Abdulla Hesham
Botany Department, Faculty of Science, Suez Canal University, 41522, Ismailia, Egypt.
Microb Ecol. 2009 Nov;58(4):753-61. doi: 10.1007/s00248-009-9549-1. Epub 2009 Jul 10.
Actinomycetes inhabiting granitic rocks at St. Katherine, Egypt were investigated for their bioweathering potential. Actinomycete counts ranged between 174 and 360 colony forming units per gram. Counts were positively correlated to rock porosity (r = 0.65) and negatively correlated to rock salinity (r = -0.56). Sixty-six actinomycete isolates originating from rocks could be assigned into eight genera, with a high frequency of Nocardioides and Streptomyces. Organic acids were produced by 97% of the isolates. Strains belonging to Actinopolyspora, Actinomadura, Kitasatospora, Nocardioides, and Kibdelosporangium showed the highest acid production indices. Representatives from all eight genera could precipitate metals Cu, Fe, Zn, Cd, and Ag up to concentrations of 2.5 mM each. An actinomycete consortium of two Nocardioides strains and one Kibdelosporangium strain was studied for its potential to cause rock weathering in batch experiments. Results indicated a high ability of the consortium to leach the metals Cu, Zn, and Fe up to 2.6-, 2.1-, and 1.3-fold, respectively, compared to the control after 4 weeks. The pH significantly decreased after 1 week, which was parallel to an increased release of phosphate and sulfate reaching a 2.2- and 2.5-fold increase, respectively, compared to control. Highly significant weight loss (p = 0.005) was achieved by the consortium, indicating a potential multiple role of actinomycetes in weathering by acid production, metal leaching, and solubilization of phosphate and sulfate. This study emphasizes the diverse and unique abilities of actinomycetes inhabiting rock surfaces which could be of potential biotechnological applications, such as in the bioremediation of metal-contaminated environments and metal biorecovery.
对埃及圣凯瑟琳地区花岗岩中的放线菌进行了生物风化潜力研究。放线菌数量在每克174至360个菌落形成单位之间。数量与岩石孔隙度呈正相关（r = 0.65），与岩石盐度呈负相关（r = -0.56）。从岩石中分离出的66株放线菌可归为8个属，其中诺卡氏菌属和链霉菌属的频率较高。97%的分离株能产生有机酸。属于放线多孢菌属、马杜拉放线菌属、北里孢菌属、诺卡氏菌属和小孢囊菌属的菌株产酸指数最高。所有8个属的代表菌株都能沉淀金属铜、铁、锌、镉和银，每种金属的沉淀浓度可达2.5 mM。在分批实验中，研究了由两株诺卡氏菌属菌株和一株小孢囊菌属菌株组成的放线菌联合体引起岩石风化的潜力。结果表明，与对照组相比，该联合体在4周后浸出金属铜、锌和铁的能力分别高达2.6倍、2.1倍和1.3倍。1周后pH值显著下降，同时磷酸盐和硫酸盐的释放量增加，与对照组相比分别增加了2.2倍和2.5倍。该联合体实现了极显著的重量损失（p = 0.005），表明放线菌在通过产酸、金属浸出以及磷酸盐和硫酸盐的溶解进行风化过程中可能具有多种作用。本研究强调了栖息在岩石表面的放线菌具有多样且独特的能力，这些能力在生物技术应用中具有潜在价值，例如在金属污染环境的生物修复和金属生物回收方面。
