Extracellular deoxyribonucleases (exDNases) from microbial origin contribute substantially to the restriction of extracellular DNA (exDNA) in the soil. Hence, it is imperative to understand the diversity of bacterial species capable of performing this important soil function and how crop species influence their dynamics in the soil. The present study investigates the occurrence of DNase-producing bacteria (DPB) in leachate samples obtained from soils in which the crop species of alfalfa (Medicago sativa L.), canola (Brassica napus L.), soybean (Glycine max [L.] Merr.) and wheat (Triticum aestivum L.) were raised in a growth room. Selective media containing methyl green indicator was used to screen for DPB from leachate samples, whereas the 16S rRNA sequence analysis was employed to identify the isolates. The proportion of culturable DPB ranged between 5.72 and 40.01%; however, we did observe specific crop effects that shifted throughout the growing period. In general, higher proportions of exDNase producers were observed when the soils had lower nutrient levels. On using the 16S rRNA to classify the DPB isolates, most isolates were found to be members of the Bacillus genera, while other groups included Chryseobacterium, Fictibacillus, Flavobacterium, Microbacterium, Nubsella, Pseudomonas, Psychrobacillus, Rheinheimera, Serratia and Stenotrophomonas. Five candidate exDNase/nuclease-encoding proteins were also identified from Bacillus mycoides genomes using online databases. Results from this study showed that crop species, growth stage and soil properties were important factors shaping the populations of DPB in leachate samples; however, soil properties seemed to have a greater influence on the trends observed on these bacterial populations. It may be possible to target soil indigenous bacteria that produce exDNases through management to decrease potential unintended effects of transgenes originating from genetically modified organisms (GMOs) or other introduced nucleic acid sequences in the environment.

中文翻译：

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作物种类对两种土壤中产生DNase的细菌的影响

来自微生物的细胞外脱氧核糖核酸酶（exDNases）在很大程度上限制了土壤中细胞外DNA（exDNA）的表达。因此，必须了解能够执行这种重要土壤功能的细菌物种的多样性以及农作物物种如何影响其在土壤中的动力学。本研究调查了从苜蓿（Medicago sativa L.），低芥酸菜子（Brassica napus L.），大豆（Glycine max [L.] Merr。）和小麦（Triticum aestivum L.）在生长室中饲养。含甲基绿色指示剂的选择性培养基用于从渗滤液样品中筛选DPB，而16S rRNA序列分析用于鉴定分离物。可培养DPB的比例为5.72〜40.01％。但是，我们确实观察到了特定的作物效应，这些效应在整个生长期都发生了变化。通常，当土壤中的营养水平较低时，会观察到较高比例的exDNase生产者。在使用16S rRNA对DPB分离株进行分类时，发现大多数分离株是芽孢杆菌属的成员，而其他组包括金边杆菌，短杆菌，黄杆菌，微细菌，纳贝氏菌，假单胞菌，Psychrobacillus，Rheinheimera，Serratia和Stenotrophomonas。使用在线数据库，还从分枝杆菌芽孢杆菌基因组中鉴定了五个候选的exDNase /核酸酶编码蛋白。这项研究的结果表明，农作物的种类，生长阶段和土壤特性是影响渗滤液样品中DPB种群的重要因素。然而，土壤特性似乎对这些细菌种群上观察到的趋势有更大的影响。通过管理可以靶向产生exDNase的土壤土著细菌，以减少环境中源自转基因生物（GMO）或其他引入的核酸序列的转基因的潜在意外影响。