摘要:

Two strains ofEscherichia colisublethally treated in acidic environments showed an increased sensitivity to violet red bile agar. The death of cells, treated in tryptic soy broth which had been acidified with two inorganic and five organic acids, was followed on both nutrient agar and the selective medium violet red bile agar. The death rates determined on violet red bile agar were much faster than those established on nutrient agar. Therefore, it appeared that unreliable results may occur if selective media are used for the detection and enumeration of Enterobacteriaceae in acid foods.

ISSN:0008-4166    

DOI:10.1139/m71-160

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Sodium deoxycholate treatment of adenovirus-infected cell cultures was found to release rapidly sedimenting penton components with a buoyant density in CsCl of about 1.34 g/ml. The high-density penton material derived from human and simian adenovirus-infected cells occurred in monomeric form, while that derived from canine adenovirus-infected cells was in the form of non-symmetrical groupings of pentons aggregated at the vertex capsomere. Deoxyribonuclease treatment and3H-thymidine-DNA labeling experiments revealed that the high-density of the pentons so obtained was due to a small associated segment of nuclease-sensitive material. A possible explanation of the nature of the nuclease-sensitive material is given.

ISSN:0008-4166    

DOI:10.1139/m71-161

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A species ofPseudomonaspreviously used to study the degradation ofp-fluorophenylacetic acid was used to investigate the degradation ofp-fluorobenzoic acid. During growth on the latter substrate all organic fluorine was released into the culture medium as fluoride. Several metabolic intermediates were isolated from the culture medium of resting cells. The major compounds have been identified as 4-fluorocatechol, β-acetylacrylic acid, (+)-4-carboxymethyl-4-fiuorobut-2-enolide, (−)-4-carboxymethyl-but-2-enolide, and β-ketoadipic acid. A small quantity of a compound tentatively identified as β-fiuoroacrylic acid was also isolated. On the basis of these findings, together with respiratory studies onp-fluorobenzoic acid grown cells with various substrates, two metabolic pathways are proposed which involve elimination of fluorine at either of two alternative stages in the breakdown ofp-fluorobenzoic acid.

ISSN:0008-4166    

DOI:10.1139/m71-162

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Whole cells ofPseudomonas aeruginosapossessL-asparaginase activity. The enzyme is released by suspension in 0.2 MMgCl2and resuspension in 0.1 MTris buffer, pH 8.4. Under these conditions neither the plasma membrane enzyme, NADH oxidase, nor the scluble enzyme, lactic acid dehydrogenase, are released. TheL-asparaginase and the periplasmic alkaline phosphatase are completely inactivated by treatment of whole cells with diazonaphthalene–disulfonic acid, a reagent which does not penetrate the cytoplasmic membrane. Under the conditions used no inactivation of NADH oxidase or lactic acid dehydrogenase was observed.L-Asparaginase is also released by converting whole cells to spheroplasts. The results suggest thatL-asparaginase ofP.aeruginosais located exterior to the cytoplasmic membrane, possibly in the periplasmic space.

ISSN:0008-4166    

DOI:10.1139/m71-163

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A proteolytic enzyme present in culture filtrates ofScopulariopsis brevicauliswas purified about 200-fold by (NH4)2SO4and ethanol fractionations followed by chromatography on DEAE-cellulose, DEAE-Sephadex, and hydroxylapatite. Ultracentrifugation of the purified enzymes showed only one sedimenting component and its molecular weight was estimated to be about 24 000. The protease hydrolyzed casein, urea-denatured hemoglobin, gelatin, fibrinogen, fibrin, insulin chains A and B, but not human serum albumin or ovalbumin. It also coagulated milk. The enzyme had no action on the various peptides tested and showed low esterase activity. Optimum pH for casein hydrolysis was 10.5 to 11; for hemoglobin hydrolysis 7.0–9.5, and for gelatin hydrolysis, 6.0–8.0. The enzyme activity was unaffected by most metal ions, SH-reagents, and some natural trypsin inhibitors. The protease was strongly inhibited by diisopropylfluorophosphate and phenylmethanesulfonyl fluoride. Although similar in some respects to CA-7, the enzyme isolated fromAspergillus oryzae, and other alkaline proteases, theS.brevicaulisprotease does not appear to be identical with any one of them.

ISSN:0008-4166    

DOI:10.1139/m71-164

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The initiation of germination of spores ofBacillus cereuswas induced byL-alanine orL-phenylalanine and a combination of the amino acids showed an additive effect. Several compounds such as β-phenethylamine, phenylacetonitrile, benzyl alcohol, and phenethyl alcohol inhibited the initiation mechanism. The initiation of germination byL-alanine was more sensitive to β-phenethylamine while theL-phenylalanine induction was more sensitive to phenethyl alcohol. Selected antibiotics, known to block macro-molecular syntheses, were not effective as inhibitors of initiation. The results suggest that the receptor site may be compatible with an allosteric enzyme model and β-phenethylamine and phenethyl alcohol act as allosteric effectors.

ISSN:0008-4166    

DOI:10.1139/m71-165

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Nitrogen fixation in waterlogged, soil–straw, and sand–clay–straw mixtures was measured with the C2H2reduction assay, the15N-tracer technique, and the Kjeldahl method. The reduction of 6 to 15 moles C2H2corresponded to the fixation of 1 mole N2. The theoretical ratio is 3 moles C2H2to 1 mole N2. A ratio of 3 moles C2H2reduced for each mole of N2fixed was obtained when samples of sand–clay–straw were incubated under conditions that minimized effects that were due to gas diffusion through the aqueous phase. Calculations indicated that N2at a partial pressure of 0.2 atm above the samples was not sufficient to saturate the nitrogenase enzyme of the organisms in lower layers of soil–straw samples. Thus the concentration of N2dissolved in the aqueous phase limited nitrogen fixation. C2H2is more soluble in water than N2; the C2H2reduction was not as limited by the C2H2concentration in the aqueous phase.N2was experimentally shown to be limited at depth in a sand–clay–glucose system in that fixation decreased from 128 to 36 μg N/g of sand–clay incubated so that the total sample depth ranged from 0.2 to 3 cm.The C2H2reduction assay provides a method for measuring the potential nitrogenase activity in the waterlogged soil amended with straw; however, this assay must be calibrated for specific conditions. The data also indicate that where N2diffusion rates may limit N fixation, a normal atmosphere (80%) of N2should be used in the experiment.

ISSN:0008-4166    

DOI:10.1139/m71-166

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Bacillus pumilusNRRL B-3275 cultures contained spherical, osmotically sensitive cells after incubation for 7 days in a tryptone broth containing 7% NaCl. Subcultures from cells growing in the saline broth produced only L-form colonies when plated on tryptone agar with 7% NaCl and only rod-form colonies on nutrient agar. When the tryptone agar medium was supplemented with 1.7% NaCl, colonies of cells irregular in shape and size were observed in addition to L-form and rod-form colonies. Platings from successive weekly transfers made in tryptone broth with 7% NaCl yielded an increasing proportion of L-form and pleomorphic-form colonies while the ratio of rod-form colonies declined. Cells of the pleomorphic form are morphologically distinct from both the rod form and L form but are identical with the rod form in their growth requirements.

ISSN:0008-4166    

DOI:10.1139/m71-167

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

This investigation was prompted by the reported formation of HCN from isoleucine by way of the cyanogenic glycoside lotaustralin in a psychrophilic basidiomycete. In comparable experiments we found steam distillates from cultures incubated withL-isoleucine-U-14C were radioactive but this was shown not to be due to H14CN, by removal of the HCN as AgCN. This was confirmed using isoleucine-2-14C from which H14CN recovery was negligible. Evidence was obtained that the steam volatile radioactive material regarded by other workers as H14CN consisted largely of organic acids. Hence isoleucine cannot be considered to be a precursor of HCN in this fungus and the occurrence of lotaustralin as an intermediate is therefore doubtful. Under the same conditions HCN was shown to arise from carbon-2 of glycine, confirming previous reports from this laboratory.

ISSN:0008-4166    

DOI:10.1139/m71-168

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Feather meal, fermented by a methionine-excreting mutant ofStreptomyces fradiaein the presence of a mineral salts solution and glucose, was 90% digestible in acidified pepsin solution as compared with 65–70% for unfermented meal. Feeding trials with chicks, however, indicated that no significant difference in nutritional value existed between fermented and unfermented meal. Lack of product acceptability may have been partly responsible.

ISSN:0008-4166    

DOI:10.1139/m71-169

出版商:NRC Research Press    

年代:1971

数据来源: NRC