CONTROL OF PYRIDOXINE BIOSYNTHESIS IN ESCHERICHIA COLI

Dempsey, Walter B. (University of Florida, Gainesville). Control of pyridoxine biosynthesis in Escherichia coli J. Bacteriol. 90:431-437. 1965.-The total pyridoxine in a culture of exponentially growing Escherichia coli was 3.6 x 10(-10) moles per mg of dry cells. One-fourth of this total was present in the medium, and was at least 90% pyridoxal 5'-phosphate. Both pyridoxol and pyridoxal, when present initially at 6 x 10(-7)m, substituted entirely for de novo synthesis of pyridoxine. The other four forms of the pyridoxine group were ineffective at this concentration. Pyridoxine biosynthesis in exponentially growing cultures of E. coli was immediately stopped by adding pyridoxol to the medium to a final concentration of 4 x 10(-7)m. Amino acid auxotrophs of E. coli suspended in minimal medium without the required amino acid produced extracellular pyridoxine for several hours at an average rate of 1.3 x 10(-10) moles per hr per mg of dry cells. The rate of production of extracellular pyridoxine by a threonine-starved threonine auxotroph was not altered by growing the culture before starvation in media containing 6 x 10(-5)m pyridoxol. The extracellular form of pyridoxine produced in these starvations required hydrolysis to be detected in the bioassay used in these measurements. The total findings suggest that pyridoxine biosynthesis is controlled by a rapidly acting mechanism but not by repression.

COLONIAL DIMORPHISM IN NONMOTILE SALMONELLA

Enomoto, Masatoshi (National Institute of Genetics, Mishima, Japan) and Tetsuo Iino. Colonial dimorphism in nonmotile Salmonella. J. Bacteriol. 86:473-477. 1963.-Two distinct colonial types, LP-type and SD-type, appeared among the nonmotile mutant clones originated from a strain of Salmonella typhimurium when they were cultivated on semisolid gelatin-agar medium (NGA) at 37 C. These colonial types reflect the nonmotile character of the mutant clones: a nonflagellated clone formed an LP-type colony which was large, translucent, and pale yellowish-gray, whereas a paralyzed flagellated clone formed an SD-type colony which was small, opaque, and dense yellowish-gray. Colonial dimorphism was also present in cells paralyzed by nonheritable change: flagellated cells, immobilized by treatment with homologous anti-H serum, formed SD-type colonies, while cells which had lost flagella, growing in the NGA medium containing 0.12% phenol, formed LP-type colonies. The distinction between the two colonial types was not impaired by addition of motility phage or various sugars to NGA, but became obscure when gelatin was omitted from the medium or the temperature of cultivation was lowered. It is concluded that the difference between the two colonial types is due to the presence or absence of flagella on the surface of the bacterial cells. Such correlation between flagellation and colonial type was observed on nonmotile mutants of several other smooth-type Salmonella strains and Escherichia coli but was not found in a rough-type Salmonella strain.

ALTERATIONS IN THE MOUSE VIRULENCE OF SALMONELLA TYPHIMURIUM BY GENETIC RECOMBINATION

Krishnapillai, V. (Walter Reed Army Institute of Research, Washington, D.C.), and L. S. Baron. Alterations in the mouse virulence of Salmonella typhimurium by genetic recombination. J. Bacteriol. 87:598-605. 1964.-The genetic basis of mouse virulence was investigated with an avirulent strain of Salmonella abony as chromosomal donor and a virulent strain of S. typhimurium as recipient in recombination experiments. In these genetic crosses, the transfer of partial avirulence was found to segregate among the hybrids that were examined. At least two determinants controlling avirulence were depicted to account for the partial avirulence of the hybrids. One of these determinants is indicated as being in the region of the locus for streptomycin sensitivity or resistance, and the other was adjacent to the locus for inositol utilization. Moreover, both determinants were essential for the phenotypic expression of complete avirulence in a hybrid. This was established by the results of experiments in which an initial, partially avirulent hybrid was backcrossed with the S. abony donor so that it further received the additional determinant.

GENETIC ALTERATION OF ADENYLIC PYROPHOSPHORYLASE IN SALMONELLA

A mutant of Salmonella typhimurium, resistant to inhibition by 2, 6-diaminopurine, differs from its sensitive wild-type parent by an altered adenylic acid pyrophosphorylase. The altered enzyme, though still active with adenine as substrate, is inactive in the conversion of diaminopurine to its nucleotide. It also differs from the wildtype enzyme in a number of physical and chemical properties.

NEW TYPE OF SEX FACTOR-SPECIFIC BACTERIOPHAGE OF ESCHERICHIA COLI

Watanabe, Tsutomu (Keio University, Tokyo, Japan), and Motoyuki Okada. New type of sex factor-specific bacteriophage of Escherichia coli. J. Bacteriol. 87:727-736. 1964.-A virulent phage, W-31, isolated from sewage water, was found to have a specific relationship to the sex factor of Escherichia coli K-12; this phage formed large, clear plaques on F(-) and stable Hfr strains but small, turbid plaques on F(+) strains. Unstable Hfr strains gave intermediate-type responses to phage W-31. Further, adsorption and nucleic acid injection of phage W-31 occurred equally in F(-) and F(+) strains. In addition, a majority of F(+) cells were killed by infection with phage W-31 without producing progeny phage. These results suggest that some step(s) after nucleic acid injection is suppressed by an autonomous F but not by an integrated F. Colicinogenic factor B was also found to suppress the production of progeny of phage W-31, although colicinogenic factor E(2), prophage lambda, and R factors did not show such inhibitory effects against this phage. Colicinogenic factor B in an F(-) strain derived from an Hfr strain did not suppress the multiplication of phage W-31; this strain was further found to carry out chromosome transfer in the same order as the original Hfr strain.

CHROMOSOME TRANSFER KINETICS OF SALMONELLA HFR STRAINS

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Stanley Falkow, and L. S. Baron. Chromosome transfer kinetics of Salmonella Hfr strains. J. Bacteriol. 88:395-400. 1964.-The kinetics of chromosome transfer of an Hfr strain of Salmonella typhosa and an Hfr strain of S. typhimurium were examined in interrupted matings with multiply auxotrophic S. typhimurium recipients. The S. typhosa Hfr, TD-7, was found to transfer the pro-A, met-A, arg (A, C, F, or H), and ile markers at 8, 32, 36, and 51 min, respectively, after contact with the recipient strain. Comparison of these entry times with those of the analogous Escherichia coli Hfr P4X-6 for the same markers showed the gene order to be identical. However, the TD-7 entry times were considerably extended over those of P4X-6, which transfers these markers of E. coli F(-) strains at, respectively, 5, 20, 22.5, and 28 min. A similar extension of the entry times was noted with the S. typhimurium Hfr, SR-305, which transfers the markers in the reverse order, ile-met-A-pro-A, at 3 to 4, 18, and 46 min, respectively. Examination of P4X-6/Salmonella Hfr entry time ratios showed them to be constant at 0.63 for the earlier markers transferred by both TD-7 and SR-305. These data suggest that the physical length of the Salmonella chromosome is the same as that of E. coli, and that the rate of chromosome transfer of the Salmonella Hfr strains to S. typhimurium recipients is only 0.63 that of P4X-6 to E. coli F(-) strains under the same physical conditions.

GENETIC MAPPING OF VI AND SOMATIC ANTIGENIC DETERMINANTS IN SALMONELLA

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Barbara Krauskopf, and L. S. Baron. Genetic mapping of Vi and somatic antigenic determinants in Salmonella. J. Bacteriol. 90:302-308. 1965.-The Vi antigen and somatic antigen 9 were transferred to Salmonella typhimurium recipients by mating with S. typhosa Hfr TD-7, and the genetic determinants of these antigens were located. A gene responsible for Vi antigen expression, ViB was found to be associated with the inlpurA-pyrB linkage group, and the order ViB-inl-purA-pyrB was established. The determinant of somatic antigen 9 was found closely linked to the his gene, and cotransduction of these determinants was accomplished with phage PLT-22. Moreover, all conjugation and transduction hybrids which received the somatic antigen 9 determinant concurrently lost somatic antigen 4. Similarly, S. typhosa hybrids produced by transfer of his and the gene for somatic antigen 4 from S. typhimurium Hfr B2, or by cotransduction of these genes with PLT-22, also lost somatic antigen 9. These results indicated that the genetic determinants of the somatic antigen 9 and 4 are probably allelic. A second Vi antigen determinant, ViA, located near his, was discovered in matings of S. typhimurium Hfr B2 with a Vi-negative S. typhosa recipient. Vi-positive S. typhosa hybrids were obtained from this cross in which neither parent expressed the Vi antigen, indicating that this Vi determinant of S. typhosa is present also in S. typhimurium.

EXPERIMENTAL RUNT DISEASE IN MICE CAUSED BY SALMONELLA TYPHIMURIUM, VAR. COPENHAGEN

The strain of Salmonella typhimurium isolated from the subcutaneous abscess of a runted mouse and used in this study was somewhat unusual, but not unique, in that it had a high virulence for young mice, yet low infectivity. This strain could mimic many of the features, signs, and symptoms of immunological runting when injected into neonates, either in pure culture, or when mixed with spleen cells, or when present in infected isologous or F₁ hybrid spleen cells. Thus, the incidence of Salmonella runting was dose-dependent and related to the age of the neonate. Runts failed to gain weight, were sickly, and usually died within 30 days. They had a marked splenomegaly and hepatomegaly associated with areas of necrosis. However, in marked contrast to immunological runts they did not have lymphoid atrophy. The incidence of runting was diminished when frozen-thawed spleen cell suspensions were used, but not with sonicated or heated suspensions or spleen cells from lethally irradiated mice. Runting could be prevented by immunizing breeders with S. typhimurium, and serum from mice immunized against S. typhimurium protected neonates injected with this organism. Isologous adult spleen cells did not protect against Salmonella runting. It is suggested that in studies on runting only the intravenous route be used and that heated cells serve as a control. More rigid criteria should be applied to runting than those frequently accepted and mice should be autopsied whenever possible.

EFFECTS OF BACTERIAL ENDOTOXINS ON METABOLISM. VI. THE ROLE OF TRYPTOPHAN PYRROLASE IN RESPONSE OF MICE TO ENDOTOXIN

Cortisone is known to protect mice against the lethal effects of endotoxin. It also elevates liver tryptophan pyrrolase (TP) activity, an enzyme that converts tryptophan into an intermediate which, in turn, is transformed in a series of reactions into nicotinamide, a component of the pyridine nucleotides. In the present report, results of experiments attempting to link the prophylactic action of cortisone in endointoxication to metabolism of tryptophan are described. It was shown first that both nicotinamide and diphosphopyridine nucleotide (DPN), compounds along the pathway initiated by TP, are each as effective as cortisone in protecting mice against lethality of different amounts of endotoxin. L-Tryptophan, which alone results in an increase in liver TP, fails to protect against endotoxin when it is given either 4 hours before or concurrently with the toxin while it potentiates the toxin when administered 4 hours later. Cortisone, nicotinamide, and DPN all fail to protect mice against lethality when given 4 hours after endotoxin but they do not potentiate it as does tryptophan. Additional evidence linking tryptophan metabolism to endotoxin poisoning was derived from assays for TP. Activity of the enzyme in livers of mice 17 hours after injecting an LD₅₀ of endotoxin is less than one-half the control value. It remains below normal for 48 hours. In adrenalectomized mice, TP activity is about the same as in mice 17 hours after endotoxin. Animals protected against lethality of endotoxin by cortisone have normal levels of TP but if the cortisone is given 4 hours after the toxin, TP activity is the same as in mice given endotoxin alone. Tryptophan is unable to maintain a normal level of TP when it is given concurrently with endotoxin. TP activity is not depressed when mice made tolerant to endotoxin are given an injection of endotoxin at the LD₅₀ level for normal animals. Normal activity of the enzyme was always observed in livers of mice protected against endotoxin but not in those where protection failed. The total amount of oxidized pyridine nucleotides (PN⁺) in livers of mice 17 hours after an LD₆₀ of endotoxin is about two-thirds the normal level. Animals injected with either cortisone or nicotinamide at the same time as endotoxin maintain the PN⁺ level in liver. Mice exposed to 5°C during the postinjection period can be protected with cortisone or nicotinamide against lethality of endotoxin but not with DPN. Changes in TP activity do not parallel those found in mice kept at 25°C. The toxic manifestations of endotoxin appear to be different, therefore, in animals stressed by cold.