The fatty acid compositions and multiple antibiotic resistance patterns of 32 strains of Bradyrhizobium japonicum correlated with two major deoxyribonucleic acid homology groups. In group I, the fatty acid composition was 1.3% 16:l cis9 acid, 3.6% 16:lC acid, 8.8% 16:O acid, 1.2% 19:0 cyclopropane acid, and 81.2% 18:l acid. Group I1 contained 0.5% 16:lC acid, 11.1% 16:O acid, 0.8% 17:O cyclopropane acid, 24.7% 19:O cyclopropane acid, and 62.3% 18:l acid. Group I strains were susceptible to rifampin (500 pglml), tetracycline (100 pglml), streptomycin (100 pg/ml), chloramphenicol (500 pg/ml), erythromycin (250 pglml), carbenicillin (500 pg/ml), and nalidixic acid (50 pg/ml), whereas group I1 strains were resistant to these antibiotics. Both groups were resistant to trimethoprim (50 pg/ml) and vancomycin (100 pglml).Bradyrhizobium japonicum (Jordan 1982) (formerly Rhizobium japonicum) is the slow-growing symbiont of soybeans. This species is comprised of two highly divergent taxonomic groups which should be phenotypically distinguishable. The deoxyribonucleic acid (DNA)-DNA hybridization studies of Hollis et al. (8) established DNA homology groups I, Ia, and 11. These groups were characterized with respect to acidic extracellular polysaccharide composition and phenotypic ex planta nitrogenase expression. Groups I and Ia were reported to be quite distinct from DNA homology group I1 according to both of these criteria (9). Using some of the same strains, Stanley et al. (21) characterized the DNA nucleotide sequence divergences in and proximal to known symbiotic genes and concluded that strains of B . japonicum comprise two symbiotic genotypes (sTI and sTII) consistent with separate species designations.Whole-cell fatty acid profiles of strains grown under standardized conditions have been used for identification (1, 4,18) and classification of many bacteria (10, 17), but not in the genus Bradyrhizobium. Pankhurst et al. (20) correlated rifampin resistance in some slow-growing rhizobial strains with in vitro nitrogenase activity. This observation, together with that of Huber et al. (9) that only DNA homology group I1 strains express nitrogenase in vitro, suggested to us that patterns of antibiotic resistance might also distinguish the groups. In this paper we report that whole-cell fatty acid profiles correlate with DNA homology groups I and I1 of Hollis et al. (8) and that patterns of high-level resistance to antibiotics distinguish the two DNA homology groups. MATERIALS AND METHODSBacterial strains. All USDA strains were obtained from H. H. Keyser and D.Weber, U. S. Department of Agriculture (USDA), Beltsville, Md.; strain ATCC 10324 was obtained from the American Type Culture Collection, Rockville, Md.; strains 5631, 5633, D193, D209, THA6, and 8' were obtained from G. H. Elkan, North Carolina State University, Raleigh; and strains 61A.50 and 61A76 were obtained from S. Smith, Nitragin Co., Milwaukee, Wis. Strains that exhibit rifampin resistance and tetracycline resistance were purified by streaking onto a mediu...

Transgenic plants have facilitated our understanding of the functional roles of genes and the metabolic processes affected in plants. Recently, the Or gene was isolated from an orange cauliflower mutant and it was shown that the Or gene could serve as a novel genetic tool to enrich carotenoid content in transgenic potato tubers. An in-depth characterization of these Or transgenic lines is presented here. It was found that the Or transgene may facilitate the identification of potential rate-limiting step(s) of the carotenoid biosynthetic pathway. The Or transgenic tubers accumulated not only increased levels of carotenoids that normally are present in the controls, but also three additional metabolite intermediates of phytoene, phytofluene, and zeta-carotene, indicating that the desaturation steps became limiting following the expression of the Or transgene. Moreover, we observed that long-term cold storage greatly enhanced carotenoid content in the Or transgenic tubers to a level of 10-fold over controls. Expression of the Or transgene in the transgenic plants caused no dramatic changes in the transcript levels of the endogenous carotenoid biosynthetic genes, which is in agreement with the Or gene not directly controlling carotenoid biosynthesis. Microscope analysis revealed that the Or transgene conferred the formation of chromoplasts containing carotenoid sequestering structures in a heterologous system. Such structures were not observed in tubers of potato cultivars that accumulate high levels of carotenoids. Collectively, these results provide direct evidence demonstrating that the Or gene indeed controls chromoplast differentiation and that regulation of chromoplast formation can have a profound effect on carotenoid accumulation in plants.

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Background: To determine whether previously reported loci predisposing to nonsyndromic high myopia show linkage to common myopia in pedigrees from two ethnic groups: Ashkenazi Jewish and Amish. We hypothesized that these high myopia loci might exhibit allelic heterogeneity and be responsible for moderate /mild or common myopia.