the normal fermentation of glucose by Streptococcus faecalis FB82, as shown by the production of increased amounts of CO2 , formate, acetate, and acetoin, and decreased formation of lactate and ethanol. Experiments with D-glucose-l-C'4, in which low levels of labeled CO2 were recovered, indicated that C-1 cleavage of the glucose molecule was not involved. The presence of fumarate afforded consistently larger cell crops in growth studies with glucose and other energy sources. On a molar growth-yield basis, anaerobically grown, glucose-fumarate cultures were equivalent to aerobically grown, glucose cultures. The reduction of fumarate by cell suspensions indicated that glucose, gluconate, and, to a lesser extent, glycerol and mannitol could serve as hydrogen donors. Several common metabolic inhibitors had no effect upon the fumarate reductase system in cell suspensions, although some sensitivity to acidic pH was noted. Significant levels of succinate oxidation activity were not detected. Fumarate reductase activity was demonstrated in all five S. faecalis strains tested. Distribution of this ability in S. faecium strains was variable, ranging from activity comparable with that of S. faecalis to total inactivity. The observations support the conclusion that fumarate functions as an alternate hydrogen acceptor, thus allowing pyruvate to participate in the energy-yielding phosphoroclastic and dismutation pathways. In a previous communication (Deibel, 1964b), 1 Journal paper no. 277, American Meat Institute Foundation.
KVETKAS, M. J., R. E. KRISCH, and M. R. ZELLE. 1972. Phenotypic properties of a large-cell, radiationresistant strain of Eschericlrin coli. Can. J. Microbiol. 18: 1417-1425. Mean cell volumes, total amount of deoxyribonucleic acid (DNA), number of nuclear bodies, and X-ray responses were determined for exponential cultures of Escllericlria coli P6, a large-cell radiationresistant mutant strain, and for E. coli 82/r, the parent strain of P6, growing in three different media at varying growth rates. Combined results comparing cultures in the same growth medium indicated that exponentially growing P6 cells are 2.5 k0.2 times larger, contain 3.6 f 0.3 times more DNA, and 1.8 t 0 . 1 times nlore nuclear bodies than comparable 8211 cells. Individual P6 nuclear bodies contained 2.01 k0.13 times as much DNA as 82/r nuclear bodies in comparable cultures, suggesting that each P6 nuclear body may contain two complete 82/r genomes. All P6 cultures gave sigmoidal X-ray survival curves with extrapolation numbers averaging 2.0 and with limiting slopes smaller in absolute value than the slopes of the exponential survival curves obtained for 82/r cultures. P6 cells appeared to be no more efficient than 82/r cells in enzymatic dark repair of X-ray or ultraviolet damage, suggesting that the greater X-ray resistance of P6 cells may be associated with the doubled DNA content of each P6 nuclear body. KVETKAS, M. J., R. E. KRISCH et M. R. ZELLE. 1972. Phenotypic properties of a large-cell, radiationresistant strain of Esclrericlria coli. Can. J. Microbiol. 18: 1417-1425. Les volumes cellulaires moyens, la quantite totale d'acide deoxyribonucleique (ADN), le nombre de corps nucleaires et la reponse aux rayons-X furent determines sur des cultures en phase exponentielle d'Esclrerichia coli P6 (un mutant A larges cellules et resistant aux radiations), et sur des cultures de E.coli 82/r (la lignee mere de P6). Ces cultures se sont dheloppees sur trois diffirents milieux de croissance & des taux variables. Les resultats combines oh I'on compare les cultures dans le m&me milieu indiquent que cellules P6 en phase exponentielle sont 2.5 f 0.2 fois plus grosses, contiennent 3.6 k 0.3 fois plus d'ADN, et ont 1.8 -1 0.1 fois plus de corps nucltaires que les cellules 82/r au m&me stage. Dans des cultures semblables, les corps nucleaires des cellules P6 contiennent 2.01 + 0.13 fois plus d'ADN que ceux des cellules 82/r; ce fait suggere que chaque corps nucleaire P6 peut contenir deux genomes complets 82/r. Toutes les cultures P6 donnent des courbes sigmoldes de survie aux rayons-X avec des nombres moyens extrapoles de 2.0, et avec des pentes limites plus faibles en valeur absolue que celles des courbes exponentielles de survie obtenues avec les cultures 82/r. Les cellules P6 n'apparaissent pas plus efficaces que les cellules 82/r en ce qui concerne la reparation enzymatique des dornmages causes par les rayons-X ou le U.V. Ceci suggere que la plus grande resistance aux rayons-X des cellules P6 peut &tre associee avec la quantit6 deux fois plus grande...
A genetic analysis of Escherichia coli P6, a large-cell, radiation-resistant strain of E. coli, established that it originated as the result of a mutational event. The gene responsible for the complex P6 phenotype was located at 61 i 0.5 min on the E. coli linkage map. The close resemblance of conjugal and transductional recombinants to one or the other parent without indication of an intermediate class suggests that only a single gene may be involved. Escherichia coli P6 was isolated by Ogg and Zelle (16) after camphor treatment of E. coli 82/r, an adenine-dependent derivative of E. coli B/r. P6 cells were larger, weighed about three times more, contained approximately three times more deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), and were more resistant to X-rays than the parent (16, 21). Preliminary genetic experiments (F+ X F-crosses) showed that colonial morphology, cell size, radiation resistance, and an unselected property, Ti resistance, segregated as a unit (21). These results suggested that a pleiotrophic mutation was responsible for the complex phenotype of P6. The results of experiments designed to establisht the genetic constitution of E. coli P6 are reported here. Using both conjugation and transduction techniques, we mapped the P6 gene, lar-J, at 61 + 0.5 min on the E. coli linkage map. Recombinants characterized in terms of the properties originally used to describe the two parental strains resembled either one or the other parent. There were no indications of intermediate-type recombinants. Thus, the complex phenotype of E. coli P6 appears to be due to the mutation of a single gene. MATERIALS AND METHODS Symbols. The recommendations of Demerec et al. (6) with regard to genotypic and phenotypic designa-I Part of a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree,
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