Role of chromosomal and plasmid-borne receptor homologues in the response of Bacillus megaterium QM B1551 spores to germinants.
Spores of Bacillus megaterium QM B1551 germinate in response to a number of trigger compounds, including glucose, proline, leucine, and inorganic salts. An approximate 6-kb region of the 165-kb plasmid was found to harbor a tricistronic receptor operon, gerU, and a monocistronic receptor component, gerVB. The gerU operon was observed to complement the germination response in plasmidless strain PV361 to glucose and leucine, with KBr acting as a cogerminant. Proline recognition is conferred by the monocistronic gerVB gene, the presence of which also improves the germination response to other single-trigger compounds. A chimeric receptor, GerU*, demonstrates interchangeability between receptor components and provides evidence that it is the B protein of the receptor that determines germinant specificity. Introduction of the gerU/gerVB gene cluster to B. megaterium KM extends the range of germinants recognized by this strain to include glucose, proline, and KBr in addition to alanine and leucine. A chromosomally encoded receptor, GerA, the B component of which is predicted to be truncated, was found to be functionally redundant. Similarly, the plasmid-borne antiporter gene, grmA, identified previously as being essential for germination in QM B1551, did not complement the germination defect in the plasmidless variant PV361. Wild-type spores carrying an insertion-deletion mutation in this cistron germinated normally; thus, the role of GrmA in spore germination needs to be reevaluated in this species.
Christie
Graham
G
Institute of Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, England, CB2 1QT. gc301@cam.ac.uk
Lowe
Christopher R
CR
D001410:Bacillus megaterium / Q000235:genetics / Q000254:growth & development*; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics / Q000502:physiology*; D001965:Bromides / Q000378:metabolism; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005947:Glucose / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids / Q000235:genetics*; D017680:Potassium Compounds / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D013171:Spores, Bacterial / Q000235:genetics / Q000254:growth & development*; D014169:Transformation, Bacterial
D001426:Bacterial Proteins; D001965:Bromides; D004269:DNA, Bacterial; C099513:GrmA protein, Bacillus megaterium; D008565:Membrane Proteins; D017680:Potassium Compounds; D011392:Proline; D007930:Leucine; D005947:Glucose; C039004:potassium bromide