Identification of host range determinants in the Rhizobium species MPIK3030

Summary R. meliloti primarily nodulates Medicago sativa but cannot nodulate Macroptilium atropurpureum. By introducing an 11.4 kb region into R. meliloti from the Symplasmid of Rhizobium strain MPIK3030, the host range of the R. meliloti transconjugants were shown to be extended to M. atropurpureum, one of the hosts of MPIK3030 but not normally nodulated by R. meliloti. The region responsible for host range extension was isolated by mass conjugating a clone bank from MPIK3030 into the R. meliloti wild type, and subsequent screening for nodulation on M. atropurpureum. Using deleted derivatives of a plasmid reisolated from endosymbiotic bacteria, the host range region was further narrowed down to three EcoRI fragments. Tn5 mutagenesis allowed the isolation of three discrete regions on an 11.4 kb section, which are involved in the extension of host range to M. atropurpureum. Finally, complementation experiments performed with R. meliloti common nod and hsn mutants indicated that none of the genes involved in the early steps of nodulation, including host-range functions, can be complemented by genes carried on the 11.4 kb fragment derived from MPIK3030.     

Specificity of intestinal brush-border proline transport: cyanine dye studies

The ability of rabbit jejunal brush borders to transport inhibitors of the imino carrier was investigated in membrane vesicles by measuring their ability to depolarize the membrane potential. Membrane potentials were monitored using a voltage-sensitive cyanine dye. Piperidine and pyrrolidine carboxylic acids, which are potent inhibitors of Na+-dependent proline transport (Ki less than 0.5 mM) depolarize the potential in a Na+-dependent, saturable manner indicating transport. On the other hand, N-methylated amino acids, which are fair inhibitors (Ki 2-10 mM), do not depolarize the membrane to any significant extent, but they competitively inhibit the L-proline transport signal. This indicates that these analogs are nontransported inhibitors of the imino carrier. The poor inhibitors niacin and pipolinic acid (Ki greater than 60 mM) depolarize the membrane about twice as much as proline and with low Kf values. This suggests separate carriers for these substrates.     

Plasmid-borne Tn5 insertion mutation resulting in accumulation of gentisate from salicylate.

Plasmid-borne Tn5 insertion mutants of a Pseudomonas species which accumulated 2,5-dihydroxybenzoate (gentisate) following growth on 2-hydroxybenzoate (salicylate) were obtained from a pool of mutants that were unable to grow on naphthalene. One such mutant was characterized further. The ability of this mutant to oxidize gentisate was 100-fold less than the ability of a Nah+ Sal+ strain harboring the unmutagenized plasmid, although both strains oxidized and grew on salicylate. These bacteria were presumably able to metabolize salicylate via catechol, since they possessed an inducible, plasmid-encoded catechol 2,3-dioxygenase. Our results suggest that there is an alternate, plasmid-encoded route of salicylate degradation via gentisate and that some plasmid-associated relationship between this pathway and naphthalene oxidation exists.     

A restriction endonuclease map of Streptomyces phage VWB

Summary A physical map of the actinophage VWB has been constructed using the restriction endonucleases BglII, ClaI, EcoRI, EcoRV, HindIII, KpnI and SphI. Phage VWB, genome size 47.3 kb, propagates on Streptomyces venezuelae, and it can also lysogenise this species. The three BglII-generated fragments of VWB DNA were cloned in pBR322, and subsequently mapped. In this manner the restriction map of the VWB phage genome was constructed.Abbreviations dam DNA adenine methylase activity - kb kilobase pairs - :: novel joint     

Frequencies of simultaneous transformation with different T-DNAs and their relevance to the Agrobacterium/plant cell interaction

Summary We investigated whether the efficiency of transformation of plant cells by Agrobacterium tumefaciens during cocultivation is limited by the properties of the plant cells or by the infecting bacteria.Therefore, tobacco protoplasts were infected by cocultivation with two different agrobacteria strains carrying Ti plasmids with distinguishable T-DNAs. These T-DNAs cotransform plant cells at a frequency equal to the product of their independent transformation frequencies, which indicates that all plant cells are equally competent. On the other hand, when these T-DNAs are located on the same Ti plasmid vector within one bacterial strain, the cotransformation frequency is significantly higher than the product of the single transformation frequencies. We interpret these results to indicate that transformation is limited more by the establishment of effective bacteria/plant cell interaction than by (i) the process of DNA integration and (ii) by the number of plant cells capable of being transformed by Agrobacterium. We found that most plant cells are transformed by only one or a few agrobacteria. Analysis of the number of T-DNA copies in these clonally transformed lines indicates amplification of the original, infecting T-region copy.     

Phaeoannellomyces and the Phaeococcomycetaceae, new dematiaceous blastomycete taxa

Phaeoannellomyces McGinnis et Schell gen. nov., which is based upon P. elegans McGinnis et Schell sp. nov., is proposed for dematiaceous yeasts which produce percurrently proliferating conidiogenous cells. Cladosporium werneckii Horta is transferred to Phaeoannellomyces as P. werneckii (Horta) McGinnis et Schell comb. nov. because the most stable and distinctive synanamorph produced by this fungus consists of annellidic yeast cells. The Phaeococcomycetaceae McGinnis et Schell fam. nov. is proposed in the class Blastomycetes, division Fungi Imperfecti for the dematiaceous yeast genera Phaeoannellomyces and Phaeococcomyces de Hoog.     

Construction of a heat-inducible gene for plants. Demonstration of heat-inducible activity of the Drosophila hsp70 promoter in plants

A chimeric gene containing the neomycin phosphotransferase II coding region under the control of the hsp70 promoter from Drosophila was integrated and found to be expressed, in a heat-regulated fashion, in tobacco tissue.     

Airport noise exposure and the postnatal growth of children

To determine whether chronic exposure to airport noise affects children, a study was conducted of the physical growth of children, aged 5-13 years, from two communities, one exposed to airport noise (n = 148) and another, not exposed (n = 102). Ten standard anthropometric measurements were made according to U.S. Health Examination Survey guidelines, and information on the social and biological characteristics of each family was collected in interviews. Hotelling's T2-tests were performed comparing the noise-exposed and nonnoise-exposed samples. There was no significant difference between the sample for measurements of social and biological characteristics of the families (including socioeconomic status and maternal reproductive history). Parental anthropometrics differed significantly (T2 = 24.32, P = 0.0001) as did child anthropometrics (T2 = 21.01, P = 0.032). For the child anthropometrics, noise-exposed children's slightly smaller measures of body bulk, together with their larger facial breadths, contributed to the significant T2. When the entire sample (n = 250) was analyzed by multiple linear regression, noise exposure was a significant predictor only of male triceps and subscapular skinfolds. For these two variables, and most other anthropometrics, however, the beta coefficients were negative for both sexes. In order to include information on the covariance structure among all variables, a canonical correlation analysis was performed. Noise exposure loaded negatively on the third canonical variate and was paired with positively loaded measures of body bulk. Taken together, the three analyses suggest that while there is some evidence for a slight effect of airport noise on measures of body bulk for males in this sample, most measures of postnatal growth for both males and females were unaffected by the noise levels experienced.