Transfer of the Pea Symbiotic Plasmid pJB5JI in Nonsterile Soil

Transfer of the pea (Pisum sativum L.) symbiotic plasmid pJB5JI between strains of rhizobia was examined in sterile and nonsterile silt loam soil. Sinorhizobium fredii USDA 201 and HH003 were used as plasmid donors, and symbiotic plasmid-cured Rhizobium leguminosarum 6015 was used as the recipient. The plasmid was carried but not expressed in S. fredii strains, whereas transfer of the plasmid to R. leguminosarum 6015 rendered the recipient capable of nodulating pea plants. Confirmation of plasmid transfer was obtained by acquisition of plasmid-encoded antibiotic resistance genes, nodulation of pea plants, and plasmid profiles. Plasmid transfer in nonsterile soil occurred at frequencies of up to 10⁻⁴ per recipient and appeared to be highest at soil temperatures and soil moisture levels optimal for rhizobial growth. Conjugation frequencies were usually higher in sterile soil than in nonsterile soil. In nonsterile soil, transconjugants were recovered only with strain USDA 201 as the plasmid donor. Increasing the inoculum levels of donor and recipient strains up to 10⁹ cells g of soil⁻¹ increased the number of transconjugants; peak plasmid transfer frequencies, however, were found at the lower inoculum level of 10⁷ cells g of soil⁻¹. Plasmid transfer frequencies were raised in the presence of the pea rhizosphere or by additions of plant material. Transconjugants formed by the USDA 201(pJB5JI) × 6015 mating in soil formed effective nodules on peas.     

MULTIVARIATE PHENOTYPIC DIFFERENTIATION AMONG BOTTLENECK LINES OF THE HOUSEFLY

Multivariate phenotypic differentiation in eight morphometric traits was examined in bottleneck lines of the housefly initiated with one, four, or 16 pairs of flies from a natural outbred population. Differentiation was assessed using a Mahalanobis' distance metric in units of additive genetic variance and covariance estimated from the ancestral population (i.e., generalized genetic distance). This distance metric was partitioned into contributions of size and shape to total distance. Bottleneck lines of all sizes diverged significantly from the ancestral line, but the direction of these shifts differed among the lines of different initial founding size. Those populations founded with single pairs diverged from the ancestral line mostly in shape; the 16-pair lines differentiated almost entirely in size, and the four-pair lines were intermediate in the relative contribution of shape to differentiation from the control. Bottlenecks serve to alter the genetic relationships among traits within the derived populations and in doing so could promote speciation by permitting differentiation of the populations along evolutionary trajectories less accessible to the base population.     

PHYLOGENETIC IMPLICATIONS OF DIFFERENCES IN NUMBER OF PLASTID PHOSPHOGLUCOSE ISOMERASE ISOZYMES IN NORTH AMERICAN COREOPSIS (ASTERACEAE: HELIANTHEAE: COREOPSIDINAE)

Enzyme electrophoresis was employed to ascertain the number of loci encoding plastid phosphoglucose isomerase (PGI) in species representing all sections of North American Coreopsis. Several species from each of the closely related genera Bidens, Coreocarpus, Cosmos, and Thelesperma were also examined. Species in nine of the 11 sections of North American Coreopsis have two isozymes for plastid PGI, and nearly all species examined in the four other genera also have two (one species has three) isozymes. Since most diploid vascular plants have one plastid PGI isozyme, a gene duplication probably occurred in an ancestor that is common to Coreopsis and the other four genera. That is, two isozymes represent the ancestral number for Coreopsis. The two sections (Electra and Anathysana) apparently lacking the duplication are closely related woody plants restricted largely to Mexico. One gene encoding plastid PGI ostensibly was silenced in a common ancestor of these two sections. This is concordant with other data suggesting a close relationship between the two sections, i.e., they appear to represent a monophyletic group. The electrophoretic data also indicate that 1) the enigmatic monotypic section Silphidium is more closely related to eastern North American sections and not derived from section Electra; and 2) section Anathysana is not ancestral to the three California sections Leptosyne, Pugiopappus, and Tuckermannia; rather, it represents a terminal element closely related to and possibly derived from section Electra.     

Accumulation of a Polyhydroxyalkanoate Containing Primarily 3-Hydroxydecanoate from Simple Carbohydrate Substrates by Pseudomonas sp. Strain NCIMB 40135

A number of Pseudomonas species have been identified which accumulate a polyhydroxyalkanoate containing mainly 3-hydroxydecanoate monomers from sodium gluconate as the sole carbon source. One of these, Pseudomonas sp. strain NCIMB 40135, was further investigated and shown to accumulate such a polyhydroxyalkanoate from a wide range of carbon sources (C₂ to C₆); however, when supplied with octanoic acid it produced a polyhydroxyalkanoate containing mainly 3-hydroxyoctanoate monomers. Polymer synthesis occurred in batch culture after cessation of growth due to exhaustion of nitrogen. In continuous culture under nitrogen limitation up to 16.9% (wt/wt) polyhydroxyalkanoate was synthesized from glucose as the carbon source. The monomer units are mainly of the R-(−) configuration. Nuclear magnetic resonance studies confirmed the composition of the polymer. Differential scanning calorimetry suggested that the solvent-extracted polymer contained a significant proportion of crystalline material. The weight-average molecular weight of the polymer from glucose-grown cells was 143,000.     

Effects of temperature on the size and shape of Escherichia coli cells

Two substrains of Escherichia coli B/r were grown to steady-state in batch cultures at temperatures between 22 and 42° C in different growth media. The size and shape of the cells were measured from light and electron micrographs and with the Coulter channelizer. The results indicate that cells are shorter and somewhat thicker at the lower temperatures, especially in rich growth media; cell volume is then slightly smaller. A lower temperature was further found to increase the relative duration of the constriction period. The shapes of the cell size distributions are indistinguishable, indicating that the pattern of growth of the cells is the same at all temperatures. The adaptation of the cells to a temperature shift lasted several generations, indicating that the morphological effects of temperature are mediated by the cell's physiology.     

Effect of Canavanine on Murine Retrovirus Polypeptide Formation

Canavanine is an arginine analog which is widely used to inhibit proteolytic processing of viral polyproteins. Certain results obtained with canavanine have suggested that it may have other effects. Therefore, we examined the effects of canavanine on the cell-free synthesis of murine retrovirus proteins. It was found that the electrophoretic mobility of the major gag-related cell-free product of both Rauscher murine leukemia virus (R-MuLV) and Moloney murine sarcoma virus 124 (Mo-MuSV-124) RNA was dependent on the concentration of canavanine used during translation. As the canavanine concentration was increased up to 4 mM, the apparent size of the major gag-related polypeptide also increased from 65,000 (R-MuLV RNA) or 63,000 (Mo-MuSV-124 RNA) to approximately 80,000 daltons. Additional increases in the canavanine concentration up to 12 mM did not increase the size of the gag gene product beyond 80,000 daltons. This change in electrophoretic mobility appeared to be due to a substitution of canavanine for arginine residues in the polypeptides, not to a change in their actual size. If amber suppressor tRNA and canavanine were used together during translation of Mo-MuSV-124 RNA and Mo-MuLV RNA, the results were also in agreement with this proposal. Translation experiments done with ovalbumin mRNA and mengovirus 35S RNA indicated that canavanine incorporation caused a shift in the electrophoretic mobility of ovalbumin from 43,000 to 45,000 daltons and caused the appearance of two slightly larger polypeptides in the 155,000- and 115,000- dalton regions of the mengovirus RNA cell-free product.     

Genetic polymorphism of PIF (parotid isoelectric focusing variant) proteins with linkage to the PPP (parotid proline-rich protein) gene complex

Genetic polymorphism is found among the PIF (parotid isoelectric focusing variant) salivary proteins after separation by prolonged isoelectric focusing in pH 3.5–5.2 urea polyacrylamide slab gels subsequently stained for protein. Two PIF proteins are either present (PIF +) or absent (PIF –) from all salivas. The phenotypes are determined by autosomal inheritance of two alleles, PIF ⁺ and PIF ^–. Gene frequencies in randomly collected samples show marked racial differences: among 148 whites, PIF ⁺ is 0.66 and PIF ^– is 0.34; among 90 blacks, PIF ⁺ is 0.35 and PIF ^– is 0.65; among 78 Chinese, PIF ⁺ is 0.56 and PIF ^– is 0.44. Studies in 41 families including 129 children support the interpretation of control of PIF by a single autosomal locus. In 8 PIF+ × PIF– matings, there were 8 PIF– (6.34 expected) children. In 33 PIF+ × PIF+ matings, there were 7 PIF– (6.70 expected) children. Linkage studies indicate that PIF is closely linked to the proline-rich protein (PPP) gene complex (e.g., for six families, lod score at =0.00 of PIF/G1 is 3.58). In 107 randomly collected samples from whites, PIF is strongly associated with Db (x ₁ ² =20.02; P<0.0001) and Gl (x ₁ ² =12.58; P=0.0005) but not with Pr, Ps, Pm, and Pa proteins. These data (probably reflecting genetic disequilibrium) suggest that PIF may be closer to Db and G1 than to other identified loci of the PPP gene complex. The PPP gene complex includes at least seven genes (and probably more) that produce many acidic and basic proline-rich proteins, constituting about two-thirds of parotid salivary proteins that are thought to have important functions at the tooth surfaces.This study was supported by a grant from the National Institutes of Dental Research (DEO 3658-15). Paper No. 2435 of the Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706.     

Smith degradation of gum exudates from some prosopis species

The polysaccharide of P. hymantophora has been shown to be composed of (1→4)-linked galactopyranosyl, (1→3)-linked galactopyranosyl, (1→3)-linked galactopyranosyl 2- and 4-sulphate and 2,6-disulphate residues. The (1→3)- and (1→4)-linked units are present in approximately equal amounts. The polysaccharide of P. hieroglyphica has been shown to possess (1→4)-linked galactopyranosyl, (1→3)-linked galactopyranosyl, and (1→3)-linked galactopyranosyl 2- and 4-sulphate residues. The (1→3)- and (1→4)-linked units are present in a 4:1 ratio. Both polysaccharides contain small proportions of non-reducing xylosyl end-groups.