摘要:

Treatment of milled defatted capon feathers with filtrates ofStreptomyces fradiaeATCC 10745 that had been concentrated 20 times showed that the most keratin degradation in 0.5 h occurred at pH 8.0 and 60 °C. If assay time was extended, however, a decrease in reaction rate occurred and appeared to result from keratinase instability at elevated temperatures. Exposure of commercial feather meal to unconcentrated culture filtrates for 15 h produced greatest degradation at 50 °C.

ISSN:0008-4166    

DOI:10.1139/m75-084

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Methionine-excreting mutant strains ofStreptomyces fradiaeATCC 10745, produced by exposure toN-methyl-N′-nitro-N-nitrosoguanidine, were selected on the basis of ethionine-resistance and ability to support the growth of an auxotroph which required methionine or methionine precursors. When acid hydrolysates of dehydrated liquid cultures were analyzed for amino acid content, one of the mutants had produced 268% more methionine than the parental strain. To obtain an accurate analysis of methionine content, it was necessary to determine the amount of diaminopimelic acid which had been synthesized. This compound appeared in eluates during column chromatography at about the same time as methionine, and its presence increased apparent methionine concentrations by 25 to 40%.

ISSN:0008-4166    

DOI:10.1139/m75-085

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

R-factors of the P-2 (prototype R-factor R931) incompatibility group pf plasmids detected inPseudomonasare compatible with group P, C, W, and N R-factors which are plasmids that can be transferred toPseudomonas aeruginosarecipients. Members of the P-2 group (R130, R931) have significant homology by DNA–DNA hybridization. R-factors of the P-group (RP1, RP9) and F-group (R1) exhibited homology with P-2 R-factors but to a lesser extent than R130 with R931. Members of the 1, C, and W groups showed no significant homology with P-2 R-factors. Minicircular DNA of strain 931(R931) was not homologous with R931 DNA. The host range of R931 and R130 is limited mainly to certainPseudomonasspecies includingP.aeruginosa,P.fluorescens,P.putida, andP.stutzeri. These R-factors could not be transferred at detectable frequencies to any member of the Enterobacteriaceae examined. R-factor-specified pili were strongly suggested by the detection of pili by electron microscopy in R+but not R−non-piliated mutants ofP.aeruginosastrain PA01. The combined properties of R-factors 931 and similar R-factors reported before and in this study strongly support our previous contention that this group of R-factors form a significant new group of plasmids. A classification scheme previously proposed for plasmids occurring inPseudomonashas been modified and four groups have been specified.

ISSN:0008-4166    

DOI:10.1139/m75-086

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Pythium aphanidermatum, with an optimum temperature for growth at 35C, grew well and was readily isolated from soil on pimaricin–vancomycin medium (MPVM) when incubated for24 h at 38–40C. The pH of the medium affected recovery; maximum numbers developed above pH 6.0. OtherPythiumspp. were recovered on MPVM at 20–25C, but were excluded by incubation at 38–40C. ThesePythiumspp. includedP.ultimum,P.paroecandrum,P.irregulare,P.mamillatum, and an unidentifiedPythiumsp. These species grew well and were readily isolated from soil on gallic acid medium (GAM) when incubated for 24–48 h at 20C.P.aphanidermatumandP.myriotylumgrew from mycelium on GAM, but their oospores did not germinate nor could they be isolated from soil on this medium.P.myriotylumgrew well on MPVM, but was only rarely isolated, even from soils with known high potential for disease caused byP.myriotylum. Propagules ofPythiumwere enumerated by a plate-dilution frequency method or by a smear-plate method in serial dilutions of soil in 0.3% water agar. This differential isolation method is valuable for studies on the ecology, survival, and inoculum potential in soils with mixed populations ofP.aphanidermatumand otherPythiumspp.

ISSN:0008-4166    

DOI:10.1139/m75-087

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Seventy-four of 110 strains ofPseudomonas aeruginosatested produced detectable amounts of HCN from growth in 2% peptone or nutrient agar. Of the 25 species of 12 bacterial and fungal genera tested, other thanP.aeruginosa, onlyP.fluorescensandP.polycolorgave positive HCN tests. Cyanide is produced after cessation of active growth. Iron was stimulatory to cyanogenesis in concentrations above 1 μM, while copper, zinc, cobalt, and manganese at concentrations of 20 μM had no effect. Cyanogenesis is dependent on the temperature of incubation within ranges which allow complete growth. Inorganic phosphate in concentrations between 90 and 300 mM allows growth but inhibits HCN production. Growth of cells anaerobically, using nitrate as the electron acceptor, results in low cyanide yields, which can be partially reversed by subsequent aerobic incubation. These results indicate that HCN is a secondary metabolite ofP.aeruginosa.

ISSN:0008-4166    

DOI:10.1139/m75-088

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Partially purified cellulase and a cellulase-containing polygalacturonase but not lysozyme extensively degraded the walls ofChlamydomonas reinhardtiiandUlothrix fimbrataand converted intact cells of the algae to spheroplasts. A streptomycete cellulase cochromatographed with the enzyme system releasing glucose from walls of these organisms, and this preparation also converted the algal cells to spheroplasts. The dominant constituent in the walls was carbohydrate, and glucose and small quantities of galacturonic acid but no amino sugars were present in acid hydrolysates of the walls. Glucose accounted for essentially all of the material solubilized by the cellulase preparation. Lysozyme acted onCylindrospermumsp. walls, and it, but not the other enzymes, converted some of theCylindrospermumsp. cells to spheroplasts. Streptomycete enzymes lysingMicrococcus lysodeikticuscochromatographed with the proteins releasing reducing sugars fromCylindrospermumsp. walls, and components in the active fraction converted cells of this alga into spheroplasts. X-ray diffraction revealed that the walls ofC.reinhardtiiandU.fimbratabut not those ofCylindrospermumsp. contained cellulose. The data suggest that the susceptibility of the first two species to microbial degradation in natural ecosystems results from an attack on the cellulose in their walls, and the susceptibility of the third is linked with the microbial production of a lysozyme.

ISSN:0008-4166    

DOI:10.1139/m75-089

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Studies with artificially inoculated fresh beef showed that lactobacilli markedly restrict the growth ofMicrobacterium thermosphactumwhen the beef is vacuum-packaged. High concentrations of carbon dioxide (up to 75%) had little effect on the growth ofM.thermosphactumunder either aerobic or anaerobic conditions. Tests were made with samples of lean beef inoculated with pure cultures of lactobacilli and (or)M.thermosphactumand stored unpackaged in air, in air enriched with carbon dioxide, in nitrogen – carbon dioxide mixtures, or vacuum-packaged as in commercial practice. On vacuum-packaged meat, growth ofM.thermosphactumwas extensive in the absence of lactobacilli, but was restricted in the presence of lactobacilli. On unpackaged meat (i.e. stored in air) this inhibition did not occur, showing that anaerobic conditions are necessary for it to take place. These results show the importance of lactobacilli on the storage life of vacuum-packaged fresh beef.

ISSN:0008-4166    

DOI:10.1139/m75-090

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A nucleosidase activity has been isolated fromLactobacillus acidophiluswhich rapidly hydrolysesN6-(Δ2-isopentenyl)adenosine to its corresponding base,N6-(Δ2-isopentenyl)adenine. The activity can be distinguished from the spleen exzyme (EC. 2.4.2.1), a purine nucleoside transferase, on the basis of its substrate specificity, electrophoretic behavior, and non-dependence on phosphate. The bacterial enzyme hydrolyzes both inosine and isopentenyl adenosine, givingKmvalues of 63.3 μM and 177 μM respectively. The presence of this enzyme in bacteria accounts for the rapid conversion of the parent nucleoside to isopentenyl adenine, which has been observed in these cells. The enzyme thus assumes importance as one of the catabolic activities available to the cell for metabolizing the cytokinin,N6-(Δ2-isopentenyl)adenosine.

ISSN:0008-4166    

DOI:10.1139/m75-091

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

In cells ofBacillusthere is evidence that deoxyribonucleic acid forms an association with some membranous structure within the cell, possibly mesosomes. Cells of varieties ofBacillus cereusandBacillus subtiliswere examined to see if any quantitative relationship existed between the numbers of mesosomes and DNA content. No direct relationship could be demonstrated. However, cells ofBacillus cereusvar.alestiA(−) maintained a characteristic and constant DNA content and number of mesosomes regardless of growth conditions.During sporulation, a variant of A(−), termed A(−)3, sequesters its DNA at both ends of the cell, leaving a small amount of DNA but no mesosomes in the center compartment. Since this center compartment is capable of growth and division upon replacement in fresh medium (rejuvenation) it was examined for mesosome content as DNA synthesis and division were initiated. In most cells, a central mesosome was formed at the site of cell septum formation; however, the presence of a mesosome was not an absolute prerequisite for cell division.We propose that at the onset of cell growth, mesosomes primarily function in the process of cell septum formation. As growth and division proceed, mesosomes are produced in characteristic numbers and may act as the site of DNA synthesis and (or) segregation.

ISSN:0008-4166    

DOI:10.1139/m75-092

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A comparative study of the pathogenicity ofCandida albicansmorphological mutant strains was made to relate chlamydospore production, germ tube formation, and proteolytic activity to candidiasis in mice. It was observed that the mycelium strains were more lethal than the yeast-like strains and that neither chlamydospore production, germ tube formation, nor nutritional requirements was related to pathogenicity in mice. Statistical analysis indicated that the culture media of the organisms and the strain and sex of the mice into which the cells were injected were important factors in the development of pathogenicity.

ISSN:0008-4166    

DOI:10.1139/m75-093

出版商:NRC Research Press    

年代:1975

数据来源: NRC