Molecular method for rapid detection of the red tide dinoflagellate Karenia mikimotoi in the coastal region of Xiangshan Bay, China

The species Karenia mikimotoi is a common nearshore red tide alga that can secrete hemolytic exotoxin and ichthyotoxin, which can induce the death of fish and shellfish, causing severe economic losses. In this study, loop-mediated isothermal amplification (LAMP) was employed in combination with the lateral flow dipstick (LFD) visual detection method to establish the LAMP-LFD rapid detection method for K. mikimotoi. The internal transcribed spacer ITS1-5.8S-ITS2 of K. mikimotoi was used as the target sequence and was amplified with specific primers designed in this study. The results indicated that the amplification optimal reaction conditions for LAMP in this paper were for 20 min at 65 °C. Moreover, LAMP had excellent specificity, showing negative results for other common red tide causing algal species. In field samples, we successfully reduced the total time, with only 23 min needed from LAMP amplification to LFD result display, which was shorter than that of conventional PCR. Consequently, LAMP-LFD should be useful for rapid field detection of low-density K. mikimotoi and for the early prevention of red tide induced by such algae.

Detection of Skeletonema costatum based on loop-mediated isothermal amplification combined with lateral flow dipstick

We developed a new assay method, which combines loop-mediated isothermal amplification (LAMP) with a chromatographic lateral flow dipstick (LFD) for the rapid and special detection of the diatom Skeletonema costatum. Four groups of LAMP primers were derived from a conserved DNA sequence unique to S. costatum. The amplifications were carried out at 61, 63, and 65 °C for 60 min in various combinations by the quantitative PCR thermal cycler to confirm optimal primers and reaction temperature. The LAMP-LFD detection limit was 0.94 pg/μL of S. costatum genomic DNA and was 100 times more sensitive than conventional PCR. The LAMP-LFD method had high specificity and accurately identified S. costatum algal isolates, but not other algal isolates. The new LAMP-LFD assay can be used as a reliable and easy method to detect S. costatum.

The development of loop-mediated isothermal amplification combined with lateral flow dipstick for detection of Karlodinium veneficum

The aim of this study was to develop a loop-mediated isothermal amplification (LAMP) combined with a chromatographic lateral flow dipstick (LFD) assay to rapidly and specifically detect the Karlodinium veneficum ITS gene. Four groups of LAMP primers were specially designed to target the K. veneficum ITS gene. The LAMP-LFD detection limit was 7.4pg/μL (approximately 6.5cells/mL) of K. veneficum genomic DNA and was 10 times more sensitive than standard PCR. The LAMP-LFD method exhibited high specificity and accurately identified K. veneficum algal isolates, but not other algal isolates. To test the assay's accuracy, samples from positive results were further analyzed by sequencing and phylogenetic analysis, all of which were identified as K. veneficum. Over all, the LAMP-LFD assay established in this paper can be used as a reliable and simple method to detect the K. veneficum.