The feasibility of automated online flow cytometry for in-situ monitoring of microbial dynamics in aquatic ecosystems

Abstract

Fluorescent staining coupled with flow cytometry (FCM) is often used for the monitoring, quantification and characterization of bacteria in engineered and environmental aquatic ecosystems including seawater, freshwater, drinking water, wastewater, and industrial bioreactors. However, infrequent grab sampling hampers accurate characterization and subsequent understanding of microbial dynamics in all of these ecosystems. A logic technological progression is high throughput and full automation of the sampling, staining, measurement, and data analysis steps. Here we assess the feasibility and applicability of automated FCM by means of actual data sets produced with prototype instrumentation. As proof-of-concept we demonstrate examples of microbial dynamics in (i) flowing tap water from a municipal drinking water supply network and (ii) river water from a small creek subject to two rainfall events. In both cases, automated measurements were done at 15-min intervals during 12–14 consecutive days, yielding more than 1000 individual data points for each ecosystem. The extensive data sets derived from the automated measurements allowed for the establishment of baseline data for each ecosystem, as well as for the recognition of daily variations and specific events that would most likely be missed (or miss-characterized) by infrequent sampling. In addition, the online FCM data from the river water was combined and correlated with online measurements of abiotic parameters, showing considerable potential for a better understanding of cause-and-effect relationships in aquatic ecosystems. Although several challenges remain, the successful operation of an automated online FCM system and the basic interpretation of the resulting data sets represent a breakthrough toward the eventual establishment of fully automated online microbiological monitoring technologies.

Long-Term Bacterial Dynamics in a Full-Scale Drinking Water Distribution System

“…Spearman’s rank-order correlations) between microbial and environmental parameters is available in S1 Fig. This approach is analogous to the one developed and used in [7] and [32]. …”

“…Computational multivariate analyses were conducted in R with dedicated packages [31] according to the numerical ecology framework proposed by Weissbrodt et al [32] and applied by Besmer et al [7], following Borcard et al [33]. …”

Portable LED fluorescence instrumentation for the rapid assessment of potable water quality

“…The observed correlation between fluorescence and TOC shown here, although strong, is lower than that typically reported for the UV absorbance-DOC/TOC relationship, which typically has r 2 N 0.9 (Matilainen et al, 2002;Spencer et al, 2009;Carter et al, 2012), but has the advantage of also providing information on total microbial counts. On-line microbial monitoring has yet to be established; the first feasibility study has recently been reported (Besmer et al, 2014) but the authors note the challenges of instrument cost and the handling of large datasets. Advantages of the fluorescence instrumentation, in addition to the ability to measure both organic and microbial matter, include low cost, small size and portability, low power requirements and a simple data output.…”

Implementing and Innovating Marine Monitoring Approaches for Assessing Marine Environmental Status

“…Moreover, sample collecting, processing, flow cytometry and data analysis can be automated (Besmer et al, 2014) and even commercial (Dubelaar et al, 1999) and non-commercial (Olson and Sosik, 2007;Swalwell et al, 2011) instruments can be submerged and send the data via cabling or radio. This allows their inclusion in environmental monitoring systems such as SmartBuoys, whose multiple sensors provide complementary information of the environmental settings in which cytometry data are acquired.…”