Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Rd., Unit 3125, Storrs, CT 06269, USA.
Arch Microbiol. 2012 Jan;194(1):21-8. doi: 10.1007/s00203-011-0734-5. Epub 2011 Jul 20.
Filamentous actinobacteria from the genus Frankia grow by hyphal tip extension and branching. The growth kinetics and branching pattern of Frankia are not well studied, especially at the early stages of mycelial development. Here, we compare the growth of Frankia sp. strain CcI3 in liquid cultures with and without proteose peptone #3 (PP3) using time-lapse photomicrography and image analysis. Individual hyphae showed a pseudolinear increase in length at early stages of development, whereas at the mycelial level, the aggregate length of hyphae described an exponential rate before slowing. Growth based on optical density or microscopic observations was similar in medium with or without PP3. However, PP3 altered the pattern of mycelial development by increasing branching. Distances between the hyphal apex and first branches were on average shorter in PP3-containing media. The final interbranch distances were also shorter in PP3 medium indicating that hyphae tended to branch earlier and more often when supplemented with PP3 to give a more compact mycelium. Vesicle development in nitrogen-fixing cultures limited cell expansion as a result of vesicles truncating growth on new branches. The results provide some explanation for the growth kinetics of Frankia and some indication of how growth rates may be improved.
弗兰克氏放线菌属中的丝状放线菌通过菌丝尖端延伸和分支来生长。弗兰克氏放线菌的生长动力学和分支模式尚未得到很好的研究，尤其是在菌丝发育的早期阶段。在这里，我们使用延时显微摄影术和图像分析比较了弗兰克氏菌菌株 CcI3 在有和没有蛋白胨 #3（PP3）的液体培养基中的生长情况。在发育的早期阶段，单个菌丝呈现出伪线性长度增加，而在菌丝水平上，菌丝的总长度在减缓之前呈指数速率增加。在含有或不含有 PP3 的培养基中，基于光密度或微观观察的生长情况相似。然而，PP3 通过增加分支改变了菌丝体发育的模式。在含有 PP3 的培养基中，菌丝尖端和第一个分支之间的距离平均更短。在 PP3 培养基中最终的分支间距离也更短，这表明当补充 PP3 时，菌丝更倾向于更早和更频繁地分支，从而形成更紧凑的菌丝体。固氮培养物中的泡囊发育限制了细胞的扩展，因为泡囊截断了新分支上的生长。这些结果为弗兰克氏放线菌的生长动力学提供了一些解释，并为如何提高生长速率提供了一些线索。
