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Cascade Regulation a Model of Integrative Control of Gene Expression in Eukaryotic Cells and Organisms
Published in M. Gerald, M.D. Kolodny, Eukaryotic Gene Regulation, 2018
A first reason relates to the requirements of efficiency and versality of regulation in a multiceli (or multiorgan) system which must adapt rapidly and locally to changes in physiological or functional state. To point out this necessity, we may recall the well-known phenomenon of diauxic growth of E. coli;109 there the bacterial regulation system has to retrieve information from the central genetic memory in order to adapt to new growth requirements. It takes a bacterial population about 20 min, i.e., two generation times, to adapt its enzyme systems to a new substrate; for evident reasons, such a time-lag would be ruinous to higher organism. Indeed, it will be more efficient to activate an mRNA or polypeptide already present in the cytoplasm than to produce a new message through transcription and the whole assembly line of processing. Thus, in the formal consideration of optimal function, there is an advantage to store genetic information in peripheral memories.
The effect of different carbon sources on biofouling in membrane fouling simulators: microbial community and implications
Published in Biofouling, 2022
Johny Cabrera, Hao-yu Guo, Jia-long Yao, Xiao-mao Wang
A series of experiments were run in parallel with a 1:1 mixture of acetate and glucose, a 1:1:1 mixture of acetate, glucose, and fructose, and solely acetate to see what effect mixing the different carbon sources had and how increasing carbon complexity affects pressure profiles, biomass accumulation on the membrane surface, and the microbial community. In all cases, the concentration of the inlet water was 0.2 mg-C L−1. The pressure profiles for these membranes are shown in Figure 3. After the pressure drop reached 40 kPa, all of the membranes in these experiments were removed and analyzed. The membrane with only acetate increased in pressure difference faster than mixtures of acetate and glucose, and acetate, glucose, and fructose in these experiments. One explanation for acetate promoting the largest growth rate, in this case, is related to the growth strategy of microbes exposed to mixed carbon sources. In a diauxic growth mode (Enjalbert 2015; Wang 2019), the carbons are consumed sequentially, and the carbons used are not co-utilized. In the case of acetate, glucose, and fructose, acetate may be consumed first; therefore, water with only acetate present will have faster biofilm growth.
Effect of reduced nutritional supply on the metabolic activity and survival of cariogenic bacteria in vitro
Published in Journal of Oral Microbiology, 2019
Furthermore, one should consider that lactic acid is not only a metabolic end product. Lactic acid bacteria can also utilize lactate as a carbon source by conversion into pyruvate using two different enzymes, a lactate oxidase or a NAD-independent lactate dehydrogenase [15,29,30]. Jyoti et al. [31] described for the cultivation of L. rhamnosus in a glucose-containing medium a diauxic growth profile, with a second growth phase on the fermentation product lactic acid. This metabolic feature might explain why only very low lactate contents could be detected for the L. rhamnosus grown in CLM.