Legionella sainthelensi: a new species of Legionella isolated from water near Mt. St. Helens

Six strains of a new species, Legionella sainthelensi, were isolated from freshwater in areas affected by the volcanic eruptions of Mt. St. Helens in the state of Washington. Strains of L. sainthelensi are culturally and biochemically similar to other legionellae. They grow on buffered charcoal yeast agar but not on media that lack cysteine. They are gram-negative, nonsporeforming, motile rods that are positive in reactions for catalase, oxidase, gelatin liquefaction, and beta-lactamase. They are negative in reactions for urease, hydrolysis of hippurate, reduction of nitrates, fermentation of glucose, and blue-white autofluorescence. Their cell wall fatty acid composition is qualitatively similar to those of other legionellae, with 50 to 62% branched-chain fatty acids. They contain the isobranched-chain 14- and 16-carbon acids and anteisobranched-chain 15- and 17-carbon acids and relatively large amounts of straight-chain 16-carbon acid. All strains of L. sainthelensi contain approximately equal amounts of ubiquinones Q9, Q10, Q11, and Q12, a pattern similar to those of Legionella bozemanii, Legionella dumoffi, and Legionella longbeachae. Serological cross-reactions were observed between L. sainthelensi, both serogroups of L. longbeachae, and Legionella oakridgensis. Three strains of L. sainthelensi were greater than 90% related by DNA hybridization. The type strain of L. sainthelensi, Mt. St. Helens 4, was 36% related to the type strain of L. longbeachae and 3 to 14% related to the other nine described Legionella species.     

Analysis of Escherichia coli TonB membrane topology by use of PhoA fusions.

Alkaline phosphatase (PhoA) fusions to TonB amino acids 32, 60, 125, 207, and 239 (the carboxy terminus) all showed high PhoA activity; a PhoA fusion to TonB amino acid 12 was inactive. The full-length TonB-PhoA fusion protein was associated with the cytoplasmic membrane and retained partial TonB function. These results support a model in which TonB is anchored in the cytoplasmic membrane by its hydrophobic amino terminus, with the remainder of the protein, including its hydrophobic carboxy terminus, extending into the periplasm.     

Evolution of Multilocus Genetic Structure in an Experimental Barley Population

Data from 311 selfed families isolated from four generations (F8, F13, F23, F45) of an experimental barley population were analyzed to determine patterns of change in character expression for seven quantitative traits, and in single-locus allelic frequencies, and multilocus genetic structure, for 16 Mendelian loci that code for discretely recognizable variants. The analyses showed that large changes in single-locus allelic frequencies and major reorganizations in multilocus genetic structure occurred in each of the generation-to-generation transitions examined. Although associations among a few traits persisted over generations, dynamic dissociations and reassociations occurred among several traits in each generation-transition period. Overall, the restructuring that occurred was characterized by gradual decreases in the number of clusters of associated traits and increases in the number of traits within each cluster. The observed changes in single-locus frequencies and in multilocus genetic structure were attributed to interplay among various evolutionary factors among which natural selection acting in a temporally heterogeneous environment was the guiding force.     

Genetic and Molecular Organization of Ribosomal DNA (Rdna) Variants in Wild and Cultivated Barley

Twenty rDNA spacer-length variants (slvs) have been identified in barley. These slvs form a ladder in which each variant (with one exception) differs from its immediate neighbors by a 115-bp subrepeat. The 20 slvs are organized in two families, one forming an eight-step ladder (slvs 100-107) in the nucleolus organizer region (NOR) of chromosome 7 and the other a 12-step ladder (slvs 108a-118) in the NOR of chromosome 6. The eight shorter slvs (100-107) segregate and serve as markers of eight alleles of Mendelian locus Rrn2 and the 12 longer slvs (108a-118) segregate and serve as markers of 12 alleles of Mendelian locus Rrn1. Most barley plants (90%) are homozygous for two alleles, including one from each the 100-107 and the 108a-118 series. Two types of departures from this typical pattern of molecular and genetic organization were identified, one featuring compound alleles marked by two slvs of Rrn1 or of Rrn2, and the other featuring presence in Rrn1 of alleles normally found in Rrn2, and vice versa. The individual and joint effects on adaptedness of the rDNA alleles are discussed. It was concluded that selection acting on specific genotypes plays a major role in molding the strikingly different allelic and genotypic frequency distributions seen in populations of wild and cultivated barley from different ecogeographical regions.     

Estimation of outcrossing rates in Duglas-fir using isozyme markers

Summary Seeds produced under open-pollination were collected from eight natural stands and a plus-tree seed orchard of Douglas-fir. These seeds were germinated and both diploid embryos and haploid gametophytes were analyzed by starch-gel electrophoresis. Eleven variable loci were resolved for both kinds of tissue and used as genetic markers for estimating outcrossing rates. Estimates made with single-locus and multilocus methods both indicated that the proportion of viable embryos resulting from outcrossing is about 0.90 for the natural stands, and for the seed orchard. Comparison of single-locus and multilocus estimates of outcrossing rates indicated that little or no inbreeding other than selfing occurred. Estimated outcrossing rates were higher for seeds from the upper portion of the crown than for seeds from the lower crown. It was also found that some trees selfed at a much higher rate than other trees.     

Worldwide patterns of genetic variation among four esterase loci in Barley (Hordeum vulgare L.)

Summary Electrophoretic assays of 1506 accessions of domestic (Hordeum vulgare L.) and wild (H. spontaneum Koch.) barley, maintained in the USDA World Barley Collection, led to the following conclusions: (1) worldwide the four esterase loci, Est 1, Est 2, Est 3, and Est 4, have a minimum of 7, 12, 6, and 7 alleles, respectively; (2) little or no genetic differentation has developed between H. vulgare and H. spontaneum at these four esterase loci; (3) substantial genetic polymorphism and heterozygosity occur within many of the accessions despite the heavy inbreeding which results from the mating system of predominant self fertilization and from genetic drift associated with maintenance in small populations; (4) patterns of geographical distribution of alleles at these four loci are not at random over both small and large geographical areas, including differences on a continental scale; (5) four among 16 four-locus combinations of alleles are found in excess and all other combinations occur in deficiency on a worldwide basis.This work was supported in part by National Science Foundation Grant DEB 78-02046     

NARC-1/PCSK9 and its natural mutants: zymogen cleavage and effects on the low density lipoprotein (LDL) receptor and LDL cholesterol

The discovery of autosomal dominant hypercholesterolemic patients with mutations in the PCSK9 gene, encoding the proprotein convertase NARC-1, resulting in the missense mutations suggested a role in low density lipoprotein (LDL) metabolism. We show that the endoplasmic reticulum-localized proNARC-1 to NARC-1 zymogen conversion is Ca2+-independent and that within the zymogen autocatalytic processing site SSVFAQ [downward arrow]SIP Val at P4 and Pro at P3' are critical. The S127R and D374Y mutations result in approximately 50-60% and > or =98% decrease in zymogen processing, respectively. In contrast, the double [D374Y + N157K], F216L, and R218S natural mutants resulted in normal zymogen processing. The cell surface LDL receptor (LDLR) levels are reduced by 35% in lymphoblasts of S127R patients. The LDLR levels are also reduced in stable HepG2 cells overexpressing NARC-1 or its natural mutant S127R, and this reduction is abrogated in the presence of 5 mm ammonium chloride, suggesting that overexpression of NARC-1 increases the turnover rate of the LDLR. Adenoviral expression of wild type human NARC-1 in mice resulted in a maximal approximately 9-fold increase in circulating LDL cholesterol, while in LDLR-/- mice a delayed approximately 2-fold increase in LDL cholesterol was observed. In conclusion, NARC-1 seems to affect both the level of LDLR and that of circulating apoB-containing lipoproteins in an LDLR-dependent and -independent fashion.     

Draft genome sequences of six Escherichia coli isolates from the stepwise model of emergence of Escherichia coli O157:H7

Enterohemorrhagic Escherichia coli (EHEC) of serotype O157:H7 has been implicated in food-borne illnesses worldwide. An evolutionary model was proposed in which the highly pathogenic EHEC O157:H7 serotype arose from its ancestor, enteropathogenic E. coli (EPEC) O55:H7 (sorbitol fermenting [SOR(+)] and β-glucuronidase positive [GUD(+)]), through sequential gain of virulence, phenotypic traits, and serotype change. Here we report six draft genomes of strains belonging to this evolutionary model: two EPEC O55:H7 (SOR(+) GUD(+)) strains, two nonmotile EHEC O157:H(-) strains (SOR(+) GUD(+)) containing plasmid pSFO157, one EHEC O157:H7 (SOR(-) GUD(+)) strain, and one O157:H7 strain containing plasmid pSFO157 (SOR(+) GUD(+)).     

Diffusion of kinesin motors on cargo can enhance binding and run lengths during intracellular transport

Cellular cargoes, including lipid droplets and mitochondria, are transported along microtubules using molecular motors such as kinesins. Many experimental and computational studies focused on cargoes with rigidly attached motors, in contrast to many biological cargoes that have lipid surfaces that may allow surface mobility of motors. We extend a mechanochemical three-dimensional computational model by adding coupled-viscosity effects to compare different motor arrangements and mobilities. We show that organizational changes can optimize for different objectives: Cargoes with clustered motors are transported efficiently but are slow to bind to microtubules, whereas those with motors dispersed rigidly on their surface bind microtubules quickly but are transported inefficiently. Finally, cargoes with freely diffusing motors have both fast binding and efficient transport, although less efficient than clustered motors. These results suggest that experimentally observed changes in motor organization may be a control point for transport.     

Lion,Ungulate, and Visitor Reactions to Playbacks of Lion Roars at Zoo Atlanta

Felids in captivity are often inactive and elusive in zoos, leading to a frustrating visitor experience. Eight roars were recorded from an adult male lion and played back over speakers as auditory enrichment to benefit the lions while simultaneously enhancing the zoo visitor experience. In addition, ungulates in an adjacent exhibit were observed to ensure that the novel location and increased frequency of roars did not lead to a stress or fear response. The male lion in this study roared more in the playback phase than in the baseline phases while not increasing any behaviors that would indicate compromised welfare. In addition, zoo visitors remained at the lion exhibit longer during playback. The nearby ungulates never exhibited any reactions stronger than orienting to playbacks, identical to their reactions to live roars. Therefore, naturalistic playbacks of lion roars are a potential form of auditory enrichment that leads to more instances of live lion roars and enhances the visitor experience without increasing the stress levels of nearby ungulates or the lion themselves, who might interpret the roar as that of an intruder.