College of Urban Construction, Nanjing Tech University, PuZhu Road, Nanjing, China.
Division of Environmental Engineering, Ichikawa Koumuten Co., Ltd, Gifu, Japan.
Water Res. 2018 Mar 1;130:115-126. doi: 10.1016/j.watres.2017.10.070. Epub 2017 Nov 20.
Better understanding the responses of riverbed sediment bacteria to heavy metals is a key for considering using riverbed sediment bacterial community as an indicator of river water contamination by heavy metals. For this, integrated evaluation based on bacterial density, activity and community structure through incubation experiments under well-controlled conditions is necessary to obtain more closely relevant findings that are difficult to achieve through field studies. The findings may also include those that can serve as new evidence to clarify contrary findings reported in previous studies. In this study, sequencing batch incubation experiments were performed using sediment suspensions from three rivers with catchment of different land covers and uses. The effects of four metals (Pb, Cr, Cd and Cu) were investigated by spiking them separately under three different concentration levels. Glucose was added once every day as the carbon source throughout the whole incubation lasted for 30 days. The changing trends of the density of general and heterotrophic bacteria showed clearly that the responses of sediment bacteria to Cu were obviously stronger, followed by that to Cd; whereas, the responses to Pb and Cr were not apparent. For incubation with Cu, a short-term inhibition effect appeared in the initial 3 days and was then followed by a long-term promotion effect reflected by obvious increases of bacterial density against control. In regard of bacterial activity evaluated based on the first-order consumption rate for glucose, a trend of decreases was revealed. The results of PCR-DGGE and sequence analysis of extracted 16S rDNA further suggested there were bacterial species that had strong tolerance against the metal and could grow readily to become new dominating ones. The existence of such bacterial species was inferred as the reason leading to the observed increases of bacterial density during incubation with the metal.
更好地理解河床沉积物细菌对重金属的响应，是将河床沉积物细菌群落作为河流重金属污染指示物的关键。为此，有必要通过在良好控制条件下进行的孵育实验，基于细菌密度、活性和群落结构进行综合评估，以获得更相关的发现，这是通过野外研究难以实现的。这些发现还可能包括可以作为新证据的发现，以澄清以前研究中报告的相反发现。在这项研究中，使用来自三个流域的沉积物悬浮液进行了序批式孵育实验，这些流域的集水区具有不同的土地覆盖和用途。通过在三种不同浓度水平下分别添加四种金属（Pb、Cr、Cd 和 Cu）来研究它们的影响。在整个 30 天的孵育过程中，每天添加一次葡萄糖作为碳源。总细菌和异养细菌密度的变化趋势清楚地表明，沉积物细菌对 Cu 的响应明显更强，其次是 Cd；而对 Pb 和 Cr 的响应不明显。对于 Cu 的孵育，在最初的 3 天内出现了短期抑制效应，随后是长期促进效应，表现为细菌密度明显高于对照。就基于葡萄糖一阶消耗率评估的细菌活性而言，呈现出下降的趋势。PCR-DGGE 和提取的 16S rDNA 序列分析的结果进一步表明，存在对金属具有较强耐受性的细菌物种，可以迅速生长成为新的优势种。这种细菌物种的存在被推断为导致在孵育过程中观察到细菌密度增加的原因。
