MODE OF ACTION OF STREPTOMYCIN ON TYPE b HEMOPHILUS INFLUENZAE : II. NATURE OF RESISTANT VARIANTS.
MODE OF ACTION OF STREPTOMYCIN ON TYPE b HEMOPHILUS INFLUENZAE : II. NATURE OF RESISTANT VARIANTS.
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DOI：
10.1084/jem.85.6.607
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发表时间：
1947-05-31
影响因子：
15.3
通讯作者：
Leidy, G
中科院分区：
文献类型：
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作者：
Alexander, H E;Leidy, G
在接触链霉素之前对10株流感嗜血杆菌进行检测，发现每立方厘米含1000单位链霉素的环境下，只有极少数细菌能形成菌落。这些变异体具有细菌突变体的特征。
1. 同一菌株在不同时间进行的不同独立培养，甚至在单次试验中用同一接种物接种的培养物，在规模相当的菌群中，耐药变异体的出现频率都有显著差异。这种差异在基因同质的培养源和异质培养源中同样显著。有证据表明这些耐药菌是持续随机出现的。
2. 所研究的10株菌中耐药菌出现的频率没有显著差异；每细菌每代的频率从2.6×10⁻¹¹到7.0×10⁻¹¹不等。对同一菌株进行的5次不同试验结果显示出类似的差异，从2.9×10⁻¹¹到5.3×10⁻¹¹。这种低频率为突变假说提供了佐证。
3. 对每立方厘米1000单位链霉素表现出耐药性的变异体，其耐药特性在多代中保持不变。在无链霉素培养基中进行12次或更多次传代培养后的结果表明，在部分对链霉素有耐药性的菌落中，存在一种与亲代培养物所表现出的特性不同的额外特性；这些培养物的营养需求不同。
In all of ten strains of H. influenzae examined prior to exposure to streptomycin a very small fraction of the bacteria formed colonies in the presence of 1,000 units of streptomycin per cc. These variant organisms possess the characteristics of bacterial mutants. 1. Different independent cultures of the same strain on different occasions, and even cultures seeded in a single test with the same inoculum, show marked variation in prevalence of resistant variants in populations of comparable size. This variation is just as great in genetically homogeneous culture sources as in heterogeneous sources. Evidence is presented for the continuous random occurrence of these resistant organisms. 2. The rate of occurrence of the resistant members is not significantly different for the ten strains studied; it varies from 2.6 x 10–11 to 7.0 x 10–11 per bacterium per bacterial generation. The results of five different tests on the same strain show comparable variation, 2.9 x 10–11 to 5.3 x 10–11. This low rate contributes evidence consistent with the mutation hypothesis. 3. Variants exhibiting resistance to 1,000 units of streptomycin per cc. transmit this trait unchanged in degree through many generations. The results obtained after twelve or more subcultures in streptomycin-free media suggest that in a portion of the colonies resistant to streptomycin an additional trait, differing from those exhibited by the parent culture, is associated; the nutritional requirements of these cultures are different.