In vitro cultivation of the exoerythrocytic stage of Plasmodium berghei from sporozoites

When inoculated with sporozoites of Plasmodium berghei, the human embryonic lung cell line WI38 supports the complete asexual developmental cycle of the exoerythrocytic stage. Cultured parasites were sensitive to primaquine, were shown to resemble parasites in living hosts by immunofluorescent antibody tests, and on subinoculation into mice induced a red blood cell infection, the gametocytes of which produced sporozoites in anopheline mosquitoes.

Two-dimensional spectroscopy of electrophoretic gels

Optical techniques are described which permit one to analyze two-dimensional electrophoretic gels in a fashion which is analogous to the one-dimensional spectroscopy of solutions. In the methods described, an electrophoretic gel is irradiated with monochromatic light and isozyme patterns are detected by the absorption of light or the fluorescent emission of light. The system described can both generate and detect monochromatic light in a range from 200 to 1100 nm. Without the use of histochemical stains, several isozymes have been visualized by purely optical means. Five methods for the visualization of lactate dehydrogenase and five methods for the demonstration of trypsin isozymes are described. In addition, general methods have been formulated for hydrolases and oxidases. Gel spectroscopy should permit the investigation of a wide range of new isozymes.

Molecular cloning and expression of the ilvGEDAY genes from Salmonella typhimurium

The ilvGEDAY genes of Salmonella typhimurium were cloned in Escherichia coli K-12 by in vitro recombination techniques. A single species of recombinant plasmid, designated pDU1, was obtained by selecting for Valr Ampr transformants of strain SK1592. pDU1 was shown to contain a 14-kilobase EcoRI partial digestion product of the S. typhimurium chromosome inserted into the EcoRI site of the pVH2124 cloning vector. The ilvGEDAY genes were found to occupy a maximum length of 7.5 kilobases. Restriction endonuclease analysis of the S. typhimurium ilv gene cluster provided another demonstration of the gene order as well as established the location of ilv Y between ilvA and ilvC. The presence of a ribosomal ribonucleic acid operon on the pDU1 insert, about 3 kilobases from the 5' end of ilvG, was shown by Southern hybridization. The expression of the ilvGEDA operon from pDU1 was found to be elevated, reflecting the increased gene dosage of the multicopy plasmid. A polarity was observed with respect to ilvEDA expression which is discussed in terms of the possible translational effects of the two internal promoter sequences, one located proximal to ilvE and the other located proximal to ilvD.

Identification and characterization of Col plasmids from classical colicin E-producing strains

A series of transformants have been derived which carry the Col plasmids from 11 E-colicin-producing strains isolated by Fredericq or Hamon. The ColE plasmids identified included four of type E1, five of type E2, and two of a type designated E4 by Horak (Zentralbl. Bakteriol. Parasitenkd. Infektionskr. Hyg. Abt. 1 Orig. Reihe A 233:58-63, 1975). Strain K317 was shown to carry a ColE7 plasmid and a 2.7-megadalton (Md) ColE2imm plasmid which confers immunity to colicin E2 but not the ability to produce colicin. Other plasmids identified in the colicinogenic isolates were a 3.4-Md ColN plasmid and a 1.3-Md Col plasmid of unknown type. The ColE1 plasmids all continued replicating in cultures treated with chloramphenicol. Strains carrying the ColE4 or ColE3-CA38 plasmid exhibited partial sensitivity to their own colicins and exhibited an unusual clearing-zone morphology when overlaid on stabs of colicin E2- or E7-producing strains. Except for ColE1-K53, ColE1-K47, ColE2-CA42, and ColE7-K317, all of the ColE plasmids were found to be about 4.3 Md in size. ColE2-CA42 and ColE7-K317 are both about 3.9 Md and are the only two plasmids of the E2, E3, E4, and E7 types that did not yield a 0.39-Md deoxyribonucleic acid fragment as an EcoRI digestion product. The comparisons of the ColE plasmids suggest several structural and functional relationships among them.

Cloning of genes involved in membrane lipid synthesis: effects of amplification of phosphatidylglycerophosphate synthase in Escherichia coli

The structural gene (pgsA) for the CDP-diacylglycerol:sn-glycero-3-phosphate phosphatidyltransferase (EC 2.7.8.5, phosphatidylglycerophosphate synthase) from Escherichia coli has been cloned, using pSC101 as the vector. The resulting hybrid plasmids not only correct the lack of in vitro synthase activity in pgsA strains but also cause an amplification (6- to 40-fold over wild-type levels) in enzymatic activity in direct proportion to the copy number of the plasmids found in vivo. The cloned gene also corrects the abnormally low level of polyglycerophosphatides found in pgsA strains and actually increases the level of phosphatidylglycerol to above that normally found in E. coli. The degree of alteration in phospholipid composition brought about by these hybrid plasmids is not of the order expected if fluctuations in enzyme levels in vivo were an important regulatory mechanism in phospholipid metabolism. The isolated hybrid plasmids have been mapped by restriction endonuclease analysis. The presence and location of other genetic markers have also been established. The above data, along with analysis of deletion derivatives of these plasmids and subcloning of appropriate restriction fragments, have established the position of the pgsA locus on the hybrid plasmids. From this data, the position of the pgsA locus has been determined to le between flaI and uvrC on the E. coli genetic map.

High frequency of genetic duplications in the dnaB region of the Escherichia coli K12 chromosome

The region that includes the dnaB locus on the E. coli K12 chromosome was shown to be duplicated at high frequency in cell populations. The duplications were shown to be arranged in tandem and segregated at various frequencies. Segregation was dependent on the recA recombination system, but independent of recB,C. Though most of the data was obtained with dnaB::Tn10 insertion mutants, the duplications were shown to occur in the absence of Tn10.

Molecular cloning of chemotaxis genes and overproduction of gene products in the bacterial sensing system

The chemotaxis genes cheR, cheB, cheY, cheZ, and tar of Salmonella typhimurium were cloned into bacteriophage lambda vectors and onto pBR322 plasmids by recombinant DNA techniques. The genes were linearly arranged in the order tar-cheR-cheB-cheY-cheZ (and were read from a promoter on the upstream side of the tar or cheR gene). However, their stoichiometries of expression were found to be 4:1:1:18:3, respectively. The overexpression of the cheY gene appeared to be a function of translational control. These five che genes were placed on a multicopy plasmid, and the gene products were overproduced in the cells, as shown by enzyme assays. The overproduction of the products of these five genes relative to those of the other che genes caused some changes in chemotactic properties, but no dramatic destruction of sensing ability.

Detection and composition of immune complexes in experimental African trypanosomiasis

Humoral immune responses in experimental African trypanosomiasis were assessed in rabbits infected with Trypanosoma rhodesiense. Immune complexes as measured by a Clq binding assay or a Clq solid-phase assay were detected by day 10 and increased progressively through day 28. Immune complexes analyzed by double diffusion in agar or enzyme immunoassay contained immunoglobulin M (IgM) and IgG consistently, and usually C3. In one serum, immune complexes contained trypanosomal antigens in addition to C3, IgG, and IgM. By sucrose density gradient ultracentrifugation Clq-binding immune complex-like materials were shown to contain IgG, IgM, and C3, sedimentating as intermediate (between 7S and 19S) or as higher-molecular-weight (greater than 19S) aggregates. Serum IgM and IgG antibodies to trypanosomes were measured by enzyme immunoassay. IgM antibodies were detected by day 7, rose to peak by day 14, and declined slowly thereafter. IgG antibodies were detected by day 14 and continued to rise through day 32. Total IgM and IgG measured by radial immunodiffusion paralleled the corresponding changes in antibody levels. Host immune responses, in part directed to trypanosomal antigens, produced circulating immune complexes containing bound C3; these may be deposited in tissue or may serve as a serological marker of immune complex-mediated tissue injury.

ColV plasmid-specific aerobactin synthesis by invasive strains of Escherichia coli

Certain strains of Escherichia coli associated with bacteremia of humans and domestic animals harbor plasmids that promote efficient iron uptake. The mechanism, which is an important component of the virulence of invasive strains, is independent of the enterobactin system for iron uptake. Plasmid-specified siderophore was assayed by its ability to support the growth of a chelator-deficient mutant in conditions of iron deprivation. The chelator, which was chemically determined to be a hydroxamate compound, was identical on the basis of field desorption mass spectrometry with aerobactin, a siderophore synthesized by Aerobacter aerogenes. In conditions of iron stress, aerobactin is secreted into the culture medium of plasmid-bearing E. coli strains. Reconstruction experiments involving a chelator-deficient mutant growing with exogenous chelator suggested that association of a small fraction of the total siderophore synthesized with cellular material is due to transient binding of aerobactin to membrane receptors during active bacterial growth.

Physical map of the Salmonella typhimurium histidine transport operon: correlation with the genetic map

A detailed restriction map of a 12.4-kilobase EcoRI fragment of Salmonella typhimurium deoxyribonucleic acid (DNA) containing the entire histidine transport operon and the argT gene is presented. Subclones of specific regions of the transport operon of S. typhimurium were constructed in plasmid vectors. An accurate correlation between the restriction map and the location of genetically defined deletions was obtained by hybridizing restriction digests of chromosomal DNA from strains carrying each deletion with cloned transport operon DNA as a probe. These data were used to position the histidine transport genes on the cloned 12.4-kilobase fragment of DNA.

The number of ribosomal RNA genes in Mycoplasma capricolum

We have examined the number of rRNA genes in Mycoplasma capricolum (KID) by hybridization of Bg/II-, EcoRI- and Xbal-digests of DNA to [3'-32P] 16S, 23S and 5S rRNAs according to the Southern procedure (1975). All the restriction gels gave two radioactive bands with three kinds of rRNA. Furthermore, band positions were indistinguishable from one another when 16S, 23S and 5S rRNAs were used as probes, indicating that each band contains sequences corresponding to the 3'-termini of 16S, 23S and 5S rRNAs. It is thus concluded that Mycoplasma capricolum chromosome carries at least two sets of genes for 16S, 23S and 5S rRNAs.

Immunological comparison of ribosomal proteins from archaebacteria

Antisera were raised in rabbits against ribosomal proteins of Methanobacterium bryantii and used to analyze immunological relationships to ribosomes from other archaebacteria, from eubacteria, and from yeasts. Cross-reaction could be detected within the methanogens and with a member of the extreme halophiles; the degree of immunological similarity reflected the relationship delineated by 16S ribosomal ribonucleic acid oligonucleotide analysis (Fox et al., Science 209:457-463, 1980). With the methods and the anti-total-protein sera employed, there was no detectable cross-reaction with ribosomal proteins or ribosomes from Sulfolobus sp., eubacteria, or yeast.

Uptake and metabolism of sucrose by Streptococcus lactis

Transport and metabolism of sucrose in Streptococcus lactis K1 have been examined. Starved cells of S. lactis K1 grown previously on sucrose accumulated [14C]sucrose by a phosphoenolpyruvate-dependent phosphotransferase system (PTS) (sucrose-PTS; Km, 22 microM; Vmax, 191 mumol transported min-1 g of dry weight of cells-1). The product of group translocation was sucrose 6-phosphate (6-O-phosphoryl-D-glucopyranosyl-1-alpha-beta-2-D-fructofuranoside). A specific sucrose 6-phosphate hydrolase was identified which cleaved the disaccharide phosphate (Km, 0.10 mM) to glucose 6-phosphate and fructose. The enzyme did not cleave sucrose 6'-phosphate(D-glucopyranosyl-1-alpha-beta-2-D-fructofuranoside-6'-phosphate). Extracts prepared from sucrose-grown cells also contained an ATP-dependent mannofructokinase which catalyzed the conversion of fructose to fructose 6-phosphate (Km, 0.33 mM). The sucrose-PTS and sucrose 6-phosphate hydrolase activities were coordinately induced during growth on sucrose. Mannofructokinase appeared to be regulated independently of the sucrose-PTS and sucrose 6-phosphate hydrolase, since expression also occurred when S. lactis K1 was grown on non-PTS sugars. Expression of the mannofructokinase may be negatively regulated by a component (or a derivative) of the PTS.

Relationship of siderophore-mediated iron assimilation to virulence in crown gall disease

Three classes of mutants defective in the biosynthesis of the siderophore agrobactin were isolated from Agrobacterium tumefaciens A217 after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. Class I mutants produced uniquely the catechol 2,3-dihydroxybenzoic acid, whereas classes II and III produced no detectable catechol. Class II differed from class III mutants in that exogenous 2,3-dihydroxybenzoic acid was utilized only by the former to synthesize agrobactin. Growth of strains B6 and A217, under iron starvation, led to enhanced production of several envelope proteins migrating in the 80,000-dalton range upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. One mutant, defective in agrobactin iron utilization, lacked one of these proteins. This protein may represent a siderophore receptor or fragment or subunit thereof. With a single exception, all of the mutants obtained in this work were capable of initiating tumorous growth in sunflower plants and on carrot root disks, provided pTiB6806 was present. Comparison of the catechols produced by strain B6806 and its nononcogenic, Ti-plasmid-deficient derivative A217, indicated that the genes encoding agrobactin synthesis are not associated with the virulence plasmid of A. tumefaciens B6806. Analysis of gall tissue for agrobactin did not reveal the presence of this siderophore. Finally, citrate, an iron-carrier in plants, enhanced significantly the growth of the agrobactin-deficient mutants in a low-iron medium. These results suggest that the production of agrobactin in planta is not requisite to infection and that citrate may serve as an alternative carrier of iron for A. tumefaciens within the host.

Defective enzyme II-BGlc of the phosphoenolpyruvate:sugar phosphotransferase system leading to uncoupling of transport and phosphorylation in Salmonella typhimurium

Transport and phosphorylation of glucose via enzymes II-A/II-B and II-BGlc of the phosphoenolpyruvate:sugar phosphotransferase system are tightly coupled in Salmonella typhimurium. Mutant strains (pts) that lack the phosphorylating proteins of this system, enzyme I and HPr, are unable to transport or to grow on glucose. From ptsHI deletion strains of S. typhimurium, mutants were isolated that regained growth on and transport of glucose. Several lines of evidence suggest that these Glc+ mutants have an altered enzyme II-BGlc as follows. (i) Insertion of a ptsG::Tn10 mutation (resulting in a defective II-BGlc) abolished growth on and transport of glucose in these Glc+ strains. Introduction of a ptsM mutation, on the other hand, which abolishes II-A/II-B activity, had no effect. (ii) Methyl alpha-glucoside transport and phosphorylation (specific for II-BGlc) was lowered or absent in ptsH+,I+ transductants of these Glc+ strains. Transport and phosphorylation of other phosphoenolpyurate:sugar phosphotransferase system sugars were normal. (iii) Membranes isolated from these Glc+ mutants were unable to catalyze transphosphorylation of methyl alpha-glucoside by glucose 6-phosphate, but transphosphorylation of mannose by glucose 6-phosphate was normal. (iv) The mutation was in the ptsG gene or closely linked to it. We conclude that the altered enzyme II-BGlc has acquired the capacity to transport glucose in the absence of phosphoenolpyruvate:sugar phosphotransferase system-mediated phosphorylation. However, the affinity for glucose decreased at least 1,000-fold as compared to the wild-type strain. At the same time the mutated enzyme II-BGlc lost the ability to catalyze the phosphorylation of its substrates via IIIGlc.

Isolation and genetic characterization of toxin-deficient mutants of Pseudomonas aeruginosa PAO

Two independently derived, exotoxin A-deficient (Tox- phenotype), nitroso-guanidine-induced mutants of Pseudomonas aeruginosa PAO1 were isolated by using sensitive immunological assays. One mutant, designated PAOT10, was detected as a colony which failed to produce a halo of immunoprecipitation in an antiserum-agar assay. The other mutant (PAOT20) was independently isolated and was detected by a negative reaction in a staphylococcal coagglutination assay with protein A-containing staphylococci and affinity-purified antibodies. Both mutants produced parental levels of extracellular protein. However, whereas the qualitative and quantitative compositions of proteins produced by PAOT20 were indistinguishable from those of the parental strain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and measurement of extracellular protease, there were marked differences between PAOT10 and the parental strain. The mutation in PAOT10 (tox-1) as mapped by linkage analysis was located between trp-6 and proA. In contrast, linkage analysis and cotransduction placed the mutation in PAOT20 (tox-2), very near trp-6. Data are presented which suggest that tox-1 and tox-2 are regulatory loci.

Ability of Neisseria gonorrhoeae, Neisseria meningitidis, and commensal Neisseria species to obtain iron from transferrin and iron compounds

The ability of Neisseria species to use iron compounds and to compete with iron-binding proteins was examined with deferrated defined medium and the iron chelator deferoxamine. All Neisseria species were able to assimilate a variety of ferric and ferrous iron salts. They were not able to efficiently solubilize an inorganic iron salt such as ferric nitrate, but were able to use iron chelated by citrate, oxalacetate, pyrophosphate, or nitrilotriacetate. Each of the 95 Neisseria isolates examined was able to use hemin as a sole source of iron, and most, but not all, of the isolates were able to obtain iron from hemoglobin. Heated human serum stimulated growth of all gonococci, meningococci, and some commensal Neisseria species in iron-deficient medium. All gonococci and meningococci were able to scavenge iron from 25% saturated transferrin, whereas most commensal organisms were inhibited by this iron-binding protein. The ability to compete with transferrin was specific, since partially saturated conalbumin was bacteriostatic for all Neisseria species. Although the pathogenic Neisseria species were able to compete more efficiently with transferrin for iron than were the nonpathogenic Neisseria species, no correlation was observed between the virulence of different strains or colony types of gonococci and the ability to scavenge iron in vitro from transferrin or other chelators.

A Pseudomonas aeruginosa mutant non-derepressible for orthophosphate-regulated proteins

Using a rapid screening assay based on the hydrolysis of p-nitrophenylphosphorylcholine, we isolated several mutants of Pseudomonas aeruginosa deficient in the production of phospholipase C. One, designated strain A50N, was also markedly deficient in the synthesis of alkaline phosphatase and several unidentified extracellular proteins. Because strain A50N produces these proteins under conditions of derepression at levels equal to those produced by the parental strain PAO1 grown in medium containing excess phosphate, it appears to have a mutation in a genetic element involved in the derepression of phosphate-repressible proteins.

Characterization of a membrane-associated cytidine diphosphate-diacylglycerol-dependent phosphatidylserine synthase in bacilli

The synthesis of phosphatidylserine in two gram-positive aerobic bacteria has been partially characterized. We have located a cytidine 5'-diphospho-diacylglycerol:L-serine O-phosphatidyltransferase (phosphatidylserine synthase) activity in the membrane fraction of Bacillus licheniformis and Bacillus subtilis. The activity was demonstrated to be membrane associated by differential centrifugation, sucrose gradient centrifugation, and detergent solubilization. The direct involvement of cytidine 5'-diphospho-diacylglycerol in the reaction was demonstrated by the conversion of the liponucleotide phosphatidyl moiety to phosphatidylserine. This activity is dependent on divalent metal ion (manganese being optimal) and is stimulated by nonionic detergent and its product phosphatidylserine. Based on studies with various combinations of products and substrates, the reaction appears to follow a sequential BiBi kinetic mechanism.

Genetical and structural analysis of a group of lambda ilv and lambda rho transducing phages

Eight lambda ilv C transducing phages generated from E. coli K12 secondary site lysogens have been analysed genetically and physically. Two of them carry, in addition, the rho gene and its promotor region, but not the cya gene. The ilv O 603 mutation has been located between ilv G and ilv E. Electrophoretic analysis of the proteins synthesized by these phages in a system of UV irradiated cells allowed us to assign molecular weights of 55000 and 66000 daltons to the ilv C and the ilv D gene products, respectively, and to show that an ilv G-encoded polypeptide of 60000 daltons is made from an ilv O- but not from an ilv O+ phage. The expression of the ilv G gene is discussed in the light of the recent finding of a promoter-attenuator region lying upstream to ilv G. Finally, we have found that one of the lambda ilv phages does not have the classical structure of a transducing phage.

Bacitracin and protease production in relation to sporulation during exponential growth of Bacillus licheniformis on poorly utilized carbon and nitrogen sources

Growth of Bacillus licheniformis in a chemically defined medium containing glucose and ammonium chloride yielded a doubling time of 1.00 h. Examination of the culture during exponential growth revealed a lack of heat-resistant spores together with a complete absence of detectable concentrations of bacitracin or extracellular serine protease. Replacement of glucose as the sole carbon source by glycerol, pyruvic acid, citric acid, or lactic acid resulted in doubling times of 1.13, 2.00, 3.16, and 3.95 h, respectively. Bacitracin, protease, and heat-resistant spores were produced during exponential growth in amounts related to these doubling times. A qualitatively similar pattern was observed when ammonium chloride was replaced by sodium nitrate, alanine, or glutamic acid which gave doubling times of 1.65, 1.77, and 1.90 h, respectively. Protease, but not bacitracin, concentrations were substantially higher when the growth rate was restricted by use of poor nitrogen rather than poor carbon sources. The relationships between bacitracin production, protease production, and the sporulation process are discussed.

Colicin Ib does not cause plasmid-promoted abortive phage infection of Escherichia coli K-12

A 2.2 kilobase (kb) fragment of ColIdrd-1 cloned in pBR325 causes phage T5 and BF23 infections of Escherichia coli K-12 to abort. This abortive infection is associated with leakage of beta-galactosidase from the cell. A recombinant plasmid containing a 2.8 kb fragment of ColIdrd-1 encodes colicin Ib but fails to cause abortive infection. Tn5 and Tn10 insertions into ColIdrd-1 that abolish colicin Ib production have no effect on the abortive infection phenotype. These findings are inconsistent with a previously proposed role for colicin Ib in causing phage infections to abort.

Application of Arrhenius kinetic theory to viral eclipse: selection of bacteriophage phi X174 mutants

Analysis of the bacteriophage phi X174 eclipse period in terms of Arrhenius kinetic theory suggests the following hypothesis: mutants should exist with two concomitant physiological characteristics as their phenotype. These are an eclipse rate lower than that of the wild type at permissive temperatures for plaque formation and an eclipse rate too low at lower temperatures to permit plaque development. Thus, enrichment of a mutagenized virus population for mutants that fail to eclipse during a short period at permissive temperatures should yield eclipse mutants with the cold-sensitive (cs; nonpermissive temperature, 25 degrees C), and not the temperature-sensitive (ts; nonpermissive temperature, 42 degrees C), plaque phenotype. In several trials, the frequency of the cs phenotype in the population increased from less than 0.2% to between 2 and 4% after the enrichment step, whereas the frequency of the ts phenotype remained unchanged (less than 0.2%). Moreover, 80% of these cs mutants have eclipse rates that are 3- to 40-fold lower than that of the wild type at both 37 degrees C and 25 degrees C. The successful application of the Arrhenius theory to phi X eclipse may provide insights into the molecular mechanism whereby the phi X174 genome is delivered into the host cell. Since the eclipse kinetics of other nonenveloped viruses are similar to those of phi X174, kinetic theory may be broadly applicable in the selection and characterization of viral eclipse mutants.

Structural studies of lambda transducing bacteriophage carrying bacterial deoxyribonucleic acid from the metBJLF region of the Escherichia coli chromosome

The structures of several lambda dmet and related lambda darg transducing phage were studied by restriction fragment mapping and electron microscopic measurements of homoduplexes and heteroduplexes. A new transducing phage (lambda dmet141), in which metF is the only functional gene of the cluster, was isolated. In contrast, lambda dmet117, which expresses the entire metBJLF cluster, has only 3 kilobases more bacterial deoxyribonucleic acid (DNA) than lambda dmet141. An EcoRI restriction fragment of lambda dmet117, which carries the leftmost 6 kilobases of the bacterial DNA insert, was isolated and shown to contain a functional copy of metB. Small structural differences at the attachment sites of some of the phage were shown to result from different sites of lambda integration in the two parent insertion lysogens.

ampC cephalosporinase of Escherichia coli K-12 has a different evolutionary origin from that of beta-lactamases of the penicillinase type

A 1536-nucleotide-long sequence that carries the ampC beta-lactamase gene of the Escherichia coli K-12 chromosome has been determined. This gene codes for a protein of 377 amino acids, of which the first 19 amino acids form a signal peptide. The molecular weight of the mature enzyme was determined to be 39,600. The ampC beta-lactamase with a substrate specificity for cephalosporins showed no significant sequence homologies with beta-lactamases of the penicillinase type or with D-alanine carboxypeptidases. However, because the region around serine-80 of the ampC beta-lactamase has extensive homology with an active-site fragment of the Pseudomonas aeruginosa cephalosporinase, we suggest that the ampC cephalosporinase as well as related cephalosporinases form a distinct group of serine beta-lactamases that have an evolutionary origin different from that of the serine penicillinases and thus constitute a new class of beta-lactamases.

Use of transposons in cloning poorly selectable genes of Escherichia coli: cloning of uvrA and adjacent genes

A transposon was introduced close to a poorly selectable gene. This gene could be cloned by using selection for the antibiotic resistance marker of the transposon.

The DNA sequence of the promoter-attenuator of the ilvGEDA operon of Salmonella typhimurium

The isolation of a lambda gt . ilvGEDA . S.t. hybrid transducing phage has permitted the characterization of the promoter-attenuator region of the ilvGEDA operon of Salmonella typhimurium. In vitro transcription and Southern hybridization indicate that the promoter-attenuator resides on a 400 nucleotide Rsa I restriction fragment. DNA sequence analysis shows only seven base pair differences exist between the DNA sequence of the ilvGEDA promoter-attenuator of S. typhimurium and that previously published for Escherichia coli K12.

Increased virulence of Neisseria meningitidis after in vitro iron-limited growth at low pH

At low pH (6.6) and under conditions of iron limitation, Neisseria meningitidis group B (strain SD1C) exhibited an atypical outer membrane protein profile and an increased relative virulence for the mouse. Cells grown in a buffered medium were effectively deprived of iron by the addition of ethylenediamine-diorthohydroxyphenylacetate. The pH of the medium selected for characteristic colonial morphologies: type M3 predominated at pH 6.6, and type M5 predominated at pH 7.7. A mixed population of M1, M3, and M5 colonies was observed at pH 7.2. Isolated outer membrane proteins were analyzed by sodium dodecyl 99 99 sulfate-polyacrylamide gel electrophoresis, and surface exposed proteins were labeled by the [125I]lactoperoxidase method and subsequently identified by autoradiography. Cells grown at pH 6.6 elaborated a major outer membrane protein (protein III; molecular weight, 69,000), which was also present in the outer membrane of iron-limited cells grown at pH 7.2. At pH 7.2 in an iron-sufficient medium, protein III was present only in small quantities in sodium dodecyl sulfate-polyacrylamide gel was present only in small quantities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. A study of the relative virulence (50% lethal dose) of the meningococcus for C57/BL mice revealed that iron-limited cells grown at low pH had an increased relative virulence 1,200-fold (50% lethal dose, 4.0 CFU) greater than that of cells grown in the same medium but at pH 7.2 and with sufficient iron. These studies indicate that pH and iron can be important factors in the determination of meningococcal virulence.

Evolution of alkaline phosphatase in marine species of Vibrio

The evolution of alkaline phosphatase was studied in marine species of Vibrio. Two antisera prepared against purified alkaline phosphatases from Vibrio splendidus and Vibrio harveyi were used to estimate the amino acid sequence divergence of this enzyme in 51 strains belonging to nine species. The methods used were the quantitative microcomplement fixation technique and the Ouchterlony double-diffusion procedure. There was a high degree of congruence between the measurement of the amino acid sequence divergence of alkaline phosphatase and the percentage of deoxyribonucleic acid homology of the different organisms relative to both reference strains (correlation coefficient of -0.89) as well as between the amino acid sequence divergence of alkaline phosphatase and superoxide dismutase (correlation coefficient of 0.92) relative to V. splendidus. These findings supported the view that the evolution of marine species of Vibrio is primarily vertical and that horizontal evolution (involving genetic exchange between species), if significant, is restricted to a minor fraction of the bacterial genome.

The initiation of chromosome replication in a dnaAts46 and a dnaA+ strain at various temperatures

The regulation of chromosome replication initiation was studied at various temperatures with an E. coli dnaA46 strain and its dnaA+ parent. We find that, in both strains, the "initiation mass" varies depending upon growth temperature while the replication time remains constant relative to the cell doubling time. In the permissive temperature range, the initiation mass of the dnaA46 mutant strain is larger by a constant factor than that for a dnaA+ strain. We conclude that, even at temperatures permissive for growth of the dnaA46 strain, the activity of the dnaA46 product is lower than that of the wild-type protein. The dnaA gene product, therefore, plays an important role in regulating initiation.

Measurement of zinc flux through plasma in normal and endotoxin-stressed pigs and the effects of Zn supplementation during stress

1. The rates of transport of zinc through plasma have been investigated in normal and endotoxin-stressed pigs. 2.65Zn added to porcine plasma in vitro rapidly equilibrated with the Zn originally present. 3. 65 Zn bound to albumin and injected intravascularly into pigs rapidly equilibrated with two kinetically distinguishable pools. The first of these pools was mainly associated with the plasma but was significantly larger than the plasma volume and substantially so in Zn-deficient pigs. The second pool appeared to represent a summation of the rapidly-exchangeable Zn within the extravascular tissues. 4. In non-stressed animals, the flux of Zn from the plasma of Zn-deficient pigs was only half that in Zn-supplemented animals. 5. Administration of endotoxin reduced the plasma Zn concentration of Zn-supplemented pigs but not of Zn-deficient animals. The fractional turnover rates of Zn were not altered in eight of the two pools following endotoxin. 6. At 10 h after giving endotoxin neither the Zn content of the two pools nor the flux of Zn through them differed significantly between Zn-deficient and control pigs. 7. Intravascular infusion of Zn at the rate which essentially prevented the usual depression in plasma Zn concentration following endotoxin failed to alleviate the effects of endotoxin on Zn-supplemented pits. 8. The reduction in plasma Zn concentration following endotoxin stress appears to be a normal physiological response which is not indicative of an increased metabolic requirement for Zn.

High-frequency chromosome transfer in Rhodopseudomonas sphaeroides promoted by broad-host-range plasmid RP1 carrying mercury transposon Tn501

Insertion of the mercury resistance transposon Tn501 into broad-host-range plasmid RP1 greatly enhanced the ability of this plasmid to promote chromosome transfer in the photosynthetic bacterium Rhodopseudomonas sphaeroides. Compared with the wild-type RP1, which produced less than 10(-8) recombinants per donor cell, RP1::Tn501 produced between 10(-3) and 10(-7) recombinants per donor cell depending upon the marker selected. Plasmid RP1::Tn501 promoted polarized transfer of the chromosome from one or perhaps two origins on the chromosome, giving rise to two linkage groups. All of the biosynthetic and antibiotic resistance genes that have been mapped, including those involved in photosynthesis, occur on one or another of these linkage groups.

Localization of phoE, the structural gene for outer membrane protein e in Escherichia coli K-12

To localize the structural gene for outer membrane protein e, mutants resistant to the protein e-specific phage TC45 were isolated and characterized. Three classes of TC45-resistant strains were found: (i) mutants in phoB, a regulatory gene for protein e, (ii) mutants with an altered lipopolysaccharide, and (iii) mutants unaltered in the regulation of the pho regulon and producing an apparently normal lipopolysaccharide. Mutations in the latter class of mutants are probably altered in the structural gene for protein e and are cotransducible with proA,B at min 6 on the chromosomal map. As class (iii) includes mutants with an electrophoretically altered protein e, in both an nmpA and an nmpB background, we conclude that the structural gene for protein e, designated as phoE, is localized at min 6 on the chromosomal map, the gene order being phoE proA argF.

Conversion of glucose to fatty acids and methane: roles of two mycoplasmal agents

Two species of obligately anaerobic mycoplasmas were the major components of a methanogenic glucose-limited enrichment culture. In pure culture, one of these organisms, tentatively named Anaeroplasma sp. strain London, was shown to be responsible for the fermentation of glucose to fatty acids, hydrogen, and carbon dioxide; the other mycoplasma was shown to produce methane from hydrogen and carbon dioxide and was named Methanoplasma elizabethii. This same methanogenic mycoplasma contained a low-molecular-weight fluorescent cofactor which had a maximum light absorbance at 430 nm. When both species of mycoplasmas were grown together on glucose, fermentation products included fatty acids and methane. For the first time, mycoplasmas are implicated as agents of anaerobic degradation and methanogenesis in a sewage sludge digester.

The growth-promoting effect of bacterial iron for serum-exposed bacteria

Bacterial ability to obtain iron in bovine serum or in media containing transferrin (Tr) or conalbumin (Ca) was investigated by using serum-resistant (virulent) and serum-sensitive (avirulent) strains of Escherichia coli and Salmonella typhimurium. Bacteria growing in bovine serum enriched with radioactive iron-saturated Tr or with radioactive iron-saturated enterobactin (E) did not acquire radioactive iron. It has been found that the passage of siderophore (Si)-iron complexes into bacteria is blocked in serum by Tr and in Ca-containing medium by Ca. The investigation of bacterial ability to take iron in synthetic media showed that bacteria take in Si-bound but no Tr-bound radioactive iron. In the absence of free iron, the growth of serum-exposed virulent bacteria was supported by their stored iron. Virulent bacteria passaged in medium void of usable iron became depleted in stored iron and did not grow in animal sera unless sera were enriched by the addition of exogenous iron. Experiments with serum-exposed avirulent bacteria showed that their growth in Si-enriched serum should not be attributed to the iron-providing activity of Si but to the stimulating effect of Si which facilitates the use of stored iron. As distinct from avirulent bacteria, virulent bacteria used stored iron without the stimulating activity of extracellular Si.

Genetic analysis of a temperature-sensitive Salmonella typhimurium rho mutant with an altered rho-associated polycytidylate-dependent adenosine triphosphatase activity

A conditional-lethal rho mutant of Salmonella typhimurium LT2 has been isolated. The mutation was selected as a suppressor of the polarity of an insertion sequence (IS)2-induced mutation (gal3) carried on an F' plasmid. In addition to suppression of IS2-induced polarity, the rho-111 mutation suppressed nonsense and frameshift polarity. The rho-associated polycytidylic acid-dependent adenosine triphosphatase activity in the mutant strain was elevated 15-fold above that in the parental strain, and the mutant rho protein was thermally unstable. A temperature-resistant revertant of the mutant strain did not suppress polarity and contained normal levels of polycytidylic acid-dependent adenosine triphosphatase, suggesting that the phenotype of the rho-111-bearing strain is the consequence of a single mutation. The rho-111 mutation was located on the S. typhimurium linkage map midway between the ilv and cya loci by phage P22 cotransduction studies. F' plasmid maintenance was not impaired in the mutant strain, and the mutation was recessive to the wild-type allele. The rho-111 mutation did not alter in vivo expression of either the tryptophan or histidine operons.

Dynamics of B-lymphocytes in the lungs of mice exposed to aerosolized influenza virus

Immunoglobulin-containing cells were revealed by immunofluorescence in lung sections from mice infected with influenza virus by the aerosol route. The numbers of immunoglobulin A (IgA)- and IgM-containing cells were increasing by day 3 of the infection, whereas IgG-containing cells appeared a few days later. The responding B-cell populations appeared in two principal locations: along major airways and in consolidated lesions within lung parenchyma. IgA-containing cells were the most numerous isotype, occurring predominantly in the lamina propria of the airways. IgG-containing cells were the least frequently encountered class along airways and appeared most often within consolidated lung lesions in clustered groupings. Cells staining for mu chain appeared along the airways and in lung lesions. The population of IgM-containing cells declined approximately 30 days after infection. Cells producing alpha and gamma chains were still numerous on day 46. Assays for virus-reactive antibodies in lung secretions were positive on day 8 of the infection. The IgM titers were the first to decline, but virus-binding antibodies for all classes were still present on day 33. The implications of immune responses in viral pneumonitis were considered.

Genetic complementation by cloned bacteriophage T4 late genes

Bacteriophage T4 containing nonsense mutations in late genes was found to be genetically complemented by four conjugate T4 genes (7, 11, 23, or 24) located on plasmid or phage vectors. Complementation was at a very low level unless the infecting phage carried a denB mutation (which abolishes T4 DNA endonuclease IV activity). In most experiments, the infecting phage also had a denA mutation, which abolishes T4 DNA endonuclease II activity. Mutations in the alc/unf gene (which allow dCMP-containing T4 late genes to be expressed) further increased complementation efficiency. Most of the alc/unf mutant phage strains used for these experiments were constructed to incorporate a gene 56 mutation, which blocks dCTP breakdown and allows replication to generate dCMP-containing T4 DNA. Effects of the alc/unf:56 mutant combination on complementation efficiency varied among the different T4 late genes. Despite regions of homology, ranging from 2 to 14 kilobase pairs, between cloned T4 genes and infecting genomes, the rate of formation of recombinants after T4 den:alc phage infection was generally low (higher for two mutants in gene 23, lower for mutants in gene 7 and 11). More significantly, when gene 23 complementation had to be preceded by recombination, the complementation efficiency was drastically reduced. We conclude that high complementation efficiency of cloned T4 late genes need not depend on prior complete breakage-reunion events which transpose those genes from the resident plasmid to a late promoter on the infecting T4 genome. The presence of the intact gene 23 on plasmids reduced the yield of T4 phage. The magnitude of this negative complementation effect varied in different plasmids; in the extreme case (plasmid pLA3), an almost 10-fold reduction of yield was observed. The cells can thus be said to have been made partly nonpermissive for this lytic virus by incorporating a part of the viral genome.

Effect of cycloheximide on the infective yield of a genital strain of Chlamydia trachomatis in McCoy cells

The yield of infectious progeny of a genital strain of Chlamydia trachomatis in cycloheximide-treated McCoy cell cultures was 11-fold lower than that in untreated monolayers.

Initiation of chromosomal DNA synthesis in vitro

An in vitro complementation assay for initiation of chromosomal DNA replication is described. The initiation reaction is dependent upon extract from either of two hybrid-plasmid containing strains. Each hybrid plasmid carries a suppressor of dna A-ts mutations. The in vitro DNA synthesis is heavily biased toward the origin region, and the origin of replication (oriC) is replicated as determined by DNA-DNA hybridizations.

Metabolism of L-fucose and L-rhamnose in Escherichia coli: differences in induction of propanediol oxidoreductase

Escherichia coli is capable of growing on L-fucose or L-rhamnose as a sole source of carbon and energy. When grown under anaerobic conditions on either sugar, a nicotinamide adenine dinucleotide-linked L-lactaldehyde:propanediol oxidoreductase activity is induced. The functioning of this enzyme results in the regeneration of oxidized nicotinamide adenine dinucleotide. Conditions of induction of the enzyme activity were studied and were found to display different characteristics on each sugar. In the rhamnose-grown cells, the increase in enzyme activity detected under inducing conditions was accompanied by the synthesis of propanediol oxidoreductase, as measured by the appearance in the extracts of a protein that reacts with propanediol oxidoreductase antibodies. In contrast, in fucose-grown cells, the level of propanediol oxidoreductase as measured by enzyme antibody-reacting material was high under noninducing and inducing conditions. Thus, the increase in enzyme activity detected in going from noninducing to inducing conditions in fucose-grown cells did not depend on the appearance of the specific protein but on the activation of the propanediol oxidoreductase already present in the cells in an inactive form. The propanediol oxidoreductase of both homologous systems should consequently be regulated by different control mechanisms.

Cloning and restriction map of the first part of the histidine operon of Salmonella typhimurium

The first part of the histidine operon of Salmonella typhimurium, hisGpeaGD, has been cloned onto the vector plasmid mini-ColE1 (pVH51). The resulting plasmid, pWB91, has a single EcoRI site and is 11,500 base pairs in size. The HindII restriction map was determined by the method of two-dimensional cross-annealing between a partial digest pattern and a complete digest pattern. The restriction fragment containing the genetic control region was identified with the aid of the small (35-base pair) internal deletion 01242 and the observation that heteroduplexed restriction fragments containing this deletion have markedly reduced mobility on polyacrylamide gels. The genetic control region was then mapped in more detail with other restriction enzymes. The genetic orientation of the restriction map was determined with the aid of several deletions of integral HindII fragments generated in vitro.

Role of Fc fragments in antibody-mediated recovery from ocular and subcutaneous herpes simplex virus infections

The contributions of the Fc fragment of virus-specific antibody in the resistance of mice to peripheral herpes simplex virus infection were investigated. Rabbit anti-herpes simplex virus-specific F(ab')2 fragments prepared by pepsin digestion of immune immunoglobulin G (IgG) were found to be inactive in complement-mediated cytolysis while retaining their capacity to neutralize virus infectivity in vitro. When F(ab')2 fragments were passively transferred either before or simultaneously with virus inoculation, they were as efficient as intact IgG was in protecting animals from virus challenge. However, if passive transfer was delayed until 8 h after herpes simplex virus infection, only IgG antibody was protective. The loss of protective activity could not be attributed to a rapid disappearance of F(ab')2 fragments, because comparable levels of F(ab')2 fragments and IgG antibody were maintained in the blood of recipients during the time that antibody mediated its protective effects. The inability of F(ab')2 subunits to activate complement was also not a factor, because complement-deficient A/J mice and complement-sufficient SJL/J mice recovered from herpes simplex virus infection after the passive transfer of IgG. We concluded that the Fc component of the antibody molecule is needed to resolve intracellular infection and that the mechanism by which antibody mediates recovery remains undefined but does not appear to involve virus neutralization or complement activation.

Identification of promoter-proximal oligonucleotides and a unique dinucleotide, pppGpC, from in vitro transcription products of vesicular stomatitis virus

The oligonucleotides synthesized by purified vesicular stomatitis virus in vitro in the absence of one or more ribonucleoside triphosphate precursors have been studied. The oligonucleotides contained the 5'-terminal sequences of the leader RNA and one or more mRNA's. The promoter-proximal oligonucleotides lacked 5'-terminal cap structure and contained triphosphate A. These results suggest that the RNA polymerase is located at multiple promoter sites on the genome RNA from where it initiates transcription. The capping reaction appears to occur subsequently during RNA chain elongation. We have also demonstrated that a unique dinucleotide, pppGpC, of presently unknown function is synthesized in vitro in large amounts during RNA synthesis or in the presence of GTP and CTP only.