Department of Integrative Biology, University of South Florida, Tampa, FL, USA.
Environ Microbiol. 2010 May;12(5):1271-81. doi: 10.1111/j.1462-2920.2010.02169.x. Epub 2010 Feb 18.
Enterococcus spp. are utilized worldwide as faecal indicator bacteria, but certain strains exhibit extended survival in environmental habitats and the factors influencing their persistence are poorly understood. We used flowing freshwater mesocosms to explore the effect of submerged aquatic vegetation (SAV) on the persistence of natural enterococci populations from a subtropical lake. The highest mean densities of culturable enterococci over 2 weeks occurred in SAV [8.6 x 10(2) colony-forming units (cfu) per 100 g wet weight], followed by sediments (1.3 x 10(2) cfu per 100 g) and water (18 cfu per 100 ml). However, due to relative differences in the total mass of each substrate in the entire system (water > sediments > SAV), SAV-associated enterococci represented only a minor proportion of the total population. Vegetated mesocosms harboured significantly higher mean cfu per mesocosm and cfu densities in sediments compared with their unvegetated counterparts, suggesting that SAV indirectly facilitates persistence in aquatic habitats. Populations were dominated (> 96%) by a single Enterococcus casseliflavus strain according to BOX-PCR genotyping, which did not change over the 10-month study and strongly suggests bacterial replication in the lake. The presence of such strains in the environment may represent highly competitive, naturalized and reproducing indicator bacteria populations that are not directly related to pollution events.
粪肠球菌属被广泛用作粪便指示菌，但某些菌株在环境栖息地中有较长的存活时间，其生存的影响因素了解甚少。我们使用流动的淡水中观模型来研究水生植被（SAV）对亚热带湖泊中天然肠球菌种群持久性的影响。在 2 周内，可培养肠球菌的最高平均密度出现在 SAV 中[每 100 克湿重 8.6×10(2)个菌落形成单位（cfu）]，其次是沉积物（每 100 克 1.3×10(2)cfu）和水（每 100 毫升 18 cfu）。然而，由于每个基质在整个系统中的总质量相对差异（水>沉积物>SAV），与 SAV 相关的肠球菌仅占总种群的一小部分。与无植被中观模型相比，植被中观模型中的每个中观模型的平均 cfu 和沉积物中的 cfu 密度都显著更高，这表明 SAV 间接促进了水生栖息地的持久性。根据 BOX-PCR 基因分型，种群主要由单一肠球菌属 casseliflavus 菌株组成（>96%），在 10 个月的研究中没有变化，这强烈表明该细菌在湖中复制。此类菌株在环境中的存在可能代表了高度竞争、适应和繁殖的指示菌种群，与污染事件没有直接关系。
