...