F. Joe Hanus

Hydrogenase in Rhizobium japonicum Increases Nitrogen Fixation by Nodulated Soybeans

Some Rhizobium strains synthesize a unidirectional hydrogenase system in legume nodule bacteroids; this system participates in the recycling of hydrogen that otherwise would be lost as a by-product of the nitrogen fixation process. Soybeans inoculated with Rhizobium japonicum strains that synthesized the hydrogenase system fixed significantly more nitrogen and produced greater yields than plants inoculated with strains lacking hydrogen-uptake capacity. Rhizobium strains used as inocula for legumes should have the capability to synthesize the hydrogenase system as one of their desirable characteristics.

[67] Techniques for measurement of hydrogen evolution by nodules

Publisher Summary This chapter discusses the techniques for the measurement of hydrogen evolution by nodules. The evolution of H2 by nodules has been measured by mass spectrometry, gas chromatography, and amperometry. All of these methods, except the amperometric technique, require sampling of the gas mixture over nodules at intervals and subsequent analyses. The amperometric technique allows continuous measurement of H2 evolution by samples of nodules or bacteroids isolated from nodules. Hoch employed mass spectrometry to measure H2 evolution by nodules. The gas mixture above them was sampled and analyzed for masses 2 and 4. In these experiments, helium was used as an internal standard. A gas chromatograph equipped with a thermal conductivity detector has been used for the quantitation of H2 evolved from legume nodules. In this method, investigators employed a column 6.5 mm diameter by 2 m length of silica gel at room temperature with N2 as the carrier gas. Argon (Ar), whose thermal conductivity is one-tenth that of H2, is the most readily available carrier gas for use in the detection of H2 with a thermal conductivity detector. Nitrogen, whose thermal conductivity is one-seventh that of H2, is less expensive than Ar and may be used as a carrier gas with only a slight loss of sensitivity.

HyperSQL: web-based query interfaces for biological databases

HyperSQL is an interoperability layer that enables database administrators to rapidly construct browser-based query interfaces to remote Sybase databases. Current browsers (i.e., Netscape, Mosaic, Internet Explorer) do not easily interoperate with databases without extensive CGI (Common Gateway Interface) programming. HyperSQL can be used to create forms and hypertext-based database interfaces for non-computer experts (e.g., scientists, business users). Such interfaces permit the user to query databases by filling out query forms selected from menus. No knowledge of SQL is required because the interface automatically composes SQL from user input. Database results are automatically formatted as graphics and hypertext, including clickable links which can issue additional queries for browsing through related data, bring up other Web pages, or access remote search engines. Query interfaces are constructed by inserting a small set of HyperSQL descriptors and HTML formatting into text files. No compilation is necessary because commands are interpreted and carried out by the special gateway, positioned between the remote databases and the Web browser. Feedback from developers who have used the initial release of HyperSQL has been encouraging. At present, query interfaces have been successfully implemented for three major NSF-sponsored biological databases: Microbial Germplasm Database, Mycological Types Collection, and Vascular Plants Types Collection.

Characterization of R. Japonicum Hup Gene Cosmids

We have reported the isolation of a number of recombinant cosmids from a gene bank of the Hup+ R. japonicum strain 122DES DNA which return hydrogen uptake (Hup) activity to Hup− mutants of R. japonicum (Cantrell et al, 1983). We now describe experiments conducted to determine the physical location and genetic organization of Hup determinants within cosmid sequences and the capability of these cosmids to return hydrogenase activity to additional Hup− Rhizobium strains. We also describe work in progress which is directed toward the use of subcloned DNA fragments from these cosmids to localize hup gene point mutations and isolate additional DNA flanking the presently isolated sequences.