title: Caulobacter and Asticcacaulis stalk bands as indicators of stalk age.
abstract: The prosthecae (stalks) of dimorphic caulobacters of the genera Caulobacter and Asticcacaulis are distinguished among such appendages by the presence of disk-like components known as stalk bands. Whether bands are added to a cell's stalk(s) as a regular event coordinated with the cell's reproductive cycle has not been settled by previous studies. Analysis of the frequency of stalks with i, i + 1, i + 2, etc. bands 'among more than 7,000 stalks of Caulobacter crescentus revealed that in finite (batch) cultures (in which all offspring accumulate), the proportion of stalks with i + 1 hands was regularly 50% of the proportion of stalks with i bands. This implied that the number of bands correlated with the number of reproductive cycles completed by a stalked cell. In chemostat-maintained perpetual cultures, the proportion was greater than 50% because stalked cells, with their shorter reproductive cycle times, contributed a larger proportion of offspring to the steady-state population than did their swarmer siblings. In Asticcacaulis biprosthecum cells, which bear twin prosthecae, the twins on a typical cell possessed the same number of bands. For both genera, stalk bands provide a unique morphological feature that could be employed in an assessment of age distribution and reproductive dynamics within natural populations of these caulobacters.
authors.affiliation: Department of Biological Sciences, Barnard College/Columbia University, New York 10027, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Poindexter
authors.forename: J T
authors.initials: JT
authors.lastname: Staley
mesh_terms: D016935:Caulobacter crescentus / Q000254:growth & development* / Q000648:ultrastructure; D006090:Gram-Negative Bacteria / Q000254:growth & development* / Q000648:ultrastructure