Characterization of the Spiroplasma P58 Multigene Family

Abstract

<em>Spiroplasma citri</em> and <em>S. kunkelii</em> are phytopathogenic mollicutes. Among genetic differences between <em>S. citri</em> lines BR3-3X (insect transmissible) and BR3-G (insect non-transmissible) was the absence, in BR3-G, of a gene encoding a 58kDa membrane protein, P58. Multiple P58-like gene sequences were present in <em>S. citri</em> BR3-3X (three detected) and<em> S. kunkelii</em> CR2-3X (seven detected), indicating a putative multigene family in the small spiroplasma genome. P58 sequence alignments revealed one or more intragenic recombination events among the P58-like sequences. Determined by PSI-BLAST, the N-terminal portion of P58 was related to bacteriophage terminases, proteins usually found in tailed bacteriophages. Tailed bacteriophages, SpV2 and SpV3, have been reported to infect spiroplasmas. The C-terminal portion shared similarity with the <em>Mycoplasma hominis</em> P50/Vaa adhesin. Thus, the P58 termini may have different origins. Recombination events, like those described here, may have implications for <em>Spiroplasma</em> evolution and niche adaptation.