New insights into the kinetics of bacterial growth and decay in pig manure–wheat straw aerobic composting based on an optimized PMA–qPCR method

Abstract

Summary Aerobic composting is a bacteria‐driven process to degrade and recycle wastes. This study quantified the kinetics of bacterial growth and decay during pig manure–wheat straw composting, which may provide insights into microbial reaction mechanisms and composting operations. First, a propidium monoazide–quantitative polymerase chain reaction ( PMA – qPCR ) method was developed to quantify the viable bacteria concentration of composting samples. The optimal PMA concentration and light exposure time were 100 μM and 8 min respectively. Subsequently, the concentrations of total and decayed bacteria were quantified. Viable and decayed bacteria coexisted during the entire composting period (experiments A and B), and the proportion of viable bacteria finally fell to only 35.1%. At the beginning, bacteria grew logarithmically and decayed rapidly. Later, the bacterial growth in experiment A remained stable, while that of experiment B was stable at first and then decomposed. The duration of the stable stage was positively related to the soluble sugar content of composting materials. The logarithmic growth and rapid decay of bacteria followed Monod equations with a specific growth (0.0317 ± 0.0033 h −1 ) and decay rate (0.0019 ± 0.0000 h −1 ). The findings better identified the bacterial growth stages and might enable better prediction of composting temperatures and the degree of maturation.

Formic acid, an organic acid food preservative, induces viable-but-non-culturable state, and triggers new Antimicrobial Resistance traits in Acinetobacter baumannii and Klebsiella pneumoniae

“…Cell viability was also determined on the basis of membrane integrity by using PMA dye. A combination of membrane impermeability and strong DNA-binding ability enables PMA to be used as a viability marker ( Nocker and Camper, 2006 ; Ge et al, 2019 ). In the last few years, qPCR is being increasingly used for the detection of viability and membrane integrity in combination with DNA-binding dye PMA ( Zhong et al, 2016 , 2018 ; Bao et al, 2017b ; Liu et al, 2018b ; Zhao et al, 2020 ).…”

An Optimized Method to Assess Viable Escherichia coli O157:H7 in Agricultural Soil Using Combined Propidium Monoazide Staining and Quantitative PCR

“…In addition, viable cells have intact cell membranes that prevent PMA from penetrating into cells, so PMA cannot form covalent bonds with DNA. PMA-qPCR assay has been applied to the detection of viable pathogens including E. coli , Legionella pneumophila , Salmonella typhimurium , and Staphylococcus aureus in food and water ( Li et al, 2015 ; Gyawali et al, 2016 ; Heise et al, 2016 ; Casanovas-Massana et al, 2018 ; Yuan et al, 2018 ; Ge et al, 2019 ). Recently, PMA method has also been applied in agricultural soil ( Gustave et al, 2019 ).…”