WATER MICROBIAL LOAD MEASUREMENT: CLASSICAL CULTIVATION METHODS vs. ALTERNATIVE METHODS

Presented at PWWA conference, Manilla, 20-22/03/2019. Written in collaboration with Laurent Garrelly, GLBiocontrol, Clapiers, France

This article is based on some results of the BIOWYSE European project (http://biowyse.eu/)

for the development of a monitoring method of water microbiological load applicable to the

International Space Station and longer lasting space missions (Amalfitano et al., 2018).

Adenosine Tri Phosphate (ATP) measurements, Flow Cytometry (FCM) and quantitative real

time PCR (qPCR) have been compared to Heterotrophic Plate Counts (HPC) measurements

(R2A and Yeast Extract Agar media) on waters presenting different microbial loads. In addition to the objectives of the BIOWYSE European project, the aims of this study were: i. to identify alternative methods which could be used on earth instead of classical HPCs methods as routine operational monitoring measurement tools ii. to obtain results on a faster way so that the reaction time in case of observed deviation in microbiological water quality could be shortened.

The obtained results show that Heterotrophic Plate Counts measurements are influenced

significantly by cultivation media with HPC-R2A >> HPC-YEA3 and HPC-YEA7. Besides,

HPC-R2A show the best correlations with other parameters in comparison to HPC-YEA. The

best fit is found in the log-log linear relation between ATP and HPC-R2A (Spearman’s r =

0.91) and qPCR data (Spearman’s r = 0.97), while the weakest between ATP and FCM data

(Spearman’s r = 0.81).

Finally, if the 3 methods (FCM, ATP and qPCR) appear as interesting alternatives to HPC,

ATP measurement seems to be the most appropriate method when considering analyses

duration, analyses cost and analyst required level of technical skills.