Phospholipid biosynthesis in some anaerobic bacteria

We have identified and characterized enzymes of phospholipid synthesis in two plasmalogen-rich anaerobes. Megasphaera elsdenii and Veillonella parvula, and one anaerobe lacking plasmalogens. Desulfovibrio vulgaris. All three species contained phosphatidate cytidylyltransferase and phosphatidylserine synthase. Phosphatidylglycerophosphate synthesis was detected only D. vulgaris extracts. Phosphatidylserine (diacyl form) was the major product of the phosphatidylserine synthase assay with particles from M. elsdenii or V. parvula. The amounts of phosphatidylethanolamine formed were very low. Only D. vulgaris particles had an active phosphatidylserine decarboxylase.

The nitrogen requirements of Gluconobacter, Acetobacter and Frateuria

The nitrogen requirements of 96 Gluconobacter, 55 Acetobacter and 7 Frateuria strains were examined. Only some Frateuria strains were able to grow on 0.5% yeast extract broth or 0.5% peptone broth. In the presence of D-glucose or D-mannitol as a carbon source, ammonium was used as the sole source of nitrogen by all three genera. With ethanol, only a few Acetobacter strains grew on ammonium as a sole nitrogen source. Single L-amino acids cannot serve as a sole source of carbon and nitrogen for growth of Gluconobacter, Acetobacter or Frateuria. The single L-amino acids which were used by most strains as a sole nitrogen source for growth are: asparagine, aspartic acid, glutamine, glutamic acid, proline and alanine. Some Acetobacter and Gluconobacter strains deaminated alanine, asparagine, glutamic acid, threonine, serine and proline. No Frateuria strain was able to develop on cysteine, glycine, threonine or tryptophan as a sole source of nitrogen for growth. An inhibitory effect of valine may explain the absence of growth on this amino acid. No amino acid is "essential" for Gluconobacter, Acetobacter or Frateuria.

Leakage induced in Escherichia coli cells by A protein-RNA complexes from bacteriophage f2

Complexes of f2 phage RNA and its A protein, or maturation protein, transfect Escherichia coli cells much better than does protein-free RNA. We used these complexes to introduce the bacteriophage f2 lysis gene into cells. The A protein-RNA complex was found to kill cells, probably by causing them to leak large macromolecules. Previously induced beta-galactosidase leaked from cells treated either with the A protein-RNA complex or with lethal but noninfectious complexes that had been treated with formaldehyde. This observation was consistent with an earlier finding that formaldehyde-treated f2 RNA stimulates the in vitro synthesis of a lysis protein. The complexes did not stimulate the rate of leakage of beta-galactosidase from a streptomycin-resistant mutant known to be lysis defective. On the other hand, the rate of leakage was increased in a double mutant resistant to both streptomycin and rifampin and which is lysed normally by f2 bacteriophage.

Genetic mapping of chromosomal determinants for the production of the exopolysaccharide alginate in a Pseudomonas aeruginosa cystic fibrosis isolate

Mucoid Pseudomonas aeruginosa strain FRD, a sputum isolate from a cystic fibrosis patient, was used to develop a genetic system. The mucoid appearance is due to the biosynthesis of the exopolysaccharide alginate and is a potential virulence factor of the organism. The sex factor plasmid FP2 was used for uninterrupted genetic exchange to investigate the nature of spontaneous mutations which produce frequent alginate-negative (Alg-) derivatives. Crosses between Alg+ donors and Alg- recipients demonstrated linkage between alginate genes and chromosomal markers. Crosses between an Alg- donor and Alg- recipients produced Alg+ recombinants at frequencies that varied, depending on the recipient strains used. This indicated that more than one genetic locus was associated with spontaneous mutation leading to loss of the mucoid character. Three classes of Alg- mutants were identified. Genetic exchange experiments showed that the loci of the alginate (alg) mutations of the three mutant classes are in the same region of the chromosome. The sex factor plasmid R68.45 was used for nonpolarized chromosome transfer and demonstrated close linkage between chromosomal markers (his-1, met-1) and alg markers. This was consistent with the data obtained in FP2-mediated crosses. Thus, the evidence obtained indicated that the alg genes which undergo frequent mutation are chromosomal, that several loci are involved, and that these alg loci are apparently clustered on the chromosome.

Niacin Reduces Paraquat Toxicity in Rats

Rats poisoned with paraquat benefited from daily niacin therapy. Niacin-treated rats showed delayed and reduced dyspnea. Deaths began approximately 30 hours later. The time required for niacin-treated rats to reach 50 percent mortality increased from 60 to 120 hours, and the dealth rate was reduced form 75 to 55 percent. The benefit by niacin is consistent with the demonstrated role of niacin in preventing cellular decreases of nicotinamide adenine dinucleotide during poisoning of bacteria by paraquat and by hyperbaric oxygen.

L-Lactate dehydrogenase from leaves of higher plants. Kinetics and regulation of the enzyme from lettuce (Lactuca sativa L)

1. L-Lactate dehydrogenase from lettuce (Lactuca sativa) leaves was purified to electrophoretic homogeneity by affinity chromatography. 2. In addition to its NAD(H)-dependent activity with L-lactate and pyruvate, the enzyme also catalyses the reduction of hydroxypyruvate and glyoxylate. The latter activities are not due to a contamination of the enzyme preparations with hydroxypyruvate reductase. 3. The enzyme shows allosteric properties that are markedly by the pH. 4. ATP is a potent inhibitor of the enzyme. The kinetic data suggest that the inhibition by ATP is competitive with respect to NADH at pH 7.0 and 6.2. The existence of regulatory binding sites for ATP and NADH is discussed. 5. Bivalent metal cations and fructose 6-phosphate relieve the ATP inhibition of the enzyme. 6. A function of leaf L-lactate dehydrogenase is proposed as a component of the systems regulating the cellular pH and/or controlling the concentration of reducing equivalents in the cytoplasm of leaf cells.

Genetic transformation of Streptococcus mutans

Three strains of Streptococcus mutans belonging to serotypes a, c, and f were transformed to streptomycin resistance by deoxyribonucleic acids derived from homologous and heterologous streptomycin-resistant strains of S. mutans and Streptococcus sanguis strain Challis. Homologous transformation of S. mutans was less efficient than heterologous transformation by deoxyribonucleic acids from other strains of S. mutans.

Selective enrichment of Pseudomonas spp. defective in catabolism after exposure to halogenated substrates

Significant selective enrichments of mutants defective in catabolic pathways can be achieved by exposure of pseudomonad cells to halogenated analogs of growth substrates. Between 3 and 95% of viable clones rescued from such enrichments have been defective in specific catabolic pathways. This has been demonstrated for eight different catabolic pathways for aromatic compounds in pseudomonads, in which the genes are located on plasmids or on the chromosome. The plasmid-encoded pathways studied include those for the catabolism of p-cymene (CYM), m- and p-xylenes (TOL), naphthalene (NAH), salicylate (SAL), and 4-methylphthalate (MOP), and the chromosome-encoded pathways include those for p-hydroxybenzoate, monohydric phenols, and p-anisate utilization. The recalcitrance of halogenated compounds may, in part, be explained by these observations, which introduce an as yet not widely recognized factor in assessment of biodegradability of halogenated compounds and their effects on the transformation of the natural substrates.

Possible relationship between yeast deoxyribonucleases and deoxyribonucleic Acid yield

The deoxyribonucleic acid (DNA) yield and deoxyribonuclease (DNase) activity of several yeasts were correlated. Debaryomyces castellii and Debaryomyces franciscae were found to contain active DNases which carry out DNA hydrolysis, whereas the amounts of DNA as determined by extraction with Sarkosyl buffer (pH 7.8) were found to be small. On the other hand, Candida parapsilosis, Saccharomyces carmosousae, and Lodderomyces elongisporus produced no detectable DNases active at pH 7.8, and their DNA yield was correspondingly high. L. elongisporus was found to possess DNase only at pH 4.0.

Isolation and characterization of hypertoxinogenic (htx) mutants of Escherichia coli KL320(pCG86)

The structural genes for heat-labile enterotoxin (LT) are present on plasmid pCG86. Escherichia coli KL320(pCG86), LT was found to be cell associated. LT was present as a soluble protein in sonic lysates of KL320(pCG86). Thirty-one mutants of KL320(pCG86) that produced increased amounts of extracellular LT were isolated. These hypertoxinogenic (htx) mutants were assigned to four phenotypically distinct classes based on the amounts of cell-associated and extracellular LT in early-stationary-phase cultures. Type 1 and type 2 htx mutants produced significantly increased amounts of cell-associated LT. Type 3 and type 4 htx mutants produced normal or decreased amounts of cell-associated LT was similar to that of the wild type. In the mutants of types 1, 3, and 4, the ratios of extracellular to cell-associated LT were higher than that of the wild type and were characteristic for each strain. Cell lysis or leakage of macromolecular cytoplasmic constituents appeared to be significant for release of LT by mutants of types 1, 3, and 4, because supernatants from cultures of these mutants also contained increased amounts of protein and of the cytoplasmic enzyme glucose 6-phosphate dehydrogenase. In all four representative htx mutants, the hypertoxinogenic phenotypes were dependent on chromosomal mutations. The resident pCG86 plasmids were eliminated from the htx mutants of types 2 and 3. After wild-type plasmid pCG86 was introduced into the cured strains by conjugation, their hypertoxinogenic phenotypes were restored. We conclude that chromosomal loci in E. coli KL320 are important in regulating expression of the LT structural genes of plasmid pCG86.

Luciferase inactivation in the luminous marine bacterium Vibrio harveyi

Luciferase was rapidly inactivated in stationary-phase cultures of the wild type of the luminous marine bacterium Vibrio harveyi, but was stable in stationary-phase cultures of mutants of V. harveyi that are nonluminous without exogenous aldehyde, termed the aldehyde-deficient mutants. The inactivation in the wild type was halted by cell lysis and was slowed or stopped by O2 deprivation or by addition of KCN and NaF or of chloramphenicol. If KCN and NaF or chloramphenicol were added to a culture before the onset of luciferase inactivation, then luciferase inactivation did not occur. However, if these inhibitors were added after the onset of luciferase inactivation, then luciferase inactivation continued for about 2 to 3 h before the inactivation process stopped. The onset of luciferase inactivation in early stationary-phase cultures of wild-type cell coincided with a slight drop in the intracellular adenosine 5'-triphosphate (ATP) level from a relatively constant log-phase value of 20 pmol of ATP per microgram of soluble cell protein. Addition of KCN and NaF to a culture shortly after this drop in ATP caused a rapid decrease in the ATP level to about 4 pmol of ATP per microgram whereas chloramphenicol added at this same time caused a transient increase in ATP level to about 25 pmol/microgram. The aldehyde-deficient mutant (M17) showed a relatively constant log-phase ATP level identical with that of the wild-type cells, but rather than decreasing in early stationary phase, the ATP level increased to a value twice that in log-phase cells. We suggest that the inactivation of luciferase is dependent on the synthesis of some factor which is produced during stationary phase and is itself unstable, and whose synthesis is blocked by chloramphenicol or cyanide plus fluoride.

6-Methylsalicylic Acid Production in Solid Cultures of Penicillium patulum Occurs Only When an Aerial Mycelium Is Present

When Penicillium patulum was grown on Czapek-Dox agar, 6-methylsalicylic acid was produced as an aerial mycelium was forming. Nutrients were often plentiful in the medium when biosynthesis began. If the formation of an aerial mycelium was prevented by growing the fungus between two sheets of dialysis membrane, no 6-methylsalicylic acid was produced even when nutrients were completely consumed. If the upper sheet of dialysis membrane was stripped off cultures of the latter type, an aerial mycelium formed; concomitantly, 6-methylsalicylic acid biosynthesis was observed. We conclude that 6-methylsalicylic acid was produced only by P. patulum colonies that possessed an aerial mycelium.

Genetic and biochemical requirements for chemotaxis to L-proline in Escherichia coli

Chemotaxis to L-proline was examined by the capillary assay, using a set of Escherichia coli strains bearing well-defined defects in the enzymes of proline transport and utilization. Aspartate taxis was measured as a constitutive, control activity whose receptor and transducer requirements are known. Proline chemotaxis showed a pattern of induction more analogous to that of proline dehydrogenase than of that of proline transport, but chemotaxis to proline was eliminated by mutations eliminating either or both of these activities. No response to proline was observed in the absence of a proline concentration gradient or when succinate was provided as an oxidizable carbon source. These data suggest that the chemotactic response to proline results from a direct impact of proline oxidation on the energy metabolism of the cell.

Changes in the rate of chitin-plus-chitosan synthesis accompany morphogenesis of Mucor racemosus

The in vivo differential rates of chitin-plus-chitosan biosynthesis in Mucor racemosus were determined under a variety of conditions, leading to yeast cell or mycelial morphology. Chitin-chitosan was determined as hot NaOH-insoluble radioactivity derived from N-acetyl-D-[1-3H]glucosamine in the medium. Control experiments demonstrated that the labeled material possessed the properties of chitin-plus-chitosan. Our results indicate that Mucor yeasts have a relatively low differential rate of chitin-plus-chitosan synthesis and that mycelial cells have a threefold-elevated differential rate. Treatment of aerobic cells with exogenous N6, O2-dibutyryl cyclic adenosine 3',5'-monophosphate, an agent which induces yeast cell morphology, also results in a lowered rate of chitin-plus-chitosan synthesis. Control experiments eliminated the possibility that the observed rate changes were due to changes in endogenous pool size, uptake of exogenous N-acetyl-p-[1-3H]glucosamine, or alterations in growth rate. Therefore, the changes are seemingly linked to morphogenesis. These results strengthen the idea that cyclic adenosine 3',5'-monophosphate plays an important role in dimorphism in Mucor. In addition, pulse-chase experiments suggest that considerable modification of newly synthesized chitin plus chitosan in both yeast cells and mycelia occurs in vivo.

Genetics of L-proline utilization in Escherichia coli

L-Azetidine-2-carboxylate (AC) and 3,4-dehydro-D,L-proline (DHP) are toxic L-proline analogs that can be used to select bacterial mutants defective for L-proline transport. Mutants resistant to AC and DHP are defective for proline transport alone (putP mutants), and mutants resistant to AC but not to DHP are defective both in putP and in the closely linked proline dehydrogenase gene putA. Proline dehydrogenase oxidizes DHP but not AC, probably detoxifying the former compound. These observations were exploited in preparing an otherwise isogenic set of Escherichia coli K-12 strains with well-defined defects in the putP and putA genes. The results of this study suggest that the genetic and biochemical characteristics of proline utilization in E. coli K-12 are closely analogous to those of Salmonella typhimurium.

Roles of the CDC24 gene product in cellular morphogenesis during the Saccharomyces cerevisiae cell cycle

Temperature-sensitive yeast mutants defective in gene CDC24 continued to grow (i.e., increase in cell mass and cell volume) at restrictive temperature (36 degrees C) but were unable to form buds. Staining with the fluorescent dye Calcofluor showed that the mutants were also unable to form normal bud scars (the discrete chitin rings formed in the cell wall at budding sites) at 36 degrees C; instead, large amounts of chitin were deposited randomly over the surfaces of the growing unbudded cells. Labeling of cell-wall mannan with fluorescein isothiocyanate-conjugated concanavalin A suggested that mannan incorporation was also delocalized in mutant cells grown at 36 degrees C. Although the mutants have well-defined execution points just before bud emergence, inactivation of the CDC24 gene product in budded cells led both to selective growth of mother cells rather than of buds and to delocalized chitin deposition, indicating that the CDC24 gene product functions in the normal localization of growth in budded as well as in unbudded cells. Growth of the mutant strains at temperatures less than 36 degrees C revealed allele-specific differences in behavior. Two strains produced buds of abnormal shape during growth at 33 degrees C. Moreover, these same strains displayed abnormal localization of budding sites when growth at 24 degrees C (the normal permissive temperature for the mutants); in each case, the abnormal pattern of budding sites segregated with the temperature sensitivity in crosses. Thus, the CDC24 gene product seems to be involved in selection of the budding site, formation of the chitin ring at that site, the subsequent localization of new cell wall growth to the budding site and the growing bud, and the balance between tip growth and uniform growth of the bud that leads to the normal cell shape.

Mobilization of the genes for photosynthesis from Rhodopseudomonas capsulata by a promiscuous plasmid

Plasmid pBLM2, a derivative of RP1 with enhanced chromosome mobilization activity in Rhodopseudomonas capsulata, was isolated by screening rare exconjugant clones for sex factor activity. pBLM2 mobilized all known genes affecting photosynthesis as well as chromosomal genes for streptomycin and rifampin resistance and tryptophan and cytochrome biosynthesis. Tight linkage was exhibited among the genes affecting photosynthesis. The frequency of successful transfer of chromosomal markers reached 6 X 10(-4) per donor cell. R-primes were occasionally formed during conjugation, and a number of R-primes bearing the genes for photosynthesis were isolated by screening R. capsulata exconjugants with complementation phenotypes for the ability to transmit plasmid-borne R. capsulata genes to Escherichia coli cells. These R-primes were unstable in R. capsulata, but stable in E. coli or Pseudomonas fluorescens. Complementation and recombination events that occurred upon introduction of R-primes into R. capsulata mutants with altered photosynthetic apparatuses could be visualized as variations in colony pigmentation. Each R-prime studied complemented all known types of mutation affecting the differentiation of the photosynthetic apparatus, and no other R. capsulata gene was identified on those plasmids. The R. capsulata genes borne on the R-primes were not functional in E. coli or P. fluorescens.

Regulation of methyl-beta-d-thiogalactopyranoside-6-phosphate accumulation in Streptococcus lactis by exclusion and expulsion mechanisms

Starved cells of Streptococcus lactis ML3 (grown previously on galactose, lactose, or maltose) accumulated methyl-beta-D-thiogalactopyranoside (TMG) by the lactose:phosphotransferase system. More than 98% of accumulated sugar was present as a phosphorylated derivative, TMG-6-phosphate (TMG-6P). When a phosphotransferase system sugar (glucose, mannose, 2-deoxyglucose, or lactose) was added to the medium simultaneously with TMG, the beta-galactoside was excluded from the cells. Galactose enhanced the accumulation of TMG-6P. Glucose, mannose, lactose, or maltose plus arginine, was added to a suspension of TMG-6P-loaded cells of S. lactis ML3, elicited rapid expulsion of intracellular solute. The material recovered in the medium was exclusively free TMG. Expulsion of galactoside required both entry and metabolism of an appropriate sugar, and intracellular dephosphorylation of TMG-6P preceded efflux of TMG. The rate of dephosphorylation of TMG-6P by permeabilized cells was increased two-to threefold by adenosine 5'-triphosphate but was strongly inhibited by fluoride. S. lactis ML3 (DGr) was derived from S. lactis ML3 by positive selection for resistance to 2-deoxy-D-glucose and was defective in the enzyme IIMan component of the glucose:phosphotransferase system. Neither glucose nor mannose excluded TMG from cells of S. lactic ML3 (DGr), and these two sugars failed to elicit TMG expulsion from preloaded cells of the mutant strain. Accumulation of TMG-6P by S. lactis ML3 can be regulation by two independent mechanisms whose activities promote exclusion or expulsion of galactoside from the cell.

Changes in the promoter range of RNA polymerase resulting from bacteriophage T4-induced modification of core enzyme

Primary transcripts made in vitro on bacteriophage T4 DNA by RNA polymerase isolated from normal or T4-infected Escherichia coli were compared by gel electrophoresis. Bacteriophage-modified RNA polymerase fails to initiate transcription at certain promoters recognized by unmodified enzyme. In the T4tRNA gene region, only one of the two promoters is active with the modified RNA polymerase. Reconstitution of separated RNA polymerase components demonstrates that this change in promoter site selection results from the modification of core enzyme and not sigma factor.

Isolation and genetic characterization of Escherichia coli mutants defective in propionate metabolism

Escherichia coli mutants defective in propionate metabolism (Prp-) were isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Prp- mutants demonstrate a phenotypic inability to grow on odd-chain-length fatty acids. The new genetic locus for the Prp- phenotype maps at approximately 98 min on the E. coli chromosome.

Hemagglutination method for detection of freshwater cyanobacteria (blue-green algae) toxins

Strains of the freshwater cyanobacteria (blue-green algae) Anabaena flosaquae and Microcystis aeruginosa produced toxins that caused intermittent but repeated cases of livestock, waterfowl, and other animal deaths. They also caused illness, especially gastrointestinal, in humans. The most common group of toxins produced by these two species were peptide toxins termed microcystin, M. Aeruginosa type c, and anatoxin-c. A method was found to detect the toxins which utilizes their ability to cause agglutination of isolated blood cells from mice, rats, and humans. The method could detect the toxin in samples from natural algal blooms, laboratory cultures, and toxin extracts. The method consists of: (i) washing lyophilized cyanobacteria cells with physiological saline (0.9% NaCl), (ii) centrifuging the suspension and then mixing portions of the cell-free supernatant with equal volumes of saline-washed erythrocytes in V-shaped microtiter plates, (iii) allowing the mixture to stand for 3 to 4 h, and (iv) scoring the presence of the toxin as indicated by blood cell agglutination. Nontoxic strains, as determined by intraperitoneal mouse bioassay of cyanobacteria or green algae, did not produce an agglutination response.

Identification of the dnaQ gene product and location of the structural gene for RNase H of Escherichia coli by cloning of the genes

By in vitro recombination we have constructed hybrid plasmids capable of complementing a conditional lethal mutator mutation, dnaQ49, in Escherichia coli K12. The dnaQ+ plasmids consist of a full-length pBR322 DNA and a 1.5-kilobase DNA fragment derived from the E. coli chromosome. Specific labeling of plasmid-encoded proteins by the maxicell method revealed that the 1.5-kilobase insert codes for two proteins, one whose molecular weight is 25,000 [the 25-kilodalton (kDal) protein] and the other whose molecular weight is 21,000 (the 21-kDal protein). Because insertion of gamma delta sequence into the dnaQ gene of the plasmid resulted in disappearance of the 25-kDal protein, it was concluded that the 25-kDal protein is the dnaQ gene product. The 21-kDal protein was identified as RNase H on the basis of the following evidence. (i) Cells harboring the dnaQ+ plasmids, with or without the gamma delta insertion in the dnaQ gene, had a 5- to 7-fold higher level of RNase H activity than cells harboring pBR322. (ii) After induction of cells that are lysogenized with dnaQ+-transducing lambda phages, RNase H activity increased considerably. A similar high level of RNase H activity was observed with transducing phages whose dnaQ function was inactivated by insertion of a transposon, Tn3, into the gene, (iii) The plasmid-encoded RNase H, labeled with [35S]methionine, was purified in a manner essentially similar to that of the chromosome-encoded enzyme. These results suggest that the dnaQ gene and the structural gene for RNase H, termed gene rnh, are closely linked and located at 5 min on the linkage map.

Acridine dyes and other DNA-intercalating agents induce the luminescence system of luminous bacteria and their dark variants

Acridine dyes and other DNA-intercalating agents such as ethidium bromide, theophylline, and caffeine induce luminescence in dark variants (K variants) different luminous species of bacteria, as well as in their wild-type luminous cells, prior to induction. The increase in luminescence appears 10-20 min after addition of these agents and is inhibited by chloramphenicol or rifampicin. Addition of these agents affects the synthesis of both luciferase and aldehyde-synthesizing enzymes. It is hypothesized that these agents, through their intercalation into DNA, cause configurational changes resulting in derepressed transcription of the luminescence operon.

Mitochondrial DNA of chloramphenicol-resistant mouse cells contains a single nucleotide change in the region encoding the 3' end of the large ribosomal RNA

The complete DNA sequence of the rRNA genes of mouse L cell mtDNA provides a basis for the examination of the nucleotide sequence of this region in a mutant mouse cell line that is resistant to chloramphenicol, a known inhibitor of mitochondrial protein synthesis. Resistance to chloramphenicol (CAPr) is conferred by a cytoplasmic determinant that is linked to mtDNA restriction endonuclease site polymorphisms. We have determined the sequence of a 212-nucleotide region of mtDNA from a CAPr mouse cell line that encodes a portion of the 1582-nucleotide large rRNA. This sequence is located 107-318 nucleotides from the 5' end of the heavy strand coding sequence, which corresponds to the 3' end of the rRNA. There is a single nucleotide difference in the large rRNA gene from CAPr cells, an A-to-G transition 243 nucleotides from the 5' end of the coding sequence. This single transition is located within a region of 10 nucleotides tht is otherwise completely homologous to human and yeast mitochondrial large rRNAs and Escherichia coli 23S rRNA and is positioned immediately adjacent to a single nucleotide transversion known to occur in a yeast CAPr mutant. This characterization of a mammalian mitochondrial mutant at the nucleotide level directly demonstrates that a mutant phenotype may result from a single mtDNA nucleotide change in an animal cell.

Genetic mapping of a mutation conferring sensitivity to bacteriophage Mu in Salmonella typhimurium LT2

Two strains of Salmonella typhimurium LT2, SA1475 and MA411, were fortuitously found to be sensitive to bacteriophage Mu. The Mu-sensitivity allele of SA1475 was called musA1 and shown to be linked to the histidine operon both in conjugation and transduction experiments. The Mus allele of MA411 was unlinked to the his region and was tentatively designated musB2. Strains carrying large deletions of the his operon were also tested for Mu sensitivity; those of which the his-rib region is deleted were also sensitive to Mu. Transduction data led to the order zee-2 hisOGDCBAHFIE gnd musA. An Hfr injecting the his operon early (HfrK9) an carrying hisG9424::Tn10 delta 4 delta 11 and musA1 was isolated; this Hfr made it possible to introduce the Mus character into most derivatives of S. typhimurium LT2. Since strain SA1475 is resistant to bacteriophage P1, it could be used to select a new P1-Mu hybrid which has the host range of Mu and the transduction properties of P1.

Respiration-associated components of Mollicutes

No cytochrome pigments were detected by difference (reduced minus oxidized) spectroscopy at liquid nitrogen temperature in whole-cell preparations or membrane fractions of Acholeplasma axanthum S273, Acholeplasma equifetale N93, Acholeplasma granularum BTS39, Acholeplasma laidlawii B-PG9, Acholeplasma modicum PG-49, Acholeplasma oculi 19L, Mycoplasma arginini G230, Mycoplasma arthritidis 07, Mycoplasma pneumoniae FH, and Mycoplasma pulmonis JB. All ten Mollicutes species examined contained iron of unknown function (3.0 to 15.3 nmol of iron per mg of protein). Relatively small amounts of acid-labile sulfide were found in all fractions (0.10 to 1.07 nmol of acid-labile sulfide per mg of protein). The data suggest that, as Mollicutes lack cytochrome pigments, they would synthesize most if not all adenosine triphosphate at the substrate level.

Inducible plasmid-determined resistance to arsenate, arsenite, and antimony (III) in escherichia coli and Staphylococcus aureus

Plasmids in both Escherichia coli and Staphylococcus aureus contain an "operon" that confers resistance to arsenate, arsenite, and antimony(III) salts. The systems were always inducible. All three salts, arsenate, arsenite, and antimony(III), were inducers. Mutants and a cloned deoxyribonucleic acid fragment from plasmid pI258 in S. aureus have lost arsenate resistance but retained resistances to arsenite and antimony, demonstrating that separate genes are involved. Arsenate-resistant arsenite-sensitive S. aureus plasmid mutants were also isolated. In E. coli, plasmid-determined arsenate resistance and reduced uptake were additive to that found with chromosomal arsenate resistance mutants. Arsenate resistance was due to reduced uptake of arsenate by the induced plasmid-containing cells. Under conditions of high arsenate, when some uptake could be demonstrated with the induced resistant cells, the arsenate was rapidly lost by the cells in the absence of extracellular phosphate. Sensitive cells retained arsenate under these conditions. When phosphate was added, phosphate-arsenate exchange occurred. High phosphate in the growth medium protected cells from arsenate, but not from arsenite or antimony(III) toxicity. We do not know the mechanisms of arsenite or antimony resistance. However, arsenite was not oxidized to less toxic arsenate. Since cell-free medium "conditioned" by prior growth to induced resistant cells with toxic levels of arsenite or antimony(III) retained the ability to inhibit the growth of sensitive cells, the mechanism of arsenite and antimony resistance does not involve conversion of AsO2- or SbO+ to less toxic forms or binding by soluble thiols excreted by resistant cells.

Adenylate energy charge in Acholeplasma laidlawii

Adenosine 5'-triphosphate, adenosine 5'-diphosphate, and adenosine 5'-monophosphate were produced by Acholeplasma laidlawii B-PG9 growing in modified Edward medium. The adenylate energy charge was calculated to be 0.84 +/- 0.07 and ranged from 0.91 to 0.78 during exponential growth (12 to 24 h). During exponential growth, A. laidlawii contained, at 17.5 h, 2.3 X 10(-17) mol of adenosine 5'-triphosphate per colony-forming unit and, at 16 h, 27.3 nmol of adenosine 5'-triphosphate per mg (dry weight). The medium supported a doubling time of 0.95 h. The molar growth yields (Yglucose = grams [dry weight] per mole of glucose used) were 40.2 +/- 3.4 (16 h) and 57.1 +/- 9.7 (20 h) during midexponential growth. A maximum yield of 8.3 X 10(9) colony-forming units was reached at 24 h, when 56% of the initial concentration of glucose had been used. At 40 h, during the stationary phase, 14.95 +/- 3.75 mumol of glucose per ml of medium had been used. At this time, the culture fluids contained 21.86 +/0 mumol of lactate per ml and 3.14 +/- 0.13 mumol of pyruvate per ml.

Virally induced alterations in cellular permeability: a basis of cellular and physiological damage?

Virally induced permeability changes occur when haemolytic paramyxoviruses are added to cells; similar (though not identical) changes take place during infection of cells with viruses from several families (including paramyxoviruses). These changes occur in intact, viable cells, and precede subsequent cytopathic effects, to which they are likely to contribute. There is accumulating evidence to suggest that virally induced permeability changes may also underlie the physiological and clinical consequences of viral infection in certain situations.

The atp operon: nucleotide sequence of the region encoding the alpha-subunit of Escherichia coli ATP-synthase

Part of the atp (or unc) operon encoding the alpha, beta, gamma, delta, and epsilon subunits of Escherichia coli ATP-synthase has been cloned into the plasmid pACYC 184. The DNA coding for the largest of these proteins, the alphas subunit, has been sequenced by cloning into the bacteriophage M13 and sequencing with dideoxy nucleotide chain terminators. It comprises 1539 nucleotides corresponding to a protein of 513 amino acids.

Assmilation of iron by pathogenic Neisseria spp

Iron assimilation by Neisseria meningitidis and Neisseria gonorrhoeae has been shown to be important to their growth and virulence. Iron acquisition in vitro was studied in an agar diffusion assay employing the iron-binding protein conalbumin. The ability of various iron compounds to alter the growth-inhibitory effect of conalbumin was investigated. On an equimolar iron basis, citrate-containing iron compounds were most effective; hemin was slightly less effective; ferrous sulfate and ferrous ammonium sulfate were even less effective; and the ferric compounds, ferric nitrate, ferric chloride, and ferric dextran (Imferon), were least effective. The results suggested that, as with Escherichia coli and certain other bacteria, the Neisseria spp. may utilize a citrate-mediated iron transport system. Microbial siderophores were also tested for their ability to relieve the growth-inhibitory effect of conalbumin. Two phenolate siderophores and Desferal enhanced growth inhibition in the deferrated form, but were inactive in the ferrated form. Several trihydroxamates of the ferrichrome family and coprogen were inactive in either the deferrated or ferrated forms. Of the 12 different siderophores tested, only the dihydroxamates (schizokinen, arthrobactin, and aerobactin) were stimulatory, but then only in the ferrated forms. Apparently, even though those siderophores could be utilized as specific iron transport agents by the Neisseria spp., they could not compete with conalbumin for iron under these assay conditions.

Presence of the cap-binding protein in initiation factor preparations from poliovirus-infected HeLa cells

Crude preparations of initiation factors from mock-infected and poliovirus-infected HeLa cells were analyzed for the presence of proteins which could be cross-linked to the 5' cap group of mRNA. A protein having an apparent molecular weight of 26,000, similar to the cap-binding protein in rabbit reticulocytes described by Sonenberg and Shatkin (Proc. Natl. Acad. Sci. U.S.A. 75:4843-4847, 1978), was found in the ribosomal salt wash from both uninfected and infected cells. Cross-linking of this polypeptide was inhibited by the cap analog m7GMP. In addition, cross-linking of a protein having an approximate molecular weight of 60,000 was similarly inhibited by cap analog. The smaller cap-binding protein fractionated in a 0 to 40% ammonium sulfate precipitate of ribosomal salt wash; the larger protein was found in the 40 to 70% ammonium sulfate fraction. Although the cap-binding proteins were present in both mock-infected and poliovirus-infected ribosomal salt wash, only preparations from uninfected HeLa cells were able to restore translation of capped vesicular stomatitis virus mRNA by extracts prepared from poliovirus-infected cells.

Role of ribonucleic acid synthesis in conjugational transfer of chromosomal and plasmid deoxyribonucleic acids

A strain of Escherichia coli K-12 containing mutations that allow for the experimental control of RNA and DNA syntheses was constructed to investigate the role that RNA synthesis plays in conjugational DNA transfer when DNA replication is inhibited. The mutations possessed by this strain and its donor derivatives include: (i) thyA, which blocks synthesis of dTMP, causing a requirement for thymine; (ii) deoC, which blocks breakdown of deoxyribose 5-phosphate, permitting growth with low levels of thymine; (iii) pyrF, which blocks synthesis of UMP from OMP, imposing a requirement for uridine; (iv) cdd and pyrG, which block the deamination of cytidine to uridine and the synthesis of CTP from UTP, respectively, causing a requirement for cytidine; (v) codA and codB, which block the deamination of cytosine to uracil and cytosine transport, respectively, preventing the substitution of cytosine for cytidine; and (vi) dnaB, which blocks vegetative but not conjugational DNA replication at 42 degrees C. DNA synthesis can be blocked in the donor strains by the addition of excess uridine when exogenous thymine is not present. We found that RNA synthesis can also be blocked by addition of excess uridine when exogenous cytidine is not present. Blocking RNA synthesis prior to mating, under conditions in which DNA synthesis either is or is not inhibited, depresses DNA transfer. However, under conditions in which DNA synthesis is inhibited, the blocking of RNA synthesis immediately after mating has commenced had no effect on continued conjugational transfer of DNA. Thus, RNA synthesis is needed to initiate but not to continue conjugational DNA transfer.

Regulation of methyl beta-galactoside permease activity in pts and crr mutants of Salmonella typhimurium

We have studied the regulation of the synthesis and activity of a major galactose transport system, that of methyl beta-galactoside (MglP), in mutants of Salmonella typhimurium. Two classes of mutation that result in a (partially) defective phosphoenolpyruvate: sugar phosphotransferase system (PTS) interfere with MglP synthesis. pts mutations, which eliminate the general proteins of the PTS Enzyme I and/or HPr and crr mutations, which result in a defective glucose-specific factor IIIGlc of the PTS, lead to a low MglP activity, as measured by methyl beta-galactoside transport. In both ptsH,I, and crr mutants the amount of galactose binding protein, one of the components of MglP, is only 5%-20% of that in wild-type cells, as measured with a specific antibody. We conclude that synthesis of MGlP is inhibited in pts and crr mutants. Once the transport system is synthesized, its transport activity is not sensitive to PTS sugars (i.e., no inducer exclusion occurs). The defect in pts and crr mutants with respect to MGlP synthesis can be relieved in two ways: by externally added cyclic adenosine 3',5-monophosphate (cAMP) or by a mutation in the cAMP binding protein. The conclusion that MglP synthesis is dependent on cAMP is supported by the finding that its synthesis is also defective in mutants that lack adenylate cyclase. pts and crr mutations do not affect growth of S. typhimurium on galactose, however, since the synthesis and activity of the other major galactose transport system, the galactose permease (GalP), is not sensitive to these mutations. If the galactose permease is eliminated by mutation, growth of pts and crr mutants on low concentrations of galactose becomes very slow due to inhibited MglP synthesis. Residual growth observed at high galactose concentrations is the result of yet another transport system with low affinity for galactose.

Three-factor reciprocal cross mapping of a gene that causes expression of feedback-resistant acetohydroxy acid synthase in Escherichia coli K-12

The ilv-662 allele was previously identified as a mutation that caused acetohydroxy acid synthase activity to be resistant to feedback inhibition by valine (Davis et al. 1977). This allele was mapped between thr and leu by cotransduction analysis and labeled ilvJ. This report describes the mapping of ilvJ relative to genes that lie between thr and leu (ara, carA and pdxA) by three factor reciprocal cross analyses. We find that the probable gene order is thr-carA-pdxA-ilvJ-ara-leu. Although the phenotypic properties of ilvJ662 appear to be quite distinct from brnS, a gene reported to involve branched chain amino acid transport (Guardiola et al. 1974), we do not rule out possible allelism because of the uncertainty of the map position of brnS.

Asymmetric repair of bacteriophage T7 heteroduplex DNA

Heteroduplex DNA molecules were prepared in vitro using one strand of DNA carrying a point mutation and one strand of the corresponding wild-type DNA. The heteroduplex DNA was transfected into competent bacteria and the progeny genotypes in the resulting infective centers were determined. From the results we conclude that about 80% of all transfected DNA molecules are repaired before DNA replication starts. This fraction of repaired DNA is independent of the location of the mismatched nucleotide pair. However, mismatch correction occurs preferentially on the H strand of the heteroduplex DNA. The repair does not depend on a known phage coded function but requires the active bacterial genes mutU, mutH, mutS and probably mutL.

Transduction in Streptomyces hygroscopicus mediated by the temperate bacteriophage SH10

The temperate actinophage SH10 mediates generalized transduction in Streptomyces hygroscopicus at low frequency. The efficiency of transduction depends on the average phage input, age of outgrowing spores of the recipient and on the selective marker. The highest EOT was found for the auxotrophic mutants 21(phe-) and 5(try-) (4.2 x 10(-6) and 2.7 x 10(-6), respectively). Transduction of the thermosensitive mutant NG14-216 ts 35 was two orders of magnitude lower (2.5 x 10(-8)). The transductant colonies segregated into stable and unstable clones. Stable transductants were never found to be lysogenic for phage SH10.

Changes in DNA during meiosis in a repair-deficient mutant (rad 52) of yeast

The kinetic patterns of DNA synthesis in wild-type (RAD+) and rad 52 mutants of yeast, which exhibit high levels of synchrony during meiosis, are comparable. However, RAD 52 mutants accumulate single-strand breaks in parental DNA during the DNA synthesis period. Thus, the product of the RAD 52 gene has a role in meiotic DNA metabolism, as well as in the repair of DNA damage during mitotic growth. The observed breaks may be unresolved recombination intermediates.

Role of the recF gene of Escherichia coli K-12 in lambda recombination

When Escherichia coli K12(lambda) lysogens are infected with heteroimmune lambda phage, which are unable to replicate, general recombination between phage and prophage depends on the bacterial recF gene. It has been shown that in E. coli K12 postconjugational recombination, the RecF pathway only works with full efficiency if exonuclease I is absent (Clark 1973). However, results presented in this paper indicate that under conditions in which lambda replication is blocked, the recombination pathway dependent on the recF gene is fully active in producing viral recombinants even, if the phage is Red+, in the presence of exonuclease I. In contrast, removal of lambda exonuclease and beta protein requires elimination of exonuclease I for an efficient RecF pathway. It is concluded that the Red system cooperates with the RecF pathway and that this cooperation involves overcoming the inhibitor effects of exonuclease I. In the absence of lambda exonuclease, beta protein stimulates recF-dependent recombination but does not suffice to prevent the negative effect of exonuclease I. In the presence of beta protein, full efficiency of the RecF pathway can be obtained either via cooperation with lambda exonuclease I or, if the viral exonuclease is defective, via inactivation of exonuclease I. Since activity of lambda exonuclease appears necessary to overcome the inhibitory effects of exonuclease I, it is proposed here that lambda exonuclease diverts material from the RecF pathway in a shunt reaction which allows completion of recF-initiated recombinational intermediates via a mechanism insensitive to exonuclease I. When lambda replication is allowed, the Rec system produces viral recombinants mainly via a recF-independent mechanism. However, a major contribution to the RecF pathway to lambda recombination is observed after removal of the Red system and exonuclease.

Adherence of Streptococcus mutans and Streptococcus sanguis to salivary components bound to glass

Adherence of radiolabeled Streptococcus mutans and Streptococcus sanguis to saliva-treated glass surfaces was studied under conditions which minimized bacteria-glass interactions. Treatment of glass with an alkylsilane solution decreased nonspecific bacterial adherence and enhanced adsorption of radiolabeled salivary components to these surfaces. Addition of Triton X-100 to the bacterial suspensions also reduced nonspecific adherence to siliconized glass, but did not affect adherence to salivary components attached to siliconized glass. Calcium stimulated S. mutans adherence to saliva-free glass, but inhibited adherence to saliva-treated glass. S. sanguis adherence to either saliva-free or saliva-treated glass was inhibited slightly at high calcium ion concentrations. Adherence of streptococci to saliva-treated glass exhibited saturation kinetics, and the numbers of binding sites on the experimental salivary pellicle and the affinity constants for bacteria-saliva attachment were determined. Preincubation of the streptococci with whole saliva decreased their capacity to adhere to saliva-treated glass, but not to saliva-free glass. Bacteria adherent to saliva-treated glass surfaces were readily desorbed by washing with saliva. The addition of homologous antisera, ammonium sulfate-precipitated immunoglobulins, or Fab fragments to the bacterial suspensions inhibited cell adherence to saliva-treated glass.

Isolation and characterization of lambda phages carrying the basic replicon of the resistance plasmid R1

Specialized transducing lambda phages, lambda oriR1, harboring DNA from the resistance plasmid R1drd-19 and its copy mutant pKN103 were isolated. From measurements of CCC-DNA content it is concluded that upon infection the phages can establish themselves as self-replicating plasmids in recA hosts lysogenic for lambda. It is thought that this bypassing of lambda immunity is due to the presence of the R1 origin of replication. The plasmids are sensitive to the incompatibility expressed by plasmid R1. This has been shown mainly by transduction of lambda oriR1 into recipients containing R1 plasmids or plasmid pBR322 carrying the basic replicon. We were able to demonstrate that a copy mutant of plasmid R1 was insensitive to copA+, but sensitive to the concerted action of PstI fragments F1 and F2. This mutant was previously assumed to be of dominant type. Physical mapping of the lambda oriR1 derivatives verified that they carry the basic replicon of plasmid R1. The plasmids are not stably maintained, but are lost in a frequency of 1%-2% per cell generation, which is consistent with their lack of the R1par region.

Cloning and characterization of the Escherichia coli gene coding for alkaline phosphatase

The Escherichia coli structural gene for alkaline phosphatase, phoA, and a promoter-like mutant of phoA, called pho-1003(Bin) phoA+, were cloned by using plasmid vectors. Initially, these genes were cloned on deoxyribonucleic acid fragments of 28.9 kilobases (kb). Subsequently, they were subcloned on fragments and 4.8 and then 2.7 kilobases. A restriction map was developed, and phoA was localized to a 1.7-kb region. The promoter end of the gene was inferred by its proximity to another gene cloned on the same deoxyribonucleic acid fragment, proC. The stability of the largest plasmid (33.3 kb) was found to be recA dependent, although the subcloned plasmids were stable in a recA+ strain. Synthesis of alkaline phosphatase directed by the phoA+ and pho-1003(Bin) phoA+ plasmids in a phoA deletion strain was assayed under repressing and derepressing levels of phosphate. These data were compared with the copy numbers of the plasmids. It was found that synthesis of alkaline phosphatase was tightly regulated, even under derepressing conditions: a copy number of 17 enabled cells to synthesize only about twofold more enzyme than did cells with 1 chromosomal copy of phoA+. Enzyme levels were also compared for cells containing pho-1003(Bin) phoA+ and phoA+.

Effect of siderophores on virulence of Neisseria gonorrhoeae

The virulence of Neisseria gonorrhoeae for chicken embryos can be modified in a predictable manner by the addition of microbial siderophores to the inoculum. "Meningobactin" and "gonobactin," siderophores isolated from iron-limited cultures of meningococci and gonococci, respectively, enhance the virulence of the relatively avirulent colony type 3 (T3) organisms, but have essentially no effect on the virulence of T1 organisms. Both of these compounds were found previously to stimulate in vitro growth of the pathogenic Neisseria spp. under conditions made iron limiting by the addition of conalbumin, the transferrin counterpart of chickens. Similarly, ferrated schizokinen and arthrobactin, both dihydroxamate siderophores which stimulated growth in iron-limited conditions in vitro, also enhanced virulence of T3 organisms, whereas desferrioxamine B mesylate (Desferal), a trihydroxamate previously shown to be inhibitory in vitro, decreased the virulence of the T1 colony form. This was due to the iron-binding function of the molecule, as the iron-saturated form, ferrioxamine B mesylate, did not affect virulence. An additional trihydroxamate siderophore, ferrichrome A, which was inactive on Neisseria spp. in either the deferri- or ferrated forms in vitro, likewise did not affect virulence in the chicken embryo model. The neisserial siderophores were more effective than the other microbial siderophores in enhancing virulence of T3 gonococci. The results add to the evidence that the ability to acquire iron is an important determinant of virulence.

Gene rfaH, which affects lipopolysaccharide core structure in Salmonella typhimurium, is required also for expression of F-factor functions

Mutations in gene rfaH of Salmonella typhimurium at 84 units on the linkage map make lipopolysaccharide of chemotypes Ra, Rb2, Rb3, and Rc (A. A. Lindberg and C. G. Hellerqvist, J. Gen. Microbiol, 116:25--32, 1980). F-factor expression in RfaH- strains was reduced in the following properties when compared with RfaH+ strains: transfer of Flac, number of phage f2 infective centers, lysis by and propagation of phages f2 and M13, proportion of cells with visible F-pili, and formation of mating aggregates with F- cells. Inhibition of multiplication of Br60, a female-specific phage, was not reduced in RfaH- Flac strains. Plasmid transfer from RfaH- strains was reduced for Inc groups FI, FII, and T, unaffected for Inc groups beta, I alpha, L, N, P, and W. and increased for Inc group M when compared with plasmid transfer from RfaH+ strains. Reduced F-factor function in RfaH- strains was not due to defective lipopolysaccharide since strains with mutations in other rfa genes were unaffected in plasmid transfer. Gene rfaH appears to be homologous with gene sfrB in Escherichia coli K-12, which maps at the same location, influences F-factor function, and affects synthesis of lipopolysaccharide. The gene product of sfrB has been proposed to be a transcription antiterminator.