摘要:

Adenosine triphosphatase (ATPase) fromThiobacilhis ferrooxidanswas purified 55-fold. Polyacrylamide gel electrophoresis of the most purified fraction showed only one major band; histochemical analysis showed that the ATPase activity was associated with this band. The pH optimum is 9–10. The enzyme hydrolyzed ATP stoichiometrically to ADP and inorganic phosphate, theKmfor this substrate being 7.75 × 10−3 M. GTP and ITP are alternate substrates, theKmvalues for these being 6.71 × 10−3 M and 3.12 × 10−3 M, respectively. ADP is slightly hydrolyzed. Magnesium, manganese, and calcium can serve as cofactors;Kmvalues for these are 2.0 × 10−3 M, 9.4 × 10−4 M, and 8.0 × 10−4 M, respectively. The enzyme activity was not activated by either sodium or potassium, but a combination of the two ions were inhibitory. Azide andp-hydroxymercuribenzoate strongly inhibited the enzyme activity, whereas cyanide, dinitrophenol, andN,N′-dicyclohexylcarbodiimide (DCCD) were without effect. The enzyme was cold labile at 0 °C, but was more stable at 18–24 °C.

ISSN:0008-4166    

DOI:10.1139/m75-001

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Alkaline phosphatase (APase) ofPseudomonas aeruginosaexists primarily in the periplasmic region of the cell, i.e., between the cytoplasmic membrane and the outer tripartite layer. The enzyme is also found in the culture filtrate or associated with the outer layer of the cell wall. APase forms a complex with released outer cell wall material, and lipopolysaccharide (LPS) is associated with the complex. Since the enzyme was purified to homogeneity, it became desirable to determine whether complex formation with LPS, or the outer cell wall, affected any properties of the purified phosphatase. The ratio of activities of purified APase withp-nitrophenylphosphate and β-glycerolphosphate as substrates is about 4:1. The ratio of activities with enzyme complexed with LPS is about 1:1. The energy of activation of sucrose or magnesium released enzyme is 9500 cal/mol whereas the values for purified enzyme plus LPS, purified enzyme, purified enzyme plus phosphatidylethanolamine (PE), and purified enzyme plus LPS plus PE range from 3400 to 8700 cal/mol. These changes occur in the physiological temperature range, 27 to 39C, of this organism. Sucrose-released enzyme in the presence of substrate is inactivated at 47C whereas pure enzyme plus substrate is affected at 41C. The addition of LPS, PE, or a combination of both increases the temperature of inactivation from 45 to 51C. The results suggest that certain properties of the purified enzyme differ from those of the enzyme released from whole cells by either sucrose or magnesium resuspension. The addition of cell wall components such as LPS and PE to purified APase restores these properties. The evidence suggests that artificial complex formation changes the environment of the enzyme protein such that the environment now resembles that which exists within the whole cell wall.

ISSN:0008-4166    

DOI:10.1139/m75-002

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The ability of selected fungi to degrade the soil insecticide Dyfonate (O-ethylS-phenyl ethylphosphonodithioate) into water-soluble, noninsecticidal metabolites was found to be dependent on the supply of nutrients, incubation time, temperature, pH, as well as other factors. With yeast extract as the carbon source (5 g/liter) and ammonium nitrate (1 g/liter) as the nitrogen source, bothRhizopus arrhizusandPenicillium notatumdegraded the insecticide to a larger extent than with any other combination of nutrients used. With glucose as the carbon source, concentrations of ammonium nitrate above 5 g/liter inhibited the degradation of Dyfonate byR.arrhizus. Time-course studies on the metabolism of the insecticide indicated that Dyfonate was first absorbed by the fungal mycelium, where it was metabolized followed by the release of water-soluble, noninsecticidal, breakdown products into the culture media. The degradation appeared to involve the breakdown of Dyfonate into ethyl acetate soluble metabolites, such as ethylethoxyphosphonothioic acid, ethylethoxyphosphonic acid, methyl phenyl sulfoxide, and methyl phenyl sulfone. These compounds were then further degraded into water-soluble products. The optimum conditions for the degradation of the insecticide byR.arrhizuswere observed at pH 6.0 to 7.0 and at 15–25 °C. Aged fungal mycelia were as active as mycelia in the logarithmic growth phase.

ISSN:0008-4166    

DOI:10.1139/m75-003

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The degradation of DNA in a repair-proficient strain (B/r) and in two repair-defective strains (Bs–1and pol A) ofEscherichia coliwas studied in the presence and absence of three metabolic inhibitors after exposure of the cells to X-radiation. The radiation-induced degradation of DNA was dependent on energy production in freshly harvested log-phase cells and was closely related to the repair capacity of the cells. A different system, probably involving nonspecific deoxyribonucleases acting at radiation-induced strand breaks, appeared to be responsible for the degradative processes in stationary-phase cells or in log-phase cells which had been aged by standing in buffered saline for 2 days before irradiation. The three inhibitors tested (caffeine, rifampin, and carbonyl cyanidem-chlorophenyl hydrazone) were all found to inhibit partially the radiation-induced degradation of DNA inE.colicells. Under other conditions, the same three compounds amplified the degradative process. The data suggested that the amplification was due to a selective inhibition of repair processes. The degradative processes which were stimulated by X-radiation ofE.colicells show many parallels to those which are evoked by phleomycin or colicine.

ISSN:0008-4166    

DOI:10.1139/m75-004

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Under carefully controlled laboratory conditions, a highly virulent strain ofErwinia amylovoracoinhabited susceptible host tissues with a yellow saprophytic bacterium, which was invariably isolated from fire blight infected trees, with or without producing symptoms of the disease depending on the status of a number of environmental factors, both climatic and physiological. In particular, variation of temperature and sucrose concentration determined, independently, the equilibrium of a readily reversible alternation of predominance of the two bacteria.It is suggested thatE.amylovoramay sometimes exist as an avirulent resident on the surface or within healthy host plants when environmental conditions favor growth of the yellow saprophyte rather than the pathogen. Such conditions, which are more likely to be obtained in midsummer and the fall, include temperature fall or rise below or above the optimum forE.amylovora, decreased humidity or diminution of sap flow, and increased sugar content in the host tissues.

ISSN:0008-4166    

DOI:10.1139/m75-005

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Sodium ion is required for transport ofL-alanine and α-aminoisobutyric acid (AIB) into cells and membrane vesicles of a marine pseudomonad. Initial rate data obtained at various Na+and amino acid concentrations were tested for fit by least squares analysis to sequential and Ping-Pong equations. The sequential case is preferred statistically at the 99% confidence limit. Cotransport of AIB and Na+in cells could not be detected, perhaps explained by efflux of Na+shown to occur from these cells. The kinetic analysis is consistent with formation of a ternary complex involving Na+and the amino acid.

ISSN:0008-4166    

DOI:10.1139/m75-006

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The location of cellulase inC.fulvusdepends on the carbon source for growth and the age of the culture. When cells were grown on glucose or cellobiose all CMC-hydrolyzing enzyme was cell-bound but only part of the activity was located on the cell surface. Treatment of cells with EDTA, lysozyme, and detergents and subsequent fractionation experiments showed that cellulase was also located in the periplasm and bound to a membrane fraction.Growth on cellulose gave cell-free cellulase active against CMC. The enzyme was repressed by glucose but formed at a constant differential rate on cellobiose and amylose. This rate was 8–10 times lower than on cellulose and possible reasons for this are discussed.

ISSN:0008-4166    

DOI:10.1139/m75-007

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Secondary alkylsulfatases (S-1 and S-2) were detected inPseudomonasC12B cultured in minimal media lacking alkylsulfates. The synthesis of these enzymes was not repressed by SO42−andL-cysteine or derepressed byL-methionine. Growth on 4% sodium citrate caused a 98% loss in the secondary alkylsulfatase activity of cells and 9% of this activity was detected in the culture medium. Citrate (20 mM) inhibited the activity of cell extracts (18%) but the inhibition was reversible by dialysis. The primary alkylsulfatase content of cells was not diminished by growth on citrate. The MgCl2concentration of the medium also influenced the cellular levels of secondary alkylsulfatase. Bacteria grown on MgCl2(0.05 mM – 40 mM) exhibited progressively increasing activity while the converse distribution was observed for activity present in the medium after growth at each MgCl2concentration. Both primary and secondary alkylsulfatases were released when cells were either subjected to osmotic shock or treated for cell wall removal. Cells washed with 0.085 M sodium citrate – 10 mM Tris – 20% sucrose released roughly 87% of both enzymes and MgCh (0.04 M) inhibited the release of primary alkylsulfatase by 11% and secondary alkylsulfatase by 50%. It is suggested that citrate chelates divalent cations necessary for the attachment of secondary alkylsulfatase at the cell periphery.

ISSN:0008-4166    

DOI:10.1139/m75-008

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Sensitivity to actinomycin D (AD) varies inPseudomonas fluorescenscells grown in glucose or succinate minimal salts medium. Growth is inhibited in succinate minimal medium by much lower concentrations of AD than in glucose minimal medium. Uptake of selected radioactive metabolites is inhibited by AD in cells incubated for 2 h in succinate medium containing AD but glucose-grown cells were not sensitive. EDTA treatment promotes increased sensitivity to AD in succinate-grown cells but does not alter sensitivity in glucose-grown cells. Succinate-grown cells bound 2–3 times as much3H-AD as glucose-grown cells. Glucose-grown cells had much higher lipopolysaccharide levels in the envelope than succinate-grown cells. It is proposed that the lipopolysaccharide masks the binding sites and, therefore, is responsible for the difference in binding of AD by the glucose- and succinate-grown cells. The availability of the binding sites is also reflected in the sensitivity of the cells to the antibiotic.

ISSN:0008-4166    

DOI:10.1139/m75-009

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Mucor alternans(van Tieghem) was found to be a diphasic species in that it grew exclusively in the yeast-like budding phase under anaerobic conditions in the complex medium yeast extract – peptone – glucose broth and in tissue-culture medium 199. In the latter medium this growth form occurred also at 37C, at an initial pH of 7.2, and at glucose concentrations of 0.1 and 1.0%. The authors suggest that because of its synthetic nature the tissue-culture medium could be used with advantage in the study of nutritional requirements of dimorphic mucors.

ISSN:0008-4166    

DOI:10.1139/m75-010

出版商:NRC Research Press    

年代:1975

数据来源: NRC