Department of Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-75007, Uppsala, Sweden.
Department of Soil and Environment, Swedish University of Agricultural Sciences, P.O. Box 7014, SE-75007, Uppsala, Sweden.
BMC Microbiol. 2019 Mar 21;19(1):65. doi: 10.1186/s12866-019-1432-8.
Quantification of viable microorganisms is an important step in microbiological research as well as in microbial product formulation to develop biological control products or probiotics. Often, the efficiency of the resulting product is dependent on the microbial cell density and their viability, which may decrease over time. Commonly, the number of viable cells is determined by serial dilution and plating techniques or flow cytometry. In 2017, we developed a mathematical model for isothermal microcalorimetry (IMC) data analysis and showed that the new method allows for a more rapid quantification of viable fresh and freeze-dried anaerobic Lactobacillus reuteri cells than traditional viable count methods.
This study developed the new method further by applying it to well-known aerophilic plant-beneficial microbial species (Pseudomonas brassicacearum, Bacillus amyloliquefaciens subsp. plantarum and Clonostachys rosea) used in biological control products. We utilized IMC to quantify viable cells in microbial pure cultures as well as when coated onto wheat seeds. The results from this study confirmed that thermal viable count methods are more rapid and sensitive than traditional viable count techniques. Most interestingly, a thermal viable count method was able to quantify microbes coated on seeds despite the presence of the natural microbiota of the seeds. Our results also showed that, in contrast to plating techniques for which clustered cells skew the results, IMC does not require single cells for accurate viable counts.
Thermal viable count methods are novel methods for the rapid quantification of divergent bacterial and fungal species and enhance the speed, sensitivity, and accuracy of routine viable counts of pure cultures and controlled microbiomes such as plant seed coatings.
在微生物研究以及微生物产品配方中，定量活微生物是一个重要步骤，以开发生物防治产品或益生菌。通常，产品的效率取决于微生物细胞密度及其活力，而这些可能会随时间降低。通常，活细胞的数量是通过连续稀释和平板技术或流式细胞术来确定的。2017 年，我们开发了一种等温微量热法（IMC）数据分析的数学模型，并表明该新方法比传统的活菌计数方法更能快速定量新鲜和冻干的厌氧乳杆菌活细胞。
本研究通过将其应用于用于生物防治产品的知名好氧植物有益微生物物种（铜绿假单胞菌、解淀粉芽孢杆菌亚种植物和玫瑰红链霉菌）进一步开发了新方法。我们利用 IMC 定量微生物纯培养物以及涂覆在小麦种子上的活细胞。本研究的结果证实，热活菌计数方法比传统的活菌计数技术更快、更敏感。最有趣的是，尽管种子存在天然菌群，但热活菌计数方法仍能够定量涂覆在种子上的微生物。我们的结果还表明，与需要单细胞才能进行准确活菌计数的平板技术不同，IMC 不需要单细胞。
热活菌计数方法是快速定量不同细菌和真菌物种的新方法，可提高纯培养物和受控微生物组（如植物种子涂层）的常规活菌计数的速度、灵敏度和准确性。
