Miskin Ian, Rhodes Glenn, Lawlor Kirsten, Saunders Jon R, Pickup Roger W
School of Biological Sciences, University of LiverpoolPO Box 147, Liverpool L69 7ZBUK.
Institute of Freshwater Ecology, Windermere LaboratoryThe Ferry House, Far Sawrey, Ambleside, Cumbria LA22 0LPUK.
Microbiology (Reading). 1998 Sep;144 ( Pt 9):2427-2439. doi: 10.1099/00221287-144-9-2427.
Prokaryote communities in post-glacial profundal freshwater sediments of Windermere, representing 10-12,000 years of deposition, were examined for culturability, viability and community structure. The potential for active geochemical cycles was inferred from the presence of specific groups of bacteria. Direct count procedures revealed 10(12) cells (g dry wt sediment)-1 in the surface sediments, which declined to approximately 10(9) cells (g dry wt sediment)-1 at 6 m depth of core (Representing approximately 10,000 years of deposition). The majority of the cells in the upper sediments were metabolically active when challenged with viability probes and responded to the direct viable count method. Below 250 cm, viability shown by 5-cyano-2,3-diotyl tetrazolium chloride (CTC) dye was not significantly different from the direct count; however, counts obtained with 5-carboxyfluorescein diacetate (CFDA) and the direct viable count both declined significantly from the direct count below 250 cm and 1 m, respectively. Culture was achieved from samples throughout the core, although the numbers of culturable bacteria decreased significantly with depth, from 10(7) c.f.u. (g dry wt sediment)-1 to 10(1)-10(2) c.f.u. (g dry wt sediment)-1 below 3 m depth. Among culturable isolates, Gram-positives and Gram-negatives were found at all levels of the core, and spore-forming heterotrophs dominated. Although sulphate-reducing bacteria were not detected below 20 cm, isolates demonstrating denitrifying activity were detected at all depths. PCR performed on samples taken below 3 m (deposited more than 7000 years ago) using eubacterial and archaeal primers revealed sequences similar to those found in deep sediments of the Pacific Ocean and the presence of methanogenic archaea. These observations indicate that bacteria and archaea are capable of long-term persistence and activity in deep, aged freshwater sediments.
对温德米尔湖冰川消退后的淡水深层沉积物中的原核生物群落进行了研究，这些沉积物代表了10000至12000年的沉积历史，检测了其可培养性、生存能力和群落结构。通过特定细菌群的存在推断了活跃地球化学循环的可能性。直接计数程序显示，表层沉积物中有10¹²个细胞/（克干重沉积物），在岩芯6米深处（代表约10000年的沉积）降至约10⁹个细胞/（克干重沉积物）。当用生存能力探针检测时，上层沉积物中的大多数细胞具有代谢活性，并对直接活菌计数法有反应。在250厘米以下，用5-氰基-2,3-二苯基四氮唑氯化物（CTC）染料显示的生存能力与直接计数没有显著差异；然而，用5-羧基荧光素二乙酸酯（CFDA）获得的计数和直接活菌计数分别在250厘米和1米以下与直接计数相比显著下降。尽管岩芯各处的样本都能培养出细菌，但可培养细菌的数量随深度显著减少，从10⁷个菌落形成单位/（克干重沉积物）降至3米以下深度的10¹至10²个菌落形成单位/（克干重沉积物）。在可培养的分离物中，在岩芯的各个深度都发现了革兰氏阳性菌和革兰氏阴性菌，形成孢子的异养菌占主导。尽管在20厘米以下未检测到硫酸盐还原菌，但在所有深度都检测到了具有反硝化活性的分离物。使用真细菌和古细菌引物对3米以下（沉积超过7000年前）采集的样本进行的PCR显示，其序列与在太平洋深层沉积物中发现的序列相似，并且存在产甲烷古菌。这些观察结果表明，细菌和古菌能够在深层、古老的淡水沉积物中长期存活并具有活性。
