Waterhouse R N, Allan E J, Amijee F, Undrill V J, Glover L A
Department of Molecular and Cell Biology, Marischal College, Aberdeen, UK.
J Appl Bacteriol. 1994 Nov;77(5):497-503. doi: 10.1111/j.1365-2672.1994.tb04393.x.
Cell numbers of two morphogenic forms of Bacillus subtilis (the cell-walled parental and the derived stable cell wall-deficient L-form) have been compared by two methods: DNA hybridization (i.e. deduced genome numbers) and viable cell counts (i.e. number of colony-forming units (cfu)). The DNA hybridization method was shown to be a reliable and reproducible method for estimating genome numbers. Comparison of different L-form populations showed that the two methods of enumeration gave different values, with the deduced genome numbers much higher (by several orders of magnitude) than cell numbers deduced from viable cell counts. In contrast, when a culture of the cell-walled form was enumerated, the discrepancy between the two methods was low (by a factor of about 6) The combination of a high number of L-form genomes detected by DNA hybridization and a relatively low number of cfu was thought to be a consequence of a diminished co-ordination between the DNA replication and cell division processes in L-form bacteria. This suggestion was further substantiated by assessing the stability of plasmid pPL608 in a transformed B. subtilis L-form cell line, where even in the presence of continued kanamycin selection, 25% of the population lost kanamycin resistance. The results are discussed with particular reference to cell division in cell wall-deficient, stable L-form bacteria.
已通过两种方法比较了枯草芽孢杆菌两种形态发生形式（细胞壁完整的亲代细胞和衍生的稳定细胞壁缺陷型L型细胞）的细胞数量：DNA杂交（即推断的基因组数量）和活细胞计数（即菌落形成单位（cfu）数量）。结果表明，DNA杂交方法是一种可靠且可重复的估计基因组数量的方法。对不同L型细胞群体的比较表明，这两种计数方法得出的值不同，推断的基因组数量比从活细胞计数推断的细胞数量高得多（相差几个数量级）。相反，对细胞壁完整型细胞培养物进行计数时，两种方法之间的差异较小（约为6倍）。DNA杂交检测到大量L型基因组，而cfu数量相对较低，这一现象被认为是L型细菌DNA复制和细胞分裂过程之间协调能力下降的结果。通过评估质粒pPL608在转化的枯草芽孢杆菌L型细胞系中的稳定性，进一步证实了这一推测，即使在持续进行卡那霉素选择的情况下，仍有25%的群体丧失了卡那霉素抗性。本文结合细胞壁缺陷型稳定L型细菌的细胞分裂对结果进行了讨论。
