Department of Plant Pathology, University of California at Berkeley, Berkeley, California 94720.
Appl Environ Microbiol. 1993 Jul;59(7):2056-63. doi: 10.1128/aem.59.7.2056-2063.1993.
Respiration and growth of Pseudomonas putida PpG7, containing catabolic plasmid NAH7, was determined in three agricultural field soils amended with the carbon source salicylate. The addition of salicylate to soil significantly increased the population of PpG7. However, there was a lack of relationship between microbial numbers and activity as determined by evolution of CO(2). In soils containing 30 to 1,500 mug of salicylate per g, metabolic activities of PpG7 peaked between 18 and 42 h and population densities increased approximately 10-to 10-fold. However, the metabolic activity of PpG7 rapidly declined after salicylate was utilized, whereas peak population densities were maintained for the duration of the experiments (5 to 7 days). Thus, elevated population densities of PpG7 were represented by inactive cells. Soil type had only minor effects on respiration rates or growth curves of PpG7 when amended with comparable concentrations of salicylate. Respiration and growth rates were optimal at concentrations between 300 and 1,000 mug of salicylate per g in the test soils. At 1,500 to 2,500 mug/g, respiration and growth of PpG7 were initially suppressed, but after a short lag time both attained levels similar to or greater than those resulting from the use of lower concentrations of salicylate. The culturing of PpG7 on a salicylate-amended medium to induce salicylate-degradative enzymes did not affect the lag time before utilization of salicylate in soil. Although PpG7 competed well with fungi for the substrate, suppression of fungal populations with cycloheximide resulted in significantly increased population densities of PpG7 in two of three soils amended with salicylate. The beneficial activities of bacteria in soil are discussed in relation to population density, population metabolic activity, and selective carbon source utilization.
含异化质粒 NAH7 的恶臭假单胞菌 PpG7 的呼吸和生长，在添加碳源水杨酸的三种农业土壤中进行了测定。向土壤中添加水杨酸显著增加了 PpG7 的种群。然而，微生物数量和 CO2 进化所确定的活性之间缺乏关系。在含有 30 至 1500 微克/克水杨酸的土壤中，PpG7 的代谢活性在 18 至 42 小时之间达到峰值，种群密度增加了约 10 至 10 倍。然而，在用完水杨酸后，PpG7 的代谢活性迅速下降，而峰值种群密度在实验期间（5 至 7 天）得以维持。因此，PpG7 的高种群密度是由非活性细胞代表的。当用可比浓度的水杨酸处理时，土壤类型对 PpG7 的呼吸率或生长曲线仅有微小影响。在试验土壤中，浓度在 300 至 1000 微克/克之间时，呼吸和生长速率最佳。在 1500 至 2500 微克/克时，PpG7 的呼吸和生长最初受到抑制，但在短的滞后时间后，两者都达到了与使用较低浓度水杨酸相似或更高的水平。在水杨酸添加培养基上培养 PpG7 以诱导水杨酸降解酶不会影响在土壤中利用水杨酸的滞后时间。尽管 PpG7 与真菌竞争底物，但用环己酰亚胺抑制真菌种群会导致在添加水杨酸的三种土壤中的两种土壤中 PpG7 的种群密度显著增加。讨论了土壤中细菌的有益活动与种群密度、种群代谢活性和选择性碳源利用的关系。
