Phase variation of the multiple banded protein in Ureaplasma urealyticum and Ureaplasma parvum

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Ureaplasma urealyticum and U. parvum are common inhabitants of the human urogenital tract, acting as both commensals and potential pathogens.
• These bacteria possess variable surface proteins, including the multiple banded (MB) protein, which exhibits significant molecular weight variations due to changes in C-terminal repeating units.

Purpose of the Study:

• To investigate the mechanisms underlying the variability of the multiple banded (MB) protein in Ureaplasma urealyticum and U. parvum.
• To determine if selective pressures can induce changes in MB protein expression and to characterize the nature of these changes.

Main Methods:

• Selective pressure was applied by co-incubating Ureaplasma species with erythrocytes or HeLa cells to inhibit cytadherence.
• Serial passage in broth containing polyclonal antibodies was used to select for variants with altered surface protein expression.
• PCR analysis was performed on wild-type and variant strains to examine the mba gene structure.

Main Results:

• Exposure to selective pressures, including antibody treatment and cell co-incubation, resulted in the emergence of Ureaplasma variants lacking detectable MB protein.
• PCR studies revealed significant genetic differences in the mba gene between wild-type strains and MB-negative escape variants.
• Experiments with clonal lineages demonstrated that the loss of MB protein expression is a reversible phenomenon.

Conclusions:

• The findings suggest that the multiple banded proteins of Ureaplasma urealyticum and U. parvum are regulated by a phase-switching mechanism.
• This reversible phase-switching likely contributes to the adaptability and persistence of Ureaplasma in the urogenital tract.
• The study provides insights into the dynamic nature of bacterial surface protein expression in response to environmental cues.