Nickel: A micronutrient element for hydrogen-dependent growth of \u3ci\u3eRhizobium japonicum\u3c/i\u3e and for expression of urease activity in soybean leaves

Soybean plants and Rhizobium japonicum 122 DES, a hydrogen uptake-positive strain, were cultured in media purified to remove Ni. Supplemental Ni had no significant effect on the dry matter or total N content of plants. However, the addition of Ni to both nitrate-grown and symbiotically grown plants resulted in a 7- to 10-fold increase in urease activity (urea amidohydrolase, EC 3.5.1.5) in leaves and significantly increased the hydrogenase activity (EC 1.18.3.1) in isolated nodule bacteroids. When cultured under chemolithotrophic conditions, free-living R. japonicum required Ni for growth and for the expression of hydrogenase activity. Hydrogenase activity was minimal or not detectable in cells incubated either without Ni or with Ni and chloramphenicol. Ni is required for derepression of hydrogenase activity and apparently protein synthesis is necessary for the participation of Ni in hydrogenase expression. The addition of Cr, V, Sn, and Pb in place of Ni failed to stimulate the activity of hydrogenase in R. japonicum and urease in soybean leaves. The evidence indicates that Ni is an important micronutrient element in the biology of the soybean plant and R. japonicum

Multiple Database Personalities: Facilitating Access to Research Data

We are moving from an era of largely analytical research into a time where a key research agenda will be to provide insights into relationships and interactions based on information gleaned from data repositories worldwide. Scientists have voiced the need for easy access to existing databases. As research scientists, we realize that while the today’s network infrastructure will readily support access to such data, it doesn’t ensure usability. If a database is to accommodate users beyond the research group that created it, we must find ways of giving it additional “personalities” to suit different audiences. Unfortunately, most Web-todatabase software targets professional programmers, not scientists. In this paper, we show that when Web interface software is responsive to the skill levels and preferences of scientists, it can be surprisingly easy to create Web interfaces that expose research data in different ways. We describe how a group of lichenologists exploited HyperSQL, a scientifically-oriented Web-to-database tool, to create database interfaces for two audiences. The first interface, the Synoptic Key of the Lichen, is rather terse, assuming that end-user is an experienced scientist. Using the same database, they constructed LichenLand, an interface intended for secondary school students. It uses colorful annotations and simple explanations to emphasize learning through discovery

Determination of the Hydrogenase Status of Individual Legume Nodules by a Methylene Blue Reduction Assay

We adapted a method for the rapid screening of colonies of free-living Rhizobium japonicum for hydrogenase activity to determine the hydrogenase status of individual soybean nodules. Crude bacteroid suspensions from nodules containing strains known to be hydrogen uptake positive (Hup(+)) caused a localized decolorization of filter paper disks, whereas suspensions from nodules arising from inoculation with hydrogen uptake-negative (Hup(−)) mutants or strains did not decolorize the disks. The reliability of the method was demonstrated by its successful application to 29 slow-growing rhizobia. The Hup phenotype on methylene blue filters agreed with that determined amperometrically with either methylene blue or oxygen as the electron acceptor