bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and characterization of D-serine deaminase constitutive mutants by utilization of D-serine as sole carbon or nitrogen source
Authors: Bloom F R , McFall E
Published: January 2020

Mutants constitutive for D-serine deaminase (Dsdase) synthesis were isolated by utilizing D-serine as sole nitrogen or carbon source in the chemostat. This method generated only regulatory constitutive (dsdC) mutants. The altered dsdC gene product in these strains is apparently able to bind D-serine more efficiently than the wild-type dsdC+ gene product--a selective advantage. Constitutive synthesis of Dsdase in all of these dsdC mutants is extremely sensitive to catabolite repression, and catabolite repression is reversed by the addition of D-serine. Of the 15 mutants generated by this method, none are suppressible by supD, supE, or supF. Mutations to a low level of constitutivity (maximal specific activity of 9) occur much more frequently than mutations to a high level (maximal specific activity of 79). High level constitutive synthesis of Dsdase results from the synthesis of an altered dsdC gene product--not from loss of ability to form the dsdC product. Dsdase synthesis is not regulated by the nitrogen supply in the medium, as nitrogen starvation does not result in the derepression of Dsdase synthesis.
Stability of Escherichia coli polysomes at high hydrostatic pressure
Authors: Pope D H , Connors N T , Landau J V
Published: January 2020

The stability of Escherichia coli polysomes at increased hydrostatic pressure was investigated in actively growing cells, in which the initiation of transcription was blocked by rifampin. In these cells, [3-H]uridine incorporation into messenger ribonucleic acid and the subsequent degradation of the message (and therefore of polysomes) by ribonuclease could be observed. Evidence is presented that the activity of the RNases is unaffected by a pressure of 680 atm, that protein synthesis is completely inhibited at 680 atm but immediately resumes at the 1 atm rate on release of pressure, and that no degradation of messenger ribonucleic acid in polysomes occurs at 680 atm. The effects of pressure; puromycin, and chloramphenicol on polysomal degradation are discussed. These results indicate that, contrary to some previous reports, polysomes are probably stabilized by high pressures. Therefore, we consider that polysomal instability is not a factor in the inhibition of protein synthesis by high pressures.
Pathways for the degradation of m-cresol and p-cresol by Pseudomonas putida
Authors: Hopper D J , Taylor D G
Published: January 2020

A comparison of the oxidation rates of various compounds by whole cells of Pseudomonas putida 3, 5 indicated that m-cresol is metabolized by oxidation to 3-hydroxybenzoate followed by hydroxylation to gentisate, the ring-fission substrate, when grown with 3, 5-xylenol. However, when m-cresol was the growth substrate, similar experiments suggested a different pathway involving a methyl-substituted catechol, and ring-fission by meta cleavage. Assays of ring-fission enzymes in cell-free extracts confirmed that different pathways are induced by the two growth substrates. 3, 5-Xylenol-grown cells contained high levels of gentisate oxygenase and only very small amounts of catechol oxygenase, whereas gentisate ocygenase could not be detected in m-cresol-grown cells, but levels of catechol oxygenase were greatly increased. Extracts of m-cresol-grown cells also contained 2-hydroxymuconic semialdehyde dehydrogenase and hydrolase, whose specificities enable them to metabolize the ring-fission products from catechol, 3-methylcatechol, and 4-methylcatechol. This catechol pathway is also used by m-cresol-grown cells for p-cresol metabolism. In contrast, the results for cells grown with p-cresol point to an alternative pathway involving oxidation to 4-hydroxybenzoate and hydrosylation to protocatechuate as ring-fission substrate. Extracts of these cells contained high levels of protocatechuate oxygenase and only small amounts of catechol oxygenase.
Tryptophan photoproduct(s): sensitized induction of strand breaks (or alkali-labile bonds) in bacterial deoxyribonucleic acid during near-ultraviolet irradiation
Authors: Yoakum G H
Published: January 2020

Long-wavelength ultraviolet light (300 to 400 nm) converts L-tryptophan to a photoproduct that is toxic for bacterial cells in dark conditions. We now report that similar photoproducts of l-tryptophan sensitize bacterial deoxyribonucleic acid to 365-nm radiation, increasing the yield of deoxyribonucleic acid strand breaks (or alkali-labile bonds) by approximately 11.5-fold. Evidence is also presented which indicates that thse sensitized deoxyribonucleic acid lesions contribute to lethality for Escherichia coli irradiated with 365-nm ultraviolet light in suspensions of tryptophan photoproducts.
Growth of Pseudomonas C on C1 compounds: enzyme activites in extracts of Pseudomonas C cells grown on methanol, formaldehyde, and formate as sole carbon sources
Authors: Goldberg I , Mateles R I
Published: January 2020

Pseudomonas C can grow on methanol, formaldehyde, or formate as sole carbon source. It is proposed that the assimilation of carbon by Pseudomonas C grown on different C1 growth substrates proceeds via one of two metabolic pathways, the serine pathway or the allulose pathway (the ribose phosphate cycle of formaldehyde fixation). This contention is based on the distribution of two key enzymes, each of which appears to be specifically involved in one of the assimilation pathways, glycerate dehydrogenase (serine pathway) and hexose phosphate synthetase (allulose pathway). The assimilation of methanol in Pseudomonas C cells appears to occur via the allulose pathway, whereas the utilization of formaldehyde or formate in cells grown on formaldehyde or formate as sole carbon sources appears by the serine pathway. When methanol is present together with formaldehyde or formate in the growth medium, the formaldehyde or formate is utilized by the allulose pathway.
Detection of a protein, similar to the sex pilus subunit, in the outer membrane of Escherichia coli cells carrying a derepressed F-like R factor
Authors: Beard J P , Connolly J C
Published: January 2020

The outer membranes of Escherichia coli K-12 cells carrying a derepressed F-like R factor contain about 7 times 10-4 molecules per cell of a protein similar to the subunit of the sex pili specified by the R factor. This protein pool is absent in cells carrying the repressed variant of the R factor. The size of the pool is about one-half of the amount of protein incorporated into mature sex pili at the peak of production and is independent of the phase of growth of the culture. The molecular weight of the protein in the pool and of the subunit of the sex pili specified by the cells is 12,500 plus or minus 600.
Properties of alpha-dehydrobiotin-resistant mutants of Escherichia coli K-12
Authors: Eisenburg M A , Mee B , Prakash O , Eisenburg M R
Published: January 2020

We have isolated four classes of mutants resistant to alpha-dehydrobiotin, a biotin analogue. One mutant group, referred to as bioR shows high excretion levels of biotin vitamers, derepressed levels of the biotin biosynthetic enzymes, and resistance to repression by biotin. The mutation has been mapped between argC and bfe at min 79. A second class of mutants, with lesions in the bioA operon at min 17.5, shows derepressed levels of the dethiobiotin synthetase enzyme and has been tentatively designated as bioO mutants. The other two mutant groups show alterations in permeability: biotin uptake is markedly reduced in one, whereas in the other proline uptake is also affected. The former mutation lies near metE at min 75 and has been designated as bioP. The permeability mutants in the second group also show poor growth on minimal media, suggesting a generalized permeability effect. This mutation, designated as P, has not been mapped.
Multiple forms of 7-alpha-hydroxysteroid dehydrogenase in selected strains of Bacteroides fragilis
Authors: Hylemon P B , Sherrod J A
Published: January 2020

Multiple forms of 7-alpha-hydroxysteroid dehydrogenase were detected in six of nine strains of Bacteroides fragilis. The enzymes differed with respect to pyridine nucleotide specificity, thermal stability, divalent metal cation requirement, and elution profilies from Sephadex G-200 columns. The nicotinamide adenine dinucleotide phosphate (NADP)-dependent enzyme required divalent metal cations, preferentially Mn-2+ (Km, 57 muM), for maximum catalytic activity. The NADP-dependent enzyme was labile at 65 C for 10 min, whereas the nicotinamide adenine dinucleotide (NAD)-dependent enzyme was stable at 65 C for 10 min. The specific activity of both the NAD- and NADP-dependent enzymes in crude extracts increased markedly (15- and 7.5-fold, respectively) during the transition from exponential- to stationary-phase growth in glucose medium containing 0.5 mM sodium cholate. The time course of apparent enzyme induction correlated temporally with the transformation of the 7-alpha-hydroxy group of cholate in the culture supernatant fluid. Both NAD- and NADP-dependent 7-alpha-hydroxysteroid dehydrogenase activities were found to be widely, but not universally, distributed in different strains and subspecies of B. fragilis. No NAD- or NADP-dependent 7-alpha-hydroxysteroid dehydrogenase activity could be detected in B. fragilis subsp. vulgatus Virginia Polytechnic Institute (VPI) no. 4245, subsp. thetaiotaomicron VPI 0061-1, or subsp. distasonis VPI 4243.
Five control systems preventing transfer of Escherichia coli K-12 sex factor F
Authors: Gasson M J , Willetts N S
Published: January 2020

The transfer inhibition systems of 28 Fin+ plasmids have been characterized, using Flac mutants insensitive to inhibition by R100 or R62. All F-like plasmids (except R455) and one N group plasmid determined systems analogous to that of R100; this is designated the FinOP system. None of these plasmids could supply a FinP component of the transfer inhibitor able to replace that of F itself. In addition to the FinOP and R62 transfer inhibition systems described previously, new systems were encoded by the F-like plasmid R455, the I-like plasmid JR66a, and the group X plasmid R485. Besides inhibiting F transfer, JR66a also inhibited F pilus formation and surface exclusion, whereas R485 inhibited only pilus formation and R455 inhibited neither. All three R factors inhibited transfer of J-independent Flac elements, indicating that they act directly on one or more genes (or products) of the transfer operon, rather than directly via traJ. The tral products and transfer origin sequences of two Fin+ F-like plasmids, ColB2 and R124, appear to have similar specificities to those of F itself.
Formation of chromatographically unique species of transfer ribonucleic acid during amino acid starvation of relaxed-control Escherichia coli
Authors: Fournier M J , Peterkofsky A
Published: January 2020

Examination of the transfer ribonucleic acid (tRNA) produced by starving, relaxed-control (rel minus) strains of Escherichia coli for required amino acids revealed the occurrence of a number of chromatographically unique subspecies. Leucine starvation results in the formation of new isoacceptor species of leucine-, histidine-, arginine-, valine-, and phenylalanine-specific tRNA and quantitative changes in the column profiles of serine, glycine, and isoleucine tRNA. Evidence that the unique tRNA species are synthesized de novo during amino acid starvation comes from the findings that the major unique leucine isoacceptor species is not formed in stringent control cells or in rel minus cells starved for uracil or treated with rifampin. Furthermore, heat treatment of the unique leucine tRNA does not alter its chromatographic behavior, indicating that the species is not an aggregate or nuclease-damaged form of a normal isoacceptor tRNA. The methyl acceptor activities of tRNA from leucine-starved and nonstarved rel+ or rel minus cells were found to be essentially the same. This result and the finding that the chromatographic behavior of the unique leucine-specific tRNA was not altered after treatment with tRNA methylase suggests that gross methyl deficiency is probably not the biochemical basis for the occurrence of the unique species.
Enzymatic adaptation by bacteria under pressure
Authors: Marquis R E , Keller D M
Published: January 2020

A study of enzymic adaptation under hydrostatic pressure by moderately barotolerant bacteria that can grow at pressure up to about 500 atm revealed that some adaptive processes are relatively insensitive to pressure, whereas others are sufficiently barosensitive to compromise survival capacity in situations requiring adaptation to new substrates under pressure. Examples of the former include adaptation of Escherichia coli to arabinose catabolism for growth and adaptation of Streptococcus faecalis to catabolism of lactose, ribose, or maltose. Examples of the latter include derepression of the lac operon in Escherichia coli and induction of penicillinase synthesis by Bacillus licheniformis. For both these barosensitive systems, pressure had little effect on enzyme levels in constitutive strains or in bacteria that had previously been induced at 1 atm. Moreover, it had no detectable effect on penicillinase secretion. However, pressures of 300 to 400 atm were found to reduce markedly rates and extents of enzyme synthesis by bacteria undergoing derepression or adaptation. This inhibitory effect of pressure was reflected in greater barosensitivity with extended lag and slower growth of initially unadapted Escherichia coli cells inoculated into minimal medium with lactose as sole source of carbon and fuel, and by major reductions in the minimal inhibitory concentrations of penicillin G for unadapted B. licheniformis cells inoculated into complex, antibiotic-containing media. Cyclic adenosine 5'-monophosphate did not reverse pressure inhibition of derepression of the lac operon, and catabolite repression was complete under pressure. However, derepression of the lac operon was more sensitive to pressure at low concentrations of inducer than at high concentrations. Apparent volume changes for derepression were 94 and 60 ml/mol at inducer concentrations of about 0.5 and 5 mM, respectively. Pressure was found not to be inhibitory for uptake of beta-galactosides; in fact, it was somewhat stimulatory. Therefore, results were interpreted in terms of inducer binding and subsequent conversion of an operator-inducer-repressor complex to inactive repressor and operator. Both reactions appeared to result in an increase in volume, the former more so than the latter. We found also that 200 atm was actually stimulatory for growth of Escherichia coli in minimal media, and the bacterium was in a sense barophilic.
Simple downshift and resulting lack of correlation between ppGpp pool size and ribonucleic acid accumulation
Authors: Hansen M T , Pato M L , Molin S , Fill N P , von Meyenburg K
Published: January 2020

The growth rate of Escherichia coli can be limited by the availability of carbon and energy. To impose such a limitation, alpha-methylglucoside (alpha MG), a non-metabolizable analogue, can be used to decrease uptake of glucose by competition for the transport of this sugar. Varying the ratio of glucose to alphaMG allowed shifts in growth rate without simultaneous qualitative changes in the growth medium and permitted examination of the immediate changes accompanying such shifts. Stringent (rel+) as well as relaxed (rel minus) strains were able to rapidly curtail their accumulation of ribonculeic acid (RNA) after a downshift imposed by decreasing glucose transport into the cell. Guanosine 5'-diphosphate 3'-diphosphate (ppGpp) accumulated in both rel+ and rel minus strains after a degrease in growth rate. However, the accumulation of ppGpp in relaxed derivatives was very slow, and there was no direct or obligatory correlation between the level of ppGpp and the rate of RNA accumulation. This latter conclusion is supported by measurements of ppGpp levels and rates of RNA accumulation after restoration of maximal growth rates by addition of excess glucose.
Ultrastructure of ascosporogenesis in Nannizzia gypsea
Authors: Hill T W
Published: January 2020

Ascosporogenesis in Nannizzia gypsea was studied by electron microscopy. Development of ascospores began with the formation of an ascus vesicle composed of two paired unit membranes. Myelin figures consisting of coiled or concentric membranes were regularly connected with the growing ascus vesicle. Both the ascus vesicle and the myelin figures possessed an electron-dense line between paired membranes, and both were stained by the periodic acid-silver methenamine technique. Invagination of the ascus vesicle about the haploid nuclei resulted in eight uninucleate prospores bounded by two concentric membranes. Spore wall material was deposited between the two membranes of the prospores, and deposition was greatest in areas of the wall overlying stacked elements of endoplasmic reticulum. A single myelin figure surrounded by a polysaccharide halo was observed in the spore.
Genetic mapping of sporulation operons in Bacillus subtilis using a thermosensitive sporulation mutant
Authors: Young M
Published: January 2020

A thermosensitive sporulation mutant was used to determine the order of sporulation operonsin the urs region of the Bacillus subtilis chromosome. Data from three-factor transformation crosses and three- and four-factor transduction crosses established the order metC-SPO-96(SpoII)-spo-85(SpoV)-spo-279(SpoII)-furA-ura-cysC-spo-NG1.67(SpoIII). Previously, furA was thought to lie to the right of ura and cysC to the left (Dubnau, 1970; Young and Wilson, 1972).
Genetic characterization of the metK locus in Escherichia coli K-12
Authors: Hunter J S , Greene R C , Su C H
Published: January 2020

Three independently isolated metK mutants have been shown to have leisions lying between speB and glc near 57 min on the Escherichia coli chromosome. Two deletions result in a lack of the metC gene product but neither extends into the metK glc region. The three metK mutations are recessive to the wild-type allele carried on the KLF16 episome.
PfkB and pfkC loci of Escherichia coli
Authors: Vinopal R T , Fraenkel D G
Published: January 2020

Mutants lacking Escherichia coli phosphofructokinase (pfkA, 78 min) are suppressed by the unlinked pfkB1 mutation, which restores some enzyme activity (Morrissey and Fraenkel, 1972). We here describe a secondary mutation at pfkB, "PFKB-," which abolishes the suppression as well as the low residual activity of unsuppressed pfkA mutants. pfkB is at about 33 min. with the gene order groD-pps-pheS-pfkB. A positive selection was found that yielded both the pfkB-mutations and a new similar mutation, pfkC-. pfkC is an early marker in Hfr HL16(ca. 50 to 55 min). Some pfkC-, but no pfkB-, mutations were amber. A temperature-sensitive pfkB- was also obtained. Strains carrying pfkB- or pfkC-, but wild type at pfkA, were not markedly affected in growth on sugars. A new search for suppressors such as pfkB1 gave five independent candidates, all of which suppressed both pfkA1 and pfkA2 and occurred in the pfkB region; none occurred at pfkC. Neither the pfkB nor the pfkC loci have assigned functions. It is likely that they are somehow involved in expression of phosphofructokinase activity 2 (Fraenkel, Kotlarz, and Buc, 1973).
Three yeast proteins that specifically inhibit yeast proteases A, B, and C
Authors: Lenney J F
Published: January 2020

Baker's yeast was found to contain inhibitors of yeast proteases A and C. These two proteins were partially purified, characterized, and compared with the previously described inhibitor of protease B. The A and B inhibitors were very thermostable and were extracted from intact yeast cells at 9k C. The A inhibitor appeared to be a protein with a molecular weight of about 22,000 which could be dissociated into two monomers or chains, both of which had a molecular weight of approximately 11,000. The protease C (carboxypeptidase Y)-inhibitor complex was purified and then partially disociated on an ion-exchange column. The free protease C inhibitor was very unstable, possibly because of destruction by a contaminating protease. Each inhibitor was specific for its corresponding protease and each inhibition was competitive. Whereas proteases A, B, and C destroyed the B inhibitor, only protease B had a pronounced destructive effect on the protease A inhibitor. Pepstatin was found to be a selective inhibitor of protease A, whereas chymostatin and antipain specifically inhibited protease B.
Rifampin resistance mutation of Bacillus subtilis altering the electrophoretic mobility of the beta subunit of ribonucleic acid polymerase
Authors: Linn T , Losick R , Sonenshein A L
Published: January 2020

The rifampin-resistance mutation of LS3,an asporogenous mutant of Bacillus subtilis 3610, leads to altered mobility of the beta subunit of ribonucleic acid polymerase in sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. This finding argues that the rifampin-resistance mutation is located in the structural gene coding for the beta polypeptide.
Dual role for N-2-acetylornithine 5-aminotransferase from Pseudomonas aeruginosa in arginine biosynthesis and arginine catabolism
Authors: Voellmy R , Leisinger T
Published: January 2020

In Pseudomonas aeruginosa N-2-acetylornithine 5-aminotransferase (ACOAT), the fourth enzyme of arginine biosynthesis is induced about 15-fold by cultivating the organism on a medium with L-arginine as the sole carbon and nitrogen source. Synthesis of the enzyme is subject to catabolite repression and nitrogen source. Synthesis of the enzyme is subject to catabolite repression by a variety of carbon sources. ACOAT from strain PAO 1 was purified over 40-fold to electrophoretic homogeneity. A molecular weight of approximately 110,000 was obtained by thin-layer gel filtration. Electrophoresis in sodium dodecyl sulfate gels gave a single band corresponding to a molecular weight of 55,000. Purified ACOAT catalyzes the transamination of N-2-acetyl-L-ornithine as well as of L-ornithine with 2-oxoglutarate (Km values of 1.1, 10.0, and 0.7 mM, respectively). With N-2-acetyl-L-ornithine as amino donor, the pH-optimum of the enzymatic reaction is 8.5; with L-ornithine as amino donor, 9.5. The catalytic properties of ACOAT as well as the regulation of its synthesis indicate that in P. aeruginosa this enzyme functions in the biosynthesis as well as in the catabolism of L-arginine.
Replication of R-factor R1 in Scherichia coli K-12 at different growth rates
Authors: Engberg B , Nordström K
Published: January 2020

The R-factor R1drd-19 mediates resistance to beta-lactam antibiotics via a beta-lactamase. A strain of Escherichia coli K-12 carrying R1drd-19 was grown at different growth rates by using different carbon sources. The specific rate of production of the R1 beta-lactamase increased linearly with the growth rate and with the gene dosage. The content of R1 deoxyribonucleic acid was estimated by alkaline sucrose gradient centrifugation and by analysis of the specific rate of beta-lactamase synthesis in nutritional shift-up experiments and was found to decrease fivefold when the growth rate was increased from 0.4 to 1.8 doublings per h. The number of R1 molecules per cell decreased from six to two in the same growth range. The presence of the plasmid affected the mean cell size significantly; at a growth rate of 0.4 doublings per h the R-+ cells were on the average 50% bigger than the R-minus cells, whereas the effect was less than 10% at a growth rate of 1.8 doublings per h. Several reports in the leterature state that the initiation mass of chromosome replication is constant. In this paper it is shown that the initiation mass of R1 replication is proportional to the growth rate. Thus, the replication of the plasmid R1 and of the chromosome are independently regulated processes. It is argued that plasmid replication is under negative control.
Identification of a deoxyribonuclease implicated in genetic transformation of Diplococcus pneumoniae
Authors: Lacks S , Greenberg B , Neuberger M
Published: January 2020

A mutation of Diplococcus pneumoniae, end-1, reduces the major deoxyribonuclease activity of the cell, an endonuclease, to 10% of its normal value without impairing transformation. Further mutations, called noz, abolish the residual endonuclease activity and block transformation. The residual endonuclease is similar to the wild-type enzyme in size, charge, divalent cation dependence, inhibition by ribonucleic acid, and formation of oligonucleotide products. However, the mutant endonuclease is more temperature sensitive, which suggests that the end-1 mutation occurred in a structural gene for the enzyme. Genetic analysis showed that the noz mutations occur at the same genetic locus. A number of new end mutants were analyzed. Those that retained more than 1.4% of the normal endonuclease activity were essentially normal in transformation; those with less than 1% were defective. The transformation-defective end mutants appear to be blocked in the entry of deoxyribonucleic acid (DNA) since they carry out the prior step of binding DNA to the outside of the cell. The major endonuclease of the cell may act as a DNA translocase by attacking and degrading one strand of DNA, thereby facilitating entry of the complementary strand into the cell.
Properties of the imidazolylacetolphosphate aminotransferase produced in a mutant demonstrating no apparent genetic involvement of the structural gene
Authors: Roberts J H , McCarroll D R , Levin A P
Published: January 2020

Genetic studies with strain hisBH22 of Salmonella typhimurium indicate it contains a deletion within the histidine operon involving part of the hisH gene and all of the hisB gene, but not extending into the adjacent hisC gene which is adjacent to hisB. However, the specific activity of the hisC product, imidazolylacetolphosphate aminotransferase (EC 2.6.1.9), in this strain is only 10 to 15% of that found in extracts from other mutants with a normal hisC gene. We have examined the rate of aminotransferase synthesis in this mutant and we find that the rate of synthesis of aminotransferase activity is low in mutant hisBH22, but the rate increases as the temperature of growth is lowered from 37 to 23 C. The low rate of enzyme accumulation is not due to holoenzyme instability at 37 C but instead is due to apoenzyme instability at this temperature. By transducing the hisBH22 marker into a pyridoxine auxotroph and derepressing the histidine operon under conditions where the intracellular concentration of pyridoxal phosphate would be expected to be low, we were able to demonstrate significant apoenzyme production only at the lower temperature. We suggest that the explanation for low aminotransferase specific activity at 37 C is due to the presence of reduced numbers of catalytically active units caused by normal production of an unstable mutant apoenzyme with only approximately 15% of the molecules being activated to holoenzyme. The holoenzyme from strain hisBH22 is stable during growth of this strain at 37 C.
RP1 properties and fertility inhibition among P, N, W, and X incompatibility group plasmids
Authors: Olsen R H , Shipley P L
Published: January 2020

Incompatibility group P plasmids demonstrate strong entry exclusion properties. Stringent incompatibility is also observed in the absence of entry exclusion. These observations have been facilitated by the study of a nontransmissible plasmid, RP1-S2, derived from RP1 by transductional shortening. RP1-S2 retains carbenicillin and tetracycline resistances as well as loci that cause either the loss of P plasmids (incp) or a locus specifying susceptibility to curing (sinp) in the presence of a P plasmid. RP1-S2 can be mobilized by an incompatibility group W plasmid, R388, and also freely forms recombinants with R388. P, N, and W incompatibility group plasmids all encode information for the receptor of the cell wall-adsorbing phage PRD1. Based on the premise that the location of this receptor is analogous to entry exclusion factors for F-like plasmids and hence a regulated transfer region determinant, we tested fertility inhibition relationships among these plasmid groups. We detected both reciprocal and nonreciprocal fertility inhibition relationships for bacteria containing various combinations of W, N, and P group plasmids. The nonreciprocal nature of some combinations, we believe, reflects the identity of the point mutation reading to derepression of the plasmid in question. Reciprocal fertility inhibition, on the other hand, may reflect the reconstruction of a fertility inhibition system through complementation. An X incompatibility group plasmid, known to affect the fertility of an N group plasmid, was also shown to inhibit P plasmid fertility. These observations may indicate a possible evolutionary relationship(s) of plasmids unrelated by the criteria of incompatibility, pilus phage specificity, or plasmid host range.
Ultrastructal morphology of some prokaryotic microorganisms associated with the hindgut of cockroaches
Authors: Foglesong M A , Walker D H , Puffer J S , Markovetz A J
Published: January 2020

Scanning electron microscopy and transmission electron microscopy have been used to visualize the morphology and ultrastructure of two types of microorganisms in the hindgut of the cockroach Blaberus posticus. Both organisms, designated as either short or long rods, are attached to chitinous projections from the gut wall. Micrographs suggest that the organisms are prokaryotic with a cell wall complex characteristic of gram-negative bacteria. However, certain differences were noted between the cell wall complex of the two types. Two forms of the long-rod type were noted, with one form appearing to be a "degenerate" or "transitional" cell. In the degenerate cells, vesicles are observed that often are contiguous with the cytoplasmic membrane. There are indications that the long-rod type may divide by longitudinal fission. Neither the short- nor long-rod type has been cultivated in its respective recognizable form.
Genetics of resistance to colicins in Escherichia coli K-12: cross-resistance among colicins of group B
Authors: Davies J K , Reeves P
Published: January 2020

This paper describes the isolation of mutants resistant to colicins of group B (i.e., colicins B, D, G, H, Ia, Ib, M, Q, S1, and V). The 145 mutants studied in detail can be divided into nine phentopyic classes, based on their colicin-resistance patterns. They include the previously isolated tonA, tonB exbB and cir mutants. Each of the different phenotypic classes of mutants has been partially characterized, and some approximately mapped. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis has revealed substantial changes in the composition of the outer membrane proteins of exbB and tonB mutants.
Isolation and characterization of Clostridium perfringens mutants altered in both hemagglutinin and sialidase production
Authors: Rood J I , Wilkinson R G
Published: January 2020

The relationship between the production of hemagglutinin and sialidase activities by Clostridium perfringens was investigated by screening for mutants producing reduced levels of hemagglutinin activity. Twelve mutants were isolated; all produced reduced levels of sialidase activity and several had other altered phenotypic markers. Revertants that regained the ability to produce active hemagglutinin were isolated. All of these revertants produced increased sialidase activity. These results show that the production of hemagglutinin activity is directly related to the production of sialidase activity. Evidence is also presented that the processes of sporulation and the production of extracellular proteins are interrelated.
Uptake of C4 dicarboxylates and pyruvate by Rhodopseudomonas spheroides
Authors: Gibson J
Published: January 2020

The uptake of C4 dicarboxylates by cells from exponential cultures of Rhodopseudomonas spheroides followed saturation kinetics at concentrations below 100 muM with Km values for succinate, malate, and fumarate of 2.7, 2.3, and 0.8, respectively. Corresponding Vmax values of 50, 52, and 67.5 nmol/min per mg of protein at 20 C were obtained. Each of these compounds interfered competitively with uptake of the others, and a common transport system appears to be involved. Fructose-grown cells took up C4 dicarboxylates only at very low rates, and pyruvate-grown cells took up C4 dicarboxylates at one-third the rates found with succinate-grown cultures. Malonate and maleate inhibited uptake less severely, and aspartate and alpha-ketoglutarate had no effect at 100-fold excess. Divalent metals stimulated uptake. Light or respiration was required for uptake, and entered materials were rapidly converted to other metabolities, notably amino acids. Pyruvate entry appeared to be mediated by several systems, of which only one could be resolved kinetically. This system had a Km of 13 muM and Vmax of 5.6 nmol/min per mg of protein at 20 C. A number of related mono- and dicarboxylates interfered with pyruvate uptake. The pyruvate uptake system was distinguishable from the C4 dicarboxylate system by the absence of divalent cation stimulation and by substrate and inhibitor specificity.
Mating aggregates in Escherichia coli conjugation
Authors: Achtman M
Published: January 2020

Mating mixtures of Escherichia coli cells were shown to contain mating aggregates of two to 20 cells each rather than only mating pairs of two cells each. The mating aggregate size distribution shows two broad peaks, at two to four cells and at eight to 13 cells. The quantitative mating aggregate size distribution and the proportion of male cells in mating aggregates are dependent on the input ratio of male to female cells. At an input ratio of one to one, the average mating aggregate contains equal proportions of male and female cells and most of the cells involved in mating are in large aggregates of seven or more cells each. The deoxyribonucleic acid (DNA) transfer efficiency per mating aggregate cell was constant regardless of average aggregate size or of the ratio of male to female cells in the aggregate. Under optimal conditions essentially every male cell or every female cell in a mating aggregate can be involved in DNA transfer. A comparison of light microscopy, sucrose gradient centrifugation, and analysis with a modified Coulter counter indicated that the number of cells in mating aggregates is best equantitated using a modified Coulter counter.
Interactions among substrates and inhibitors of nitrogenase
Authors: Rivera-Ortiz J M , Burris R H
Published: January 2020

Examination of interactions among various substrates and inhibitors reacting with a partially purified nitrogenase from Azotobacter vinelandii has shown that: nitrous oxide is competitive with N2; carbon monixide and acetylene are noncompetitive with N2; carbon monoxide, cyanide, and nitrous oxide are noncompetitive with acetylene, whereas N2 is competitive with acetylene; carbon monoxide is noncompetitive with cyanide, whereas azide is competitive with cyanide; acetylene and nitrous oxide increase the rate of reduction of cyanide. The results are understandable if nitrogenase serves as an electron sink and substrates and inhibitors bind at multiple modified sites on reduced nitrogenase. It is suggested that substrates such as acetylene may be reduced by a less completely reduced electron sink than is required for the six-electron transfer necessary to reduce N2.
Genetic control of yeast mannan structure: mapping genes mnn2 and mnn4 in Saccharomyces cerevisiae
Authors: Ballou D L
Published: January 2020

Two mutations concerned with mannan biosynthesis in the yeast Saccharomyces cerevisiae have been mapping. The mnn2 mutation, which affects the addition to the polysaccharide backbone of the first side-chain D-mannose unit in alpha1-leads to2 linkage, was located on chromosome II linked to the centromere and the gall locus. The mn4 locus, which regulates the synthesis of mannosylphosphate groups on the mannan side chains, was placed on chromosome XI near trp3 and ural and a locus previously reported to regulate the ability of a S. diastaticus strain to bind alcian blue (Friis and Ottolenghi, 1970). The mnn4 mutant also fails to bind alcain blue, but the gene responsible for alcian blud binding in this strain segregates independently from the dye-binding locus of S. diastaticus, and therefore must be a different gene. A diploid heterozygous for mnn4 fails to bind dye, indicating dominance of this mutant genotype. The alcian blue dye binding locus dbll, reported to Friis and Ottolenghi (1970), is also dominant. Thus, there are at least two independent genes that control the formation of the mannosylphosphate units in the mannan side chains, and both have the property of dominance in the mutant form.
Unusual cell wall ultrastructure of Leptotrichia buccalis
Authors: Listgarten M A , Lai C H
Published: January 2020

Leptotrichia buccalis was examined by transmission electron microscopy. Its cell wall structure in generally compatible with that of gram-negative bacteria. However, the scale-like membranous folds associated with the external surface of the outer cell membrane appear to be sufficiently unusual to serve as a useful morphological criterion in the identification of L. baccalis cells.
Regulation of breakdown and synthesis of L-glutamate decarboxylase in Clostridium perfringens
Authors: Cozzani I , Barsacchi R , Dibenedetto G , Saracchi L , Falcone G
Published: January 2020

L-Glutamate decarboxylase (GAD) activity of Clostridium perfringens (ATCC 8009) cells grown in various culture conditions was investigated. Remarkable variations of GAD level occur during the growth cycle in thioglycollate broth. These changes are affected by the pH of the culture medium. Addition of alkali to the culture media results in decrease of cell GAD activity, whereas increase of enzyme level occurs only in cells growing in unbuffered media. The results indicate that the mechanism regulating the GAD levels is sensitive to the changes of pH (or buffering substances) rather than to the steady pH values. Neither repression by glucose nor induction by L-glutamate was observed. Moreover, high concentrations of the free amino acid substrate in the culture media considerably decrease cell GAD activity, owing to the buffering effect of the amino acid. The molecular mechanism supporting the variations of GAD activity during the growth cycle of the cells were investigated and tentatively related to the structural and functional properties of the pure enzyme. It is shown that the drop of GAD activity during the lag phase is due to protein breakdown. Evidence is presented suggesting a control of protein degradation by its quaternary structure. Data are also reported supporting de novo synthesis of GAD during the late logarithmic phase of cell growth. Finally, the possible role of GAD as part of the pH regulation system of C. perfringens cells is discussed in relation both to physiologic conditions of the bacterial cell and to the molecular mechanisms regulating the GAD activity in vivo.
Evidence for extrusion of unfolded extracellular enzyme polypeptide chains through membranes of Bacillus amyloliquefaciens
Authors: Sanders R L , May B K
Published: January 2020

The production of extracellular alpha-amylase and protease by protoplasts of Bacillus amyloliquefaciens has been achieved. The production of enzymically active protease was totally dependent on a high concentration of either Mg2+, Ca2+, or spermidine, but production of active alpha-amylase was not. This cation dependence of protease production was seen immediately upon addition of lysozyme to intact cells. The cations could prevent the inactivation of protease and alter the cytoplasmic membrane configuration of protoplasts. Production of active alpha-amylase and protease by protoplasts was totally inhibited by proteolytic enzymes such as trypsin, alpha-chymotrypsin, or the organism's purified extracellular protease. The evidence suggests that these degradative enzymes act specifically on the emerging polypeptide of the extracellular enzyme and that the polypeptide emerges in a conformation different from that of the native molecule.
Regulation of extracellular protease secretion in Pseudomonas maltophilia
Authors: Boethling R S
Published: January 2020

Cells grown in minimal medium and harvested in late exponential phase secreted extracellular protease linearly when suspended at high density in fresh medium. If the cells were suspended with 0.2% (wt/vol) yeast extract and no additional carbon source, the rate of exoenzyme production was increased several-fold. When pyruvate, L-malate, succinate, or alpha-ketoglutarate was added, repression of exoenzyme secretion was observed. The most effective repressor was alpha-ketoglutarate. These compounds were also preferred substrates for growth of Pseudomonas maltophilia. The data suggest that exoenzyme secretion is controlled by a mechanism similar to catabolite repression. In support of this was the observation that alpha-ketoglutarate repressed exoenzyme secretion preferentially with respect to total protein synthesis. The addition of inhibitors that affect protein synthesis indicated that exoenzyme secretion is several times more sensitive than is total protein synthesis. The addition of chloramphenicol and rifamycin-SV to actively secreting cell suspensions suggested that de novo protein synthesis is required, but that exoenzyme secretion may be supported for at least 30 min in the absence of messenger synthesis. Rifamycin-insensitive protease secretion could be reversed by either alpha-ketoglutarate or chloramphenicol, suggesting that alpha-ketoglutarate is coupled to a post-transcriptional control mechanism.
Mu-induced polarity in the Escherichia coli K-12 ent gene cluster: evidence for a gene (entG) involved in the biosynthesis of enterochelin
Authors: Woodrow G C , Young I G , Gibson F
Published: January 2020

A strain of Escherichia coli K-12 has been isolated that carries a Mu bacteriophage-induced mutation in the ent gene cluster. Nutritional tests together with examination of the compounds accumulated by the mutant strain indicated that the mutant was blocked both in the synthesis of 2,3-dihydroxy-benzoate and its subsequent conversion into enterochelin. Enzymic complementation assays of the mutant with several mutants each affected in one of the ent genes showed that the Mu-induced mutant was entA-, entB-, entC+, entD+, entE+, and entF+. Since the mutant produced the entD, entE, and entF gene products but was unable to produce enterochelin from 2,3-dihydroxybenzoate, it must therefore be affected in an additional protein concerned with this conversion. It is therefore postulated that the Mu-induced mutation affects a previously unrecognized gene, entG. Genetic experiments indicate that the mutation in strain AN462 which affects the three ent genes is the result of a single insertion of Mu in the ent gene cluster. This polarity mutant therefore provides evidence that three of the ent genes are part of an operon.
Development of defined and minimal media for the growth of Bacillus stearothermophilus
Authors: Rowe J J , Goldberg I D , Amelunxen R E
Published: January 2020

Defined media, both solid and liquid, that support good growth of Bacillus stearothermophilus 1503 have been developed. Data are presented which indicate that manganese is required at relatively high concentrations for growth in a defined liquid medium. Phosphate concentrations higher than 5 times 10(-3) M have been shown to inhibit colony formation on solid media. Maximum viable counts of approximately 10(9) colony-forming units per ml were obtained in both the defined and minimal liquid media. Glucose, fructose, sucrose, glycerol, and starch support the growth of this obligate thermophile in the defined media, whereas citrate, alpha-ketoglutarate, succinate, fumarate, malate, acetate, and lactate do not. The described media have been utilized to isolate several amino acid-requiring mutants of B. stearothermophilus.
Genetic mapping of a mutation that causes ribonucleases III deficiency in Escherichia coli
Authors: Studier F W
Published: January 2020

the mutation that causes ribonuclease III (RNase III) deficiency in strain AB301-105 of Kindler et al. (1973) has been mapped by use of F' merodiploids, Hfr matings, and P1 transduction. This mutation, rnc-105, lies close to nadB, near 49 min on the genetic map of Escherichia coli. The rnc-105 mutation has been transferred from its original genetic background by transduction and conjugation, and these new strains have the same defects in ribonucleic acid processing reported previously for AB301-105. Strains that carry rnc-105 grow more slowly than parental rnc+ strains, but the difference in growth rate seems to depend on the genetic background of each strain. Bacteriophage T7 grows about equally well in RNase III+ and III- female strains of E. coli, even though the specific cuts that RNase III makes in T7 ribonucleic acid are not made in the RNase III- strains. A low-phosphate defined medium in which most E. coli strains seem to grow well was developed. This medium is equally useful for labeling ribonucleic acids with 32PO4 and as a selective medium for genetic manipulations. It was used to determine the growth requirements of strain AB301-105, which are biotin and succinate in addition to the methionine and histidine requirements of the parental strain. The biotin mutation lies near the position expected from known mutations of E. coli, but the succinate mutation apparently does not. The possibility that the succinate requirement could be due to the RNase III deficiency is discussed. A uraP mutation was isolated for use in transferring rnc-105 between strains by conjugation. It lies near 47 min, somewhat removed from the commonly accepted position for uraP.
Independent constitutive expression of the aerobic and anaerobic pathways of glycerol catabolism in Klebsiella aerogenes
Authors: Ruch F E , Lin E C
Published: January 2020

Klebsiella aerogenes dissimilates glycerol aerobically via an inducible pathway initiated by an adenosine triphosphate-linked kinase that converts the substrate to sn-glycerol 3-phosphate. Phosphorylated glycerol is then dehydrogenated to dihydroxyacetone phosphate by an enzyme characteristic of a flavoprotein. Anaerobically, the organism dissimilates glycerol via an inducible pathway initiated by a nicotinamide adenine dinucleotide-linked dehydrogenase that converts the substrate to dihydroxyacetone. The keto product is then phosphorylated by another adenosine triphosphate-linked kinase. Two kinds of constitutive mutants have been isolated: one affecting the aerobic and the other the anaerobic pathway.
Effect of mutations in the qa gene cluster of Neurospora crassa on the enzyme catabolic dehydroquinase
Authors: Jacobson J W , Hautala J A , Case M E , Giles N H
Published: January 2020

Catabolic dehydroquinase, which functions in the inducible quinic acid catabolic pathway of Neurospora crassa, has been purified from wild type (74-A) and three mutants in the qa gene cluster. The mutant strains were: 105c, a temperature-sensitive constitutive mutant in the qa-1 regulatory locus; M-16, a qa-3 mutant deficient in quinate dehydrogenase activity; and 237, a leaky qa-2 mutant which possess very low levels of catabolic dehydroquinase activity. The enzymes purified from strains 74-A, 105c, and M-16 are identical with respect to behavior during purification, specific activity, electrophoretic behavior, stability, molecular weight, subunit structure, immunological cross-reactivity, and amino acid content. The mutant enzyme from strain 237 is 1,500-fold less active and appears to have a slightly different amino acid content. It is identical by a number of the other criteria listed above and is presumed to be a mutant at or near the enzyme active site. These data demonstrate that the qa-1 gene product is not involved in the posttranslational expression of enzyme activity. The biochemical identity of catabolic dehydroquinase isolated from strains 105c and M-16 with that from wild type also demonstrates that neither the inducer, quinic acid, nor other enzymes encoded in the qa gene cluster are necessary for the expression of activity. Therefore the combined genetic and biochemical data on the qa system continue to support the hypothesis that the qa-1 regulatory protein acts as a positive initiator of qa enzyme synthesis.