Biofilm-specific cross-species induction of antimicrobial compounds in bacilli.
An air-membrane surface (AMS) bioreactor was designed to allow bacteria to grow attached to a surface as a biofilm in contact with air. When Bacillus licheniformis strain EI-34-6, isolated from the surface of a marine alga, was grown in this reactor, cells produced antimicrobial compounds which they did not produce when they were grown in shake flask cultures. An unidentified red pigment was also produced by surface-grown cells but not by planktonically grown cells. Glycerol and ferric iron were important for the production of antimicrobial compounds and the red pigment. Release of these secondary metabolites was not due to the onset of sporulation. Cell-free spent medium recovered from beneath the reactor membrane could induce production of antimicrobial compounds and red pigment in shake flask cultures. Neither glycerol nor ferric iron was required for production of these inducer compounds. Spent medium from beneath the membrane of an AMS bioreactor culture of Bacillus subtilis strain DSM10(T) and Bacillus pumilus strain EI-25-8 could also induce production of antimicrobial compounds and a red pigment in B. licheniformis isolate EI-34-6 grown in shake flask cultures; however, the corresponding spent medium from shake flask cultures of DSM10(T) and EI-25-8 could not. These results suggest that there is a biofilm-specific cross-species signaling system which can induce planktonically grown cells to behave as if they were in a biofilm by regulating the expression of pigments and antimicrobial compounds.
Yan
Liming
L
Centre for Marine Biodiversity and Biotechnology, School of Life Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, Scotland, UK.
Boyd
Kenneth G
KG
Adams
David R
DR
Burgess
J Grant
JG
D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000737:chemistry; D001407:Bacillus / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010860:Pigments, Biological / Q000096:biosynthesis / Q000737:chemistry; D000461:Rhodophyta / Q000382:microbiology*; D012623:Seawater / Q000382:microbiology; D013045:Species Specificity; D013171:Spores, Bacterial
D000900:Anti-Bacterial Agents; D003470:Culture Media; D010860:Pigments, Biological