Gentry T J, Wang G, Rensing C, Pepper I L
Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, AZ 85721, USA.
Microb Ecol. 2004 Jul;48(1):90-102. doi: 10.1007/s00248-003-1048-1. Epub 2004 Apr 19.
A study was conducted to determine the diversity of 2-, 3-, and 4-chlorobenzoate (CB) degraders in two pristine soils with similar physical and chemical characteristics. Surface soils were collected from forested sites and amended with 500 microg of 2-, 3-, or 4-CB g(-1) soil. The CB levels and degrader numbers were monitored throughout the study. Degraders were isolated, grouped by DNA fingerprints, identified via 16S rDNA sequences, and screened for plasmids. The CB genes in selected degraders were isolated and/or sequenced. In the Madera soil, 2-CB and 4-CB degraded within 11 and 42 d, respectively, but 3-CB did not degrade. In contrast, 3-CB and 4-CB degraded in the Oversite soil within 14 and 28 d, respectively, while 2-CB did not degrade. Approximately 10(7) CFU g(-1) of degraders were detected in the Madera soil with 2-CB, and the Oversite soil with 3- and 4-CB. No degraders were detected in the Madera soil with 4-CB even though the 4-CB degraded. Nearly all of the 2-CB degraders isolated from the Madera soil were identified as a Burkholderia sp. containing chromosomally encoded degradative genes. In contrast, several different 3- and 4-CB degraders were isolated from the Oversite soil, and their populations changed as CB degradation progressed. Most of these 3-CB degraders were identified as Burkholderia spp. while the majority of 4-CB degraders were identified as Bradyrhizobium spp. Several of the 3-CB degraders contained the degradative genes on large plasmids, and there was variation between the plasmids in different isolates. When a fresh sample of Madera soil was amended with 50, 100, or 200 microg 3-CB g(-1), 3-CB degradation occurred, suggesting that 500 microg 3-CB g(-1) was toxic to the degraders. Also, different 3-CB degraders were isolated from the Madera soil at each of the three lower levels of 3-CB. No 2-CB degradation was detected in the Oversite soil even at lower 2-CB levels. These results indicate that the development of 2-, 3-, and 4-CB degrader populations is site-specific and that 2-, 3-, and 4-CB are degraded by different bacterial populations in pristine soils. These results also imply that the microbial ecology of two soils that develop under similar biotic and abiotic environments can be quite different.
开展了一项研究，以确定两种物理和化学特性相似的原始土壤中2 - 氯苯甲酸（2 - CB）、3 - 氯苯甲酸（3 - CB）和4 - 氯苯甲酸（4 - CB）降解菌的多样性。从森林地区采集表层土壤，并用500微克/克土壤的2 - CB、3 - CB或4 - CB进行改良。在整个研究过程中监测CB水平和降解菌数量。分离降解菌，通过DNA指纹图谱进行分组，通过16S rDNA序列进行鉴定，并筛选质粒。分离并/或测序选定降解菌中的CB基因。在马德拉土壤中，2 - CB和4 - CB分别在11天和42天内降解，但3 - CB未降解。相比之下，在奥弗赛特土壤中，3 - CB和4 - CB分别在14天和28天内降解，而2 - CB未降解。在添加2 - CB的马德拉土壤以及添加3 - CB和4 - CB的奥弗赛特土壤中检测到约10⁷CFU/克的降解菌。在添加4 - CB的马德拉土壤中，尽管4 - CB发生了降解，但未检测到降解菌。从马德拉土壤中分离出的几乎所有2 - CB降解菌都被鉴定为含有染色体编码降解基因的伯克霍尔德氏菌属。相比之下，从奥弗赛特土壤中分离出几种不同的3 - CB和4 - CB降解菌，并且随着CB降解的进行，它们的数量发生变化。这些3 - CB降解菌大多数被鉴定为伯克霍尔德氏菌属，而大多数4 - CB降解菌被鉴定为慢生根瘤菌属。一些3 - CB降解菌在大质粒上含有降解基因，不同分离株中的质粒存在差异。当用50、100或200微克/克的3 - CB对马德拉土壤新鲜样品进行改良时，发生了3 - CB降解，这表明500微克/克的3 - CB对降解菌有毒。此外，在三个较低的3 - CB水平下，从马德拉土壤中分别分离出不同的3 - CB降解菌。即使在较低的2 - CB水平下，在奥弗赛特土壤中也未检测到2 - CB降解。这些结果表明，2 - CB、3 - CB和4 - CB降解菌群体的发展具有位点特异性，并且在原始土壤中，2 - CB、3 - CB和4 - CB由不同的细菌群体降解。这些结果还意味着，在相似的生物和非生物环境下发育的两种土壤的微生物生态可能有很大差异。
