Microbial Growth Kinetics of a Defined Mixed Culture: Genomic Assay Application

Abstract

Microbial growth kinetics is often used to optimize environmental processes owing to its linkage to the breakdown of substrate (contaminants). However the quantification of bacterial populations in the environment is difficult due to the challenges of monitoring a specific bacterial population within a diverse microbial community. Batch experiments were performed for both single and dual cultures of Pseudomonas putida and Escherichia coli K12 to obtain Monod kinetic parameters (µmax and Ks). The growth curves obtained by the conventional methods (i.e., dry weight measurement and absorbance reading) were compared to that obtained by quantitative PCR (qPCR) assay. We used qPCR assay to detect and quantify each strain’s growth separately in the mixed culture reactor because conventional method was not capable of differentiating species. This work describes a novel genomic approach to quantify each species in mixed culture and interpret its growth kinetics in mixed system. We anticipate that the adoption of genomic assay can contribute significantly to traditional microbial kinetics, modeling practice, and the operation of bioreactors, where handling of complex mixed cultures is required.