STRUCTURED HABITATS AND THE EVOLUTION OF ANTICOMPETITOR TOXINS IN BACTERIA
STRUCTURED HABITATS AND THE EVOLUTION OF ANTICOMPETITOR TOXINS IN BACTERIA
复制标题
DOI：
10.1073/pnas.78.10.6324
复制
发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
LEVIN, BR
中科院分区：
文献类型：
--
作者：
CHAO, L;LEVIN, BR
在液体培养中(大规模栖息地)，产生抗菌毒素(粘菌素)的大肠杆菌和敏感的大肠杆菌之间的竞争结果明显依赖于频率；只有在相当常见的情况下(频率和时间)，产结肠素的细菌才处于优势。10-2)。然而，在软琼脂基质(结构化的栖息地)中，即使在最初很少见的情况下(频率低至10-6)，产结肠素细菌显然也具有优势。这些不同的结果归因于产生结肠素的细菌S比敏感细菌的内在生长速度低，以及细菌和资源在两种类型的栖息地中的不同分配方式。液体培养中的细菌以随机分布的个体形式存在，结肠素对敏感细菌的杀灭增加了共生细菌可用的资源量，其程度与幸存的敏感细菌相同。另一方面，软琼脂基质中的细菌以单克隆菌落的形式存在。当产生结肠素的菌落释放结肠素时，它们会杀死邻近的敏感细菌，并在自己周围形成一个抑制区。通过这一行动，他们提高了周围资源的集中度，克服了增长速度的劣势。因此，规整的栖息地似乎更有利于结肠素来源细菌的进化。
In liquid cultures (a mass habitat) the outcome of competition between Escherichia coli that produce an antibacterial toxin (colicin) and sensitive E. coli is evidently frequency dependent; the colicinogenic bacteria are at an advantage only when fairly common (frequencies > 2 .times. 10-2). However, in a soft agar matrix (a structured habitat) the colicinogenic bacteria apparently have an advantage even when initially rare (frequencies as low as 10-6). These contrasting outcomes are attributed to the colicinogenic bacteria''s lower intrinsic growth rate relative to the sensitive bacteria and the different manner in which bacteria and resources are partitioned in the 2 types of habitats. Bacteria in a liquid culture exist as randomly distributed individuals and the killing of sensitive bacteria by the colicin augments the amount of resource available to the colincinogenic bacteria to an extent identical to that experienced by the surviving sensitive bacteria. On the other hand, the bacteria in a soft agar matrix exist as single-clone colonies. As the colicinogenic colonies release colicin, they kill neighboring sensitive bacteria and form an inhibition zone around themselves. By this action, they increase the concentration of resources around themselves and overcome their growth rate disadvantage. Thus, structured habitats are seemingly more favorable for the evolution of colicinogenic bacteria.