Isolation and Characterization of Cylindrospermopsis raciborskii Strains from Finished Drinking Water

Abstract

In the summer of 2015, an intense cyanobacterial bloom producing geosmin/2-methylisoborneol (MIB) occurred in the Roxo freshwater reservoir in Alentejo, Portugal. The drinking water supplied from the Roxo water treatment plant (WTP) exhibited an unpleasant odor/taste and a significant cyanobacteria density was detected in the finished water at the exit of the WTP. Cyanobacteria were not evaluated downstream of the WTP, namely, at the city reservoir. The aim of this work was to isolate and characterize viable cyanobacteria present in finished water (exit of the WTP and city reservoir) that withstand conventional water treatment. Treated water samples collected at both sites were inoculated in Z8 culture medium to provide the conditions for putative cyanobacterial growth. After 30 days, filamentous cyanobacteria were observed in cultures inoculated with samples from the exit point of the WTP. Viable trichomes were isolated and identified as Cylindrospermopsis raciborskii by morphometric and molecular analysis. None of the isolates were cylindrospermopsin/microcystin producers, as confirmed by ELISA and amplification of corresponding genes (PS/PKS and mcyA-cd/mcyAB/mcyB). ELISA results were positive for saxitoxin, but saxitoxin and derivatives were not detected by liquid chromatography with fluorescence detection (LC-FLD), nor were their related genes (sxtA/sxtA4/sxtB/sxtM/sxtPer/sxtI). To our knowledge, this is the first report on the establishment of cultures of C. raciborskii that resisted water treatment processes.

Rapid Changes in the Phytoplankton Community of a Subtropical, Shallow, Hypereutrophic Lake During the Rainy Season

“…C. raciborskii is one species that has been identified ( Komárek and Komárková-Legnerová, 2002 ; Valadez et al, 2005 ). Most of the studies on C. raciborskii have been carried out on reservoirs used for agriculture or recreation, and in some cases on drinking water sources ( Lei et al, 2014 ; Menezes et al, 2020 ). Agriculture is one of the main activities in Lake Cajititlán, so it is possible that the abundance of this bacterium is associated with the increase in the concentration of nutrients from fertilizers, mainly during the rainy season, which enhances the runoff of nutrients to the lake.…”

Structures, Occurrences and Biosynthesis of 11,12,13-Tri-nor-Sesquiterpenes, an Intriguing Class of Bioactive Metabolites

“…It has also been found in fungi [ 159 ], including Botrytis cinerea and Erysiphe necator [ 160 ]. It is produced by different cyanobacteria [ 161 , 162 , 163 , 164 ] and myxobacteria, where geosmin ( 28 ) is responsible for the earthy smell of the culture [ 165 ]. Geosmin ( 28 ) has also been isolated from a variety of higher plants, such as liverwort and sugar beet [ 166 ], and from mosses, protozoans and insects [ 64 , 167 ].…”