A Phenotype and Genotype Study of Micromonas micros

Micromonas micros is a Gram-positive, aerotolerant anaerobe which can be cultured from the oral cavity. Although it is described as a commensal, M. micros has been implicated in periodontal diseases, failing dental implants, and endodontic infections. Objective: The purpose of this study was: 1) To genetically characterize M. micros using DNA fingerprinting; 2) To characterize phenotypic switching and compare phenotype with genotype. Methods: A total of 88 clinical isolates from healthy and diseased sites were genotyped from six subjects with AP-PCR (arbitrarily primed polymerase chain reaction). A select subset was phenotyped. DNA was extracted from M. micros isolates. AP-PCR was performed using five, 10-base arbitrary oligonucleotide primers (OPA-3, OPA-4, OPA-7, OPA-9, and OPA-13). Isolates were scored for presence or absence of specific bands. To study phenotype, isolates were plated on BHIN agar in order to obtain isolated colonies and maintained in an anaerobic environment for two weeks. Colony phenotypes were determined by visual evaluation of the shape (smooth or rough) and size. Results: Thirteen different M. micros genotypes were identified from the 6 subjects. Each subject demonstrated unique M. micros genotypes. Two subjects were colonized with a single M. micros strain, three subjects had two strains and one subject had three unique strains. All isolates evaluated for phenotype initially exhibited a smooth phenotype; three isolates switched from a smooth to a rough phenotype during time in culture. Conclusions: AP-PCR distinguishes unrelated strains of M. micros. Utilizing DNA fingerprinting and analyzing phenotypic plasticity may be helpful in the future to associate certain strains with virulence or disease potential. Funded by NIDCR RO1 DE13334 and NIH NIGMS 5R25GM058939.