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Characterization of two cryptic plasmids from Spiroplasma citri and occurrence of their DNA sequences among various
Abstract:
Two plasmids, pMH1 with 7 kilobase pairs (Kbp) and pM41 with 8 Kbp, were purified from Spiroplasma citri strains MH and M4, respectively, and characterized by restriction mapping. Upon in vitro DNA recombination with plasmid pBR328 as a vector, pMH1 was cloned in Escherichia coli. Radioactive probes specific of the plasmids were used to investigate the occurrence of pMH1 and pM41 DNA sequences among various spiroplasmas. pM41 or a closely related plasmid was found in three other S. citri strains and also seems to be present as an 8-Kbp plasmid in three spiroplasmas not belonging to the S. citri species. Up to now, pMH1 had been found as a free 7-Kbp plasmid only in the S. citri strain MH. However, DNA sequences corresponding to the entire pMH1 DNA have been found to be integrated in the high-molecular-weight-DNA molecules and perhaps the chromosomal DNA itself of two other S. citri strains. DNA sequences hybridizable with pMH1 DNA have also been found to be integrated into high-molecular-weight-DNA molecules from several spiroplasma strains not belonging to the S. citri species.
Insights
Researchers studied Spiroplasma citri plasmids, finding that pMH1 DNA sequences can integrate into host DNA, not just exist as free plasmids. This integration was observed in Spiroplasma citri and other spiroplasma species.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Plasmids are extrachromosomal DNA elements crucial for bacterial adaptation.
- Spiroplasma citri harbors plasmids, but their distribution and integration patterns are not fully understood.
Purpose of the Study:
- To characterize Spiroplasma citri plasmids pMH1 and pM41.
- To investigate the presence and integration of these plasmid sequences in various spiroplasma strains.
Main Methods:
- Plasmid purification and restriction mapping.
- In vitro DNA recombination and cloning in Escherichia coli.
- Southern blot hybridization using radioactive probes.
Main Results:
- Plasmid pM41 was detected in other Spiroplasma citri strains and related plasmids in non-S. citri species.
- Plasmid pMH1, previously only found free in S. citri strain MH, was also found integrated into high-molecular-weight DNA in other S. citri strains.
- pMH1 DNA sequences were integrated into high-molecular-weight DNA of several non-S. citri spiroplasma strains.
Conclusions:
- Spiroplasma plasmids exhibit diverse distribution patterns, including both free and integrated forms.
- Plasmid DNA sequences can integrate into the host genome of Spiroplasma species.
- This suggests horizontal gene transfer or integration mechanisms within spiroplasma populations.