title: Ammonium and attachment of Rhodopirellula baltica.
abstract: A dimorphic life cycle has been described for the planctomycete Rhodopirellula baltica SH1(T), with juvenile motile, free-swimming cells and adult sessile, attached-living cells. However, attachment as a response to environmental factors was not investigated. We studied the response of R. baltica to nitrogen limitation. In batch cultures, ammonium limitation coincided with a dominance of free-swimming cells and a low number of aggregates. Flow cytometry revealed a quantitative shift with increasing ammonium availability, from single cells towards attached cells in large aggregates. During growth of R. baltica on glucose and ammonium in chemostats, an ammonium addition caused a macroscopic change of the growth behaviour, from homogeneous growth in the liquid phase to a biofilm on the borosilicate glass wall of the chemostat vessel. Thus, an ammonium limitation-a carbon to nitrogen supply ratio of 30:1-sustained free-living growth without aggregate formation. A sudden increase in ammonium supply induced sessile growth of R. baltica. These observations reveal a response of Rhodopirellula baltica cells to ammonium: they abandon the free-swimming life, attach to particles and form biofilms.
authors.affiliation: Department of Microbiology, Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Carsten S
authors.initials: CS
authors.lastname: Frank
authors.forename: Philipp
authors.initials: P
authors.lastname: Langhammer
authors.forename: Bernhard Maximilian
authors.initials: BM
authors.lastname: Fuchs
authors.forename: Jens
authors.initials: J
authors.lastname: Harder
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D018441:Biofilms / Q000254:growth & development*; D002244:Carbon / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D005434:Flow Cytometry; D005947:Glucose / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*
chemical_list: D003470:Culture Media; D000644:Quaternary Ammonium Compounds; D002244:Carbon; D005947:Glucose; D009584:Nitrogen