Ward D M, Santegoeds C M, Nold S C, Ramsing N B, Ferris M J, Bateson M M
Department of Microbiology, Montana State University Bozeman 59717, USA.
Antonie Van Leeuwenhoek. 1997 Feb;71(1-2):143-50. doi: 10.1023/a:1000131426164.
We have begun to examine the basis for incongruence between hot spring microbial mat populations detected by cultivation or by 16S rRNA methods. We used denaturing gradient gel electrophoresis (DGGE) to monitor enrichments and isolates plated therefrom. At near extincting inoculum dilutions we observed Chloroflexus-like and cyanobacterial populations whose 16S rRNA sequences have been detected in the 'New Pit' Spring Chloroflexus mat and the Octopus Spring cyanobacterial mat. Cyanobacterial populations enriched from 44 to 54 degrees C and 56 to 63 degrees C samples at near habitat temperatures were similar to those previously detected in mat samples of comparable temperatures. However, a lower temperature enrichment from the higher temperature sample selected for the populations found in the lower temperature sample. Three Thermus populations detected by both DGGE and isolation exemplify even more how enrichment may bias our view of community structure. The most abundant population was adapted to the habitat temperature (50 degrees C), while populations adapted to 65 degrees C and 70 degrees C were 10(2)- and 10(4)-fold less abundant, respectively. However, enrichment at 70 degrees C favored the least abundant strain. Inoculum dilution and incubation at the habitat temperature favored the more numerically relevant populations. We enriched many other aerobic chemoorganotrophic populations at various inoculum dilutions and substrate concentrations, most of whose 16S rRNA sequences have not been detected in mats. A common feature of numerically relevant cyanobacterial, Chloroflexus-like and aerobic chemorganotrophic populations, is that they grow poorly and resist cultivation on solidified medium, suggesting plating bias, and that the medium composition and incubation conditions may not reflect the natural microenvironments these populations inhabit.
我们已开始研究通过培养法或16S rRNA方法检测到的温泉微生物席种群之间不一致的原因。我们使用变性梯度凝胶电泳（DGGE）来监测富集培养物以及从中分离出的菌株。在接近灭绝的接种物稀释度下，我们观察到了类似绿弯菌属的种群和蓝细菌种群，其16S rRNA序列已在“新坑”泉绿弯菌席和章鱼泉蓝细菌席中被检测到。在接近栖息地温度的条件下，从44至54摄氏度以及56至63摄氏度的样本中富集的蓝细菌种群与之前在类似温度的席样本中检测到的种群相似。然而，从较高温度样本中进行的较低温度富集选择出了在较低温度样本中发现的种群。通过DGGE和分离法检测到的三个嗜热栖热菌种群更能说明富集是如何可能使我们对群落结构的看法产生偏差的。最丰富的种群适应栖息地温度（50摄氏度），而适应65摄氏度和70摄氏度的种群丰度分别低10²倍和10⁴倍。然而，在70摄氏度下富集有利于丰度最低的菌株。接种物稀释以及在栖息地温度下培养有利于数量上更具相关性的种群。我们在各种接种物稀释度和底物浓度下富集了许多其他需氧化学有机营养型种群，其中大多数种群的16S rRNA序列在席中未被检测到。数量上具有相关性的蓝细菌、类似绿弯菌属和需氧化学有机营养型种群的一个共同特征是，它们生长缓慢且在固化培养基上难以培养，这表明存在平板接种偏差，并且培养基成分和培养条件可能无法反映这些种群所栖息的自然微环境。
