Ordering of the flagellar genes in Pseudomonas aeruginosa by insertions of mercury transposon Tn501

The flagellar genes of Pseudomonas aeruginosa PAO cluster on the chromosome at two distinct regions, region I and region II. The order of the flagellar cistrons in this organism was established by using transducing phage G101 and plasmids FP5 and R68.45. A method to insert transposon Tn501 near the fla genes was devised. We obtained two strains in which Tn501 was inserted at sites close to the flagellar cistrons in region II. We isolated Fla mutants in which the chromosomal segment between the two Tn501 insertion sites was deleted. Using Tn501-encoded mercury resistance as an outside marker, we determined the order of 9 of the 11 flagellar cistrons in region II as follows: puuF-region I-flaG-flaC-flaI-flaH-flaD-flaB-flaA-flaF-flaE-pur-67. By using phage G101-mediated transduction, the mutation converting monoflagellated bacteria into the multiflagellated (mfl) form was closely linked to the five fla cistrons in region I. Using mfl as an outside marker, we determined the order of the five cistrons as follows: puuF-flaV-flaZ-flaW-flaX-flaY-region II. The mfl mutation was shown to be either located within the flaV cistron or linked very closely to this cistron. No linkage was observed in transductions between any of the fla cistrons in region I and any of the fla cistrons in region II.

Correlation of level and duration of Streptococcus mutans infection with incidence of dental caries

The caries incidence at various levels of Streptococcus mutans infection was analyzed in a control group and a test group. In the control group, the incidence of caries and the duration of S. mutans infection were significantly correlated. In the test group, the S. mutans infection was suppressed by antimicrobial measures when the number of S. mutans exceeded 250 X 10(3) CFU per ml of saliva. The results illustrate that the level and duration of the S. mutans infection are strongly correlated to the incidence of caries. The findings support the concept of S. mutans as a key cariogenic microorganism and illustrate the value of antimicrobial treatment in the prevention of caries.

Oxidation of hydrogen and reduction of methanol to methane is the sole energy source for a methanogen isolated from human feces

A methanogenic coccus isolated from human feces requires H2 and CH3OH for growth and uses H2 to reduce CH3OH to CH4. Growth does not occur with CH3OH alone. The organism does not grow or produce CH4 from acetate or methylamines without or with H2 or from H2 and CO2 or formate. In a complex medium. CO2 is required for formation of approximately 50% of cell carbon, whereas the methyl carbon from methanol is not incorporated into cell carbon.

Transductional analysis of the flagellar genes in Pseudomonas aeruginosa

Complementation in bacteriophage E79 tv-l-mediated transduction and the phenotypic properties of the flagellar genes in Pseudomonas aeruginosa PAO were investigated by using 195 flagellar mutants of this organism. A total of 15 fla. 1 mot, and 2 che cistrons were identified. At least 5 fla cistrons (fla V to flaZ) and one mot cistron resided in one region, and at least 10 fla cistrons (flaA to flaJ) and two che cistrons (cheA and cheB) resided in another. The flaC mutants exhibited cistron-specific leakiness on motility agar plates. The flaE cistron may be the structural gene for the component protein of the flagellar filament. The cheA mutations, which resulted in pleiotropic phenotypes for flagellar formation, motility, and taxis, belonged to the same complementation group as the flaF mutations; that is, we inferred that cheA and flaF are synonymous.

Isolation and characterization of a membrane-bound population of group B coxsackieviruses

HeLa cells infected with several group B coxsackieviruses contain a previously undetected, virus-specific ribonucleoprotein particle which we designated membrane-bound virion (MBV). MBVs of B5 virus have a pronounced polygonal appearance and are slightly smaller than virions. The particles sediment more slowly (at about 107S) and have a lower buoyant density (about 1.30). They contain 35S virion RNA; only three, and not four, capsid proteins; and at least seven additional proteins with apparent molecular weights of 21,000 to 92,000. Three of the latter proteins appear to be of host origin; the rest may be precursors of virion capsid proteins. The RNA is resistant to digestion by RNase, and EDTA treatment disrupts the particle. MBVs are infectious, although significantly less so than virions. Cells infected with MBVs produce both types of progeny, virions and MBVs. In coinfected cultures, the yield of progeny is lower than in cells infected with virions alone, suggesting interference by MBVs. Synthesis of both types can be detected within 3.5 h after infection, and synthesis continues for 24 h.

Cloning, mapping, and expression of the fumarase gene of Escherichia coli K-12

Two classes of fumarase-transducing phages, lambda fumA and lambda fumB, were isolated from populations of recombinant phages containing HindIII fragments of Escherichia coli DNA; they were isolated by virtue of their ability to complement the metabolic lesion of a fumarase-negative mutant. The strongly complementing lambda fumA phages contained a 6.2-kilobase HindIII fragment encoding: the fumA gene, located at 35.5 min in the E. coli linkage map and expressing the major fumarase activity; the mannosephosphate isomerase gene, manA; and an unidentified gene, g48. The three genes were located relative to the restriction map of the cloned fragment and the genetic linkage map (terC-g48-fumA-manA-uidAoR), their transcription polarities were defined as anticlockwise in the chromosome, and the molecular weights of the corresponding gene products were established: fumA, 61,500; manA, 42,000; g48, 48,000. Organisms containing the fumA gene sub-cloned in multicopy plasmids overproduced fumarase up to 50-fold. The weakly complementing class of transducing phages, lambda fumB, contained several genes in an 8.2-kilobase HindIII fragment, including one (fumB) that determines a minor fumarase activity. Complementation by fumB was only observed in high-copy situations such as transduction plaques and in strains containing a multicopy plasmid in which 40% of normal fumarase activity was detected. The basis for the complementation by fumB was not defined.

Precise excision of intervening sequences from precursor tRNAs by a membrane-associated yeast endonuclease

Splicing of transfer RNA precursors containing intervening sequences proceeds in two distinct stages: endonucleolytic cleavage, followed by ligation. We have physically separated endonuclease and ligase activities from extracts of yeast cells, and we report properties of the partially purified endonuclease preparation. The endonuclease behaves as an integral membrane protein: it is purified from a membrane fraction from which it can be solubilized with nonionic detergents, and the activity of the endonuclease in the membrane fraction is stimulated by nonionic detergents. The endonuclease cleaves precursor tRNAs at two sites to excise the intervening sequence precisely. Both the extent and the accuracy of cleavage are enhanced by the presence of spermidine; the degree of stimulation varies with the pre-tRNA substrate. The cleavage products possess 5'-hydroxyl and 2',3'-cyclic phosphodiester termini. The cyclic phosphodiester termini can be opened to 2'-phosphates by a cyclic phosphodiesterase activity in the preparation.

Isolation and characterization of a bacteriophage factor that confers competence for genetic transformation to an exfoliative toxin-producing strain of Staphylococcus aureus

Competence for genetic transformation in an exfoliative toxin-producing strain of Staphylococcus aureus was shown to be dependent on a virion factor that was isolated from a crude bacteriophage 80 alpha lysate. This competence-conferring factor was completely separated from infectious virus particles after either centrifugation through a neutral sucrose velocity gradient or fractionation on a Sepharose 2B gel. Since the competence-conferring factor tends to aggregate, optimal separation was obtained after treatment of the phage factor with the detergent Nonidet P-40. The competence-conferring factor had a molecular weight between 3 X 10(6) and 20 X 10(6) and an approximate sedimentation coefficient of 252. The factor was neutralized after interaction with antiserum prepared against isolated infectious 80 alpha virions. Electron microscopy of transforming cells that were exposed to isolated competence-conferring factor revealed a significant number of abnormally long and aggregated phage tail-like structures attached to the surface of recipient cells. This phenomenon was only observed in the presence of donor DNA, indicating that a phage tail-DNA-surface receptor complex might be one of the early steps in DNA-mediated transformation of S. aureus.

Escherichia coli kasugamycin dependence arising from mutation at the rpsI locus

Escherichia coli mutants with alterations in the electrophoretic mobility of ribosomal protein S9 were used to locate rpsI, the gene for this protein, on the linkage map. rpsI was located at about 70 min, roughly halfway between argG and fabE. It was very close to the gene for ribosomal protein L13, rplM. Another mutation at the rpsI locus gave rise to a phenotype of kasugamycin dependence and resistance. In this mutant, dependence on antibiotic came from kasugamycin being necessary to slow the rate of protein synthesis.

pH-sensitive CDP-diglyceride synthetase mutants of Escherichia coli: phenotypic suppression by mutations at a second site

In Escherichia coli, mutations which lower the level of CDP-diglyceride synthetase are designated cds and map at min 4. The cds-8 mutation resulted in strikingly defective enzyme activity and also rendered cells pH sensitive for growth. Both the inhibition of growth and the massive accumulation of phosphatidic acid which occur in a cds-8 mutant at pH 8 were suppressed by mutations at a second locus, designated cdsS, which mapped between argG and gltB near min 68. The cdsS3 mutation by itself did not affect CDP-diglyceride synthetase activity in wild-type cells, but it caused a twofold stimulation of the residual activity present in strains harboring cds-8. Both the insensitivity to pH and the twofold stimulation of residual activity were lost by introduction of an F' strain carrying cdsS+ into a recA1 cds-8 cdsS3 host. When a culture of a cds-8 cdsS+ strain was shifted to pH 8, the residual specific activity of synthetase dropped by 75% within 100 min. In a cds-8 cdsS3 double mutant under the same conditions, the activity declined appreciably less, about to the level found in the cds-8 cdsS+ strain under permissive conditions (pH 6). Thus, it appears that mutations in the cdsS gene suppress the pH sensitivity of cds mutants by inhibiting the decay of residual CDP-diglyceride synthetase activity at the nonpermissive pH. The cdsS locus appears to be distinct from any known nonsense or missense suppressor.

Nucleotide sequence of the amylase gene from Bacillus subtilis

The gene coding for amylase (EC.3.2.1.1) has been isolated and sequenced from Bacillus subtilis by cloning in lambda Charon4A and pBR322. The entire coding sequence and large preceding and following regions, comprising the presumed transcriptional and translational regulatory regions, were sequenced. The coding sequence shows a large open reading frame with a translated molecular weight of 72,800 and a presumed signal sequence of approximately thirty-two amino acids. When the intact gene is present in Escherichia coli, it confers the ability to degrade starch, indicating that the gene is expressed in a functional state.

Amplification of ribonuclease II (rnb) activity in Escherichia coli K-12

A 7.1 kb HindIII-XhoI fragment of E. coli DNA which contains the structural gene for ribonuclease II (rnb) has been cloned in the recombinant plasmid pDK24. At least two constitutively expressed genes are encoded on the fragment as shown by maxicell analysis. On denaturing polyacrylamide gels RNase II appears as a single 72,000 dalton species. The approximate site of transcription initiation of the rnb gene has been mapped. Although derivatives of E. coli harboring pDK24 contained 10-fold more RNase II activity that wild type strains without the plasmid, the degradation rate of mRNA was similar in all strains tested. Strains deficient in both RNase II and polynucleotide phosphorylase appear inviable.

Nucleotide sequence of the ilvB multivalent attenuator region of Escherichia coli K12

The ilvB gene of Escherichia coli K12 has been cloned into a multicopy plasmid. The regulation of the cloned gene by valine or leucine limitation and by catabolite repression is the same as for the chromosome encoded gene. The nucleotide sequence of a regulatory region preceding the ilvB structural gene has been determined. This DNA sequence includes a promoter, a region which codes for a putative 32 amino acid polypeptide containing multiple valine and leucine codons, and a transcription termination site. In vitro transcription of this region produces a 184 nucleotide terminated leader transcript. Mutually exclusive secondary structures of the leader transcript are predicted. On the basis of these data, a model for multivalent attenuation of the ilvB operon is presented. Data are presented which suggests that at least part of the postulated CRP-cyclic AMP binding site of the ilvB operon precedes the transcription start site by more than 71 base pairs.

Genes for tRNAIle and tRNAAla in the spacer between the 16S and 23S rRNA genes of a blue-green alga: strong homology to chloroplast tRNA genes and tRNA genes of the E. coli rrnD gene cluster

A 6.3 kbp Eco RI-Bam HI fragment which carries most of one of the two rRNA gene clusters of the blue-green alga Anacystis nidulans was cloned into plasmid pBR322. Sequence analysis of the spacer region between the 16S and 23S rRNA genes reveals the presence of genes for tRNAIle and tRNAAla. The 16S rRNA gene is separated from the tRNAIle gene by a 162 bp spacer which shows significant homology to the comparable region in Zea mays plastids. The spacer between the two tRNA genes is 33 bp long and can be folded into a 9 bp stem and loop structure. The 5' portion of the tRNAIle gene is 60% homologous to a "pseudogene"-like sequence which maps beyond the 5S rRNA gene.

Toxicity of staphylococcal alpha toxin for rabbit alveolar macrophages

Highly purified staphylococcal alpha toxin was toxic in vitro for rabbit alveolar macrophages. Cytotoxicity, manifested by loss of the ability to exclude trypan blue dye and by morphological evidence of cell necrosis and lysis, was observed after exposure for 4 h to 1 microgram of toxin preparation per ml and after exposure for 8 h to 0.1 microgram of toxin per ml. In addition, exposure to toxin under conditions which did not kill more than 10% of the cells (1 microgram/ml for 1.5 to 2 h) significantly reduced the phagocytic activity of the cells and their ability to respond to an activator of hexose monophosphate shunt activity.

Regulation of hydrolase formation and phosphate release in turimycin fermentations

During the turimycin fermentation hydrolytic enzymes are excreted responsible for orthophosphate release from phosphate-containing dissolved and undissolved complex medium constituents. Following a phosphate-limited growth period the phosphate release leads to a second growth period (diauxic growth). Depending on the rate of phosphate release the length of the lag phase of diauxic growth changes in different fermentations. The resulting second growth period is correlated with a transient delay in the formation of turimycin, of phosphatases and of nucleases. The amylolytic activities are formed already within the first hours after the beginning of fermentations. Phosphatases, nucleases and protease are excreted parallel to turimycin formation after extracellular phosphate limitation in presence of ammonia and glucose. A special role of phosphate limitation initiating enzyme synthesis is proposed.

Natural immunity to Sindbis virus is influenced by host tissue sialic acid content

Recent studies have shown that the sialic acid content of Sindbis virus influences both its ability to active the alternative pathway in vitro and its susceptibility to complement dependent clearance from the bloodstream in vivo. Other studies have shown that the sialic acid content of Sindbis virus is determined by the host in which it is propagated. Because individuals vary in their cell surface sialic acid content, it is possible they also vary in their ability to defend themselves against Sindbis virus infection by virtue of their ability to modify the virus sialic acid content and thereby the capacity of the virus to activate the alternative pathway. To test this hypothesis, outbred Swiss mice were injected subcutaneously with Sindbis virus. There was a significant positive correlation between the level of viremia 18 hr after infection and the sialic acid content of the host's erythrocytes. In addition, animals with erythrocyte sialic acid levels equal to or greater than the mean had a higher level of viremia than animals with erythrocyte sialic acid levels less than the mean. Finally, animals that had muscle sialic acid levels equal to or greater than the mean had a higher incidence of viremia than animals with muscle sialic acid levels less than the mean. These studies suggest that the amount of tissue sialic acid in an individual host influences its ability to resist Sindbis virus infection.

Amelioration of the ultraviolet sensitivity of an Escherichia coli recA mutant in the dark by photoreactivating enzyme

When a recA strain of Escherichia coli is transformed with a multicopy plasmid, pKY1, carrying the phr gene of E. coli, its extreme ultraviolet sensitivity is decreased. Derivatives of pKY1 were prepared in which the phr gene was inactivated by inserting transposon Tn1000. None of the 20 phr- derivatives decreased the UV sensitivity of the recA strain. In an analogous experiment, we obtained 11 derivatives which failed to decrease the UV sensitivity of the recA strain. None of them complemented phr strain. Furthermore, TN1000 insertion sites in both types of derivatives were mapped in the same region of the plasmid. From these observations, we propose that the E. coli phr gene product has repair activity in the dark.

Substrate utilization in defined media

Substrate utilization in defined media for two flower spiroplasmas (S. floricola and FS SR-3) and honeybee spiroplasma (HBS AS-576) was investigated. Glucose, fructose, and mannose were utilized by all three spiroplasmas. In addition, HBS (AS-576) could ferment trehalose; FS (SR-3), sucrose; and S. floricola, trehalose, sucrose, and raffinose. The three spiroplasmas varied greatly in growth requirements for amino acids. Only S. floricola utilized arginine. HBS (AS-576) required at least one purine and one pyrimidine base for growth, while both flower spiroplasmas grew with only one base in the medium. Oleic acid, cholesterol, and BSA were essential to all three spiroplasmas. Palmitic acid, which was non-essential, promoted growth significantly.

Porin channels in Escherichia coli: studies with beta-lactams in intact cells

Wild-type Escherichia coli K-12 produces two porins, OmpF (protein 1a) and OmpC (protein 1b). In mutants deficient in both of these "normal" porins, secondary mutants that produce a "new" porin, protein PhoE (protein E), are selected for. We determined the properties of the channels produced by each of these porins by measuring the rates of diffusion of various cephalosporins through the outer membrane in strains producing only one porin species. We found that all porin channels retarded the diffusion of more hydrophobic cephalosporins and that with monoanionic cephalosporins a 10-fold increase in the octanol-water partition coefficient of the solute produced a 5- to 6-fold decrease in the rate of penetration. Electrical charges of the solutes had different effects on different channels. Thus, with the normal porins (i.e., OmpF and OmpC proteins) additional negative charge drastically reduced the penetration rate through the channels, whereas additional positive charge significantly accelerated the penetration. In contrast, diffusion through the PhoE channel was unaffected by the presence of an additional negative charge. We hypothesize that the relative exclusion of hydrophobic and negatively charged solutes by normal porin channels is of ecological advantage to E. coli, which must exclude hydrophobic and anionic bile salts in its natural habitat. The properties of the PhoE porin are also consistent with the recent finding (M. Argast and W. Boos, J. Bacteriol. 143:142-150, 1980; J. Tommassen and B. Lugtenberg, J. Bacteriol. 143:151-157, 1980) that its biosynthesis is derepressed by phosphate starvation; the channel may thus act as an emergency pore primarily for the uptake of phosphate and phosphorylated compounds.

Characterization of an antigenic determinant of the glycoprotein that correlates with pathogenicity of rabies virus

The pathogenicity of fixed rabies virus strains for adult mice depends on the presence of an antigenic determinant on the viral glycoprotein. Two virus-neutralizing monoclonal antibodies have been used to identify this determinant. All pathogenic strains of fixed rabies virus bind to these antibodies and are neutralized by them, whereas nonpathogenic strains fail to react with these monoclonal antibodies and are not neutralized by them. Antigenic variants of the rabies virus with altered glycoprotein were selected by growing virus in the presence of one monoclonal antibody, 194-2. All variants that lost their ability to react with this antibody and an additional antibody, 248-8, were found to be nonpathogenic for adult mice. Analysis of tryptic peptides of the glycoproteins of pathogenic parent virus and nonpathogenic variants and the amino acid sequence of a specific variant tryptic peptide revealed that the change in pathogenicity corresponded to an amino acid substitution at position 333 of the glycoprotein molecule. The nucleotide sequence of the nonpathogenic variant glycoprotein gene contained a base change that confirmed the single amino acid substitution in the tryptic peptide replacing arginine-333 in the parental glycoprotein. We conclude that arginine-333 is essential for the integrity of an antigenic determinant and for the ability of rabies viruses to produce lethal infection in adult mice.

Penicillin therapy of experimental endocarditis induced by tolerant Streptococcus sanguis and nontolerant Streptococcus mitis

The response of tolerant Streptococcus sanguis and nontolerant Streptococcus mitis infections to penicillin therapy was compared in the rabbit model of endocarditis. The minimal inhibitory and bactericidal concentrations of penicillin were 0.1 and 0.1 mug/ml, respectively, for S. mitis and 0.05 and 6.2 mug/ml, respectively, for S. sanguis. Time-kill studies done in vitro with penicillin concentrations of 2 and 20 mug/ml demonstrated minimal killing of the tolerant strain, with a 3 log difference in survival between the two strains after 24 and 48 h. Both strains produced endocarditis with comparable bacterial densities on the valvular vegetations. Rabbits were treated with procaine penicillin G in two dosage regimens, 80,000 or 5,000 U/kg given every 8 h. There was no difference between bacterial densities in valvular vegetations removed from rabbits infected with either strain after 2, 4, or 6 days of treatment with the high-dose regimen (serum penicillin concentration at 0.5 h, 9.4 mug/ml), despite the fact that serum bactericidal activity against the tolerant strain at 0.5 h was minimal. With the low-dose penicillin regimen (serum concentration at 0.5 h, 2.5 mug/ml), therapy was significantly less effective in the tolerant group only after 6 days of treatment. Similar results were obtained when penicillin was administered in low and high doses to prevent infection. In this animal model of infection, penicillin tolerance was associated with a diminished response to penicillin therapy only when the dose was severely restricted. In the high-dose regimen, there was no difference in the response to penicillin therapy between animals infected with either strain, despite the presence of only minimal serum bactericidal activity in the rabbits infected with the tolerant strain.

Interaction of Clostridium difficile toxins and mouse hepatic microsomes

Intraperitoneal administration of toxins of Clostridium difficile to mice resulted in loss of hepatic cytochrome P450 and peroxidation of microsomal lipids. Pretreatment with the microsomal enzyme inducer beta-naphthoflavone partially alleviated these effects and increased survival time of intoxicated animals.

Escherichia coli mutants defective in the uncH gene

Plasmids carrying cloned segments of the unc operon of Escherichia coli have been used in genetic complementation analyses to identify three independent mutants defective in the uncH gene, which codes for the delta subunit of the ATP synthetase. Mutations in other unc genes have also been mapped by this technique. ATPase activity was present in extracts of the uncH mutants, but the enzyme was not as tightly bound to the membrane as it was in the parental strain. ATP-dependent membrane energization was absent in membranes isolated from the uncH mutants and could not be restored by adding normal F1 ATPase from the wild-type strain. F1 ATPase prepared from uncH mutants could not restore ATP-dependent membrane energization when added to wild-type membranes depleted of F1. Membranes of the uncH mutants were not rendered proton permeable as a result of washing with low-ionic-strength buffer.

Integration of R91-5::Tn501 into the Pseudomonas putida PPN chromosome and genetic circularity of the chromosomal map

Derivatives of the Pseudomonas aeruginosa plasmid R91-5, loaded with the transposon Tn501, were transferred to P. putida PPN. Over 90% of exconjugants, which arose at a frequency of ca. 10(-6) per donor cell, exhibited high-frequency (greater than 10(-2) per donor cell) polarized transfer of chromosomal markers. In one instance it was demonstrated by transduction that the plasmid had been inserted into a gene required for serine biosynthesis. The integrated nature of the plasmid in this and other P. putida (R91-5::Tn501) derivatives was supported by the failure to detect covalently closed circular DNA in these strains. The transfer origins of six different Hfr donors have been characterized genetically, and time-of-entry kinetics obtained from interrupted matings have enabled the construction of a circular genetic map 103 min in length and containing 35 markers. The genetic map of P. putida PPN shows significant differences in marker order to that of P. aeruginosa PAO.

Production of Rosamicin: Improvement of Synthetic Medium

Rosamicin is one of the important macrolide antibiotics that has clinical efficacy and broad-spectrum antibacterial activity. Using a mutant strain of Micromonospora rosaria (NRRL 3718), a chemically defined medium was developed, and some fermentation conditions that are important to rosamicin biosynthesis were optimized to achieve rosamicin productivity of 230 μg/ml. Soluble starch and l -asparagine were found to be the best carbon and nitrogen sources, and a stimulative effect of magnesium and zinc ions was also found. The medium developed contains: soluble starch, 4%; l -asparagine, 0.15%; K 2 HPO 4 , 0.075%; CaCO 3 , 0.6%; MgSO 4 · 7H 2 O, 0.05%; FeSO 4 · 7H 2 O, 10 −4 M; CuSO 4 · 5H 2 O, 10 −5 M; ZnSO 4 · 7H 2 O, 10 −5 M; and MnSO 4 · (4-6)H 2 O, 10 −6 M. The required air supply was about 40 mmol of O 2 liter −1 · h −1 · atm −1 , and the favorable culture temperature was 28 to 29°C.

Characterization of the mycoplasma genome

Recent advances on the properties of the mycoplasma genome, including size, base composition, replication, extrachromosomal DNA, and transfer of genetic material are briefly reviewed, with emphasis on their phylogenetic implications. The use of cleavage patterns of the mycoplasma genome by restriction endonucleases as "finger-prints" indicating genetic relatedness among strains is discussed. The data support the notion that strains of mycoplasma species of strict host and tissue specificity exhibit marked genetic homogeneity, suggesting a clonal origin for some species. The regions of the mycoplasma genome carrying the ribosomal RNA (rRNA) genes have been studied using restriction endonucleases, cloning, and hybridization procedures. The mycoplasmal rRNA cistrons cross-hybridized among themselves, and with the seven rRNA cistrons of Escherichia coli, demonstrating the marked conservation of structure during evolution of this part of the procaryotic genome. In most of the mollicutes tested so far the number of rRNA cistrons is two, but a few species appear to carry only one rRNA cistron in their genome.

End Products of Glucose Fermentation by Brochothrix thermosphacta

Anaerobically, Brochothrix thermosphacta fermented glucose primarily to l -lactate, acetate, formate, and ethanol. The ratio of these end products varied with growth conditions. Both the presence of acetate and formate and a pH below about 6 increased l -lactate production from glucose. Small amounts of butane-2,3-diol were also produced when the pH of the culture was low (≤5.5) or when acetate was added to the growth medium. Radioactive label from [1- 14 C]acetate was incorporated into ethanol and l -lactate, implying reversibility of pyruvate-formate lyase. In crude extracts, the following enzymes involved in pyruvate metabolism were demonstrated: lactate dehydrogenase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase (coenzyme A acetylating), ethanol dehydrogenase, pH 6 acetolactate-forming enzyme, and diacetyl (acetoin) reductase. The lactate dehydrogenase did not require fructose-1,6-disphosphate or Mn 2+ for activity.

Hyperthermic enhancement of serum antimicrobial activity: mechanism by which fever might exert a beneficial effect on the outcome of gram-negative sepsis

We have previously demonstrated heightened antibiotic activity at temperatures at the upper end of the physiological range. In the present studies we examined the effect of physiological variations in temperature on the antibacterial activity of antibiotic-free pooled human serum by comparing serum minimal inhibitory and bactericidal titers for gram-positive and gram-negative bacterial strains at 33, 37, and 41 degrees C. We observed a progressive rise in both minimal inhibitory and minimal bactericidal titers with temperature for all classes of gram-negative bacilli studied. However, gram-positive cocci were generally resistant to serum, even at the highest experimental temperature. Bacterial strains adapted to growth at temperatures normally encountered on body surfaces were more susceptible to the enhancing effect of hyperthermia on serum inhibition than were strains adapted to 37 degrees C. In addition, in vitro adaptation of one bacterial strain to different temperatures within the physiological range resulted in readily apparent variations in colonial morphology. These in vitro observations indicate that serum antibacterial activity and bacterial morphology may vary in response to minor changes in either the temperature to which bacteria are adapted before examination or the temperature of the assay system. If similar principles operate in vivo, hyperthermically augmented serum antimicrobial activity might represent one mechanism by which fever exerts a beneficial effect on the outcome of gram-negative sepsis.

Role of acetohydroxy acid isomeroreductase in biosynthesis of pantothenic acid in Salmonella typhimurium

Structural genes have been identified for all of the enzymes involved in the biosynthesis of pantothenic acid in Salmonella typhimurium and Escherichia coli K-12, with the exception of ketopantoic acid reductase, which catalyzes the conversion of alpha-ketopantoate to pantoate. The acetohydroxy acid isomeroreductase from S. typhimurium efficiently bound alpha-ketopantoate (K(m) = 0.25 mM) and catalyzed its reduction at 1/20 the rate at which alpha-acetolactate was reduced. Since two enzymes could apparently participate in the synthesis of pantoate, a S. typhimurium ilvC8 strain was mutagenized to derive strains completely blocked in the conversion of alpha-ketopantoate to pantoate. Several isolates were obtained that grew in isoleucine-valine medium supplemented with either pantoate or pantothenate, but not in the same medium supplemented with alpha-ketopantoate or beta-alanine. The mutations that conferred pantoate auxotrophy (designated panE) to these isolates appeared to be clustered, but were not linked to panB or panC. All panE strains tested had greatly reduced levels of ketopantoic acid reductase (3 to 12% of the activity present in DU201). The capacity of the isomeroreductase to synthesize pantoate in vivo was assessed by determining the growth requirements of ilvC(+) derivatives of panE ilvC8 strains. These strains required either alpha-ketopantoate, pantoate, or pantothenate when the isomeroreductase was present at low levels; when the synthesis of isomeroreductase was induced, panE ilvC(+) strains grew in unsupplemented medium. These phenotypes indicate that a high level of isomeroreductase is sufficient for the synthesis of pantoate. panE ilvC(+) strains also grew in medium supplemented with lysine and methionine. This phenotype resembles that of some S. typhimurium ilvG mutants (e.g., DU501) which are partially blocked in the biosynthesis of coenzyme A and are limited for succinyl coenzyme A. panE ilvC(+) strains which lack the acetohydroxy acid synthases required only methionine for growth (in the presence of leucine, isoleucine, and valine). This and other evidence suggested that the synthesis of pantoic acid by isomeroreductase was blocked by the alpha-acetohydroxy acids and that pantoic acid synthesis was enhanced in the absence of these intermediates, even when the isomeroreductase was at low levels. panE ilvC(+) strains reverted to pantothenate independence. Several of these revertants were shown to have elevated isomeroreductase levels under noninduced and induced conditions; the suppressing mutation in each revertant was shown to be closely linked to ilvC by P22 transduction. This procedure presents a means for obtaining mutants with altered regulation of isomeroreductase.

Expression of a Streptococcus mutans glucosyltransferase gene in Escherichia coli

Chromosomal DNA from Streptococcus mutans strain UAB90 (serotype c) was cloned into Escherichia coli K-12. The clone bank was screened for any sucrose-hydrolyzing activity by selection for growth on raffinose in the presence of isopropyl-beta-D-thiogalactoside. A clone expressing an S. mutans glucosyltransferase was identified. The S. mutans DNA encoding this enzyme is a 1.73-kilobase fragment cloned into the HindIII site of plasmid pBR322. We designated the gene gtfA. The plasmid-encoded gtfA enzyme, a 55,000-molecular-weight protein, is synthesized at 40% the level of pBR322-encoded beta-lactamase in E. coli minicells. Using sucrose as substrate, the gtfA enzyme catalyzes the formation of fructose and a glucan with an apparent molecular weight of 1,500. We detected the gtfA protein in S. mutans cells with antibody raised against the cloned gtfA enzyme. Immunologically identical gtfA protein appears to be present in S. mutans cells of serotypes c, e, and f, and a cross-reacting protein was made by serotype b cells. Proteins from serotype a, g, and d S. mutans cells did not react with antibody to gtfA enzyme. The gtfA activity was present in the periplasmic space of E. coli clones, since 15% of the total gtfA activity was released by cold osmotic shock and the clones were able to grow on sucrose as sole carbon source.

[Effector influence of oxygen-containing C1 compounds in the cultivation of the methanotrophic bacterial strain GB 25]

Addition of oxygen-containing C1-compounds to chemostat cultures of GB 25 increases both the yield of biomass and the specific growth rate. At optimum concentrations the catalytic activity of these compounds increases with increasing growth rates. Their influence on maintenance coefficients and maximum yield coefficients decreases in the order CH3OH greater than CO2 greater than HCOOH greater than HCHO. This result together with spectrophotometric NADH determinations suggests that the NADH pool determines the balance between the assimilatory and oxidative utilization of formaldehyde.

Partial Sequence Analysis of the 5S to 18S rRNA Gene Region of the Maize Mitochondrial Genome

The nucleotide sequence has been determined for a 664-base pair region of maize (Zea mays L.) mtDNA which contains the 3' end of the 18S rRNA gene, the 5S rRNA gene, and an intergenic region of 108 base pairs. Specific regions of the 18S rRNA gene show striking homology with the corresponding gene in Escherichia coli.

Kinetics and genetics of herpes simplex virus-induced antibody formation in mice

The kinetics of antibody synthesis was investigated after intraperitoneal, subcutaneous, and footpad infection of various strains of mice with herpes simplex virus. Immunoglobulin M antibodies appeared 5 days after and immunoglobulin G antibodies appeared 10 to 12 days after intraperitoneal infection with herpes simplex virus type 1. The major histocompatibility complex and the background genome of inbred mice were not found to have a systematical influence on antibody synthesis. Female mice, however, consistently produced more antibodies than did male if the infection was done intraperitoneally, but not if it was done subcutaneously or into footpads. Castration considerably increased the amount of antibodies produced by male mice. The difference in antibody formation between females and males could be abolished by injection of silica; moreover, antibody titers were enhanced by this treatment. This has also been found by immunization with a Formalin-inactivated herpes simplex virus vaccine. The effect of silica in enhancing antibody formation could be observed up to 12 days after infection. Infectious virus could be detected up to 2 days after infection, and herpes simplex virus type 1 antibody-stimulating antigens could be detected up to 4 days in ultrasonicates of macrophages. The assumption is made that androgen-sensitive cell populations, including macrophages and their soluble products, are involved in antibody-depressing mechanisms.

A plasmid in the archaebacterium Methanobacterium thermoautotrophicum

The archaebacterium Methanobacterium thermoautotrophicum Marburg (DSM 2133) was found to contain a plasmid (pME2001) in covalently closed circular form. It was isolated by CsCl gradient centrifugation of total DNA in the presence of ethidium bromide. Multimers up to the hexamer were observed upon agarose gel electrophoresis and electron microscopy of a purified plasmid preparation. A restriction map was constructed. The length of plasmid pME2001 was determined to be approximately 4,500 bp. Southern hybridization of plasmid DNA to DNA extracted from Methanobacterium thermoautotrophicum delta H (DSM1053) revealed the presence of a plasmid with homologous sequences in the delta H strain.

Molecular cloning of double-stranded RNA virus genomes

Genome double-stranded RNAs isolated from purified human reovirus (serotype 3) and rotavirus (Wa strain) were modified at the 3' termini by addition of oligo(C) approximately 15 with T4 RNA ligase. These RNAs were transcribed into cDNA by oligo(dG)-primed reverse transcriptase and cloned after insertion into pBR322 at the Pst I site. Hybridization of plasmid-transformed Escherichia coli RR1 colonies with 32P-labeled viral genome RNAs demonstrated the presence of DNA clones representative of each of the 10 reovirus RNAs and 10 of the 11 constituent segments of the rotavirus genome. Analyses of the size and terminal nucleotide sequences of insert DNAs indicated that some clones contained a full-length copy of the virus genome segment. The complete nucleotide sequence of rotavirus genome segment 11 double-stranded RNA was obtained by using this procedure. It provides a general method for cloning double-stranded RNAs and also nonpolyadenylylated single-stranded RNAs.

Orientation of succinate dehydrogenase and cytochrome b558 in the Bacillus subtilis cytoplasmic membrane

The orientation of the three subunits of the membrane-bound succinate dehydrogenase (SDH)-cytochrome b558 complex in Bacillus subtilis was studied in protoplasts ("right side out") and isolated membranes (random orientation), using immunoadsorption and surface labeling with [35S]diazobenzenesulfonate. Anti-SDH antibodies were adsorbed by isolated membranes but not by protoplasts. The SDH Mr 65,000 flavoprotein subunit was labeled with [35S]diazobenzenesulfonate in isolated membranes but not in protoplasts. The flavoprotein subunit is thus located on the cytoplasmic side of the membrane. The location of the SDH Mr 28,000 iron-protein subunit was not definitely established, but most probably the iron-protein subunit also is located on the cytoplasmic side of the membrane. Antibodies were not obtained to the hydrophobic cytochrome b558. The cytochrome was strongly labeled with [35S]diazobenzenesulfonate in protoplasts, and labeling was also obtained with isolated membranes. Cytochrome b558 is thus exposed on the outside of the membrane. In B. subtilis SDH binds specifically to cytochrome b558, which suggests that the cytochrome is exposed also on the cytoplasmic side of the membrane. The results obtained suggest that the B. subtilis SDH is exclusively located on the cytoplasmic side of the membrane where it is bound to cytochrome b558, which spans the membrane.

New class of mutations in Escherichia coli (uup) that affect precise excision of insertion elements and bacteriophage Mu growth

We have used a papillation screening technique to isolate mutations that increase the precise excision of insertion elements. The three mutations isolated stimulated precise excision of Tn5, Tn10, and the IS elements. They had a large, 20- to 600-fold, effect on excision of Tn5 at various chromosomal sites. The varied stimulation for different Tn5 insertions showed that the mutations altered the relationship between a precise excision activity and the chromosomal sequence flanking an inserted Tn5. A much smaller stimulation was observed for insertions on the plasmid F'128. The stimulation was recA independent. The mutations also reduced the rate of production of bacteriophage Mu progeny. The mutations were mapped by two- and three-factor crosses with closely linked Tn10 insertions. They defined the uup locus, located at 21.3 min on the Escherichia coli map, next to pyrD.

Processing of the encephalomyocarditis virus capsid precursor protein studied in rabbit reticulocyte lysates incubated with N-formyl-[35S]methionine-tRNAfMet

Translation of encephalomyocarditis virus RNA in rabbit reticulocyte lysates in the presence of N-formyl-[(35)S]methionine-tRNA(f) (Met) revealed that a small polypeptide is cleaved from the N-terminus of the capsid protein precursor, preA, by virus-coded protease activity. Therefore, this N-terminal segment comprising the translation initiation site is not conserved in any of the mature capsid proteins.

Attenuation control of pyrBI operon expression in Escherichia coli K-12

The pyrBI operon of Escherichia coli K-12 encodes the subunits of the pyrimidine biosynthetic enzyme aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2). Expression of this operon apparently is negatively regulated by the intracellular levels of UTP. To elucidate the regulatory mechanism in which UTP functions, the nucleotide sequence of the promoter-regulatory region of the pyrBI operon was determined and DNA fragments containing this region were transcribed in vitro. These experiments revealed a rho-independent transcriptional terminator (attenuator) located only 23 base pairs before the promoter-proximal end of the structural genes. Transcription initiated upstream at either of two potential pyrBI promoters was efficiently (approximately equal to 98%) terminated at this site, indicating that the regulation of pyrBI expression involves attenuation control. Additional features identified suggest a model for regulation in which the relative rates of UTP-dependent transcription within the pyrBI leader region and coupled translation of the leader transcript control transcriptional termination at the attenuator.

De novo purine synthesis, purine salvage, and DNA synthesis in normal and Lesch-Nyhan fibroblasts infected with Mycoplasma pneumoniae

The effects of Mycoplasma pneumoniae on host cell metabolism were studied by using two types of host cells, MRC-5 human lung fibroblasts, a normal cell line, and Lesch-Nyhan fibroblasts, a cell line deficient in hypoxanthine-guanine phosphoribosyl transferase (EC 2.4.2.8). The susceptibilities of the two cell types were determined by infecting the cells with M. pneumoniae at different multiplicities of infection (MOI). Our data indicate that the Lesch-Nyhan cells were four times more susceptible to damage by M. pneumoniae than the MRC-5 cells. The effects of different MOIs (10 and 50) on de novo purine synthesis. DNA synthesis, and the development of a cytopathic effect were determined. In both cell types, the higher MOI inhibited de novo purine synthesis to a greater extent than the lower MOI. This correlated closely with the cytopathic effect which developed in the monolayers (i.e., the more the inhibition of de novo purine synthesis, the greater the cytopathic effect which developed). In the Lesch-Nyhan cells, DNA synthesis was completely inhibited by the high MOI, whereas in the MRC-5 cells, DNA synthesis was stimulated by the high MOI. In the MRC-5 cells infected with M. pneumoniae, purine salvage activity increased, as indicated by an increase in adenosine deaminase (EC 3.5.4.4) activity. These data indicate that M. pneumoniae alters host cell metabolism, particularly the nucleic acid metabolic pathways. This may explain in part the mechanism of pathogenesis of M. pneumoniae infection.

Evaluation of Pseudomonas aeruginosa exotoxin A and elastase as virulence factors in acute lung infection

Acute Pseudomonas aeruginosa pneumonia was established in guinea pigs by intratracheal instillation of bacteria. Challenge strains included PAO-1, a strain known to produce exotoxin A, alkaline protease, and elastase, and several PAO-1 mutants deficient in either biologically active exotoxin A or elastase production. Survival, intrapulmonary killing of bacteria, and blood cultures were compared among the groups. Strains of P. aeruginosa deficient in active elastase production appeared to be less virulent than the parent strain and were more easily cleared from the lung. Opposite results were obtained for the exotoxin A-deficient mutants. These data suggest that elastase, but not exotoxin A, was an important virulence factor during acute pneumonia due to P. aeruginosa.

Vanadate uptake in Neurospora crassa occurs via phosphate transport system II

Vanadate, a potent inhibitor of plasma membrane ATPases, is taken up by Neurospora crassa only when cells are growing in alkaline medium and starving for phosphate. The appearance of a vanadate uptake system (Km = 8.2 microM; Vmax = 0.15 mmol/min per liter of cell water) occurs under the same conditions required for derepression of a high-affinity phosphate transport system. Phosphate is a competitive inhibitor of vanadate uptake, and vanadate is a competitive inhibitor of phosphate uptake. Furthermore, mutant strains which are either partially constitutive or non-derepressible for the high-affinity phosphate transport system are also partially constitutive or non-derepressible for vanadate uptake. These data indicate that vanadate enters the cell via phosphate transport system II.

Assessment of a futile cycle involving reconversion of fructose 6-phosphate to fructose 1,6-bisphosphate during gluconeogenic growth of Escherichia coli

In gluconeogenesis, fructose 6-phosphate is formed from fructose 1,6-bisphosphate, and if fructose 1,6-bisphosphate were reformed by the phosphofructokinase reaction there would be a "gluconeogenic futile cycle." We assessed the extent of this cycling in Escherichia coli growing on glycerol 3-phosphate, using a medium containing 32Pi. Fructose 1,6-bisphosphate coming from glycerol 3-phosphate should be unlabeled, but any coming from fructose 6-phosphate should contain label from the gamma-position of ATP. The amount of labeling of the 1-position of fructose 1,6-bisphosphate was only 2 to 10% of that of the gamma-position of ATP in a series of isogenic strains differing in phosphofructokinases (Pfk-1, Pfk-2, or Pfk-2). In control experiments with glucose 6-phosphate instead of glycerol 3-phosphate, the two positions were equally labeled. Thus, although the presence of Pfk-2 causes gluconeogenic impairment (Daldal et al., Eur. J. Biochem., 126:373-379, 1982), gluconeogenic futile cycling cannot be the reason.