Motility is involved in Silicibacter sp. TM1040 interaction with dinoflagellates

Environ Microbiol. 2006 Sep;8(9):1648-59. doi: 10.1111/j.1462-2920.2006.01071.x.


Silicibacter sp. TM1040, originally isolated from a culture of the dinoflagellate Pfiesteria piscicida, senses and responds to the dinoflagellate secondary metabolite dimethylsulfoniopropionate (DMSP) by flagella-mediated chemotaxis behaviour. In this report we show that swimming motility is important for initiating the interaction between the bacterium and dinoflagellate. Following transposon mutagenesis, three mutants defective in wild-type swimming motility (Mot-) were identified. The defects in motility were found to be in homologues of cckA and ctrA, encoding a two-component regulatory circuit, and in a novel gene, flaA, likely to function in flagellar export or biogenesis. Mutation of flaA or cckA results in the loss of flagella and non-motile cells (Fla-), while CtrA- cells possess flagella, but have reduced motility due to increased cell length. All three Mot- mutants were defective in attaching to the dinoflagellate, particularly to regions that colocalized with intracellular organelles. The growth rate of the dinoflagellates was reduced in the presence of the Fla- mutants compared with Fla+ cells. These results indicate that bacterial motility is important for the Silicibacter sp. TM1040-P. piscicida interaction.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Flagella / genetics
  • Flagella / microbiology*
  • Microscopy, Confocal
  • Pfiesteria piscicida / growth & development
  • Pfiesteria piscicida / microbiology*
  • Rhodobacteraceae / genetics
  • Rhodobacteraceae / physiology*
  • Rhodobacteraceae / ultrastructure
  • Symbiosis / physiology*