title: [Function of luxS gene in sulfurmetabolism of Streptococcus mutans].
abstract: OBJECTIVE
  To investigate the function of luxS in sulfurmetabolism of Streptococcus mutans (Sm).
  
  
  METHODS
  The growth with absorbency (A) of the standards and mutant strains was measured and analyzed in the sulfur-limited defined medium at different periods. The laser scanning confocal microscopy (LSCM) was used to observe and compare the biofilm thickness of the two kinds of strains at different culture conditions.
  
  
  RESULTS
  The significant increases in the thickness of mutant strain biofilm and its growth were observed after the addition of cysteine, but did not reach the standards strain levels (P < 0.05). The growth and the biofilm thickness of the mutant strains were (1.301 ± 0.009) and (45.009 ± 0.429) µm. When methionine and S-adenosylhomocysteine of certain concentrations were respectively added, the biofilm thickness and the growth of mutant strain were raised but did not reach the level of the standards strain at 24 h (P < 0.05), but at 48 h they did. When the methionine was added in the mutant strains for 24 h, the biofilm thickness and the growth of mutant strain were (0.448 ± 0.028) and (37.068 ± 2.392) µm, as for the adding of S-adenosylhomocysteine were (0.460 ± 0.005) and (27.343 ± 1.107) µm. When adding the supernatant fluid of standard strains, the biofilm thickness and the growth levels of mutant strain were much higher than those of the standards strain. The biofilm thickness and growth of both kinds of strains decreased after the addition of S-adenosylmethionine.
  
  
  CONCLUSIONS
  luxS gene plays not only a role in quorum sensing but also a role in sulfurmetabolism.
authors: Department of Stomatology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China. danni2468@eyou.com
authors: Dan-ni
authors: DN
authors: Yu
authors: Zhi-ming
authors: ZM
authors: Ren
authors: Yu-zhi
authors: YZ
authors: Han
authors: Wen-juan
authors: WJ
authors: Zhang