Mrj. Stewart et al., STABILITY OF SINGLE-STRANDED-DNA PLASMIDS DURING CONTINUOUS-CULTURE OF BACILLUS-SUBTILIS, AND THE EFFECTS OF HOST CHEMOSTAT-EXPERIENCE, FEMS microbiology letters, 136(3), 1996, pp. 317-323
The stability of a selection of single-stranded DNA plasmids was compa
red in continuous culture of Bacillus subtilis 168-CU267. Plasmid pUB1
10 and its derivatives were found to be 100% stable in long-term cultu
res with carbon, nitrogen, potassium, sulfur or magnesium as limiting
nutrients. In phosphate-limited culture, pUB110 showed only slight ins
tability, but its derivatives pPL603, pPL608 and pSM112 were rapidly l
ost from the cultures after a lag of variable length during which no p
lasmid-free bacteria were detected. The proportion of plasmid-bearing
bacteria in the culture sometimes showed temporary recovery prior to u
ltimate loss. Plasmids pHV33 and pC194 were lost rapidly without a pre
ceding lag phase. Chemostat experience (800 generations in phosphate-l
imited continuous culture) of the host bacterium greatly enhanced the
retention of pC194-carrying bacteria in phosphate-limited cultures, bu
t effects on retention of the other plasmids were not significant.