luxS基因在变异链球菌铁代谢中的作用研究

Function of luxS gene in iron metabolism of streptococcus mutans

目的探讨luxS基因在变异链球菌铁代谢中的作用。方法在不同铁限制条件培养基中对培养24 h的变异链球菌标准株和缺陷株进行吸光度(A)值的测定和分析;并对luxS基因缺陷株在铁限制培养基中加入外源性铁或者标准株无菌上清液的生长进行A值的测定和进一步分析。结果培养24 h,2种菌株在螯合剂浓度为0.1 mmol/L的培养基中均未表现明显生长抑制(P>0.05),在螯合剂浓度增大至0.3 mmol/L时,缺陷株表现出生长抑制(P<0.05),在螯合剂浓度至0.5 mmol/L时,生长抑制更为显著(P<0.001)。在铁限制培养基中生长抑制的缺陷株转移至新鲜培养基、外源性铁或标准株上清液加入的同浓度铁限制培养基中培养24 h,缺陷株的生长均能达到较高细胞密度(P<0.05)。结论 luxS基因在变异链球菌生长中具有铁代谢作用,其可能通过AI-2部分调节变异链球菌铁限制条件下的生长。

Objective To investigate the function of luxS gene in iron metabolism of streptococcus mutans. Methods The absor- bance of standard strains and deficient strains of streptococcus mutans cultured in the iron-limited defined medium for 24 hours was measured and analyzed. Exogenous iron or the supematant fluid of standard strains was added into iron-limited defined medium of defi- cient strains of luxS gene mutant, and the A value was further measured and analyzed. Results After incubation for 24 hours, the growth of both standard and luxS gene mutant strains in medium containing 0.1 mmol/L of 2,2＇-bipyridyl was not significantly inhibi- ted. However,the growth of luxS gene mutant strains in medium containing 0.3 mmol/L and O. 5 mmol/L of 2,2＇-bipyridyl was signifi- cantly inhibited. The growth inhibition of luxS gene mutant strains in medium containing 0.3 mmol/L of 2,2＇-bipyridyl was relieved by adding exogenous iron and culture supernatant of standard strain into the medium, so was it when the luxS gene mutant strains were tran- ferred into fresh medium,and the growth of luxS gene mutant strains could get relatively high cell concentrations. Conclusions luxS gene plays a role in iron metabolism, and it may regulate the growth of streptococcus mutans to a certain degree in iron-limited medium via AI-2.