Group-beneficial traits, frequency-dependent selection and genotypic diversity: an antibiotic resistance paradigm
Group-beneficial traits, frequency-dependent selection and genotypic diversity: an antibiotic resistance paradigm
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DOI：
10.1098/rspb.2004.2916
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发表时间：
2005-01-07
影响因子：
4.7
通讯作者：
Atlas, R
中科院分区：
文献类型：
--
作者：
Dugatkin, LA;Perlin, M;Atlas, R
群体有益性状的进化可能会让那些原本不适合的“骗子”生存下来。在这里，我们描述的实验工作组有益的性状和频率依赖性选择的细菌抗生素耐药性的背景下的后果。我们构建了一个“自限性抗生素耐药”（SLAR）大肠杆菌菌株，其中TEM-1 β-内酰胺酶锚定到内膜。在SLAR菌株和氨苄青霉素敏感菌株之间的成对竞争实验中，只有SLAR菌株在氨苄青霉素存在下存活。我们还构建了一个“共享抗生素耐药”（SAR）菌株，其中TEM-1 β-内酰胺酶保护SAR菌株和附近的敏感细胞，从而作为一个模型的遗传定义的群体有益性状。在SAR菌株与两种不同敏感菌株的成对竞争实验中，大肠杆菌，我们发现敏感菌株在氨苄青霉素存在下保持在5-12%的频率。当SAR菌株的相对成本降低时，其平衡频率上升。敏感菌株也来自SAR菌株的纯培养物。在这些情况下，敏感的“作弊者”也保持在氨苄青霉素中，其频率与以前的比赛中观察到的频率相当。这些结果表明，有益于其他群体成员的性状可以使原本会被自然选择淘汰的基因型存活下来，并允许维持更大的遗传变异，从而使进化得以运作。
The evolution of group-beneficial traits potentially allows the survival of 'cheaters' that would otherwise be unfit. Here we describe experimental work on group-beneficial traits and the consequences of frequency-dependent selection in the context of bacterial antibiotic resistance. We constructed a 'self-limited antibiotic resistant' (SLAR) strain of Escherichia coli in which a TEM-1 P-lactamase was anchored to the inner membrane. In pairwise competition experiments between the SLAR strain and ampicillin-sensitive strains, only the SLAR strain survived in the presence of ampicillin. We also constructed a 'shared antibiotic resistant' (SAR) strain in which TEM-1 beta-lactamase protected both the SAR strain and nearby sensitive cells, thus acting as a model for a genetically defined group-beneficial trait. In pairwise competition experiments of the SAR strain against two different sensitive strains of E. coli, we found that the sensitive strains maintained themselves at frequencies of 5-12% in the presence of ampicillin. When the relative cost of the SAR strain was lowered, its equilibrial frequency rose. Sensitive strains also arose from pure cultures of the SAR strain. In these cases, too, the sensitive 'cheaters' were maintained in ampicillin at frequencies comparable to those observed in the previous competitions. These results suggest that traits which benefit other group members can permit survival of genotypes that otherwise would be eliminated by natural selection, and allow the maintenance of greater genetic variation upon which evolution can operate.