Chromosomal gene transfer in Spiroplasma citri

Area of Science:

• Microbiology
• Genetics
• Bacterial Physiology

Background:

• Mollicutes, including Spiroplasma citri, are bacteria characterized by extensive degenerative evolution.
• Understanding gene transfer mechanisms in these organisms is crucial for evolutionary and genetic studies.
• Previous reports on chromosomal transfer and recombination in mollicutes are limited.

Purpose of the Study:

• To investigate the occurrence and mechanism of chromosomal information transfer and recombination in Spiroplasma citri mutants.
• To determine if Spiroplasma citri retains bacterial functions for chromosomal transfer and recombination despite degenerative evolution.
• To characterize the properties of the observed gene transfer mechanism.

Main Methods:

• Induction of resistance marker rearrangement in Spiroplasma citri mutants.
• Analysis of double-resistant phenotypes for stability under varying conditions.
• Investigation of the gene transfer mechanism's sensitivity to deoxyribonuclease and requirement for cell contact.
• Comparison of observed transfer properties with known mechanisms like protoplast fusion.

Main Results:

• Evidence of chromosomal information transfer followed by recombination in Spiroplasma citri mutants.
• Stable double-resistant phenotypes were obtained, persisting even without selection pressure.
• The gene transfer mechanism was found to be deoxyribonuclease-insensitive and required cell contact, suggesting membrane fusion.
• The mechanism shares properties with protoplast fusion observed in Gram-positive bacteria.

Conclusions:

• Spiroplasma citri retains bacterial functions for chromosomal transfer and recombination.
• This study provides the first in vivo evidence of chromosomal transfer and recombination in mollicutes.
• The identified gene transfer mechanism offers insights into bacterial evolution and genetic exchange in minimal organisms.