Insights into the persistence and phenotypic effects of the endogenous and cryptic plasmid pMF1 in its host strain Myxococcus fulvus 124B02
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Xiao-Jing Chen1,2, Zheng Zhang1, Ya-Jie Li1
1State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, Shandong, 266237, China.
Abstract:
Many endogenous plasmids carry no noticeable benefits for their bacterial hosts, and the persistence of these 'cryptic plasmids' and their functional impacts are mostly unclear. In this study, we investigated these uncertainties using the social bacterium Myxococcus fulvus 124B02 and its endogenous plasmid pMF1. pMF1 possesses diverse genes that originated from myxobacteria, suggesting a longstanding co-existence of the plasmid with various myxobacterial species. The curing of pMF1 from 124B02 had almost no phenotypic effects on the host. Laboratory evolution experiments showed that the 124B02 strain retained pMF1 when subcultured on dead Escherichia coli cells but lost pMF1 when subcultured on living E. coli cells or on casitone medium; these results indicated that the persistence of pMF1 in 124B02 was environment-dependent. Curing pMF1 caused the mutant to lose the ability to predate and develop fruiting bodies more quickly than the pMF1-containing strain after they were subcultured on dead E. coli cells, which indicated that the presence of pMF1 in M. fulvus 124B02 has some long-term effects on its host. The results provide some new insights into the persistence and impacts of cryptic plasmids in their natural bacterial cells.
Insights
Cryptic plasmids, like pMF1 in Myxococcus fulvus, can persist in bacteria depending on the environment. This plasmid impacts predation and development, revealing long-term effects on bacterial hosts.
Area of Science:
- Microbiology
- Bacterial Genetics
- Plasmid Biology
Background:
- Cryptic plasmids are common in bacteria but their persistence and functional roles remain largely unknown.
- The social bacterium Myxococcus fulvus 124B02 harbors the endogenous plasmid pMF1, whose evolutionary significance is unclear.
Purpose of the Study:
- To investigate the persistence and functional impacts of the cryptic plasmid pMF1 in Myxococcus fulvus 124B02.
- To understand the environmental factors influencing cryptic plasmid maintenance in bacterial hosts.
Main Methods:
- Plasmid curing experiments were performed on Myxococcus fulvus 124B02.
- Laboratory evolution experiments involved subculturing strains on different media (dead E. coli, living E. coli, casitone).
- Phenotypic analysis focused on predation and fruiting body development.
Main Results:
- Curing pMF1 from M. fulvus 124B02 resulted in minimal immediate phenotypic changes.
- Plasmid pMF1 persistence was environment-dependent, with retention on dead E. coli but loss on living E. coli or casitone medium.
- Loss of pMF1 accelerated predation and fruiting body development in the evolved strain on dead E. coli.
Conclusions:
- The cryptic plasmid pMF1 exhibits environment-dependent persistence in Myxococcus fulvus 124B02.
- While not essential for immediate survival, pMF1 influences long-term host traits like predation and development.
- This study provides insights into the ecological relevance and evolutionary dynamics of cryptic plasmids in bacteria.
