Automated analytical method for monitoring micro-organisms in marine waters

Growing interest in oceanology and oceanography has made it possible to determine the fundamental role of the oceans in sustaining life on Earth, and to discover that aquatic environments offer a rich biodiversity and a privileged habitat for many species. Aquatic environments also contribute to the economies of many countries through fishing, aquaculture, and coastal tourism, they are a major source of food for the world’s population. Nevertheless, the presence of pathogenic microorganisms in coastal waters can have a negative impact on human and animal health, as well as on marine ecosystems. Bacteria of the Vibrio spp genus, for example, shelter many species that are pathogenic to humans and marine fauna [1]. Although the seasonal dynamics of their abundance are now recognized, better knowledge of their abundance on a finer temporal scale and of their spatial distribution requires the use of in-situ measuring instruments for real-time monitoring of these bacterial populations in water. Early detection of abnormally high levels of these bacteria will enable rapid and appropriate health decisions to be taken. Thanks to the integration of new digital and engineering technologies, new types of sensors are making it possible to direct research towards enhanced biomonitoring of the oceans. However, the few sensors able to monitor marine bacteria, are still very bulky, heavy and costly and can’t be quickly deployed in certain environments such as coastal areas, to perform high resolution monitoring [2] [3].

In this study, we propose to develop a new measuring tool for in situ monitoring of microbial populations. It’s a small tool, can be used by non-expert personnel and would enable monitoring in all types of aquatic environments. The sensor under development uses a molecular biology approach based on sandwich hybridization using nucleotide probes complementary to an RNA sequence of the target bacteria, and a colorimetric revelation to quantify bacteria.  The procedure has already been used to detect Vibrio spp bacteria [4]. To make the system autonomous, the methodology used will be transferred to an integrated, reusable platform currently under development. This will enable rapid analysis of small volumes, as well as a reduction in the volumes of reagents used, and, consequently, lowering the final analytical cost. To optimize the device development time, the use of rapid prototyping methods such as stereolithography 3D printing was employed for the fabrication of most system components. Similarly, literature-validated subsystems were used and adapted to meet the methodology requirements. The platform will enable several functional blocks to be built, such as the distribution of calibrated microvolumes via three-way solenoid valves, a magnetic trap for capturing functionalized beads and a block for optical signal detection. A low-cost multispectral detector was fabricated by 3D printing to create this functional block. A proportional relationship can be established between the target concentration and the absorbance measured by the detector.

[1] C. Baker-Austin et al., Nat Rev Dis Primers. 4(1):1-19, (2018)

[2] C.Scholin et al., Oceanog., 22(2):158-167, (2009)

[3] D. Fries et al., Microscopy and Microanalysis. 13(S02):514-515, (2007)

[4] E. Da-Silva., Environ Sci Pollut Res. 24(6):5690-5700, (2017)