Osmotic regulation of transcription: induction of the proU betaine transport gene is dependent on accumulation of intracellular potassium

The proU locus, which encodes a high-affinity betaine transport system, and the kdp operon, which encodes a potassium transport system, are the principal osmoresponsive genes in Escherichia coli and Salmonella typhimurium. The kdp operon is known to be induced in response to changes in cell turgor. We have investigated the control of proU expression and shown that it differs from that of kdp in a number of fundamental ways. Rather than responding to changes in turgor, proU expression is principally determined by the intracellular accumulation of potassium ions. Potassium and betaine were shown to play distinct osmoprotective roles. Potassium serves as the principal osmoprotectant and is accumulated in response to low-level osmotic stress to restore turgor. As external osmolarity is increased to a level at which the corresponding increase in internal potassium concentrations is potentially deleterious to enzyme function, betaine (when available) is accumulated in preference to potassium. The different mechanisms of proU and kdp regulation reflect the different physiological roles of these two osmoprotectants.     

Inhibition of beta-lactam antibiotics at two different times in the cell cycle of Streptococcus faecium ATCC 9790.

Treatment of Streptococcus faecium ATCC 9790 with sublytic concentrations of beta-lactam antibiotics revealed two different division blocks in the cell division cycle. One block, induced by N-formimidoyl thienamycin and methicillin, occurred before the completion of chromosome replication, whereas the other, induced by cefoxitin and cephalothin, took place later in the cycle. In addition, these antibiotics gave rise to distinct morphological forms; the antibiotics acting at the earlier block point produced mainly "dumbbells," whereas those affecting the later time formed "lemons." When used in combination N-formimidoyl thienamycin and cefoxitin exerted synergistic killing on this strain. These data suggest that beta-lactam antibiotics have at least two sites of action in S. faecium.     

Predictors of success in hypertensives treated with biofeedback-assisted relaxation

This paper describes differences in response in seventeen patients with essential hypertension who participated in a treatment program consisting of electromyograph biofeedback assisted relaxation training. Responders were found to have higher treatment values of urinary and plasma cortisol, Trait Anxiety and forehead muscle tension compared to treatment failures. Responders also sustained greater decreases in plasma, and urinary cortisol after treatment. These data are discussed in light of the ability to predict which hypertensive patients may be most benefitted by a relaxation based treatment.We would like to thank Dr. Charles Spielberger for his permission to use the State-Trait Anxiety Inventory. We thank Michael Robinson for assistance with statistical analysis.     

Studies on the Inoculation and Competitiveness of a Rhizobium leguminosarum Strain in Soils Containing Indigenous Rhizobia

The competitiveness of a Rhizobium leguminosarum strain was investigated at two separate locations in field inoculation studies on commercially grown peas. The soil at each location (sites I and II) contained an indigenous R. leguminosarum population of ca. 3 × 10⁴ rhizobia per g of soil. At site I it was necessary to use an inoculum concentration as large as 4 × 10⁷ CFU ml⁻¹ (2 × 10⁶ bacteria seed⁻¹) to establish the inoculum strain in the majority of nodules (73%). However, at site II the inoculum strain formed only 33% of nodules when applied at this (10⁷ CFU ml⁻¹) level. Establishment could not be further improved by increasing the inoculum concentration even as high as 10⁹ CFU ml⁻¹ (9.6 × 10⁷ bacteria seed⁻¹). The inoculum strain could be detected at both sites 19 months after inoculation. Analysis by intrinsic antibiotic resistance patterns and plasmid DNA profiles indicated that a dominant strain(s) and plasmid pool existed among the indigenous population at site II. Competition experiments were carried out under laboratory conditions between a dominant indigenous isolate and the inoculum strain. Both strains were shown to be equally competitive.     

Nucleotide binding by membrane components of bacterial periplasmic binding protein-dependent transport systems.

Bacterial periplasmic binding protein-dependent transport systems require the function of a specific substrate-binding protein, located in the periplasm, and several membrane-bound components. We present evidence for a nucleotide-binding site on one of the membrane components from each of three independent transport systems, the hisP, malK and oppD proteins of the histidine, maltose and oligopeptide permeases, respectively. The amino acid sequence of the oppD protein has been determined and this protein is shown to share extensive homology with the hisP and malK proteins. Three lines of evidence lead us to propose the existence of a nucleotide-binding site on each of these proteins. A consensus nucleotide-binding sequence can be identified in the same relative position in each of the three proteins. The oppD protein binds to a Cibacron Blue affinity column and can be eluted by ATP but not by CTP or NADH. The oppD protein is labelled specifically by the nucleotide affinity analogue 5'-p-fluorosulphonylbenzoyladenosine. The identification of a nucleotide-binding site provides strong evidence that transport by periplasmic binding protein-dependent systems is energized directly by the hydrolysis of ATP or a closely related nucleotide. The hisP, malK and oppD proteins are thus responsible for energy-coupling to their respective transport systems.     

The nucleotide sequence of the RAD3 gene of Saccharomyces cerevisiae: a potential adenine nucleotide binding amino acid sequence and a nonessential acidic carboxyl terminal region.

The RAD3 gene of Saccharomyces cerevisiae is required for excision of pyrimidine dimers and is essential for viability. We present the nucleotide sequence of the RAD3 protein coding region and its flanking regions, and the deduced primary structure of the RAD3 protein. In addition, we have mapped the 5' end of RAD3 mRNA. The predicted RAD3 protein contains 778 amino acids with a calculated molecular weight of 89,779. A segment of the RAD3 protein shares homology with several adenine nucleotide binding proteins, suggesting that RAD3 protein may react with ATP. The twenty carboxyl terminal amino acids of RAD3 protein are predominantly acidic; however, deletion of this acidic region has no obvious effect on viability or DNA repair.     

Effects of pre- and post-prandial starvation on meal size and evacuation rate of juvenile Atlantic salmon, Salmo salar L.

After a pre-prandial period of starvation or feeding with unlabelled food, 0+ salmon parr (0.8–11.7 g) were fed a test meal of iron particle labelled food and subsequently were again either starved or fed unlabelled food. The quantity of labelled food consumed and the evacuation rate was determined by serial radiographs. In fish of all sizes, pre-prandial starvation causes a larger test meal (as a percentage of body weight) to be consumed when compared to pre-prandially fed fish. In addition, pre-prandial starvation results in relatively larger meals as a percentage of body weight being taken by smaller compared to larger fish. This result was not evident for pre-prandially fed fish. Evacuation rate was unrelated to body size irrespective of feeding history. Post-prandial starvation decreased evacuation rate but this effect was inversely related to the quantity of food consumed. Larger meals were not evacuated differently from smaller meals if feeding occurred post-prandially, irrespective of pre-prandial starvation.     

Interfacing similarity search software with the sequence retrieval system ACNUC

A method of interfacing sequence similarity search softwarewith the fast sequence retrieval system ACNUC is described.The method is written in FORTRAN 77 and is straightforward toimplement because no textprocessing code is required —a minimum of 12 extra lines of FORTRAN provided the interfacefor most applications. The method is also efficient, since sequencesare located by simple indexing techniques, with no linear searchesof large database files necessary. Received on November 20, 1986; accepted on January 8, 1987     

Metabolic and mitochondrial disturbances in streptozotocin-treated Sprague-Dawley and Sherman rats

This study provides explanation for conflicting evidence in the literature relating to changes in mitochondrial function and metabolic parameters during chemically induced diabetes. Diabetes of 3 days' duration (early ketosis) did not alter heart, kidney, or liver mitochondrial respiratory rates with glutamate or succinate even though serum glucose and triglycerides were elevated. Diabetes of 5 weeks' duration did not alter kidney or liver mitochondrial function in the fed adult rat although weight gain was depressed. The amount of kidney mitochondrial protein isolated per gram of tissue was increased by 30% in the diabetic. This increase was reversed by insulin treatment as were the other biochemical modalities measured. Superimposition of a 24-hr fast resulted in enhanced gluconeogenesis as measured by an animal weight loss of 17% within 24 hr (liver weight loss, 21%) and an elevation of serum urea nitrogen by 180% compared to fasted control. Respiratory rates of diabetic kidney mitochondria with glutamate were unaffected in the fasted animal whereas diabetic liver mitochondrial respiratory rates during succinate oxidation were reduced by 43%. Respiratory control was unchanged in the fasted diabetic rat. All the observed changes were reversed by insulin. Variation in the serum and liver metabolic indices (urea nitrogen, creatinine, glycerol, free fatty acids, free amino acids, triglycerides, and glucose) and liver mitochondrial responses to 7 weeks of chemically induced diabetes was affected by the rat strain, Sprague-Dawley versus Sherman, and rat weight, 72 g versus 222 g. Liver mitochondrial respirations in fed Sherman rats were not depressed by diabetes. Both rat strains had elevated liver free fatty acids and glutamate dehydrogenase activity in the diabetic state. Serum leucine, isoleucine, and valine were more elevated and serum lysine and arginine were more depressed in the diabetic Sprague-Dawley rat than in the Sherman rat. Conjectures on these results are presented in the text.