title: The Variable Internal Structure of the Mycoplasma penetrans Attachment Organelle Revealed by Biochemical and Microscopic Analyses: Implications for Attachment Organelle Mechanism and Evolution.
abstract: Although mycoplasmas have small genomes, many of them, including the HIV-associated opportunistMycoplasma penetrans, construct a polar attachment organelle (AO) that is used for both adherence to host cells and gliding motility. However, the irregular phylogenetic distribution of similar structures within the mycoplasmas, as well as compositional and ultrastructural differences among these AOs, suggests that AOs have arisen several times through convergent evolution. We investigated the ultrastructure and protein composition of the cytoskeleton-like material of theM. penetransAO with several forms of microscopy and biochemical analysis, to determine whether theM. penetransAO was constructed at the molecular level on principles similar to those of other mycoplasmas, such asMycoplasma pneumoniaeandMycoplasma mobileWe found that theM. penetransAO interior was generally dissimilar from that of other mycoplasmas, in that it exhibited considerable heterogeneity in size and shape, suggesting a gel-like nature. In contrast, several of the 12 potential protein components identified by mass spectrometry ofM. penetransdetergent-insoluble proteins shared certain distinctive biochemical characteristics withM. pneumoniaeAO proteins, although not withM. mobileproteins. We conclude that convergence betweenM. penetransandM. pneumoniaeAOs extends to the molecular level, leading to the possibility that the less organized material in bothM. pneumoniaeandM. penetransis the substance principally responsible for the organization and function of the AO.IMPORTANCEMycoplasma penetransis a bacterium that infects HIV-positive patients and may contribute to the progression of AIDS. It attaches to host cells through a structure called an AO, but it is not clear how it builds this structure. Our research is significant not only because it identifies the novel protein components that make up the material within the AO that give it its structure but also because we find that theM. penetransAO is organized unlike AOs from other mycoplasmas, suggesting that similar structures have evolved multiple times. From this work, we derive some basic principles by which mycoplasmas, and potentially all organisms, build structures at the subcellular level.
authors.affiliation: Department of Microbiology, Miami University, Oxford, Ohio, USA.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Distelhorst
authors.affiliation: Department of Microbiology, Miami University, Oxford, Ohio, USA.
authors.forename: Dominika A
authors.initials: DA
authors.lastname: Jurkovic
authors.affiliation: Division of Biology and Bioengineering, California Institute of Technology, Pasadena, California, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Shi
authors.affiliation: Division of Biology and Bioengineering, California Institute of Technology, Pasadena, California, USA.|Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California, USA.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Jensen
authors.affiliation: Department of Microbiology, Miami University, Oxford, Ohio, USA balishmf@MiamiOH.edu.
authors.forename: Mitchell F
authors.initials: MF
authors.lastname: Balish
mesh_terms: D056226:Bacterial Structures / Q000737:chemistry* / Q000648:ultrastructure*; D005075:Biological Evolution; D013058:Mass Spectrometry; D018661:Mycoplasma penetrans / Q000737:chemistry* / Q000648:ultrastructure*; D009177:Mycoplasma pneumoniae / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D015388:Organelles / Q000737:chemistry* / Q000648:ultrastructure*
keywords: Mycoplasma; cytoskeleton; electron microscopy; evolution; fractionation; mass spectrometry; transcriptomics