Effects of garlic and diallyl trisulfide on the growth, photosynthesis, and alkaline phosphatase activity of the toxic cyanobacterium Microcystis aeruginosa

Abstract

To identify a botanical algicide and elucidate the response of cyanobacteria to the extract from higher plants, the effects of garlic and garlic-derived diallyl trisulfide on Microcystis aeruginosa were studied. Effects were evaluated by changes in cell density, chlorophyll a, maximum effective quantum yield (Fv/Fm), effective quantum yield (YII), non-photochemical quenching (NPQ), and rapid light curves of M. aeruginosa. In addition, alkaline phosphatase activity (APA) was measured when M. aeruginosa was incubated with diallyl trisulfide. Results indicated that the inhibition by garlic and diallyl trisulfide was significant. The 120-h 50 % effective concentrations of garlic and diallyl trisulfide (EC50) were 0.75 g L(-1) and 2.84 mg L(-1), respectively. Moreover, the inhibitory rate increased with increasing concentration and the growth of M. aeruginosa was inhibited by 90.0 % at the highest concentrations. We also show that the response of M. aeruginosa to stress could involve both impairment of the photosynthetic center PSII and alteration of APA. For example, at high garlic concentration (2.0 g L(-1)), Fv/Fm significantly decreased from 0.501 to 0.084 (p < 0.05) after 120 h of exposure. Furthermore, the total APA was significantly decreased by exposure to a high diallyl trisulfide concentration after 24 h exposure. As new algal inhibitors, there are several advantages for their utilization, such as being common, cheap, non-toxic, and with high efficiency. It would be meaningful to further research on garlic as an environmentally friendly algicide.

Effects of Dihydroartemisinin and Artemether on the Growth, Chlorophyll Fluorescence, and Extracellular Alkaline Phosphatase Activity of the Cyanobacterium Microcystis aeruginosa

“…It is thought that a primary method of impairing cyanobacteria growth by algaecide is by impairing the photosynthetic system of phytoplankton [ 14 , 32 ], although this mechanism has yet to be fully understood. Chlorophyll fluorescence has proven to be a useful tool for studying the behavior of PSII as it is a powerful, non-invasive, and reliable method [ 6 , 31 , 33 ]. As the fluorescence transient reflects the state of the primary bound plastoquinone, the secondary bound plastoquinone, the fluxes of photons, excitons, and electrons, the fast fluorescence curves were determined to show the changes of fluorescence intensity and relative variable fluorescence parameters [ 34 ].…”

“…The functions of alkaline phosphatase in phytoplankton have been studied in recent years. It has been proposed that, cyanobacteria can overcome conditions of serious phosphorous depletion by alkaline phosphorous production [ 6 , 39 , 41 , 43 ]. In the present study, we found that dihydroartemisinin and artemether could both inhibit the extracellular APA.…”

“…The measurement of Chl- a followed the method described by Wang et al [ 6 ]. Briefly, 3-mL samples were filtered through a 0.45-μm Millipore filter and then extracted with 3 mL of 90% acetone at 4°C for 24 h. The extract was then centrifuged and the Chl- a content was measured with a spectrophotometer at wavelengths of 750, 663, 645, and 630nm.…”

“…These methods include mechanical, physical (ultrasonication, coagulation/flocculation and centrifugal separation), biological (Traditional biomanipulation and Non-Traditional biomanipulation), and chemical (oxidants and metal-ion compounds) methods [ 4 – 5 ]. Although these approaches can efficiently remove cyanobacteria from polluted surface water, most of them have operational, economic, and environmental limitations [ 6 ]. Taking these limitations into account, it is necessary to develop a new generation of algal inhibitors to only target HAB communities.…”

“…Several studies have confirmed that the discovery of anti-algal allelochemicals, extracted from autotrophs, might provide potential cyanobacterial growth inhibitors to control HABs [ 6 – 8 ]. The production and excretion of allelochemicals from natural macrophytes and advanced plants is considered an environmentally friendly strategy to control cyanobacterial blooms.…”