ISSN:
1550-7408
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
SYNOPSIS. A number of small molecules including CO2, certain Krebs cycle acids and certain amino acids stimulated growth and glucose utilization of a colorless strain of Euglena gracilis in a phthalate-buffered mineral salts medium. Their major effect was to shorten markedly the lag period; some compounds also gave small increases in maximum growth rate and total cell yield. The stimulatory substances were effective in small (sparking) amounts. It is suggested that all the stimulatory substances acted similarly, by keeping the internal concentration of oxaloacetate at a sufficiently high level to allow effective operation of the terminal respiratory cycle.Glucose utilization was initiated within a pH range of 3.0 to 5.0. This range could be extended by the addition of glycine to the growth medium. Cells cultured at pH 4.5 could be adapted to growth at pH 7.0 in a phosphate-buffered mineral salts medium containing a small amount of citrate. Neither adaptation nor growth occurred at pH 7.0 in the absence of citrate. Since no evidence of citrate utilization was obtained and since EDTA replaced citrate, it is concluded that citrate was acting as a chelator.The major enzymes of the Embden-Meyerhof-Parnas and pentose phosphate pathways were demonstrated in cell-free extracts. The data presented indicate that glucose metabolism in Euglena is similar to that found in a wide variety of other cells. Indirect evidence was also obtained for the operation of a uridine linked pathway in hexose metabolism.With the exception of hexokinase, for which results were inconsistent, all the enzymes demonstrated were routinely found in the supernatant fraction of the cell-free extracts. The pH optima of a number of the enzymes were found to be between pH 7.5 and 8.6, although the cells from which the enzymes were obtained were grown in acid medium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1550-7408.1962.tb02602.x
