University of Rostock, Institute of Medical Microbiology, Virology, and Hygiene, Schillingallee 70, 18057 Rostock, Germany.
Appl Environ Microbiol. 2011 Jan;77(2):612-7. doi: 10.1128/AEM.01838-10. Epub 2010 Nov 19.
Several lactic acid bacteria use homolactic acid fermentation for generation of ATP. Here we studied the role of the lactate dehydrogenase enzyme on the general physiology of the three homolactic acid bacteria Lactococcus lactis, Enterococcus faecalis, and Streptococcus pyogenes. Of note, deletion of the ldh genes hardly affected the growth rate in chemically defined medium under microaerophilic conditions. However, the growth rate was affected in rich medium. Furthermore, deletion of ldh affected the ability for utilization of various substrates as a carbon source. A switch to mixed acid fermentation was observed during glucose-limited continuous growth and was dependent on the growth rate for S. pyogenes and on the pH for E. faecalis. In S. pyogenes and L. lactis, a change in pH resulted in a clear change in Y(ATP) (cell mass produced per mole of ATP). The pH that showed the highest Y(ATP) corresponded to the pH of the natural habitat of the organisms.
一些乳酸菌利用同型乳酸发酵来产生 ATP。在这里，我们研究了乳酸脱氢酶（lactate dehydrogenase enzyme）在三种同型乳酸发酵菌——乳球菌（Lactococcus lactis）、粪肠球菌（Enterococcus faecalis）和酿脓链球菌（Streptococcus pyogenes）的一般生理学中的作用。值得注意的是，ldh 基因的缺失几乎不会影响微需氧条件下化学定义培养基中的生长速率。然而，在丰富的培养基中，生长速率会受到影响。此外，ldh 的缺失会影响利用各种底物作为碳源的能力。在葡萄糖限制的连续生长过程中，观察到混合酸发酵的转变，这取决于酿脓链球菌的生长速率和粪肠球菌的 pH 值。在酿脓链球菌和乳球菌中，pH 值的变化导致 ATP 产生的细胞质量（Y(ATP)）发生明显变化。显示最高 Y(ATP)的 pH 值对应于生物体自然栖息地的 pH 值。
