  Recent experiments have illuminated a remarkable growth mechanism of
rod-shaped bacteria: proteins associated with cell wall extension move at
constant velocity in circles oriented approximately along the cell
circumference (Garner et al., Science (2011), Dominguez-Escobar et al. Science
(2011), van Teeffelen et al. PNAS (2011). We view these as dislocations in the
partially ordered peptidoglycan structure, activated by glycan strand extension
machinery, and study theoretically the dynamics of these interacting defects on
the surface of a cylinder. Generation and motion of these interacting defects
lead to surprising effects arising from the cylindrical geometry, with
important implications for growth. We also discuss how long range elastic
interactions and turgor pressure affect the dynamics of the fraction of
actively moving dislocations in the bacterial cell wall.
