Tokajian Sima T, Hashwa Fuad A, Hancock Ian C, Zalloua Pierre A
Department of Biology, the Lebanese American University, PO Box 36, Byblos, Lebanon.
Can J Microbiol. 2005 Apr;51(4):325-35. doi: 10.1139/w05-007.
Determination of a heterotrophic plate count (HPC) for drinking-water samples alone is not enough to assess possible health hazards associated with sudden changes in the bacterial count. Speciation is very crucial to determine whether the population includes pathogens and (or) opportunistic pathogens. Most of the isolates recovered from drinking water samples could not be allocated to a specific phylogenetic branch based on the use of conventional diagnostic methods. The present study had to use phylogenetic analysis, which was simplified by determining and using the first 500-bp sequence of the 16S rDNA, to successfully identify the type and species of bacteria found in the samples. Gram-positive bacteria alpha-, beta-, and gamma-Proteobacteria were found to be the major groups representing the heterotrophic bacteria in drinking water. The study also revealed that the presence of sphingomonads in drinking water supplies may be much more common than has been reported so far and thus further studies are merited. The intermittent mode of supply, mainly characterized by water stagnation and flow interruption associated possibly with biofilm detachment, raised the possibility that the studied bacterial populations in such systems represented organisms coming from 2 different niches, the biofilm and the water column.
仅对饮用水样本进行异养平板计数（HPC）不足以评估与细菌数量突然变化相关的潜在健康危害。物种鉴定对于确定菌群中是否存在病原体和（或）机会致病菌至关重要。基于传统诊断方法，从饮用水样本中分离出的大多数菌株无法被归类到特定的系统发育分支。本研究不得不采用系统发育分析方法，通过测定并使用16S rDNA的前500个碱基对序列来简化该分析，从而成功鉴定样本中发现的细菌类型和种类。革兰氏阳性菌、α-、β-和γ-变形菌被发现是代表饮用水中异养细菌的主要菌群。该研究还表明，饮用水供应中鞘氨醇单胞菌的存在可能比迄今报道的更为普遍，因此值得进一步研究。以水停滞和水流中断（可能与生物膜脱落有关）为主要特征的间歇性供水模式，增加了这样一种可能性，即此类系统中所研究的细菌菌群代表了来自两个不同生态位（生物膜和水柱）的生物体。
