从链霉菌中发现新抗生素的趋势分析

到目前为止，链霉菌是微生物中产生抗生素最多的菌种，据报道，从20世纪40年代后期到70年代，每年由链霉菌产生的抗生素几乎呈现指数增长，并在20世纪70年代达到最高峰，20世纪80年代后期到90年代增加幅度下降。收集到的数据显示一条S形曲线，比对数方程预测的曲线要平缓得多，在不断优化参数后为这条曲线建立1个较好的数学模型，根据这一模型可以估计链霉菌中还有多少没有被发现的抗生素，同时也便于预测不远的将来新抗生素产生的趋势。此模型估计在这类菌种中能产生的抗菌化合物的总数量约100000多种，而这只是迄今为止未发现抗生素中很微小的一部分。曲线中斜率的减少是由于筛选方法的减少，而不是由于新抗生素的枯竭，如果这种趋势任其发展下去，在近10～20年内斜率将会趋近于零，但如果不断地探索新的筛选方法，在未来的几十年里发现新抗生素的速度是不会下降的。

Analysis on the Trends of Finding new Antibiotics Form the Genus Streptomyces

Streptomyces is the largest antibiotic-producing genus in the microbial world discovered so far.The number of antimicrobial compounds reported from the species of this genus per year increased almost exponentially from the late 1940s to 1970s,followed by a peak in the 1970s,and with a decline in the late 1980s and 1990s.The cumulative number shows a sigmoid curve that is much flatter than what a logistic equation would predict.A good mathematical model is fit to this curve after optimizing parameters.According to this model we can estimate the number of antibiotics undiscovered so far from this genus as well as to predict the trends in the near future.The model estimated the total number of antimicrobial compounds that this genus is capable of producing to be more than 100 000-a tiny fraction of which has been undiscovered so far.The decline in the slope appeared to be due to a decline in screening efforts rather than an exhaustion of compounds.Left to itself,the slope will become zero in the next one or two decades,but if the screening efforts are maintained constant,the rate of discovery of new compounds will not decline for several decades to come.