Use of glucose and carbon isotope fractionation by microbial cells immobilized on solid-phase surface

• Published in: Microbiology (New York) 2013-05, Vol.82 (3), p.280-289
• Main Authors: Zyakun, A. M., Kochetkov, V. V., Baskunov, B. P., Zakharchenko, V. N., Peshenko, V. P., Laurinavichius, K. S., Anokhina, T. O., Siunova, T. V., Sizova, O. I., Boronin, A. M.
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Experimental Articles; Life Sciences; Medical Microbiology; Microbiology
• ISSN: 0026-2617; 1608-3237
• DOI: 10.1134/S0026261713030156

By the example of glucose uptake by the soil bacteria Pseudomonas aureofaciens BS1393(pBS216) and Rhodococcus sp. 3–30 immobilized on a solid-phase surface (quartz sand), their growth parameters were determined: growth rate (doubling time), total CO 2 production, CO 2 production per cell, lag period with respect to substrate uptake, respiratory quotient. The growth of P. aureofaciens and Rhodococcus sp. on glucose revealed (1) differences of the lag period with respect to substrate (lag time of ∼4 h for P. aureofaciens and ∼26 h for Rhodococcus sp.); (2) differences between the maximal rates of CO 2 production (∼50 μg C-CO 2 g −1 sand h −1 for P. aureofaciens and ∼8.5 μg C-CO 2 g −1 sand h −1 for Rhodococcus sp.); (3) differences in CO 2 production per cell (∼1.94 × 10 −9 μM CO 2 /CFU for P. aureofaciens and more than ∼3.4 × 10 −9 μM CO 2 /CFU for Rhodococcus sp.). The kinetics of the metabolic CO 2 isotopic composition was shown to be determined by the difference in the carbon isotopic characteristics of products in the cell. Upon introduction of glucose into the medium (the preparatory stage of the metabolism), the uptake of intracellular 13 C-depleted products (lipids) is noted; at the stage of the maximal cell growth rate, introduced glucose is mainly metabolized; and at the final stage, upon exhaustion of substrate, the “stored” products—the lipid fraction—get involved in the metabolism. At the maximal rate of glucose uptake, the CO 2 carbon isotopic fractionation coefficient relative to organic products of microbial biosynthesis was determined to be α = 1.009 ± 0.002.