Kim Kwang, Kim Joong-Jae, Masui Ryoji, Kuramitsu Seiki, Sung Moon-Hee
Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka 560-0043, Japan.
BMC Res Notes. 2011 Oct 24;4:437. doi: 10.1186/1756-0500-4-437.
Symbiobacterium toebii is a commensal symbiotic thermophile that absolutely requires its partner bacterium Geobacillus toebii for growth. Despite development of an independent cultivation method using cell-free extracts, the growth of Symbiobacterium remains unknown due to our poor understanding of the symbiotic relationship with its partner bacterium. Here, we investigated the interrelationship between these two bacteria for growth of S. toebii using different cell-free extracts of G. toebii.
Symbiobacterium toebii growth-supporting factors were constitutively produced through almost all growth phases and under different oxygen tensions in G. toebii, indicating that the factor may be essential components for growth of G. toebii as well as S. toebii. The growing conditions of G. toebii under different oxygen tension dramatically affected to the initial growth of S. toebii and the retarded lag phase was completely shortened by reducing agent, L-cysteine indicating an evidence of commensal interaction of microaerobic and anaerobic bacterium S. toebii with a facultative aerobic bacterium G. toebii. In addition, the growth curve of S. toebii showed a dependency on the protein concentration of cell-free extracts of G. toebii, demonstrating that the G. toebii-derived factors have nutrient-like characters but not quorum-sensing characters.
Not only the consistent existence of the factor in G. toebii during all growth stages and under different oxygen tensions but also the concentration dependency of the factor for proliferation and optimal growth of S. toebii, suggests that an important biosynthetic machinery lacks in S. toebii during evolution. The commensal symbiotic bacterium, S. toebii uptakes certain ubiquitous and essential compound for its growth from environment or neighboring bacteria that shares the equivalent compounds. Moreover, G. toebii grown under aerobic condition shortened the lag phase of S. toebii under anaerobic and microaerobic conditions, suggests a possible commensal interaction that G. toebii scavengers ROS/RNS species and helps the initial growth of S. toebii.
户田共生杆菌是一种共生嗜热菌，其生长绝对依赖于伙伴细菌户田地芽孢杆菌。尽管已开发出使用无细胞提取物的独立培养方法，但由于我们对其与伙伴细菌的共生关系了解不足，共生杆菌的生长情况仍不清楚。在此，我们使用户田地芽孢杆菌的不同无细胞提取物，研究了这两种细菌之间对户田共生杆菌生长的相互关系。
户田共生杆菌生长支持因子在户田地芽孢杆菌的几乎所有生长阶段以及不同氧张力下均持续产生，这表明该因子可能是户田地芽孢杆菌以及户田共生杆菌生长的必需成分。户田地芽孢杆菌在不同氧张力下的生长条件对户田共生杆菌的初始生长有显著影响，还原剂L - 半胱氨酸完全缩短了迟缓期，这表明微需氧和厌氧细菌户田共生杆菌与兼性需氧细菌户田地芽孢杆菌之间存在共生相互作用的证据。此外，户田共生杆菌的生长曲线显示出对户田地芽孢杆菌无细胞提取物蛋白质浓度的依赖性，表明户田地芽孢杆菌衍生的因子具有类似营养物质的特性，而非群体感应特性。
不仅该因子在户田地芽孢杆菌的所有生长阶段和不同氧张力下持续存在，而且该因子对户田共生杆菌增殖和最佳生长的浓度依赖性表明，户田共生杆菌在进化过程中缺乏重要的生物合成机制。共生细菌户田共生杆菌从环境或共享等效化合物的邻近细菌中摄取某些对其生长普遍存在且必不可少的化合物。此外，在有氧条件下生长的户田地芽孢杆菌缩短了厌氧和微需氧条件下户田共生杆菌的迟缓期，这表明户田地芽孢杆菌可能清除活性氧/氮物种并帮助户田共生杆菌初始生长，存在一种可能的共生相互作用。
