- Volume 59, Issue 1, 1969

SUMMARY: Mucor rouxii grew aerobically and anaerobically with glucose as carbon source; with maltose as carbon source the fungus grew only aerobically. Spores germinated in a glucose medium utilized anaerobically glucose but not maltose. Acetone powders or cell-free extracts obtained from glucose-grown mycelium, hydrolysed maltose aerobically and anaerobically. Maltose uptake and fermentation were inhibited by appropriate concentrations of KCN, DNP and amytal. These results are interpreted to mean that a functional respiratory chain is required for maltose penetration into the cell.

SUMMARY: The DNA-RNA hybrid technique of Gillespie & Spiegelman (1965) was used to measure the genetic relatedness among ten different species within the genus Candida and among three of these species and their counterparts within perfect genera. Close relationships were found between Candida albicans (guanine + cytosine content (% GC), 35.1), C. claussenii (% GC, 34.9) and C. stellatoidea (% GC, 35.7), which showed a relative homology of 63 to 73%, and between C. brumptii (% GC, 54.1) and C. catenulata (% GC, 54.5), relative homology 75%. Very close relationships were seen between the three pairs of perfect and imperfect counterparts, C. pelliculosa (% GC, 36.8) and Hansenula anomala (% GC, 36.6), relative homology 81%, C. melinii (% GC, 40.9) and H. wingei (% GC, 41.2), relative homology 97%, and C. pseudotropicalis (% GC, 41.3) and Kluyveromyces fragilis (% GC, 41.6), relative homology 92%. Some degree of homology (32%) was also found between C. pelliculosa and C. pseudotropicalis. The relatedness between C. albicans and the seven other Candida species (% GC, 36.6 to 57.6) examined was low, relative homology 4 to 13%. This also applies to C. tropicalis (% GC, 34.9).

SUMMARY: Asexual sporulation of Aspergillus niger occurred in submerged culture in a liquid minimal medium without added nitrogen, in low ammonium-N concentrations, and in a wide range of nitrate-N concentrations. Ammonium salts containing more than 48 mg. atom N/l. were inhibitory to conidiation. Most amino acids overcame the ammonium inhibition of conidiation when added to an ammonium nitrate medium. Glyoxylate and several intermediates of the tricarboxylic acid (TCA) cycle also promoted conidiation in the presence of ammonium. Changes in the medium of conidiating and non-conidiating cultures were examined with respect to nitrogen and glucose concentrations, dry weight and pH value. The activities of two glutamate dehydrogenases, one requiring NAD and the other specific for NADP, and of aspartate and alanine amino transferases varied during growth as a function of the stage of the life cycle and of the growth medium. There was no clear correlation between the activities of these enzymes and conidiation of this fungus.

SUMMARY: The amidohydrolase formed in the later stages of growth on glucose peptone medium by Candida utilis was purified 60-fold from cell-free extracts. The purified enzyme hydrolysed mono- and di-carboxylic acid amides, benzamide, nicotinamide, pyrazinamide and certain β-hydroxyl substituted fatty acid amides, was inactive on l-asparagine and l-glutamine and was competitively inhibited by urea and N-methylurea. Acetamide and nicotinamide together showed mutual competition.

SUMMARY: Sixty-nine Agrobacterium strains, including representatives of six current species, were tested: for colony formation on sucrose + salts medium, 3-ketoglycoside production, response on litmus milk medium, infectivity on carrot-root discs, infectivity and rate of tumour appearance on primary pinto bean leaves. These tests separated the majority of the strains into species. Forty-four strains were tumourigenic on pinto bean leaves, ten of which did not form colonies on a sucrose + salts medium and nine of these showed a rate of tumour appearance typical of auxotrophs. Glutamate was required for colony formation by seven of the ten auxotrophs, two required only pantothenate and one strain required either glutamate or pantothenate. The two A. rubi strains among the ten auxotrophs required nicotinic acid + pantothenate + glutamate. Strains that required either pantothenate or pantothenate + nicotinic acid for colony formation also required these compounds in liquid medium. None of the strains which required glutamate for growth on plates required it in liquid medium though glutamate shortened lag and division times. The growth requirements of the auxotrophs did not obviously correlate with their specific infectivity. Six of the ten auxotrophs produced no 3-ketoglycosides, but this response did not correlate with infectivity or nutritional requirements. Three auxotrophs initiated more tumours when appropriate growth factors were added to inoculated leaves. The agrobacteria that induced pinto bean leaf tumours fell into four groups: I, strains which infected all wound sites with equal efficiency regardless of wound size; II, strains which infected all but the smallest wound sites with equal efficiency; III, phototrophic strains which infected only larger wound sites; IV, auxotrophic strains which, in the typical examples, infected only the larger wound sites. Nineteen of the tumourigenic strains (43%) were restricted in their ability to infect small wound sites and were assigned to groups III and IV. Because loss of the ability to initiate tumours at small wound sites is due to nutritional limitations imposed on the infecting bacteria by the wound site medium, these group III and IV strains were nutritionally limited in their ability to infect this host. The large proportion of strains which showed this defect indicates that variation in the ability of tumefacient strains to adapt to the wound medium supplied by a host is quite common and hence represents one major pathway by which pathogenicity within the genus may have evolved.

SUMMARY: Genetic mapping of the structural phoA and the linked regulatory phoR genes for alkaline phosphatase synthesis in Escherichia coli was carried out by conjugation. Distal markers were selected and the segregation of proximal markers was determined. The gene order lac-phoA-phoR-tsx is proposed.

SUMMARY: Micro-organisms can be grown in continuous culture at maximum specific growth rate (μ max) by a new method based on control through carbon dioxide production. A carbon dioxide analyser regulates, through a controller unit, the supply of medium to the culture. Unlike the turbidostat, the new method allows almost indefinite, uninterrupted operation. The apparatus was tested in the determination of Arrhenius plots of log μ max against the reciprocal of absolute temperature for a strain of Saccharomyces cerevisiae and a respiratory-deficient mutant prepared from it.

SUMMARY: Vibrio cholerae and V. eltor underwent considerable lysis after treatment with tris+EDTA, tris+EDTA+lysozyme or sodium lauryl sulphate. Lysis induced by tris+EDTA or tris+EDTA+lysozyme was completely inhibited by 0·3 m-sucrose, 0·15 m-NaCl or 0·01 m-MgCl2. The extent of death after treatment with tris+EDTA depended on EDTA concentration: 10 min. with 10 μg. EDTA/ml. left 43 to 50% of V. eltor viable and 71 to 75% of V. cholerae. Labelled organisms exhibited maximum leakage of 32P compounds when exposed to 71% (v/v) ethanol for V. cholerae and 50% (v/v) ethanol for V. eltor; leakage in 100% ethanol was about 77% of maximum for V. cholerae and 66% for V. eltor. Both 32P labelled and unlabelled vibrios released considerable amounts of nucleic acid, phospholipid, protein and carbohydrate and practically all their acid soluble phosphates with EDTA.

SUMMARY: Unlike some other photosynthetic bacteria, Rhodopseudomonas spheroides directly carboxylates pyruvate in a reaction catalysed by a pyruvate carboxylase (E.C. 6.4.1.1). A partially purified preparation of the enzyme was acetylCoA-dependent. No phosphoenolpyruvate synthetase or phosphoenolpyruvate carboxylase activity was detected in extracts of R. spheroides. The organisms dependence upon its pyruvate carboxylase was shown by the fact that a mutant strain which lacked this enzyme was unable to grow either anaerobically in the light, or aerobically in the dark, on glucose or pyruvate (with CO2). Convenient spectrophotometric assays for pyruvate carboxylase are reported.

SUMMARY: Cell-wall fractions were obtained from Aspergillus niger and Chaetomium globosum. Non-structural protein was removed by successive washes in urea, NH4OH and formic acid. Amino acid analyses indicated that structural wall proteins were acidic. Aspartic acid was the free amino terminal residue of the protein in both species. Comparison of the ‘maps’ of peptic peptides indicate that there may be some homology between the wall proteins of the two fungi.

SUMMARY: Acetohydroxyacid synthetase produced by Penicillium chrysogenum q 176 and a high penicillin-producing mutant have been compared. Both were sensitive to valine as the major feedback inhibitor. Inhibition of the enzyme in q 176 appears to be effected through two valine binding sites, but only one of these remains in the high yielding strain and it is non-competitive with respect to pyruvate. The amount of enzyme activity detectable in the high yielding strain is more than twice the level in q 176. Control of acetohydroxy-acid synthetase by other related amino acids was shown to be complex and involved sites other than the valine binding site.

SUMMARY: Nine strains of Aspergillus flavus and one each of A. versicolor, A. penicilliformis and A. niger isolated from Delhi soils were screened for ability to produce aflatoxins on different media. Seven strains of A. flavus produced aflatoxins B1 and B2 but no aflatoxin G. The other five isolates produced no detectable aflatoxins. Yields of aflatoxins were low on glucose-salts or sucrose-yeast extract media. The latter with added salts or a modified Czapek agar medium gave enhanced yields.

SUMMARY: Among 20 locally isolated fungi, Aspergillus niger isolate no. 58 proved to be suitable for the production of active extracellular milk-clotting enzyme. The addition of acetate buffer to the reaction mixture enhanced the clotting of milk by the enzyme whereas citrate + phosphate buffer hindered the process. The general properties of the crude enzyme were studied. Precipitation with ammonium sulphate, ethanol, acetone and tannin showed that ammonium sulphate was unsuitable for precipitation while the other precipitants produced sufficiently active fractions.

SUMMARY: The electrophoretic separation of partially purified milk-clotting enzyme from Aspergillus niger no. 58 with 0.02 m-acetate buffer showed four protein components. The milk-clotting enzyme fraction constituted the major part of the preparation and exhibited the highest milk-clotting activity and the lowest proteolytic action. The course of proteolysis in the first stage of the enzymic action was similar to that of animal rennin. The enzyme action was optimal at 50° and pH 5.8.