Mitchell F. Balish
Associate Professor of Microbiology
The long-accepted, simplistic view of the inner workings of the prokaryotic cell has irreversibly changed. Dynamic structures with properties similar to the eukaryotic cytoskeleton have been identified and characterized in many bacteria; these structures are especially important with regard to cell shape, cell division, and subcellular organization. Also, appreciation of bacterial diversity has increased, revealing species that differ considerably from model bacteria. Among these are those bacteria of the class Mollicutes, which are the smallest organisms capable of being grown in pure culture. Many types of Mollicutes cause significant disease in humans, animals (pets, livestock, and wildlife), and plants.
- Mycoplasma pneumoniae cells. Arrows indicate attachment organelles on two of the cells.
- A pair of Mycoplasma penetrans cells dividing. The white area shows the DNA, which is excluded from the attachment organelles, indicated by the arrowheads.
- Cytoskeletal elements of Mycoplasma insons, which lives in iguanas.
- Cytoskeletal elements of the attachment organelles of Mycoplasma penetrans. Each of the smaller objects is approximately the same size as the DNA-free area in panel B.
Mollicutes, which lack cell walls, have small genomes, and are generally deficient in biosynthetic pathways, are associated with animal and plant hosts in nature, but many of the most medically and economically important species can be grown in the lab in pure culture. The best-studied Mollicutes are those of the genus Mycoplasma (trivial name mycoplasmas), which infect vertebrates, including humans. Of these, the best-characterized is the human pathogen Mycoplasma pneumoniae, which is a leading cause of tracheobronchitis and atypical ("walking") pneumonia, especially in children and young adults.
Although some mycoplasma cells are structurally simple, many have prominent polar protrusions called attachment organelles. In the species that have them, they are essential for attachment to host cells (cytadherence). Attachment organelles are comprised of special cytoskeletal proteins found only in mycoplasmas. These structures are also essential for gliding motility of mycoplasma cells along surfaces. However, how the components of attachment organelles specifically function in their architecture and virulence-related properties is largely unknown.
In addition to its roles in adherence to host cells and gliding motility, the attachment organelle is involved in cell division. Remarkably, in apparent coordination with the onset of DNA replication, the M. pneumoniae attachment organelle duplicates, and one of the two attachment organelles migrates from one pole of the cell to the other. Following division, the process begins again. The molecular basis for both gliding motility and attachment organelle duplication/migration is almost entirely unknown, not only in M. pneumoniae but also in other mycoplasmas, many of which lack homologs of the known attachment organelle proteins. Understanding these processes better at the molecular level could lead to improved treatment of people and animals with mycoplasmal disease.
The focus of the research in the Balish lab is elucidation of the molecular underpinnings of attachment organelle morphology, cell division, cytadherence, and gliding motility in a variety of mycoplasma species. This research carried out through techniques that include time-lapse microcinematographic imaging, fluorescence and electron microscopy, molecular biology, protein biochemistry, and genomics.
- Identification and characterization of virulence factors, including those associated with the attachment organelle, in Mycoplasma penetrans, an organism found in AIDS patients.
- Determination of the roles of specific components of the attachment organelle of Mycoplasma pneumoniae.
- Comparative genomics of mycoplasma species.
- Development of molecular tools for studying mycoplasmas.
- Physiological and molecular studies of mycoplasma morphogenesis and virulence.
- Jurkovic, D.A.*, M.R. Hughes, and M.F. Balish. 2013. Analysis of energy sources for Mycoplasma penetrans gliding motility. FEMS Microbiol. Lett. 338:39-45.
- Jurkovic, D.A.*, J.T. Newman**, and M.F. Balish. 2012. Conserved terminal organelle morphology in Mycoplasma penetrans and Mycoplasma iowae. J. Bacteriol. 194:2877-2883.
- Relich, R.F.*, and M.F. Balish. 2011. Insights into the function of Mycoplasma pneumoniae protein P30 from orthologous gene replacement. Microbiology 157:2871-2879.
- Relich, R.F.*, A.J. Friedberg**, and M.F. Balish. 2009. Novel cellular organization in a gliding mycoplasma, Mycoplasma insons. J. Bacteriol. 191:5312-5314.
- Atkinson, T.P., M.F. Balish, and K.B. Waites. 2008. Epidemiology, clinical manifestations, pathogenesis and laboratory detection of Mycoplasma pneumoniae infections. FEMS Microbiol. Rev. 32:956-973.
- Hatchel, J.M.*, and M.F. Balish. 2008. Attachment organelle ultrastructure correlates with phylogeny, not gliding motility properties, in Mycoplasma pneumoniae relatives. Microbiology 154:286-295.
- May, M., G.J. Ortiz, L.D. Wendland, D.S. Rotstein, R.F. Relich*, M.F. Balish, and D.R. Brown. 2007. Mycoplasma insons sp. nov., a twisted mycoplasma from green iguanas (Iguana iguana). FEMS Microbiol. Lett. 274:298-303. *: graduate student
**: undergraduate researcher