Cloning and sequencing of the Escherichia coli gyrA gene coding for the A subunit of DNA gyrase

The gene gyrA of Escherichia coli, which encodes the A subunit of DNA gyrase (topoisomerase II), has been cloned and a region of approximately 3300 base-pairs sequenced. An open reading frame of 2625 nucleotides coding for a protein of 97,000 Mr is located. The peptide weight of the subunit predicted from this open reading frame is in close agreement with previously published estimates of that of the A subunit. There is a "TATAAT" promoter motif located 44 bases upstream from the first "ATG" of the open reading frame. The amino acid sequence derived from the nucleotide sequence is about 50% homologous with that derived from the Bacillus subtilis gyrA gene sequence, with several regions showing greater than 90% homology.     

Denaturing gradient gel electrophoresis identifies genomic DNA polymorphism with high frequency in maize

Summary We have used denaturing gradient gel electrophoresis (DGGE) to identify genomic DNA polymorphism in maize (Zea mays L.). DGGE probes detect polymorphism in maize at a frequency comparable to the incidence of restriction fragment length polymorphism (RFLP). Probes identifying polymorphism were mapped to maize chromosome arms by utilizing DGGE and maize lines carrying B-A chromosomal translocations. The methods for library construction, probe screening, and genome analysis, described here for maize, can also be applied to the genomic analysis of other organisms.     

Patterns of sarcodine feeding in epipelagic oceanic plankton

The range of in situ prey composition was determined in marineplanktonic acantharia, foraminifera and radiolana collectedby divers, and quantitatively compared with the prey available,as determined by surface plankton hauls on cruises in the FloridaCurrent, Gulf Stream and Sargasso Sea. A relatively large percentageof the sarcodines (60% of acantharia, 48% of foraminifera and46% of radiolana) had no detectable prey Of those which hadfed on identifiable prey, there was considerable overlap betweensarcodine species m the types of prey captured. Nevertheless,some partitioning of food resources was evident Foraminiferaconsumed greater numbers of diatoms and copepods than otherprey types, radiolana consumed more tintinnids and mollusc larvae,and acantharia consumed mostly tintinnids. Copepods and theirnauplii dominated the biomass consumed for all three groups,though mollusc larvae were significant for both acantharia andradiolana. The results of parameteric univariate statisticalanalyses earned out on each major predator group and multivariateanalysis on a species-by-speaes basis confirmed that there wasevidence for some partitioning of prey resources among the majorsarcodine predators. The partitioning appeared to follow primarilymorphological rather than taxonomic criteria, however, and mayhave been at least partially a mechanical effect.     

Spongiose spumellarian radiolaria: The functional morphology of the radiolarian skeleton with a description ofSpongostaurus,a new genus

Two spumellarian species of the new genusSpongostaurus are described. Both construct a lobed central capsule enclosing a spongiose skeleton. The larger of the two reaches proportions of several cm in the length of the capsule lobes. The ultrastructural cytoplasmic features of the new species designate them as congeners with close affiliation with other spongiose groups. The importance of cytoplasmic characters relative to skeletal morphotypical characters is discussed in relation to radiolarian systematics.     

Elongation of synthetic RNA templates by hepatitis C virus NS5B polymerase

Here we examine the ability of seven, 3'-related, short synthetic RNAs to serve as templates for the hepatitis C virus (HCV) polymerase, non-structural protein 5B (NS5B). These RNAs, termed HL, range from 8 to 16 nucleotides in length, each with ACC at the 3' terminus. Interestingly HL12 and longer templates have a predicted secondary structure. Those with one or two unpaired adenylates at the 5'-end of a stem were increased in size by one or two nucleotides, respectively, following incubation with NS5B and UTP. Using labeled template RNA and cold UTP, extension in size could be inhibited by addition of non-labeled template of the same size. This template elongation was not inhibited by cold linear HL10 template unless pGpG was added. Fluorescence anisotropy demonstrated HL14, a template with secondary structure, bound with an apparent K(d) of 22 nm. A linear template, HL10, plus pGpG primer was bound by NS5B with a K(d) of 45 nm, whereas HL10 alone bound with an apparent K(d) of 182 nm. The amplitude of the template extension product was increased by a brief preincubation at 4 degrees C followed by incubation at 23 or 30 degrees C. The nucleotide-mediated increase in size occurred for both templates that required a mismatch or bulge at the 3'-end as well as for those without the mismatch. These results suggest an NS5B active site pocket can readily accommodate short templates with four or five base stems and initiate copy-back replication in the presence of a one nucleotide mismatch.