Chin Kuk-Jeong, Esteve-Núñez Abraham, Leang Ching, Lovley Derek R
Department of Microbiology, University of Massachusetts, Morrill Science Center IV North, 639 North Pleasant St., Amherst, MA 01003, USA.
Appl Environ Microbiol. 2004 Sep;70(9):5183-9. doi: 10.1128/AEM.70.9.5183-5189.2004.
The predominance of Geobacter species in environments in which Fe(III) reduction is important has suggested that Fe(III) reduction rates might be estimated in Geobacter-dominated environments by assessing in situ activity with molecular techniques. To determine whether mRNA levels of key respiratory genes might be correlated with respiration rates in Geobacter sulfurreducens, studies were conducted with fumarate as the electron acceptor and acetate as the limiting electron donor in anaerobic continuous cultures. Levels of mRNA for a fumarate reductase gene, frdA, quantified by real-time reverse transcription-PCR were directly correlated with fumarate reduction rates. In similar studies with Fe(III) as the electron acceptor, mRNA levels for omcB, a gene for an outer membrane c-type cytochrome involved in Fe(III) reduction, were positively correlated with Fe(III) reduction rates. Levels of mRNA for frdA and omcB were also positively correlated with fumarate and Fe(III) reduction rates, respectively, when growth was limited by the availability of fumarate or Fe(III), but mRNA levels were higher than in acetate-limited cultures. Levels of mRNA for omcC, which encodes a c-type cytochrome highly similar to OmcB but not necessary for Fe(III) reduction, followed patterns different than those of omcB. This agrees with the previous finding that OmcC is not involved in Fe(III) reduction and suggests that changes in mRNA levels of omcB are related to its role in Fe(III) reduction. These results demonstrate that mRNA levels for respiratory genes might be used to estimate in situ Fe(III) reduction rates in Geobacter-dominated environments but suggest that information on environmental conditions and/or the metabolic state of Geobacter species is also required for accurate rate estimates.
在铁（III）还原起重要作用的环境中，地杆菌属物种占优势，这表明在以地杆菌为主的环境中，可通过分子技术评估原位活性来估算铁（III）还原速率。为了确定嗜硫地杆菌中关键呼吸基因的mRNA水平是否与呼吸速率相关，在厌氧连续培养中，以富马酸为电子受体、乙酸为限制性电子供体进行了研究。通过实时逆转录PCR定量的富马酸还原酶基因frdA的mRNA水平与富马酸还原速率直接相关。在以铁（III）为电子受体的类似研究中，参与铁（III）还原的外膜c型细胞色素基因omcB的mRNA水平与铁（III）还原速率呈正相关。当生长受富马酸或铁（III）可用性限制时，frdA和omcB的mRNA水平也分别与富马酸和铁（III）还原速率呈正相关，但mRNA水平高于乙酸限制培养中的水平。编码与OmcB高度相似但对铁（III）还原不必要的c型细胞色素的omcC的mRNA水平，其变化模式与omcB不同。这与之前OmcC不参与铁（III）还原的发现一致，并表明omcB的mRNA水平变化与其在铁（III）还原中的作用有关。这些结果表明，呼吸基因的mRNA水平可用于估算以地杆菌为主的环境中的原位铁（III）还原速率，但表明准确估算速率还需要有关环境条件和/或地杆菌属物种代谢状态的信息。
