Effectiveness and Safety of Recombinant Human Erythropoietin (r-HuEPO) in the Treatment of Anemia of Chronic Renal Failure in Non Dialysis Patients

Seventy-five non-dialized patients with chronic renal failure (CRF) and severe renal anemia were enrolled in a study, receiving r-HuEPO subcutaneously thrice weekly for 6 months. In 64 patients (85%) 7 weeks of treatment with a weekly dose of 158 U/kg were required to achieve Hb concentrations within the target range of 10 to 12 g/dl. Of the 11 patients (15%) who failed to achieve the target Hb range, none were considered to be non-responders as they were excluded for unrelated reasons prior to week 16 (8 cases), or were iron deficient (2 cases), or had bleeding complications (1 patient). Maintaining the Hb concentration at a level of 10.5 g/dl required a mean r-HuEPO dose of 92 U/kg per week. Adverse events were generally mild or moderate. The most commonly reported were hypertension (8%), viral infection/including flu-like syndrome (7%), nausea (7%), and dizziness (5%). Statistically significant increases in mean creatinine concentrations observed after 12 and 24 weeks were most likely due to the progression of renal disease. These results confirm that 50 U/kg of r-HuEPO given 3 times per week subcutaneously provide a safe and effective therapy for anemic predialysis patients.

Interaction of Gram-Negative Bacteria with the Lysosomal Fraction of Polymorphonuclear Leukocytes II. Changes in the Cell Envelope of Escherichia coli

Interaction of lysosomal fraction with Escherichia coli caused damage to the cell envelope of these intact cells and to the cytoplasmic membrane of E. coli spheroplasts. The damage to the cytoplasmic membrane was manifested in the release of 260-nm absorbing material and beta-galactosidase from the spheroplasts, and by increased permeability of cryptic cells to O-nitrophenyl-beta-d-galactopyranoside; damage to the cell wall was measured by release of alkaline phosphatase. Microscope observation showed morphological changes in the cell envelope.

Interaction of Gram-Negative Bacteria with the Lysosomal Fraction of Polymorphonuclear Leukocytes I. Role of Cell Wall Composition of Salmonella typhimurium

Wild-type Salmonella typhimurium and cell wall mutants with sequential deficiencies in their cell wall polysaccharide were examined for sensitivity to the bactericidal action of the lysosomal fraction of polymorphonuclear leukocytes. The complete lipopolysaccharide basal core was essential for resistance to the bactericidal action. O-specific side chains of the wild type did not enhance the resistance. Absence of N-acetyl glucosamine considerably enhanced sensitivity, whereas absence of other core sugars did not; additional increase in sensitivity was obtained when the heptose phosphate was absent. Under conditions where appropriate supplementation of the medium permitted complete cell wall synthesis, the uridine diphosphate-gal-4-epimeraseless mutant regained resistance that was essentially equal to that of the wild type. Cells coated with specific antiserum and nongrowing cells were more resistant than normal growing cells.

Role of cell wall structure of salmonella in the interaction with phagocytes

Wild-type and cell wall mutants of Salmonella were examined for sensitivity to ingestion and intracellular killing in vitro by mouse peritoneal macrophages and guinea pig polymorphonuclear leukocytes. A complete polysaccharide core of the cell wall is important for resisting ingestion and intracellular killing, and the presence of the O-specific side chains contributes further resistance. Uridine diphosphate-gal-4-epimeraseless mutants grown on galactose-supplemented medium, rendering them smooth phenotypes, showed resistance to ingestion and intracellular killing similar to the wild type.

Comparative proteomic analysis of extracellular proteins of enterohemorrhagic and enteropathogenic Escherichia coli strains and their ihf and ler mutants

Enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC, respectively) strains are closely related human pathogens that are responsible for food-borne epidemics in many countries. Integration host factor (IHF) and the locus of enterocyte effacement-encoded regulator (Ler) are needed for the expression of virulence genes in EHEC and EPEC, including the elicitation of actin rearrangements for attaching and effacing lesions. We applied a proteomic approach, using two-dimensional polyacrylamide gel electrophoresis in combination with matrix-assisted laser desorption ionization-time of flight mass spectrometry and a protein database search, to analyze the extracellular protein profiles of EHEC EDL933, EPEC E2348/69, and their ihf and ler mutants. Fifty-nine major protein spots from the extracellular proteomes were identified, including six proteins of unknown function. Twenty-six of them were conserved between EHEC EDL933 and EPEC E2348/69, while some of them were strain-specific proteins. Four common extracellular proteins (EspA, EspB, EspD, and Tir) were regulated by both IHF and Ler in EHEC EDL933 and EPEC E2348/69. TagA in EHEC EDL933 and EspC and EspF in EPEC E2348/69 were present in the wild-type strains but absent from their respective ler and ihf mutants, while FliC was overexpressed in the ihf mutant of EPEC E2348/69. Two dominant forms of EspB were found in EHEC EDL933 and EPEC E2348/69, but the significance of this is unknown. These results show that proteomics is a powerful platform technology for accelerating the understanding of EPEC and EHEC pathogenesis and identifying markers for laboratory diagnoses of these pathogens.

The filamentous type III secretion translocon of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) uses a type III secretion system (TTSS) to inject effector proteins into the plasma membrane and cytosol of infected cells. To translocate proteins, EPEC, like Salmonella and Shigella, is believed to assemble a macromolecular complex (type III secreton) that spans both bacterial membranes and has a short needle-like projection. However, there is a special interest in studying the EPEC TTSS owing to the fact that one of the secreted proteins, EspA, is assembled into a unique filamentous structure also required for protein translocation. In this report we present electron micrographs of EspA filaments which reveal a regular segmented substructure. Recently we have shown that deletion of the putative structural needle protein, EscF, abolished protein secretion and formation of EspA filaments. Moreover, we demonstrated that EspA can bind directly to EscF, suggesting that EspA filaments are physically linked to the EPEC needle complex. In this paper we provide direct evidence for the association between an EPEC bacterial membrane needle complex and EspA filaments, defining a new class of filamentous TTSS.

Global versus local regulatory roles for Lrp-related proteins: Haemophilus influenzae as a case study

Lrp (leucine-responsive regulatory protein) plays a global regulatory role in Escherichia coli, affecting expression of dozens of operons. Numerous lrp-related genes have been identified in different bacteria and archaea, including asnC, an E. coli gene that was the first reported member of this family. Pairwise comparisons of amino acid sequences of the corresponding proteins shows an average sequence identity of only 29% for the vast majority of comparisons. By contrast, Lrp-related proteins from enteric bacteria show more than 97% amino acid identity. Is the global regulatory role associated with E. coli Lrp limited to enteric bacteria? To probe this question we investigated LrfB, an Lrp-related protein from Haemophilus influenzae that shares 75% sequence identity with E. coli Lrp (highest sequence identity among 42 sequences compared). A strain of H. influenzae having an lrfB null allele grew at the wild-type growth rate but with a filamentous morphology. A comparison of two-dimensional (2D) electrophoretic patterns of proteins from parent and mutant strains showed only two differences (comparable studies with lrp(+) and lrp E. coli strains by others showed 20 differences). The abundance of LrfB in H. influenzae, estimated by Western blotting experiments, was about 130 dimers per cell (compared to 3,000 dimers per E. coli cell). LrfB expressed in E. coli replaced Lrp as a repressor of the lrp gene but acted only to a limited extent as an activator of the ilvIH operon. Thus, although LrfB resembles Lrp sufficiently to perform some of its functions, its low abundance is consonant with a more local role in regulating but a few genes, a view consistent with the results of the 2D electrophoretic analysis. We speculate that an Lrp having a global regulatory role evolved to help enteric bacteria adapt to their ecological niches and that it is unlikely that Lrp-related proteins in other organisms have a broad regulatory function.

Hierarchy in the expression of the locus of enterocyte effacement genes of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) elicit changes in host cell morphology and cause actin rearrangement, a phenotype that has commonly been referred to as attaching/effacing (AE) lesions. The ability of EPEC to induce AE lesions is dependent upon a type III protein secretion/translocation system that is encoded by genes clustered in a 35.6 kb DNA segment, named the locus of enterocyte effacement (LEE). We used transcriptional fusions between the green fluorescent protein (gfp) reporter gene and LEE genes rorf2, orf3, orf5, escJ, escV and eae, together with immunoblot analysis with antibodies against Tir, intimin, EspB and EspF, to analyse the genetic regulation of the LEE. The expression of all these LEE genes was strictly dependent upon the presence of a functional integration host factor (IHF). IHF binds specifically upstream from the ler (orf1) promoter and appears to activate expression of ler, orf3, orf5 and rorf2 directly. The ler-encoded Ler protein was involved in activating the expression of escJ, escV, tir, eae, espB and espF. Expression of both IHF and Ler was needed to elicit actin rearrangement associated with AE lesions. In conclusion, IHF directly activates the expression of the ler and rorf2 transcriptional units, and Ler in turn mediates the expression of the other LEE genes.

The fumR gene encoding fumarase in the filamentous fungus Rhizopus oryzae: cloning, structure and expression

The filamentous fungus Rhizopus oryzae (Ro) is known for its ability to overproduce and accumulate high levels of fumaric acid (FA) under stress conditions. In order to study the molecular mechanisms involved in the increased biosynthesis of FA, the gene (designated fumR) encoding Ro fumarase was cloned and analysed for its structure and expression. Nucleotide (nt) sequence and comparison of the fumR product with fumarases from various sources established that fumR contains nine introns and encodes a deduced product of 494 amino acids (aa), related to class-II fumarases. A fumarase protein of 50 kDa was immuno-detected in crude Ro extracts. Primer extension experiments mapped the 5' end of the fumR RNA 159 nt upstream from the putative translation start codon. Both primer extension and Northern analysis showed the existence of one transcript of fumR. The level of fumR RNA increased in cells producing FA under stress conditions (high carbon and low nitrogen levels in the medium), suggesting that transcriptional regulation of fumR might be involved in the overproduction and accumulation of FA by Ro cells under stress conditions. The possibility that additional mechanisms are responsible for this phenomenon is discussed.

Identification of common motifs in unaligned DNA sequences: application to Escherichia coli Lrp regulon

We describe a relatively simple method for the identification of common motifs in DNA sequences that are known to share a common function. The input sequences are unaligned and there is no information regarding the position or orientation of the motif. Often such data exists for protein-binding regions, where genetic or molecular information that defines the binding region is available, but the specific recognition site within it is unknown. The method is based on the principle of 'divide and conquer'; we first search for dominant submotifs and then build full-length motifs around them. This method has several useful features: (i) it screens all submotifs so that the results are independent of the sequence order in the data; (ii) it allows the submotifs to contain spacers; (iii) it identifies an existing motif even if the data contains 'noise'; (iv) its running time depends linearly on the total length of the input. The method is demonstrated on two groups of protein-binding sequences: a well-studied group of known CRP-binding sequences, and a relatively newly identified group of genes known to be regulated by Lrp. The Lrp motif that we identify, based on 23 gene sequences, is similar to a previously identified motif based on a smaller data set, and to a consensus sequence of experimentally defined binding sites. Individual Lrp sites are evaluated and compared in regard to their regulation mode.

Hepatitis A virus and polymerase chain reaction amplification: methodology and results

Hepatitis A infection among patients receiving solvent/detergent inactivated factor VIII preparations in various locations in Europe have been documented recently. In investigations in Italy, Germany and Ireland, polymerase chain reaction (PCR) amplification was used to detect hepatitis A virus in frozen plasma pools, purified factor VIII, patient sera and samples from animal transmission studies; nucleic acid sequencing was used to clarify and identify the virus responsible based upon genotype analysis. Unique virus strains were found among the cases in Italy and Germany, and identical virus sequences were also found in some factor VIII lots. However, with the exception of the Italian investigation, lack of appropriate samples have precluded the identification of virus in these outbreaks. In addition, animal infectivity studies have not been successful in demonstrating infectivity under laboratory conditions. We discuss the limitations of PCR amplification with respect to detecting virus within these situations, and the necessity for the corresponding epidemiologic investigations.

The amino acid sequence of Lrp is highly conserved in four enteric microorganisms

Lrp (leucine-responsive regulatory protein) is a global regulator of metabolism in Escherichia coli (J. M. Calvo and R. G. Matthews, Microbiol. Rev. 58:466-490, 1994). The lrp genes from three other enteric microorganisms, Enterobacter aerogenes, Klebsiella aerogenes, and Salmonella typhimurium, were cloned and sequenced. An analysis of these sequences and of the previously determined sequence from E. coli indicated that the vast majority of changes were synonymous rather than nonsynonymous changes. Nucleotide changes occurred at 89 of 492 positions but resulted in amino acid changes at only 2 of 164 positions. This analysis suggests that the Lrp amino acid sequence is highly adapted for function and that almost all amino acid changes lead to a protein that functions less well than the wild-type protein.

Regulation of the Escherichia coli lrp gene

Lrp (leucine-responsive regulatory protein) is a major Escherichia coli regulatory protein which regulates expression of a number of operons, some negatively and some positively. This work relates to a characterization of lrp, the gene encoding Lrp. Nucleotide sequencing established that the coding regions of lrp and trxB (encoding thioredoxin reductase) are separated by 543 bp and that the two genes are transcribed in opposite directions. In addition, we used primer extension, deletion analyses, and lrp-lacZ transcriptional fusions to delineate the promoter and regulatory region of the lrp operon. The lrp promoter is located 267 nucleotides upstream of the translational start codon of the lrp gene. In comparison with a wild-type strain, expression of the lrp operon was increased about 3-fold in a strain lacking Lrp and decreased about 10-fold in a strain overproducing Lrp. As observed from DNA mobility shift and DNase I footprinting analyses, Lrp binds to one or more sites within the region -80 to -32 relative to the start point of lrp transcription. A mutational analysis indicated that this same region is at least partly required for repression of lrp expression in vivo. These results demonstrate that autogenous regulation of lrp involves Lrp acting directly to cause repression of lrp transcription.

Rubisco but not Rubisco activase is clustered in the carboxysomes of the cyanobacterium Synechococcus sp. PCC 7942: Mud-induced carboxysomeless mutants

The Mud technology of Groisman and Casadaban was adapted to the cyanobacterium Synechococcus sp. PCC 7942. A new high-CO2-requiring (hcr) mutant, hcr Mu28 was isolated following the integration of the Mud element 89 bp upstream of ORFI, at the 5'-flanking region of the rbc operon, which encodes RuBP carboxylase/oxygenase (Rubisco). The integration involved a 7 bp duplication that formed a direct repeat at the integration site, as previously shown in Escherichia coli. The mutant was devoid of apparent carboxysome bodies, which are considered to be important for the availability of CO2 for Rubisco. Immunolabelling studies demonstrated that Rubisco was distributed throughout hcr Mu28 cells, while in the wild type (WT) and in the carboxysome aberrant mutant hcr O221, Rubisco was markedly associated with the carboxysomes. Rubisco activase, however, was evenly distributed throughout the cytosol of the hcr and WT cells, without any preferential association with the apparent carboxysomes.

A multicenter study of Pneumocystis choroidopathy

We studied 21 patients with the acquired immunodeficiency syndrome and presumed Pneumocystic carinii choroidopathy. The lesions were characteristically yellow to pale yellow in color, appeared at the level of the choroid, and were found in the posterior pole. They varied in size from 300 to 3,000 microns, initially increasing in number before treatment and eventually resolving after systemic antimicrobial therapy. Of the 21 patients, 18 (86%) had received inhaled pentamidine as prophylaxis against Pneumocystis pneumonia. Visual acuity and visual field testing showed little evidence of retinal destruction. Survival after the diagnosis of the choroidopathy ranged from two to 36 weeks. Pneumocystic choroidopathy offers an easily accessible clue to disseminated Pneumocystis infection. When comparing drugs for Pneumocystis prophylaxis, careful ocular examination can provide one indicator of the relative efficacy of protection against extrapulmonary disease.

Molecular characterization of genes coding for wild-type and sulfonylurea-resistant acetolactate synthase in the cyanobacterium Synechococcus PCC7942

We present here the isolation and molecular characterization of acetolactate synthase (ALS) genes from the cyanobacterium Synechococcus PCC7942 which specify a sulfonylurea-sensitive enzyme and from the sulfonylurea-resistant mutant SM 3/20, which specify resistance to sulfonylurea herbicides. The ALS gene was cloned and mapped by complementation of an Escherichia coli ilv auxotroph that requires branched-chain amino acids for growth and lacks ALS activity. The cyanobacterial gene is efficiently expressed in this heterologous host. The ALS gene codes for 612 amino acids and shows high sequence homology (46%) at the amino acid level with ALS III of E. coli and with the tobacco ALS. The resistant phenotype is a consequence of proline to serine substitution in residue 115 of the deduced amino acid sequence. Functional expression of the mutant gene in wild-type Synechococcus and in E. coli confirmed that this amino-acid substitution is responsible for the resistance. Yet the deduced amino-acid sequence as compared with other ALS proteins supports the notion that the amino-acid context of the substitution is important for the resistance.

The 5'-flanking region of the gene encoding the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase is crucial for growth of the cyanobacterium Synechococcus sp. strain PCC 7942 at the level of CO2 in air

Transformation of the high-CO2-requiring mutants (hcr) O221 and E1 derived from the cyanobacterium Synechococcus sp. strain PCC 7942 by a wild-type DNA library restored their ability to grow at the level of CO2 in air. A plasmid (pE12) containing a 10-kilobase DNA insert was rescued from a O221 heterogenote and proved to transform both O221 and E1 to the wild-type phenotype. The capacity of the pE12 subclones to confer the wild-type phenotype to O221 transformants enabled the mapping of the mutation in O221 (designated hcrO221) within a 232-base-pair PstI-BstXI DNA restriction fragment. Sequence analysis revealed two open reading frames (ORFs) at positions -1745 to -1262 (ORFI) and -1218 to -393 (ORFII) upstream of the rbcL gene. A 3-kilobase PstI fragment of O221 was cloned, and hcrO221 was found to be a point mutation within the PstI-BstXI region -1309 nucleotides upstream of the rbcL gene. The significance of this flanking region for adaptation to air levels of CO2 was further demonstrated by the generation of new hcr mutants following insertional inactivation of wild-type DNA in the BstXI site. Electron microscopy revealed aberrant carboxysome structures in growing cells of the hcr mutants, a defect that was possibly related to the mutation, since transformation with pE12 derivatives restored the carboxysome structure to normal.

Is there a role for the 42 kilodalton polypeptide in inorganic carbon uptake by cyanobacteria?

Cyanobacterial cells accumulate substantial amounts of a membrane-associated 42 kilodalton polypeptide during adaptation to low CO(2) conditions. The role of this polypeptide in the process of adaptation and in particular in the large increase in the ability to accumulate inorganic carbon (C(i)), which accompanies this process, is not yet understood. We have isolated a mutant Synechococcus PCC7942 that does not accumulate the 42 kilodalton polypeptide. The mutant requires a high-CO(2) concentration for growth and exhibits a very low apparent photosynthetic affinity for extracellular C(i). The latter might be attributable to the observed defective ability of the mutant to utilize the intracellular C(i) pool for photosynthesis. The 42 kilodalton polypeptide does not appear to participate directly in the active transport of C(i), since the difference between the observed capabilities for CO(2) and HCO(3) (-) uptake of the mutant and the wild type is not sufficient to account for their different growth and photosynthetic performance. Furthermore, high CO(2)-grown wild-type cells, where we could not detect the 42 kilodalton polypeptide, transported CO(2) faster than the mutant. An analysis of the curves relating the rate of accumulation of C(i) to the concentration of CO(2) or HCO(3) (-) supplied, in the presence or absence of carbonic anhydrase, indicated that under the experimental conditions used here, CO(2) was the preferred C(i) species taken up by Synechococcus.

Linear forms of plasmid DNA are superior to supercoiled structures as active templates for gene expression in plant protoplasts

Introduction of the plasmids pUC8CaMVCAT and pNOSCAT into plant protoplasts is known to result in transient expression of the chloramphenicol acetyl transferase (CAT) gene. Also, transfection with the plasmid pDO432 results in transient appearance of the luciferase enzyme. In the present work we have used these systems to study the effect of DNA topology on the expression of the above recombinant genes. Linear forms of the above plasmids exhibited much higher activity in supporting gene expression than their corresponding super-coiled structures. CAT activity in protoplasts transfected with the linear forms of pUC8CaMVCAT and pNOSCAT was up to ten-fold higher than that observed in protoplasts transfected by the supercoiled template of these plasmids. This effect was observed in protoplasts derived from two different lines of Petunia hybrida and from a Nicotiana tabacum cell line. Transfection with the relaxed form of pUC8CaMVCAT resulted in very low expression of the CAT gene.Northern blot analysis revealed that the amount of poly(A)(+) RNA extracted from protoplasts transformed with the linear forms of the DNA was about 10-fold higher than that found in protoplasts transformed with supercoiled DNA.Southern blot analysis revealed that about the same amounts of supercoiled and linear DNA molecules were present in nuclei of transfected protoplasts. No significant quantitative differences have been observed between the degradation rates of the various DNA templates used.

Adaptation to Low CO(2) Level in a Mutant of Anacystis nidulans R(2) which Requires High CO(2) for Growth

The mutant E(1) of Anacystis nidulans R(2) requires high CO(2) concentration for growth but was able to adapt to low CO(2) concentration. This was exhibited by the increased ability to accumulate inorganic carbon within the cells and the large increase in the amount of a 42-kilodalton polypeptide located in the cytoplasmic membrane. The adaptation occurred in E(1) cells at an extracellular CO(2) concentration as high as 0.3%, which was 8 times the concentration for maximal adaptation in R(2) cells. The ability of E(1) cells to exhibit low CO(2) characteristics at a higher CO(2) concentration was attributed to lower intracellular CO(2) concentration.

High CO(2) Requiring Mutant of Anacystis nidulans R(2)

Some physiological characteristics of a mutant (E(1)) of Anacystis nidulans R(2), incapable of growing at air level of CO(2), are described. E(1) is capable of accumulating inorganic carbon (C(i)) internally as efficiently as the wild type (R(2)). The apparent photosynthetic affinity for C(i) in E(1), however, is some 1000 times lower than that of R(2). The kinetic parameters of ribulose 1,5-bisphosphate carboxylase/oxygenase from E(1) are similar to those observed in R(2). The mutant appears to be defective in its ability to utilize the intracellular C(i) pool for photosynthesis and depends on extracellular supply of Ci in the form of CO(2). The very high apparent photosynthetic K(m) (CO(2)) of the mutant indicate a large diffusion resistance for CO(2). Data obtained here are used to calculate the permeability coefficient for CO(2) between the bulk medium and the carboxylation site of cyanobacteria.

Controlled gene expression utilising lambda phage regulatory signals in a cyanobacterium host

This study presents plasmid systems that utilize regulatory signals of bacteriophage Lambda to accomplish regulated expression of cloned genes in an A. nidulans R2 derivative strain. An operator-promoter region and the temperature-sensitive repressor gene cI857 of bacteriophage Lambda were employed. Linked to a cyanobacterial replicon, the plasmid vectors efficiently transformed Anacystis and were stably maintained within this host. The cat structural gene, encoding chloramphenicol acetyltransferase, was used to demonstrate that expression can be regulated by temperature shift. We have identified in extracts from the vector bearing Anacystis, a protein similar in size and immunology to the Lambda repressor. The systems described should allow controlled expression of adventitious genes in the cyanobacterial host.

A new hybrid plasmid capable of transforming Escherichia coli and Anacystis nidulans

We have constructed a hybrid plasmid, pDF30, by combining the 8-kb pDF3 plasmid derived from the cyanobacterium Anacystis nidulans 6311 with the Escherichia coli vector pBR325. pDF30 transforms, replicates and confers chloramphenicol resistance (Cmr) and ampicillin resistance (Apr) on both A. nidulans and E. coli. The level of resistance to ampicillin in A. nidulans transformants, although low, is above background resistance and an Apr activity was demonstrated in cell-free extracts of A. nidulans that harbored pDF30. pDF30 is stably maintained within E. coli and can be isolated intact from A. nidulans after several months of subculture under chloramphenicol selection and by this criterion is stable in vivo. The unique restriction sites for XhoI, SalI and EcoRI can be used for molecular cloning of chromosomal genes in E. coli and A. nidulans. Until now pDF3 is phenotypically cryptic in both A. nidulans and E. coli. Examination of the polypeptides encoded on and expressed by pDF30 in E. coli minicells revealed only gene products from pBR325 but none from pDF3.

Phosphate transport in arsenate-resistant mutants of Micrococcus lysodeikticus

Two types of arsenate-resistant mutants of Micrococcus lysodeikticus were found: (i) mutants that grow in the presence of 10 mM but not 1 mM phosphate (Pi) with low uptake rate for Pi and arsenate, and (ii) mutants able to grow in the presence of 10 mM and 1 mM Pi, with a near-normal uptake rate for Pi but a low one for arsenate. The Km values for Pi transport and the Ki values for its competitive inhibition by arsenate were similar for the mutants and the wild type. Similar to the wild type, the mutants also accumulated Pi to high concentrations. In all strains, the transport of Pi was subject to repression by Pi. Mutant types showed lower Vmax but unaltered Km values for arsenate as compared to the wild type, and they accumulated arsenate to markedly lower levels. The results suggest a two-component transport system common to Pi and arsenate.

Growth of host dependent Bdellovibrio in host cell free system

A particulate, subcellular fraction of Escherichia coli was shown to promote the growth of host dependent (H-D) Bdellovibrio in the absence of host cells. The growth promoting activity was enhanced by both cations and trypisn, and destroyed by pronase. During the axenic growth unipolar spheres appear in the elongating Bdellovibrio forms. Thymidine monophosphate was more readily incorporated than thymidine into the Bdellovibrio DNA during growth in the host free system.

Effect of light on Bdellovibrio bacteriovorus

Bdellovibrio underwent photooxidation by visible light in the presence of exogenous photosensitizer and by near-ultraviolet light (325 to 400 nm) in its absence. The colorless, host-dependent wild type was more sensitive to the lethal effect of light than was its pigmented, facultative parasitic mutant. The latter's ability to form colonies was much more sensitive to light than was its plaque-forming capability. The biosynthesis of the mutant pigment was inhibited by diphenylamine, though this inhibition did not result in additional sensitivity to photokilling.

Membrane-associated, energy-linked reactions in Bdellovibrio bacteriovorus

Disrupted cells of Bdellovibrio bacteriovorus exhibited adenosine triphosphatase activity, 60 to 80% of which was in the soluble fraction. Dicyclohexylcarbodiimide did not inhibit the adenosine triphosphatase activity in membrane particles. The particles did not show energy-linked transhydrogenase activity. The activity of non-energy-linked transhydrogenase as well as the rate of oxygen consumption were higher in membrane particles of the host-independent strain than in the host-dependent strains. The uptake of amino acid uptake was inhibited by cyanide and by carbonyl cyanide p-trifluoromethoxyphenyl hydrazone. Valinomycin, in the presence of K+, did not inhibit the uptake, and only partial inhibition was exerted by arsenate and dicyclohexylarbodiimide. Sulfhydryl reagents inhibited amino acid uptake.

flrB, a regulatory locus controlling branched-chain amino acid biosynthesis in Salmonella typhimurium

Salmonella typhimurium strain CV123 (ara-9 gal-205 flrB1), isolated as a mutant resistant to trifluoroleucine, has derepressed and constitutive levels of enzymes forming branched-chain amino acids. This strain grows more slowly than the parent at several temperatures, both in minimal medium and nutrient broth. It overproduces and excretes sizeable amounts of leucine, valine, and isoleucine in comparison with the parental strain. Both leuS (coding for leucyl-transfer ribonucleic acid [tRNA]synthetase) and flrB are linked to lip (min 20 to 25) by P1 transduction, whereas only leuS is linked to lip by P22 transduction. Strain CV123 containing an F' lip(+) episome from Escherichia coli has repressed levels of leucine-forming enzymes, indicating that flrB(+) is dominant to flrB. Leucyl-tRNA synthetase from strain CV123 appears to be identical to the leucyl-tRNA synthetase in the parent. No differences were detected between strain CV123 and the parent with respect to tRNA acceptor activity for a number of amino acids. Furthermore, there was no large difference between the two strains in the patterns of leucine tRNA isoaccepting species after fractionation on several different columns. Several other flrB strains exhibited temperature-sensitive excretion of leucine, i.e., they excreted leucine at 37 C but not 25 C. In one such strain, excretion at 37 C was correlated with derepression of some enzymes specified by ilv and leu. These latter results suggest that flrB codes for a protein.