微生物在水环境中的存活和生长

在灭菌自来水模拟水体中,研究了7种细菌的存活和生长规律。Klebsiella pneumo-niae,Enterobacter aerogenes,Agrobacterium tumefatciens,在7天内平板计数降至0,而水体中镜检细菌总数(AODC)和活菌直接计数(DVC)结果无大变化,说明细菌已变成活的非可培养状态。Micrococcus,flavus 和 Streptococcus faecalis 的可培养菌数也可降至0。Pseudomonas sp.在48小时内由10~5降至10~2cfu/ml,随即升至10~6 cfu/ml 并持续到实验终了(41天)。Bacillus subtilis 在48小时平板计数降至10~2cfu/ml 并维持在该水平至实验结束(38天)。研究结果表明仅用涂布平板法检测多种细菌在水环境中的生存和分布是不合适的。

Survival and Growth of Microorganisms in the Aquatic Environment

Survival and growth of seven species of aquatic bacteria were examined in the sterilized tap water microcosms.The bac- teria were inoculated into the microcosms, using an inoculum of 1 ml of 108 cells washed in PBS.The microcosms were mo- nitered by plate counting,AODC and DVC. The strains of Klebsiella pneunoniae, Enterobacter aerogenes,Agrobacterium tumefaciens became viable but non-cultur- able state within seven days.The plate counts of Streptococcus faecalis and Mi- crococcus flavus dropped to 0 within 5-7 days.Psendomonas strain 719 showed an initial drop in plate count from 10~5 to 10~2 cfu/ml within 48 hrs,but immediately thereafter return to 10~5 cfu/ml until ter- mination of the experiment at 41 days. Bacillus subtilis CU-155 dropped to ca.10~2 cfu/ml plate count at 48 hr.and maintained at this level for 38 days when the experi- ment was terminated.In all cases,the AODC remained the same.The DVC also did not change except that the DVC,on average,was ca.one log lower than the AODC.The results of the study indicate that,for many species of bacteria,plate counts will not be suitable for monitering survival,persistence and distribution in the aquatic environment.