PubMed · 14045209
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P GENDREAU, N BARBOUR, R BARATTA, L JOHNSON, M LIST, S LORENZEN. 1963. QUESTIONING A PROCEDURE.. https://pubmed.ncbi.nlm.nih.gov/14045209/
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AIMS: To analyse the phenotype of a relA acid-resistant mutant of Lactococcus lactis ssp. cremoris MG1363, and to compare the glyceraldehyde-3-phosphate dehydrogenase regulation in both strains. METHODS AND RESULTS: Lactococcus lactis ssp. cremoris MG1363 and the relA mutant affected in the (p)ppGpp synthetase were grown in a series of batch-mode fermentation at different pH-regulated conditions with glucose as carbon substrate. All the determinants of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) regulation were quantified. In L. lactis MG1363, the GAPDH was strongly inhibited in vitro by decreased pH values, but this inhibition was totally compensated in vivo by the lower NADH/NAD+ ratio and more efficiently by the important increase in the intracellular amount of GAPDH. In contrast to the wild type, GAPDH activity of the relA strain was not increased when grown at low pH but the level of GAPDH remained constitutively high. However, pH homeostasis was not improved in the relA mutant and it grew slower and exhibited a lower glycolytic flux than the wild-type strain at low pH. CONCLUSIONS: Despite a better resistance to acid stress, the increased survival in L. lactis relA mutant at low pH was not related with an improved pH homeostasis but was associated with a diminished capacity to maintain a high flux through glycolysis. SIGNIFICANCE AND IMPACT OF THE STUDY: The phenotype of a strong acid-resistant L. lactis strain was established in acid conditions and some key metabolic parameters compared with the wild type. This analysis led to the conclusion that growth and survival seem to be antinomic parameters, since improving one of them leads to a decrease in the other one.
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The discovery of the tubercle bacillus and its causal relationship to tuberculosis by the general practitioner Robert Koch (1843-1910) in 1882 was truly a revolutionary discovery by a pioneer. This discovery was very well-documented, making use of optical equipment that had just appeared on the market, and was accomplished in his own home without outside support. In spite of the publication of the discovery in a German medical periodical with only local circulation, the entire scientific world quickly became aware of this fundamental discovery. Koch was relieved from his position as a provincial general practitioner and given a position in a scientific institute in Berlin where he later occupied a central position. Also because of his work on anthrax and cholera, he can be considered a founder of medical bacteriology and was justly awarded the Nobel Prize for Medicine in 1905. A shadow was thrown over all this by his misunderstanding about tuberculin, which he erroneously considered to be a potential medicine against tuberculosis.