Fleming G T, Patching J W
Department of Microbiology, University College Galway, Ireland.
J Ind Microbiol. 1994 Mar;13(2):106-11. doi: 10.1007/BF01584107.
A pUB110-derived plasmid/Bacillus subtilis host combination was segregationally unstable when grown in chemostat culture with complex or minimal medium and under starch, glucose or magnesium limitation. The kinetics of plasmid loss were described in terms of the difference in growth rates between plasmid-containing and plasmid-free cells (d mu) and the rate at which plasmid-free cells were generated from plasmid-containing cells (R). Loss of plasmid-containing cells from the population was d mu dominated. Changes in medium composition and the nature of growth limitation caused variations in both d mu and R. The plasmid was most stable in glucose-limited chemostat cultures with minimal medium and least stable under starch limitation with complex medium. R and d mu were smaller for cultures in complex media than those in minimal media. Limitation by starch induced expression of the plasmid-encoded HT alpha amylase gene and was associated with increased values of R and d mu. Magnesium limitation in minimal medium caused a significant increase in d mu and a decrease in R.
当在含有复合培养基或基本培养基的恒化器培养中，以及在淀粉、葡萄糖或镁限制条件下生长时，一种源自pUB110的质粒/枯草芽孢杆菌宿主组合在遗传上是不稳定的。质粒丢失的动力学是根据含质粒细胞和不含质粒细胞之间的生长速率差异（dμ）以及含质粒细胞产生不含质粒细胞的速率（R）来描述的。群体中含质粒细胞的丢失以dμ为主导。培养基组成的变化和生长限制的性质导致dμ和R都发生变化。该质粒在以基本培养基进行葡萄糖限制的恒化器培养中最稳定，而在以复合培养基进行淀粉限制的条件下最不稳定。复合培养基中培养物的R和dμ比基本培养基中的小。淀粉限制诱导了质粒编码的HTα淀粉酶基因的表达，并与R和dμ值的增加有关。基本培养基中的镁限制导致dμ显著增加，R降低。
