ROLES OF CITRATE AND ACETOIN IN THE METABOLISM OF STREPTOCOCCUS DIACETILACTIS

Harvey, R. J. (University of California, Davis), and E. B. Collins. Roles of citrate and acetoin in the metabolism of Streptococcus diacetilactis. J. Bacteriol. 86:1301-1307. 1963.-Streptococcus diacetilactis was unable to use citrate as a source of energy for growth, but the addition of citrate to a lactose-containing medium increased the specific growth rate 35%. Besides serving as the precursor of acetoin, some of the pyruvate formed from citrate was incorporated into cell material, primarily into lipids. A constant fraction of the weight of new cells was synthesized from the pyruvate formed from citrate. The rate of entry of citrate into cells was independent of the growth rate, and the usual result was that more pyruvate was formed from citrate than was required for cell synthesis. All excess pyruvate was converted to acetoin. Thus, acetoin formation acts as a detoxification mechanism, a means of removing intracellular pyruvate not required for synthesis of cell material.

[The quantitative composition of natural and technologically changed aromas of plants. II. Aroma compounds in oranges and their changes during juice processing (author's transl)]

After enzyme inhibition with methanol the original volatile compounds of the fruits were investigated in order to compare the quantitative composition of the aroma substances in orange fruits and juices. Aroma compounds of fresh, flash pasteurized and pasteurized juices were analysed. After aroma enrichment by liquid-liquid extraction, prefractionation of the flavor compounds by column chromatography on silicagel 56 flavor substances in the fruits and in the different juices were identified and determined by gas chromatography and mass spectrometry. In comparison to their content in the fruits only 10% of the terpenic hydrocarbons and about 30-66% of the esters were found on average in the fruits. Among the secondary flavor substances, which were not present or present only in traces in the fruits, but showed in juices concentrations up to 0,2 ppm, were 4-terpinenol, carveol and tr-2,8-menthadien-1-ol. After a thermic treatment also 3-hydroxy-2-butanone and 3-methyl-2-buten-1-ol were identified.

[Taxonomic importance of fermentation balances of Enterobacteriaceae (author's transl)]

Fermentation balances have been studied on 66 strains from 9 taxa of Enterobacteriaceae. In addition, 6 strains of Aeromonas have been investigated. Among these fermentation balances, 7 types could be distinguished. It was shown, that the taxa of Enterobacteriaceae differed with respect to the balance types involved. This is true especially for VP-positive taxa. For example, Hafnia, the Klebsiella-Enterobacter-Serratia group, Enterobacter cloacae and Erwinia are to some extend characterized by different balance types. The groups of Enterobacteriaceae with plain acid fermentation are apperently more homogenous with respect to fermentation balances. Balances are, however, not suited for classification, because no balance type turned out to be absolutely group specific. The fermentation balances of our strains of Aeromonas are closely related to the acid-type balances of Enterobacteriaceae. A numerical classification of the data showed, that this method is most potent in sorting multivariate data. A basic agreement of both techniques, the subjective and the numerical subdivision, was found. The first one, however, tends to overemphasize differences among the types. A comparison between the quantitative data of fermentation balances and the corresponding diagnostic tests (MR, VP, Gas) gives information on the reliabiity of the latter.

Enzymes of 2-oxo acid degradation and biosynthesis in cell-free extracts of mixed rumen micro-organisms

The enzymes of 2-oxo acid decarboxylation and 2-oxo acid synthesis (EC 1.2.7.1 and EC 1.2.7.2) were isolated and partially purified from cell-free extracts of rumen micro-organisms. The lyase was active with pyruvate, 3-hydroxypyruvate and 2-oxobutyrate. The synthase was active with acetate, 2-oxoglutarate or succinate. Pyruvate synthase was separated from pyruvate lyase by Sephadex G-200 gel filtration. With Sephadex filtration, approximate mol.wts. of 310000 and 210000 were determined for pyruvate lyase and pyruvate synthase respectively.

Some Factors Influencing the Efficiency of Production of Acetylmethylcarbinol by Rhizopus nigricans

Incubation time had no effect on the efficiency ratio [dry weight-acetylmethylcarbinol (AMC)] during the incubation times tested. The mycelium was more efficient in synthetic media at pH 3 and 4 than at pH 5 and 6. Mycelium also produced AMC more efficiently in apple juice and in synthetic media containing yeast extract or vitamins, especially thiamine. KCl, MgSO 4 , and KH 2 PO 4 had significant suppressing effects on AMC production in a synthetic medium.

Survey of Selected Filamentous Fungi for Voges-Proskauer Reactions

Of 16 filamentous fungi surveyed for Voges-Proskauer reactants, 81.2% were found to be positive. The total group fell into three classes: those producing considerable acetylmethylcarbinol (AMC), those producing a small amount, and those producing no AMC. Oidium lactis had a highly significant effect upon lowering the amount of Voges-Proskauer reactants produced by Rhizopus nigricans .

ACETYLMETHYLCARBINOL PRODUCTION AND THE CLASSIFICATION OF AEROMONADS ASSOCIATED WITH ULCERATIVE DISEASES OF ECTOTHERMIC VERTEBRATES

Page , L. A. (Biological Research Institute, San Diego, and University of California, Davis). Acetylmethylcarbinol production and the classification of aeromonads associated with ulcerative diseases of ectothermic vertebrates. J. Bacteriol. 84: 772–777. 1962.—Quantitative colorimetric tests were made for acetylmethylcarbinol (AMC) production by 14 Aeromonas isolates from ulcerous lesions of snakes, lizards, frogs, and other animals, and by 27 cultures of “identified” aeromonads. The tests revealed that: (i) some strains failed to produce AMC, while the other strains produced AMC in amounts of 5 to > 100 μg/ml of culture; (ii) the reagents employed in the standard method of Barritt failed to detect AMC in concentrations below 35 μg/ml; and (iii) certain strains reported as producing AMC at 23 C and not at 37 C (or vice versa) produced AMC at both temperatures, but at one temperature produced AMC at a level below the sensitivity of the qualitative test. The strains representing the two biotypes could not be distinguished on the basis of their morphology, habitat, pathogenicity for mice or snakes, or serological specificity. Therefore, the Aeromonas classification proposed by Ewing, Hugh, and Johnson, who incorporated the two biotypes into one species, was followed, and the new isolates were designated A. hydrophila .