Organization of ribosomal protein genes in Escherichia coli: I. Physical structure of DNA from transducing λ phages carrying genes from the aroE-str region

The physical structures of the genomes of five transducing bacteriophages (λaroE, λtrkA, λspc1, λspc2, and λfus2) carrying various portions of the aroE-trkA-spc-str segment of the Escherichia coli chromosome have been determined. Two methods were used: (a) heteroduplex analysis of DNA molecules from these phages, and (b) analysis of fragments obtained from digestion of the DNA by restriction endonucleases EcoRI and HindIII. In λaroE, λtrkA, λspc1 and λspc2, whose genome lengths vary from about 75% to about 104% of the λpapa genome, the right arm of λ DNA is present, whereas various portions of the left arm have been replaced by E. coli DNA. In λfus2, however, about 93% of the λ DNA molecule is replaced by E. coli DNA, the resultant genome being 103.5 %λ units long (Figs 1 and 2). All five phages contain an identical λ-E. coli junction at 1.9 %λ units from the left λ terminus, and there is complete homology between the common portions of the inserted E. coli DNA. Since these phages were independently isolated, we believe that the genetic organization of the E. coli DNA carried by these phages probably reflects the organization of the relevant segments of the E. coli chromosome. Comparison of the physical and genetic maps of these transducing phages has allowed us to assign a physical position to the ribosomal and neighbouring genes, including those coding for the α subunit of RNA polymerase and the elongation factors G and Tu, on the bacterial DNA.     

The relationship between the transport of glucose and cations across cell membranes in isolated tissues XI. The effect of vanadate on 45Ca-efflux and sugar transport in adipose tissue and skeletal muscle

(1) The effects of vanadate of hexose transport, ⁴⁵Ca-exchange and (Na⁺, K⁺)-contents have been characterized in isolated adipose tissue and skeletal muscles of the rat. (2) In whole epididymal fat pads, vanadate (0.5–5.0 mM) markedly stimulated the uptake of 2-deoxyl[¹⁴C]glucose as well as the efflux of $\text{3-O-[}{}^{14}\text{C}\text{]}\text{methylglucose}$. (3) Within the same concentration range, vanadate induced an early increase in ⁴⁵Ca-washout from preloaded fat pads. The maximum increases in the fractional losses of $\text{3-O-[}{}^{14}\text{C}\text{]}\text{methylglucose}$ and ⁴⁵Ca were significantly correlated ($\text{P < 0.001}$, $\text{r = 0.98}$). (4) In extensor digitorum longus and soleus muscles, vanadate (0.5–5.0 mM) stimulated the efflux of $\text{3-O-[}{}^{14}\text{C}\text{]}\text{methylglucose}$ and this effect was preceded by a rise in the washout of ⁴⁵Ca. The maximum increases in the fractional losses of $\text{3-O-[}{}^{14}\text{C}\text{]}\text{methyglucose}$ and ⁴⁵Ca were significantly correlated ($\text{P < 0.005}$, $\text{r = 0.98}$). (5) In extensor digitorum longus and soleus muscles, vanadate increased K⁺-contents and decreased Na⁺ contents. (6) The stimulation of ⁴⁵Ca-washout presumably reflects an increase in the cytoplasmic Ca²⁺ level, brought about by an inhibitory effect of vanadate on the Ca²⁺-sensitive ATPase of the sarcoplasmic or the endoplasmic reticulum. As demonstrated for most other insulin-like agents (Sørensen, S.S., Christensen, F. and Clausen, T. (1980) Biochim. Biophys. Acta 602, 433–445), the stimulating effect of vanadate on glucose transport appears to be associated with or mediated by a rise in the cytoplasmic Ca²⁺ level.     

Evaluation of methods for extraction of bacteria from soil

Abstract Several methods for dispersion of soil were tested for possible use in procedures for extraction of bacteria. Physical cell damage on cells and efficiency in extraction of indigenous cells from soil, were investigated. Cell damage by the dispersion methods was investigated by measuring the physical cell integrity and viability of pure cultures of Escherichia coli and Bacillus subtilis , as well as soil bacteria extracted from soil, when dispersed in slurries of γ-sterilized soil. Separation of bacteria and soil particles on the basis of buoyant density was conducted with the nonionic density gradient medium Nycodenz. When slurries of γ-sterilized soil with added pure cultured cells were centrifuged (10000 × g ) over cushions of Nycodenz (1.3 g ml⁻¹), practically all the added cells were recovered in a layer on top of the cushion. This proves that a reversible attachment and cosedimentation is not an important phenomenon in this procedure. The efficiency of the different dispersion methods for the extraction of indigenous soil bacteria, was assessed after separation of dislodged and attached soil bacteria. This separation was done either on the basis of sedimentation rate by low speed centrifugation, or buoyant density by Nycodenz density gradient centrifugation. The physical dispersion by ultrasonic treatment and chemical dispersion by the use of a chelating agent together with a detergent, were inferior to physical dispersion either by Waring blender (for large volumes) or a rotating rubber pestle treatment (for smaller volumes). The physical dispersion did not appear to be destructive to the cells tested.     

Enzyme changes accompanying thermal acclimation in two species of pleurocerid snails.

Goniobasis cahawbensis is a stream snail that experiences an annual temperature cycle. G. cochliaris is limited in distribution to springs, and their immediate vicinities, which are characterized by nearly constant annual temperatures. The present study sought to determine whether temperature dependent biochemical differences exist that might account for the differential distribution of these congeneric pleurocerid snails. Eight enzymes were examined following acclimation to 10 degrees, 17 degrees and 24 degrees C. No significant temperature dependent qualitative differences in enzyme phenotypes were demonstrable in either species by starch-gel electrophoresis for malate dehydrogenase, glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, phosphoglucomutase, superoxide dismutase and acetyl and butyryl esterases. Significant quantitative differences were observed in three of these enzymes. G. cahawbensis cytosol malate dehydrogenase activity increased significantly with increasing acclimation temperature, while G. cochliaris malate dehydrogenase activity remained unchanged. The activities of glucose-6-phosphate dehydrogenase did not differ significantly between acclimation temperatures for either species; however, the overall activity of both enzymes was significantly higher for G. cochliaris. Appreciable levels of LDH activity were not demonstrable by electrophoresis or enzymatic assay.