摘要:

By transformation analysis, a mutation (crsE1), which makesBacillus subtiliscells able to sporulate in the presence of relatively high concentrations of glucose and other carbon sources, was mapped in therpoBCoperon. The effect ofcrsE1mutation can be suppressed by another mutation in the same operon,rfm11, which confers resistance to rifamycin. Mutants carryingstvorstdmutations, which are also located in therpoBCoperon, showed partial resistance to catabolites in sporulation. It appears therefore that a change in the structure or synthesis of RNA polymerase may alter the response of cells to the inhibitory effect of catabolites on sporulation.

ISSN:0008-4166    

DOI:10.1139/m84-063

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The specificity of phenylalanine and tyrosine carriers was investigated using actively metabolizing cells ofBrevibacterium linens. The cellular protein synthesis of resting cells was very weakly inhibited, even with high concentrations of chloramphenicol or tetracycline. The nonaromatic amino acids were weak inhibitors for these carriers, while fluorinated analogues of phenylalanine and tyrosine were very potent competitive inhibitors. In practice these analogues cannot be used to replace amino acids to evaluate transport without incorporation because they are incorporated in cellular proteins.

ISSN:0008-4166    

DOI:10.1139/m84-064

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Streptomyces echinatusA8331 cultured on a maltose minimal salts medium normally produces a single antibiotic, echinomycin (quinomycin A), containing two quinoxaline-2-carbonyl chromophores. Echinomycin is powerfully active against experimental tumours and can be assayed by its activity against Gram-positive bacteria. Grown in the presence of aromatic carboxylic acids related to quinoxaline,S.echinatusresponds in favourable circumstances by incorporating the added material into analogues of the natural antibiotic having replacement chromophores. Both mono- and bis-substituted derivatives are formed. With quinoline-2-carboxylic acid as precursor, large quantities of analogues are produced, and the time course of synthesis, extraction, purification, assay, and characterization of the derivatives are described. Twenty-two other aromatic acids have been tested as potential substrates for antibiotic analogue biosynthesis. Half of them did not significantly affect growth and echinomycin production. Five appeared to stimulate antibiotic synthesis, while the remainder proved inhibitory. New biologically active antibiotics were detected in cultures supplemented with 7-chloroquinoxaline-2-carboxylic acid; 1,2,4-benzo-as-triazine-3-carboxylic acid; thieno[3,2-b]pyridine-5-carboxylic acid; and 6-methylquinoline-2-carboxylic acid.

ISSN:0008-4166    

DOI:10.1139/m84-065

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The very fine sinuous K99 pili of enterotoxigenic strains ofEscherichia colican be visualized in shadowed and in negatively stained preparations, especially if the amorphous K30 glycocalyx is not produced, but these very delicate structures cannot be directly resolved in sectioned material. The K99 pili can, however, be thickened by the nonspecific accretion of K30 glycocalyx material, during its condensation as a result of dehydration, to the point where it can be resolved in sectioned material. This visualization is enhanced if the accreted and condensed glycocalyx is stained with ruthenium red. Alternatively and additionally, the K99 pilus can be thickened by the specific accretion of monoclonal antibodies so that it is made visible in sectioned material. The condensation of the hydrated K30 antigen glycocalyx of enterotoxigenic strains ofEscherichia coliduring dehydration can be prevented by stabilization using specific antibodies so that this capsular glycocalyx structure is identified in sectioned material and is seen in its correct distribution and dimensions. These methods allow the identification and visualization of bacterial surface structures, bothin vitroandin vivo, and they provide a useful means of assessing the presence and distribution of these structures at all stages of the bacterial disease and a possible means of assessing their roles in the pathogenic process.

ISSN:0008-4166    

DOI:10.1139/m84-066

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

DX particles of poliovirus are deletion mutants that do not induce synthesis of capsid proteins or the precursor of capsid proteins (NCVPla) during infection. However, cells infected with DX particles synthesize two proteins, p68 and p25, that are not detected during growth of standard virus, and a protein of 27 000 (p27) which is comparable in molecular weight to VP3. Peptide maps of these proteins were obtained by partial digestion withStaphylococcus aureusV8 protease and elastase. The peptide map of p68 corresponded approximately 70% with the peptide map of NCVPla, and antiserum against virions reacted with p68. These data suggest that p68 is a large fragment of NCVPla. Digestion of purified structural proteins VP1, VP2, and VP3 yielded distinct peptide maps, but p25 was resistant to both V8 protease and elastase and did not react noticeably with anticapsid antibody. Peptide maps obtained forin vivoviral proteins migrating with a molecular weight of 27 000 were complex, indicating the presence of at least two and possibly three proteins. Cells infected with standardgsandgrviruses produced authentic VP3, but cells infected with defective interfering particles did not. However, onegrvariant of standard virus contained a mutation in structural protein VP2.

ISSN:0008-4166    

DOI:10.1139/m84-067

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Investigations were carried out concerning the selectivity and productivity of rabbit plasma fibrinogen (RPF) agar according to Beckers et al. (H. J. Beckers, F. M. van Leusden, W. M. Hogeboom, and E. H. M. Delfgou-van Asch. 1980. De Ware(n)-Chemicus, 10: 125 – 130). Its selectivity was compared with pork plasma fibrinogen (PPF) medium according to Hauschild et al. (A. H. W. Hauschild, C. E. Park, and R. Hilsheimer. 1979. Can. J. Microbiol. 25: 1052–1057) and its productivity was compared with PPF medium and Baird-Parker's egg yolk tellurite glycine pyruvate (ETGP) agar. In total 139 samples of naturally contaminated foodstuffs were examined. RPF agar scored higher than ETGP agar; although only small (mean value of differences 0.09 log units), the differences were statistically significant. While no significant differences in sensitivity between RPF agar and PPF medium were encountered, RPF agar was statistically more selective than PPF medium. It is concluded that RPF agar is very suitable for the enumeration ofStaphyloccus aureusin foods.

ISSN:0008-4166    

DOI:10.1139/m84-068

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A reliable and reproducible method for the estimation of the protein content of fungal cells immobilized in a carrageenan gel is described. The procedure depends upon the acid lability of the polysaccharide gel at 90 °C and on the acetone solubility of accumulated phenolics. Freeze-dried gel beads (2–3 mm) containing entrapped cells ofPenicillium urticaewere ground to a fine powder and samples of powder (~20 mg) were sequentially extracted with hot 1NHCl – 0.9% NaCl and acetone. The precipitated residue contained the cell protein, which was then solubilized with 1NNaOH at 90 °C and quantitated by the Folin–Lowry method. Interferences from both carrageenan and phenols were thus eliminated. The presence of carrageenan (20–25 mg) did not affect the recovery of varying amounts (0–2500 μg) of bovine serum albumin. The recovery of radiolabeled protein from immobilized cells was parallel to that of Folin–Lowry positive material over a range of 0–60 beads (0–60 mg powder). Cycloheximide (0–100 μg/mL) was shown to progressively inhibit the incorporation ofL-[U-14C]leucine so that the radioactivity present in the initial HCl–NaCl extract (i.e., [14C]leucine) increased as that in the final NaOH extract (i.e.,14C-labeled protein) decreased. Using this new assay for cell protein, free and immobilized cell cultures were found to exhibit virtually identical kinetics of glucose utilization, growth, and patulin production. In addition to providing a means of comparing the specific productivity of free versus immobilized cell preparations, this assay accurately measures the incorporation of [14C]leucine into cellular protein and could be used as a measure of cell viability.

ISSN:0008-4166    

DOI:10.1139/m84-069

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Specific acquired immunity to gonococci was studied in systemically immunized mice, challenged with 107gonococci by intrauterine inoculation. Protection after intraperitoneal immunization was monitored by vaginal cultures taken 24 h post-challenge, since events during the first 24 h postexposure to gonococci are crucial in determining the outcome of infection. Mice were protected against gonococcal challenge by two inoculations with either live or boiled gonococci given 4 weeks apart, whereas immunization with one inoculation did not protect against challenge 1 week later. Protection was correlated with high titers of IgG antibody in serum after two immunizations, but not with the high titers of serum IgM antibody found after the one immunization. IgG antibodies, but not IgM antibodies, were shown to pass into genital secretions. Protection could be passively transferred by serum with high titers of antibody. Of most practical importance was the finding that not only were heat-stable antigens protective, but also heterologous protection resulted after immunization with three strains differing in source (disseminated gonococcal infection versus gonorrhea), opacity–transparency characteristics, and serum sensitivity. The data indicate that IgG antibodies resulting from systemic immunization with heat-stable antigens may be able to provide cross-protection immunity against gonorrhea.

ISSN:0008-4166    

DOI:10.1139/m84-070

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The ability of the updated Abbott MS-2 system to detect methicillin-resistantStaphylococcus aureus(MRSA) was compared with disk agar diffusion and broth microdilution. Of the 87 MRSA isolates tested, the MS-2 system correctly detected 85 (97.7%) in 5 h. Seventy-two of the isolates were detected by disk agar diffusion within 24 h, and 15 more by 48 h. Broth microdilution detected 71 MRSA by 24 h of incubation and 11 more by 48 h. The updated MS-2 system yielded reliable results that were highly comparable with the standard techniques.

ISSN:0008-4166    

DOI:10.1139/m84-071

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

During 1980–1982, white-footed mice (Peromyscus leucopus) were captured in Newtown, Connecticut, an area whereRickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever, is thought to be enzootic. An indirect micro-immunofluorescence test identified specific antibodies to this organism in 16 of 237 (7%) sera; titration end points for 14 samples were relatively high (1:128–1:2048). Antibodies were detected in mice during 1980 and 1981 with monthly prevalences varying from 8 to 22%. These results suggest thatP.leucopusmay be involved in the ecology ofR.rickettsiiand that these rodents can be included along with other mammals to monitor spotted fever rickettsial infections in nature.

ISSN:0008-4166    

DOI:10.1139/m84-072

出版商:NRC Research Press    

年代:1984

数据来源: NRC