摘要:

Growth in a supplemented minimal culture medium and chlamydospore formation in supplemented corn meal agar were the criteria used to evaluate in vivo biosynthesis of sulfur containing amino acids in auxotrophs ofCandida albicans. Supplementation withL-cystathionine,L-homocysteine,L-methionine, S-adenosyl-L-methionine, or S-adenosyl-L-homocysteine resulted in growth in the minimal medium and both growth and chlamydospore formation in corn meal agar. One auxotroph (CYS) gave comparable results when inoculated into media supplemented withL-cysteine, responded minimally when O-acetyl-L-serine and sulfide comprised a dual supplement, and failed to grow or form chlamydospores when sulfide or O-acetyl-L-serine was used as a single supplement, suggesting that this organism may possess a deficiency in the synthesis or activity or cysteine synthetase. Another auxotroph (OAHS) did not grow or produce chlamydospores when O-acetyl-L-serine was added to the media in combination with sulfide, or when eitherL-cysteine, O-acetyl-L-serine, sulfide, orL-homoserine was used as a single supplement, but did respond to media supplemented with O-acetyl-L-homoserine indicating a deficiency in homoserine-O-transacetylase in this microorganism. Auxotroph OAHS grew and formed chlamydospores as well in media containing only supplemental O-acetyl-L-homoserine as it did when O-acetyl-L-homoserine was used in combination with sulfide S-methyl-L-cysteine or thiomethyladenosine, while (CYS) neither grew nor produced chlamydospores in any of these supplemented media. These results lend support for the hypothesis that cystathionine is an important intermediate in methionine biosynthesis inC.albicans. The positive results obtained when the auxotrophs were inoculated into media supplemented with S-adenosyl-L-homocysteine or S-adenosyl-L-methionine may reflect an alternate route for methionine biosynthesis which functions conditionally in this microorganism. The potential significance for endogenous formation of sulfur containing amino acids from S-adenosylmethionine is therefore considered.

ISSN:0008-4166    

DOI:10.1139/m73-024

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Cellular form inAureobasidium pullulonscan be partially controlled by nitrogen nutrition. Ammonium nitrogen supports a mixture of filamentous and yeastlike growth, whereas only a few filaments develop on nitrate nitrogen. On nitrate 97% of the cell material consists of a mixture of yeastlike cells and chlamydospores. Chlamydospores are produced on both nitrogen sources; however, with ammonium nitrogen chlamydospores occur in an intercalar position, whereas nitrate nitrogen supports development of chlamydospores as separate structures containing one, two, or occasionally three cells. This mode of production allows separation of yeast chlamydospores from other cell types and subsequent isolation of their cell walls. Yeast chlamydospores and filaments have an electron dense, melanin-rich, granular, outer cell-wall layer which yeastlike cells lack. This granular material is also found in cross walls of filaments and chlamydospores. Glucose is the main component of chlamydospore walls and accounts for 36% of the dry weight. Yeastlike cell walls contain only 13% glucose, but more mannose, galactose, and bound lipid. Most of the glucan portion of chlamydospore walls is insoluble in dilute alkali; methylation analysis indicates that this material contains linear chains of (1 → 3) and (1 → 6) linked glucose. About one residue in five forms a branch point having both (1 → 3) and (1 → 6) linkages.

ISSN:0008-4166    

DOI:10.1139/m73-025

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

α-Methyl-D-mannoside (α-MM) was used by all acetate-oxidizing strains ofB.popilliaetested at a growth limiting rate after a prolonged induction period. Those strains which did not oxidize acetate could not use α-MM for growth unless it was present at a high concentration. The period of induction was decreased, the rate of growth increased, and the extent of oxidation decreased as the α-MM concentration was increased. Theoretical levels of O2uptake and CO2evolution for the complete oxidation of the mannose moiety of α-MM were observed when the concentration of α-MM was low. Studies with resting cells and cell extracts demonstrated that an α-glucosidase was induced inB.popilliaeby either α-MM or α-methyl-D-glucoside (α-MG). The enzyme was induced more rapidly by α-MG than by α-MM. Similarly, the ability of cells to oxidize α-MM was induced more efficiently by α-MG than by the mannoside. The data indicate that the hydrolysis of both α-MG and α-MM may be catalyzed by the same enzyme, but that the affinity for α-MG is much higher than that for the mannoside. The slow hydrolysis of α-MM by this enzyme is believed to account for the type of growth response observed.

ISSN:0008-4166    

DOI:10.1139/m73-026

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

An inhibitor of coxsackievirus B5 was found in extracts of commercially ground beef; it resembled antibody in physical and chemical properties. Another inhibitor, found in a batch of fetal bovine serum, differed from the inhibitor in beef extract and specific coxsackievirus B5 antibody; it was destroyed at pH 3.0. Chemical bonds between virus and inhibitors in beef extract, fetal bovine serum, or specific antiserum against coxsackievirus B5 were formed during storage at 4 °C. The bonds were broken by treatment with hydrochloric acid at pH 3.0 for 1 h, releasing infectious virus. This finding may be of importance in the recovery of virus from ground beef.

ISSN:0008-4166    

DOI:10.1139/m73-027

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A pleomorphic, acidophilic, and chemoautotrophic microbe is described. The cell is bound by a membrane and a diffuse, amorphous layer. The isolate used either sulfur or iron as a source of energy. Morphological and nutritional similarities as well as corresponding thermophilic and acidophilic requirements suggest a relationship toSulfolobus. The organism tolerates 80 °C for longer than 2 h, but heat resistance is not attributed to a bacterial spore. The maximum temperature for growth is 70 °C; the minimum about 45 °C.The DNA base composition is 57 ± 3 mole % GC. Yeast extract enhances growth of the isolate on iron and sulfur substrates, but does not significantly enhance the isolate's respiration rate on these same substrates.The isolate requires induction by sulfur or iron for maximum respiration on these substrates, respectively. Optimum oxidation of elemental sulfur occurred at pH 2.0 and gave aof 163; oxidation on iron gave a maximumof 879.

ISSN:0008-4166    

DOI:10.1139/m73-028

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Viability of freeze-driedSerratia marcescens8UK was studied at 24.5 °C as a function of oxygen concentration and time. Results depended upon the source of the inoculum. Oxygen proved to be toxic and the kinetics (with respect to oxygen concentration) were first order at low oxygen concentrations and zero order at high oxygen concentrations. This indicates that the site for the action of oxygen can become saturated with oxygen. No simple relationship between viability and time was observed. Free radical studies were also made and showed that the detected free radicals were not involved in causing oxygen-induced loss of viability.The survival ofEscherichia coliB frozen quickly and stored at −80 °C was found to be little, if at all, influenced by oxygen. Similar results were obtained withSerratia marcescens8UK. Free radical studies were performed onE.coliB at −80 °C, but no free radicals were detected even after storingE.coliB for 30 days at −80 °C, −20 °C, and −10 °C. Under the last two conditions appreciable loss of viability occurred whenE.coliB was frozen slowly.The results indicate that oxygen-induced loss of viability in freeze-dried and frozen and thawedSerratia marcescens8UK andEscherichia coliB does not involve the formation of free radicals as has been suggested by other workers.

ISSN:0008-4166    

DOI:10.1139/m73-029

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Sensitivity of soil bacteria to bacteriostasis was assessed by an agar disk method. Most bacteria isolated from wheat rhizosphere (98%) were sensitive and those not stimulated by roots were not sensitive. Bacteriostasis was always overcome by the addition of wheat root exudates to the disks and sometimes by the addition of glucose or mineral salts. Bacteriostasis was active in all six soils studied but less so in those with acid pH. Bacteriostasis was removed partially by air-drying the soil and totally by sterilizing. Filtrates of soil extracts retained some activity unless completely sterile.

ISSN:0008-4166    

DOI:10.1139/m73-030

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A fluorescent antibody method for detection of fecal coliform pollution in water is reported. Detection ofEscherichia coliof fecal origin by this method was compared to IMVIC typing and to detection by the E C Broth method. Reliability of this method was tested by reaction of specificE.coliantisera with heterologous bacterial species and with isolates from polluted waste water and unpolluted water and soil sources. This method was found to offer the advantage of greater rapidity over conventional water quality tests, without loss of reliability.

ISSN:0008-4166    

DOI:10.1139/m73-031

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

From cultures of two strains of streptococci which were transformable to drug resistance with a very low yield of about 0.001%, efficiently transformable as well as totally nontransformable isolates were selected. Both kinds of isolates produced the competence factor and extracellular deoxyribonuclease. The nontransformable strains were lysogenic and produced bacteriophage after treatment with mitomycin C. The transformable ones were not lysogenic. Treatment of the latter strains with respective bacteriophages resulted in a loss of transformability. Determinations of deoxyribonuclease activity of all strains did not provide conclusive evidence as to the requirement for a deoxyribonuclease in transformation.

ISSN:0008-4166    

DOI:10.1139/m73-032

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Bacillus cereusthat had been exposed to chloramphenicol for 0 and 90 min synthesized walls whose thickness increased with time. These cells were washed and resuspended in fresh growth medium. Cell division was examined by electron microscopy. In untreated cells, a slight invagination of the cytoplasmic membrane with deposit of cross-wall material marked the onset of cell division. The cross wall grew inward until the septum was aboutcompleted. This was followed by splitting and bifurcation of the outer edge of the cross wall, which in turn separated the peripheral wall scars. Cross-wall penetration with further splitting continued until the daughter cells were completely partitioned. The peripheral wall scars that were located at the junction of peripheral and end walls at the time of cell separation indicated that the zone of cell division was probably not a region of active cell elongation. In cells treated with chloramphenicol for 90 min, cross-wall initiation and completion all occurred beneath a thickened peripheral wall. The circumferential portion of the peripheral wall at the zone of cell division appeared to be responsible for the hindrance of cell separation. This thick layer subsequently severed at three or four sites to allow the separation of daughter cells. For cells that had initiated cross-wall invagination at the time when chloramphenicol was added, accumulation of a large amount of cross-wall material at the zone of cell division was observed. Upon removal of the antibiotic, cells abandoned the old and initiated a new dividing site. For cells that had already completed cross-wall formation at the time of chloramphenicol treatment, the increase in wall thickness did not appear to interfere with cell separation. Models for the different stages of cell division in all these bacteria were presented.

ISSN:0008-4166    

DOI:10.1139/m73-033

出版商:NRC Research Press    

年代:1973

数据来源: NRC