Rabsch Wolfgang, Helm R Allen, Eisenstark Abraham
National Reference Centre for Salmonella and Other Enterics, Robert Koch Institute, Wernigerode Branch, D-38855 Wernigerode, Germany.
Appl Environ Microbiol. 2004 Feb;70(2):664-9. doi: 10.1128/AEM.70.2.664-669.2004.
The existence of several thousand Salmonella enterica serovar Typhimurium LT2 and LT7 cultures originally collected by M. Demerec and sealed in agar stab vials for 33 to 46 years is a resource for evolutionary and mutational studies. Cultures from 74 of these vials, descendants of cells sealed and stored in nutrient agar stabs several decades ago, were phage typed by the Callow and Felix, Lilleengen, and Anderson systems. Among 53 LT2 archived strains, 16 had the same phage type as the nonarchival sequenced LT2 strain. The other 37 archived cultures differed in phage typing pattern from the sequenced strain. These 37 strains were divided into 10 different phage types. Among the 19 LT7 strains, only one was similar to the parent by phage typing, while 18 were different. These 18 strains fell into eight different phage types. The typing systems were developed to track epidemics from source to consumer, as well as geographic spread. The value of phage typing is dependent upon the stability of the phage type of any given strain throughout the course of the investigation. Thus, the variation over time observed in these archived cultures is particularly surprising. Possible mechanisms for such striking diversity may include loss of prophages, prophage mosaics as a result of recombination events, changes in phage receptor sites on the bacterial cell surface, or mutations in restriction-modification systems.
最初由M. 德梅雷克收集并密封在琼脂穿刺管中33至46年的数千种肠炎沙门氏菌鼠伤寒血清型LT2和LT7培养物，是进化和突变研究的资源。从这些培养管中的74个培养物（几十年前密封并保存在营养琼脂穿刺中的细胞后代），通过卡洛和费利克斯、利勒根以及安德森系统进行了噬菌体分型。在53株LT2存档菌株中，16株与非存档的测序LT2菌株具有相同的噬菌体类型。其他37株存档培养物在噬菌体分型模式上与测序菌株不同。这37株菌株被分为10种不同的噬菌体类型。在19株LT7菌株中，只有1株在噬菌体分型上与亲本相似，而18株不同。这18株菌株分为8种不同的噬菌体类型。噬菌体分型系统的开发是为了追踪从源头到消费者的疫情以及地理传播。噬菌体分型的价值取决于任何给定菌株在整个调查过程中噬菌体类型的稳定性。因此，在这些存档培养物中观察到的随时间的变化尤其令人惊讶。这种显著多样性的可能机制可能包括原噬菌体的丢失、重组事件导致的原噬菌体镶嵌体、细菌细胞表面噬菌体受体位点的变化或限制修饰系统中的突变。
