Stepwise degradation of membrane sphingomyelin by corynebacterial phospholipases

The mechanism of in vitro synergistic lysis of sheep erythrocytes by Corynebacterium ovis and Corynebacterium equi was investigated. Hemolysis required (i) the action of phospholipase D from C. ovis, (ii) the action of an extracellular protein of C. equi, and (iii) Mg2+. Maximum lysis required imposition on the system of a fourth condition (step iv), such as chilling. Steps i, ii, and iv occur sequentially and in that order. Mg2+ functions in steps i and ii. The extracellular protein C. equi was purified to homogeneity and found to be a phospholipase C capable of hydrolyzing ceramide phosphate, phosphatidic acid, and all of the isolated major phospholipids of mammalian erythrocyte membranes. The principal features of the synergistic hemolytic system could be reproduced in experiments involving liposomes containing either sphingomyelin or ceramide phosphate and trapped [14C]glucose. We inferred that sphingomyelin of sheep erythrocytes is first converted to ceramide phosphate by C. ovis phospholipase D. On the basis of results with liposomes, we propose that the ceramide phosphate is then converted to ceramide by C. equi phospholipase C. We believe that the resulting in situ ceramide then undergoes dislocation by chilling and perhaps also by virtue of an affinity between ceramide and C. equi phospholipase C. The dislocation of ceramide presumably disorganizes the lipid bilayer sufficiently to result in cell lysis.

Transformation of Rhodopseudomonas sphaeroides with deoxyribonucleic acid isolated from bacteriophage R phi 6P

The transformation of the photosynthetic bacterium Rhodopseudomonas sphaeroides with the circular genome of the penicillinase-encoding, temperate bacteriophage R phi 6P was demonstrated. The transformation was dependent on the infection of the recipient by another, apparently closely related, temperature bacteriophage, R phi 9. Optimum transformation occurred in the recipient cells already lysogenic for R phi 9 when superinfected with that bacteriophage at multiplicities of infection between 1 and 10 R phi 9 particles per recipient cell.

Antibacterial effect of scandium and indium complexes of enterochelin on Klebsiella pneumoniae

A number of studies point to the conclusion that enterochelin, the iron chelator produced by a number of pathogenic enterobacteria, may be an essential metabolite for bacterial multiplication within the host. The compound removes iron from complexes with the host iron-binding proteins transferrin and lactoferrin, and the resulting ferric enterochelin is assimilated by the bacterial cell. It was reasoned that complexes of enterochelin with ions other than Fe3+ might act as antimetabolites and inhibit bacterial multiplication by interfering with the assimilation of ferric enterochelin. Enterochelin forms complexes with a number of group III and transition metal ions. The complex containing scandium exerts a bacteriostatic effect on Klebsiella pneumoniae in serum, whereas the indium complex induces a large increase in the generation time. The Fe3+ complexes of other microbial iron-transporting compounds are capable of reversing the bacteriostatic effect of the Sc3+ complex of enterochelin, suggesting that the compound acts solely by interfering with the enterochelin system of iron transport. Preliminary experiments show that the Sc3+ complex probably acts as a competitive inhibitor of ferric enterochelin. The Sc3+ complex of enterochelin exerts a therapeutic effect on intraperitoneal K. pneumoniae infections in mice similar to that obtained with kanamycin sulfate.

The nucleotide sequence of glycine tRNA from Mycoplasma mycoides sp. capri

Using in vitro labelling techniques, a tRNAGly from M. mycoides sp. capri PG3 has been shown to have the sequence : pGCAGGUGs4UAGUUUAAUGGCAGAACUUC AGCCUUCCm6AAGCUGAUUGUGAGGGU psi CGAUUCCCUUCACCUGCUCCAOH. The anticodon is UCC and no other tRNAGly has been detected in the crude tRNA isolated from this organism. As is the case with some mitochondrial tRNAs, where the genome size of the organelle is small, it is possible that this tRNA is used to read all four glycine codons GGN.

Bacterial origin of luminescence in marine animals

Bacterial luciferase activity was detected in light organ extracts of squids, fishes, and pyrosomes, suggesting that these systems are derived from bacteria-animal symbioses. In none of these cases was it possible to culture luminouis bacteria. Analyses of the decay kinetics show that the luciferases from the squid, ceratioid, and pyrosome light organs are all similar to bacterial luciferases from the genus Photobacterium, while those from the anomalopid light organs are different.

Bactericidal activity of human lactoferrin: sensitivity of a variety of microorganisms

Lactoferrin is an iron-binding protein that has been detected in secretions that bathe human mucosal tissues. Previous studies have shown that, when this protein is in the iron-free state, it is capable of a direct bactericidal effect on Streptococcus mutans and Vibrio cholerae. The present study demonstrates variable susceptibilities for a variety of different microorganisms. The list of susceptible organisms includes gram-positive and gram-negative microbes, rods and cocci, facultative anaerobes, and aerotolerant anaerobes. Similar morphological and physiological types are represented among the lalctoferrin-resistant bacteria. S. mutans was more resistant to lactoferrin when grown on a sucrose-contaning medium than when it was grown on brain heart infusion broth without added scurose. When a lactoferrin-sensitive, avirulent strain of Streptococcus pneumoniae was passed through mice, the resultant virulent culture became lactoferrin resistant. Since organisms of the same species and even of the same strain (S. pneumoniae) can differ in susceptibility to lactoferrin, it appears that accessibility to the lactoferrin target site may account for differences in susceptibility. It appears that there may be a relation between virulence and resistance to lactoferrin.

Metabolism of formate in Methanobacterium formicicum

Methanobacterium formicicum strain JF-1 was cultured with formate as the sole energy source in a pH-stat fermentor. Growth was exponential, and both methane production and formate consumption were linear functions of the growth rate. Hydrogen was produced in only trace amounts, and the dissolved H(2) concentration of the culture medium was below 1 muM. The effect of temperature or pH on the rate of methane formation was studied with a single fermentor culture in mid-log phase that was grown with formate under standard conditions at 37 degrees C and pH 7.6. Methane formation from formate occurred over the pH range from 6.5 to 8.6, with a maximum at pH 8.0. The maximum temperature of methanogenesis was 56 degrees C. H(2) production increased at higher temperatures. Hydrogen and formate were consumed throughout growth when both were present in saturating concentrations. The molar growth yields were 1.2 +/- 0.06 g (dry weight) per mol of formate and 4.8 +/- 0.24 g (dry weight) per mol of methane. Characteristics were compared for cultures grown with either formate or H(2)-CO(2) as the sole energy source at 37 degrees C and pH 7.6; the molar growth yield for methane of formate cultures was 4.8 g (dry weight) per mol, and that of H(2)-CO(2) cultures was 3.5 g (dry weight) per mol. Both formate and H(2)-CO(2) cultures had low efficiencies of electron transport phosphorylation; formate-cultured cells had greater specific activities of coenzyme F(420) than did H(2)-CO(2)-grown cultures. Hydrogenase, formate dehydrogenase, chromophoric factor F(342), and low levels of formyltetrahydrofolate synthetase were present in cells cultured with either substrate. Methyl viologen-dependent formate dehydrogenase was found in the soluble fraction from broken cells.

Isolation and characterization of Pseudomonas aeruginosa PAO mutant that produces altered elastase

Pseudomonas aeruginosa PAO mutants defective in elastase were isolated by plate assays of nitrosoguanidine-mutagenized clones. A total of 75 elastase mutants were isolated from 43,000 mutagenized clones. One mutant (PAO-E64) was apparently identical to the parental strain except for its deficiency in elastase activity. This mutant produced an enzyme which was antigenically indistinguishable from parental elastase. Furthermore, equal levels of elastase antigen were produced by this mutant and its parental strain. The mutant elastase, however, had greatly reduced enzymatic activity. Mutant PAO-E64 is presumed to have a mutation in the structural gene for elastase. We have designated the genotype of the mutation in PAO-E64 as lasA1.

Inhibition and activation of mannan synthesis in Saccharomyces cerevisiae spheroplast lysates

Mannan synthetase activity in spheroplast lysates prepared from Saccharomyces cerevisiae was measured by following the incorporation of [14C]mannose from guanosine 5'-diphosphate-[14C]mannose into material precipitable with cold 0.3 M perchloric acid. When enzyme activity was assayed at high concentrations of spheroplast lysate protein (10 mg/ml) in the presence of 7.5 mM MnCl2, a severe inhibition was observed. This inhibition could be relieved by preincubation of the spheroplast lysate at 4 degrees C for 16 to 32 h before assay, by repeated freezing and thawing of the spheroplast lysate, or by the omission of MnCl2 from assay mixtures. The addition of ethylenediaminetetraacetic acid or monovalent cations removed inhibition in the presence of Mn2+. No similar inhibition was observed when a washed membrane fraction was substituted for spheroplast lysate as the source of mannan synthetase. The supernatant fluid obtained by centrifuging spheroplast lysate at 100,000 x g, when added to assay mixtures containing either spheroplast lysate preincubated at 4 degrees C or washed membrane fraction, also caused inhibition of enzyme activity. This inhibition required 7.5 mM MnCl2 and was destroyed by heating the supernatant fluid at 60 degrees C for 10 min, or by trypsin treatment at 30 degrees C. These results indicate the existence of a protein inhibitor of mannan synthesis whose inhibitory activity in spheroplast lysates may be modulated by preincubation at low temperature or by varying the available Mn2+ concentration.

Morphology and ultrastructure of helical and nonhelical strains of Spiroplasma citri

Cells of the nonhelical strain of Spiroplasma citri underwent changes of morphology comparable to those which occurred in the normal helical strain. Cells of the nonhelical strain had the same ultrastructural features as helical cells and released long flexible fibrils similar to those seen in other spiroplasmas. Nonhelical organisms showed an increased tendency to aggregate, forming cell clusters of an unusual annular form. The cytoplasmic membrane of the nonhelical strain lacked a single protein present in all helical strains. Loss of helicity associated with the senescence of spiroplasma cells was not accompanied by the disappearance of this protein. Differences in colony morphology were shown to be a consequence of motility, and a technique was developed which facilitated the identification of nonmotile organisms.

Alcohol-induced changes in the phospholipid molecular species of Escherichia coli

In Escherichia coli, the additon of ethanol resulted in the synthesis of an increased proportion of phospholipids containing two unsaturated fatty acids. The addition of hexanol resulted in the opposite effect, an increase in the proportion of monounsaturated molecular species. The alcohol-induced changes were quantitatively similar to those caused by changing growth temperature. These results suggest that both adaptation to temperature and alcohol-induced changes in lipid composition share some common regulatory features.

Pyridine nucleotide cycle of Salmonella typhimurium: in vivo recycling of nicotinamide adenine dinucleotide

The relative contribution of the two known pyridine nucleotide cycles of Salmonella typhimurium towards the intracellular recycling of nicotinamide adenine dinucleotide was determined. The results indicate that intracellular nicotinamide adenine dinucleotide is recycled by both the four-membered pyridine nucleotide cycle (PNC IV) and the six-membered pyridine nucleotide cycle (PNC VI) with a relative contribution of 60 to 69% and 31 to 40%, respectively. These studies also revealed a nicotinic acid mononucleotide-degradative activity which converts nicotinic acid mononucleotide to nicotinic acid. This represents the first demonstration of a functional PNC IV pathway in S. typhimurium.

Comparison of outer membrane porin proteins produced by Escherichia coli and Salmonella typhimurium

The OmpC, OmpF, and Lc (NmpC) porin proteins of Escherichia coli K-12 have been shown to be similar to the OmpC (36K), OmpF (35K) and OmpD (34K) porin proteins of Salmnella typhimurium LT2 in terms of function, regulation of expression, and, in the case of OmpC and OmpF proteins, equivalence of the genetic loci determining their production. However, the corresponding pairs of proteins from these two species showed only limited similarity in peptide maps and no similarity in terms of migration on polyacrylamide gels.

Purification and preliminary characterization of Spiroplasma fibrils

Fibrils 3.5 nm in diameter were released from the honeybee spiroplasma (BC3) by treatment with detergents and then purified by isopycnic centrifugation. Purified fibrils were flexuous, of indeterminate length, and had an axial repeat of 8.5 nm. The fibrils were associated in pairs, but in 1 M salt formed aggregates with a marked striated appearance. Pronase completely degraded the fibrils, but trypsin had little effect. The fibrils were composed of a single protein of molecular weight 55,000 which represented about 1% of the total cell protein. A protein of molecular weight 26,000 appeared to be associated with the fibrils. The significance of this in relation to membrane attachment and the possible role of fibrils in maintenance of cell shape and in motility are discussed.

Phaseolotoxin transport in Escherichia coli and Salmonella typhimurium via the oligopeptide permease

Phaseolotoxin [(N delta-phosphosulfamyl)ornithylalanylhomoarginine], a phytotoxic tripeptide produced by Pseudomonas syringae pv. phaseolicola that inhibits ornithine carbamoyltransferase, is transported into Escherichia coli and Salmonella typhimurium via the oligopeptide transport system (Opp). Mutants defective in oligopeptide permease (Opp-) were resistant to phaseolotoxin. Spontaneous phaseolotoxin-resistant mutants (Toxr) lacked the Opp function as evidenced by their cross-resistance to triornithine and failure to utilize glycylhistidylglycine as a source of histidine. Growth inhibition by phaseolotoxin was prevented by peptides known to be transported via the Opp system and by treatment of the toxin with L-aminopeptidase. In both E. coli and S. typhimurium, Toxr mutations were cotransducible with trp, suggesting that the opp locus occupies similar positions in genetic maps of these bacteria.

Isolation of Methanobacterium bryantii from a Deep Aquifer by Using a Novel Broth-Antibiotic Disk Method

Methanobacterium bryantii was isolated from a mixed-culture enrichment of a water sample from a deep aquifer by using a complex growth medium supplemented with antibiotic susceptibility disks to inhibit the growth of non-methanogenic bacteria.

Glutamine- and N-acetylglutamate-dependent carbamoyl phosphate synthetase in elasmobranchs

High levels of glutamine- and N-acetyl-L-glutamate-dependent carbamoyl phosphate synthetase activity are present in liver extracts of marine species of fish that retain high levels of urea in their tissues for the purpose of osmoregulation. The function of the synthetase in these species appears to be related to urea synthesis.

Glucan-induced modification of murine viral hepatitis

Glucan, a macrophage stimulant, was evaluated for its ability to alter survival and phagocytic dysfunction in mice challenged with mouse hepatitis virus strain MHV-A59. Administration of glucan before the mice were challenged with the virus significantly prolonged median survival time but did not modify overall mortality compared with control mice given dextrose. Maximal effectiveness was achieved when glucan was administered both before and after the viral challenge. In contrast to the marked hepatic parenchymal cell necrosis observed in the control mice, glucan-treated mice exhibited reduced pathology. Intraperitoneal administration of MHV-A59 resulted in a significant depression of phagocytic activity compared with controls that were not exposed to the virus. The enhancement in phagocytic function in glucan-treated control mice was unaltered in virus-challenged, glucan-treated mice. Thus glucan is capable of increasing survival, inhibiting hepatic necrosis, and maintaining an activated state of phagocytic activity in mice challenged with MHV-A59. Macrophage stimulants may have a significant role in the modification of virally induced hepatic lesions.

Phosphatidylglycerophosphate synthease and phosphatidylserine synthase activites in Clostridium perfringens

Cytidine 5'-diphospho (CDP)-1,2-diacyl-sn-glycerol (CDPdiacylglycerol):sn-glycerol-3-phosphate phosphatidyltransferase (EC 2.7.8.5, phosphatidylglycero-P synthase) and CDPdiacylglycerol:L-serine O-phosphatidyltransferase (EC 2.7.8.8, phosphatidylserine synthase) activities were identified in the cell envelope fraction of the gram-positive anaerobe Clostridium perfringens. The association of phosphatidylglycero-P synthase and phosphatidylserine synthase with the cell envelope fraction of cell-free extracts was demonstrated by sucrose density gradient centrifugation, by both activities sedimenting with the 100,000 x g pellet and solubilization of both activities from the 100,000 x g pellet with Triton X-100. The pH optimum for both enzyme activities was 8.0 with tris(hydroxy-methyl)aminomethane-hydrochloride buffer. Phosphatidylglycero-P synthase activity was dependent on magnesium ions (100 mM). Phosphatidylserine synthase activity was dependent on manganese (0.1 mM) or magnesium ions (50 mM). Both enzyme activities were dependent on the addition of the nonionic detergent Triton X-100. Maximum phosphatidylglycero-P synthase and phosphatidylserine synthase activities were obtained when the molar ratio of Triton X-100 to CDP-diacylglycerol was 50:1 and 12:1, respectively. The Km for sn-glycero-3-P in the phosphatidylglycero-P synthase reaction was 0.1 mM. The Km for L-serine in the phosphatidylserine synthase reaction was 0.15 mM. Both enzyme activities were 100% stable for at least 20 min at 60 degrees C.

Macrophage dependence of polyriboinosinic acid-polyribocytidylic acid-induced resistance to herpes simplex virus infection in mice

The relative contributions of macrophages and lymphocytes to the induction of resistance to primary herpes simplex virus type 1 (HSV-1) infection by polyriboinosinic-polyribocytidylic acid complex [poly (I:C)] were investigated in C58 mice. The induction of resistance was found to be strongly dependent on macrophages compared to lymphocytes. Macrophage-deficient (silica-treated) mice produced less interferon and were not as responsive to prophylactic treatment of HSV-1 infections with poly (I:C) as were either normal, lymphocyte-deficient (cyclophosphamide-treated), or T-lymphocyte-deficient (anti-thymocyte serum-treated, adult-thymectomized) mice. Silica and cyclophosphamide treatments reduced the therapeutic activity of poly (I:C), whereas T-cell depletion did not have a significant effect. Similarly, the protection of mice with exogenous interferon was markedly reduced in silica-treated mice and moderately reduced in cyclophosphamide-treated mice, but unaffected in T-cell-deficient mice. Furthermore, suppression of HSV-1 plaque formation was obtained by cocultivation of infected mouse fibroblast monolayers with peritoneal (macrophage-rich) cells, but not with splenic (lymphocyte-rich) cells, from poly (I:C)-treated mice. Peritoneal cells did not protect heterologous (human) fibroblasts, suggesting that the protection of mouse embryo fibroblasts is mediated by interferon. Collectively, the data indicate that macrophages are required for the production of poly (I:C)-induced interferon and that macrophages and perhaps B-lymphocytes are important for mediating the protection against HSV-1 infection after interferon has been produced.

Salmonella typhimurium LT2 mutation affecting the deletion of resistance determinants on R plasmids

Plasmid Rms312, specifying resistance to tetracycline (Tc), chloramphenicol (Cm), streptomycin (Sm), sulfonamide (Su), and mercury chloride (Mer), deletes both Tc and Cm Sm Su Mer determinants at a high frequency in Salmonella typhimurium LT2. S. typhimurium mutants that were stable carriers of Rms312 were isolated by alternate culture of R-bearing cells in a medium containing either tetracycline or chloramphenicol. In one of these mutants the deletion frequency of drug resistance determinants was decreased by about 100-fold not only Rms312, but also in R100, R1, and R6-5. This mutation caused a slight reduction of ultraviolet resistance but did not affect generalized genetic recombination, indicating that the mutation is different from recA. The mutation, designated dor (deletion of r-determinants), was mapped to a position near 57 units in the new linkage map of S. typhimurijm LT2 (K. E. Sanderson and P. E. Hartman, Microbiol. Rev. 42:471-519, 1978). The dor mutation had no effect on IS1-mediated illegitimate deletion, indicating that the dor mutation is different from the del mutation described by Nevers and Saedler (P. Nevers and H. Saedler, Mol. Gen. Genet. 160:209-214, 1978).

Differential carbohydrate media and anaerobic replica plating techniques in delineating carbohydrate-utilizing subgroups in rumen bacterial populations

A basal (BC) medium devoid of added carbohydrates, a complete (CC) medium containing nine carbohydrates were developed for enumerating rumen bacteria. The colony counts on the BC medium were 85 to 100% of those obtained on the CC medium. These colonies were pinpoint size (less than or equal to mm in diameter) but increased in size (2 to 5 mm in diameter) when carbohydrates were subsequently added. With the CC medium or other media tested, the colony counts were 20 to 50% higher on plates than on roll tubes and were about 35% of the direct cell counts. The lower colony counts on roll tubes were shown to result primarily from the loss of viability due to heat stress. The DC media were found by plating techniques to be suitable for differentiating mixed rumen bacterial populations into subgroups based upon carbohydrate utilization as shown by differences in subgroup profiles found within solid and liquid fractions of rumen contents, within rumen contents from animals fed high-forage and high-grain diets, and by correct colony formations by pure cultures of rumen bacteria on appropriate DC media. With simple modifications and use of an anaerobic glove box, replica plating methods and the CC and DC media were found to be a suitable means of rapidly determining the range of utilizable carbohydrate energy sources of rumen bacteria.

New Method of Producing Protoplasts of Aureobasidium pullulans

A rapid and relatively inexpensive method for producing protoplasts of the black yeast Aureobasidium pullulans is described. The procedure involves anaerobic incubation with the lytic preparation Driselase.

Regulation of membrane phospholipid syntheesis in Escherichia coli during temperature up-shift

The synthesis of membrane phospholipids and that of stable ribonucleic acid were inhibited during temperature up-shift of both rel+ and relA strains of Escherichia coli. The kinetics of the inhibition of the synthesis of both molecules were correlated with the kinetics of guanosine 5'-diphosphate-3'-diphosphate synthesis. Metabolic down-shift experiments gave similar results.

Isolation of enterochelin from the peritoneal washings of guinea pigs lethally infected with Escherichia coli

Escherichia coli secretes enterochelin while infecting normal guinea pigs. Since production of enterochelin is a well-characterized response to an iron-restricted environment, this work establishes that host iron-binding proteins do indeed influence the metabolism of the invading organism.

Polyethylene glycol-assisted transfection of Streptomyces protoplasts

In the presence of polyethylene glycol (concentration optimum 20%), protoplasts of appropriate Streptomyces strains could be transfected by deoxyribonucleic acid (DNA) of five temperate phages (phi C31, VP5, R4, phi 448, and S14) belonging to four different immunity groups. Quantitation of transfection was made possible by plating the transfection mixture with excess uninfected protoplasts in soft agar overlays on protoplast regeneration medium so that plaques were easily detected. Optimum frequencies of transfection in the ranges of 10(-6)/DNA molecule and 10(-5)/viable protoplast were invariably obtained. It appeared that single DNA molecules initiated transfection events, and that the conformation of the DNA (i.e., circular or linear) was not important. Inhibition of transfection by ethylenediaminetetraacetic acid suggested that divalent cations were also observed. A minor subpopulation of protoplasts appeared to be particularly sensitive to transfection (i.e., "competent") in some DNA-host combinations. In such cases the size of this subpopulation was the major limiting factor in obtaining high transfection frequencies. The same protoplast

Methylated bases in mycoplasmal DNA

The DNAs of four Mycoplasma and one Acholeplasma species were found to contain methylated bases. All of the five species contained 6-methyladenine (m6Ade), the methylated base characteristic of prokaryotic DNA. The extent of methylation of adenine residues in the mycoplasmal DNA ranged from 0.2% in Mycoplasma capricolum to about 2% in Mycoplasma arginini and Mycoplasma hyorhinis with intermediate methylation values for Mycoplasma orale and Acholeplasma laidlawii DNAs. About 5.8% of the cytosine residues in M. hyorhinis DNA were methylated also. Analysis of cell culture DNA for the presence of m6Ade as a means for detection of contamination by mycoplasmas, and the phylogenetic implications of the finding of methylated bases in mycoplasmal DNAs are discussed.

Kinetics of nuclease digestion of Physarum polycephalum nuclei at different stages of the cell cycle

The kinetics of nuclease digestion of Physarum polycephalum nuclei by staphylococcal nuclease and DNase I has been studied at different stages of the cell cycle. Significant differences in the digestion behaviour of nuclei from metaphase and interphase have been detected with DNase I but not with staphylococcal nuclease. Furthermore the structure of newly replicated DNA in S phase differs from the bulk in that it is more easily degraded to acid-soluble products by either staphylococcal nuclease or by DNAase I. At least four types of chromatin structure can be distinguished by our digestion kinetics experiments.

Identification and mapping of a second proline permease Salmonella typhimurium

In this paper we demonstrate the existence of a second proline permease, gene proP, in Salmonella typhimurium. Uptake assays demonstrate that this second proline permease has 5 to 10% the uptake rate of the putP permease, the cell's major proline permease, when assayed at 20 microM proline. Genetic mapping by Hfr and P22-mediated genetic crosses placed the second proline permease gene at 92 min on the S. typhimurium genetic map, near the genes for melibiose utilization. F'-mediated complementation tests indicated that Escherichia coli also has the proP gene.

Biochemistry and regulation of a second L-proline transport system in Salmonella typhimurium

This paper reports some biochemical characteristics of a second L-proline transport system in Salmonella typhimurium. In the accompanying paper, R. Menzel and J. Roth (J. Bacteriol. 141:1064--1070, 1980) have identified this system by showing that it is inactivated by mutations at the locus proP. We have found that it is an active transport system with an apparent Km for L-proline of 3 x 10(-4) M and a strict specificity for L-proline and some of its analogs. Unlike the L-proline transport system encoded in putP, this second system is induced by amino acid limitation.

Relationship between R and FP plasmids in Pseudomonas aeruginosa

The plasmid FP110 possessing chromosome mobilizing ability for Pseudomonas aeruginosa but carrying no determinants for antibiotic resistance, is found to be related by incompatibility, entry exclusion, and other criteria to the independently isolated R plasmids R18-1 and R56Be which carry resistance determinants for carbenicillin. The frequency of FP plasmid appearance in clinical isolates of P. aeruginosa suggests the possibility that they may be a source of R plasmids in this bacterium.

Beta-alanine synthesis in Escherichia coli

The enzyme, aspartate 1-decarboxylase (L-aspartate 1-carboxy-lyase; EC 4.1.1.15), that catalyzes the reaction aspartate leads to beta-alanine + CO2 was found in extracts of Escherichia coli. panD mutants of E. coli are defective in beta-alanine biosynthesis and lack aspartate 1-decarboxylase. Therefore, the enzyme functions in the biosynthesis of the beta-alanine moiety of pantothenate. The genetic lesion in these mutants is closely linked to the other pantothenate (pan) loci of E. coli K-12.

Is cyclic guanosine 3',5'-monophosphate a cell cycle regulator?

Transient increases in the intracellular level of cyclic guanosine 3',5'-monophosphate have been observed at a periodicity of one generation time in two spoT strains of Escherichia coli and in Bacillus licheniformis.

Replication of herpesvirus DNA. V. Maturation of concatemeric DNA of pseudorabies virus to genome length is related to capsid formation

The maturation of pseudorabies virus DNA from the replicative concatemeric form to molecules of genome length was examined using nine DNA+ temperature-sensitive mutants of pseudorabies virus, each belonging to a different complementation group. At the nonpermissive temperature, cells infected with each of the mutants synthesized concatemeric DNA. Cleavage of the concatemeric DNA to genome-length viral DNA was defective in all the DNA+ ts mutants tested, indicating that several viral gene products are involved in the DNA maturation process. In none of the ts mutant-infected cells were capsids with electron-dense cores (containing DNA) formed. Empty capsids with electron-translucent cores were, however, formed in cells infected with six of the nine temperature-sensitive mutants; in cells infected with three of the mutants, no capsid assembly occurred. Because these three mutants are deficient both in maturation of DNA and in the assembly of viral capsids, we conclude that maturation of viral DNA is dependent upon the assembly of capsids. In cells infected with two of the mutants (tsN and tsIE13), normal maturation of viral DNA occurred after shiftdown of the cells to the permissive temperature in the presence of cycloheximide, indicating that the temperature-sensitive proteins involved in DNA maturation became functional after shiftdown. Furthermore, because cycloheximide reduces maturation of DNA in wild-type-infected cells but not in cells infected with these two mutants, we conclude that a protein(s) necessary for the maturation of concatemeric DNA, which is present in limiting amounts during the normal course of infection, accumulated in the mutant-infected cells at the nonpermissive temperature. Concomitant with cleavage of concatemeric DNA, full capsids with electron-dense cores appeared after shiftdown of tsN-infected cells to the permissive temperature, indicating that there may be a correlation between maturation of DNA and formation of full capsids. The number of empty and full capsids (containing electron-dense cores) present in tsN-infected cells incubated at the nonpermissive temperature, as well as after shiftdown to the permissive temperature in the presence of cycloheximide, was determined by electron microscopy and by sedimentation analysis in sucrose gradients. After shiftdown to the permissive temperature in the presence of cycloheximide, the number of empty capsids present in tsN-infected cells decreased with a concomitant accumulation of full capsids, indicating that empty capsids are precursors to full capsids.

Composition of cardiolipin molecular species in Escherichia coli

The composition of the molecular species of acidic phospholipids in Escherichia coli B during the late exponential growth phase at 37 degrees C was determined. Two phosphatidyl groups of cardiolipin, the 3-(3-sn-phosphatidyl) and 1-(3-sn-phosphatidyl) moieties of cardiolipin, were isolated by limited hydrolysis with phospholipase C. No significant difference in the composition of the molecular species was found between the 3-(3-sn-phosphatidyl) and 1-(3-sn-phosphatidyl) moieties. On the other hand, the composition of the molecular species of phosphatidylglycerol was different from that of cardiolipin. Phosphatidylglycerol contained more of the 1-palmitoyl 2-cis-9,10-methylenehexadecanoyl and 1-palmitoyl 2-cis-11,12-methyleneoctadecanoyl species than did cardiolipin. The difference in the composition of the molecular species between cardiolipin and phosphatidylglycerol may depend on the difference in the turnover rates of both phospholipids.

DNA and histone synthesis in mouse cells which exhibit temperature-sensitive DNA synthesis

It is demonstrated that temperature inactivation of histone synthesis is coupled to inhibition of DNA replication in ts AlS9 and ts Cl mouse L-cells, which are temperature-sensitive (ts) in an S-phase function. In contrast, uncoupling of histone and DNA synthesis occurs in BalB/C-3T3 ts 2 cells which are ts in a function of the pre-DNA-synthetic phase. Termination of histone synthesis in ts AlS9 and ts Cl cells is 16--18 h after onset of temperature inactivation of DNA replication and appears to be associated with general cessation of chromatin replication triggered by the earlier event. Synthesis of histone and other chromosomal proteins proceeds in ts 2 cells under conditions in which DNA synthesis undergoes temperature inactivation. It is suggested that the terminal phenotype of coupled temperature inactivation of DNA and histone synthesis may be diagnostic of cells ts in an S-phase function and may therefore be a useful secondary screen in designation of cell cycle mutants.