The distribution of DNA sequences hybridizing with antibiotic production and resistance gene probes within type strains and wild isolates of Streptomyces species.

Total DNA preparations from 74 antibiotic-producing type strains and 102 natural Streptomyces isolates were examined by dot blots for homology to 6 antibiotic production and resistance genes. Pattern diversity of hybridizations decreased as stringency increased from 65% to 85%. There were 146 unique profiles at 65% stringency with 13 repeated patterns, whilst there were only 14 unique and 11 repeated profiles at 85% stringency. Most of the strains which hybridized at 85% reacted with one or two probes although a few strains showed multiple homologies. This data was used to cluster strains and the groups defined were examined for phenotypic antibiotic resistance. Producers of certain classes of antibiotics clustered to specific groups and some gene homologies were more common amongst strains which produced similar antibiotics.

Within-modal and cross-modal consistency in the direction and magnitude of perceptual asymmetry.

Three auditory and three visual tests of PA were administered to 45 healthy dextrals in order to evaluate within-modal and cross-modal consistency in the direction and magnitude of perceptual asymmetry (PA). Thirty-three subjects were retested after a 4-8 week interval to determine reliability of individual measures and stability of inter-test relationships. Pairs of visual and auditory tests consisted of exactly the same stimuli. Within-modal and cross-modal concordance in the direction of PA was high, providing additional empirical support for existing models of the neural basis of PA. Cross-modal correlations in the magnitude of PA were near zero despite highly significant within-modal correlations. Meaningfulness of the stimuli did not affect the magnitude of PA, although the presence of an orienting expression prior to each dichotic pair did. These three observations provide new information about the neural processes that determine the magnitude of PA.

Discontinuous thermotropic response of Tetrahymena membrane lipids correlated with specific lipid compositional changes.

Steady-state fluorescence polarization measurements of 1,6-diphenyl-1,3,5-hexatriene in microsomal lipids from Tetrahymena pyriformis cells grown at 39 or 15 degrees C revealed discrete slope discontinuities in plots of polarization vs. temperature. Two well-defined 'break points' were present in the 0-40 degrees C temperature range examined and their precise location was dependent upon the growth temperature of the cells. By mixing phospholipids from cells grown at different temperatures, the break points at 17.5 and 32 degrees C in 39 degrees C-lipid multilayer preparations were shown to correlate with the breaks at 12 and 27 degrees C, respectively, in similar preparations from 15 degrees C-grown cells. The discrete break points were also present, but at slightly different characteristic temperatures, in a phosphatidylcholine fraction and a phosphatidylethanolamine plus 2-amino-ethylphosphonolipid fraction purified from the phospholipids and in total microsomal lipids (phospholipids plus the sterol-like triterpenoid, tetrahymanol). However, catalytic hydrogenation of the phospholipid fatty acids or mixing the non-hydrogenated phospholipids with increasing proportions or synthetic dipalmitoyl phosphatidylcholine eliminated the break points. We interpret this discontinuous thermotropic response in microsomal lipids as signalling a lipid phase separation of importance in regulating physiological events.