Anticyanobacterial activity of Emphasis Type="It

Authors: Miquel Lürling Wendy Beekman

Publish Date: 2009/11/27

Volume: 22, Issue: 4, Pages: 503-510

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Abstract

Filtrates from crushed Moringa oleifera seeds were tested for their effects on growth and Photosystem II efficiency of the common bloomforming cyanobacterium Microcystis aeruginosa M aeruginosa populations exhibited good growth in controls and treatments with 4 and 8mg crushed Moringa seeds per liter having similar growth rates of 050 ±001 per day In exposures of 20 to 160mg crushed Moringa seeds L−1 growth rates were negative and on average −023 ±005 day−1 Presumably in the higher doses of 20 to 160mg crushed seeds per liter the cyanobacteria died which was supported by a rapid drop in the Photosystem II efficiency ΦPSII while the ΦPSII was high and unaffected in 0 4 and 8 mg L−1 Highdensity populations of M aeruginosa chlorophylla concentrations of ∼270 µg L−1 were reduced to very low levels within 2 weeks of exposure to ≥80mg crushed seeds per liter At the highest dosage of 160 mg L−1 the ΦPSII dropped to zero rapidly and remained nil during the course of the experiment 14 days Hence under laboratory conditions a complete wipeout of the bloom could be achieved This is the first study that yielded evidence for cyanobactericidal activity of filtrate from crushed Moringa seeds suggesting that Moringa seed extracts might have a potential as an effectoriented measure lessening cyanobacterial nuisanceThe explosive growth of the world’s human population and subsequent water and energy demand has led to an expansion of standing surface water Rosenberg et al 2000 Many of these standing waters including small watering ponds for cattle fishing ponds irrigation impoundments and drinking water reservoirs suffer from an overenrichment of the water with nutrients Smith and Schindler 2009 Such ongoing eutrophication may lead to dense cyanobacterial blooms and floating scums Schindler et al 2008 Smith and Schindler 2009 These blooms may cause high turbidity anoxia fish kills bad smell Paerl and Huisman 2008 and serious environmental and human health problems because several cyanobacteria can produce a variety of very potent toxins eg Codd et al 2005 Dittmann and Wiegand 2006Climate change is expected to aggravate hazardous blooms Paerl and Huisman 2008 while safe and aesthetically acceptable water is a growing need in a modern society Steffensen 2008 Hence water resource management is challenged worldwide to reduce the vulnerability to the threats of harmful cyanobacterial blooms Particularly in developing countries where the high costs of chemicals for water and wastewater treatment might limit their application the development of costeffective and environmentally acceptable mitigating measures is desirable In that context water clarification and disinfection with natural products such as the seeds of the pantropical tree Moringa oleifera Lam is of particular interestCrushed M oleifera seeds are highly effective in clarifying very turbid water Muyibi and Evison 1995 Ndabigengesere and Narasiah 1998 Traditionally the seeds are used in rural areas of Sudan and Malawi for the clarification of drinking water Muyibi and Evison 1995 Anwar et al 2007 Flocculation of raw Nile water revealed that M oleifera seeds could remove up to 97 of the algae present Shehata et al 2002Dehusked M oleifera press cake is efficient in the removal of hydrophobic organic pollutants from water Boucher et al 2007 and extracts might remove other pollutants such as heavy metals and surfactants BeltránHeredia and SánchezMartín 2008 2009 M oleifera pods are efficient in absorbing organic pollutants and pesticides Akhtar et al 2007a b Highquality activated carbon can be prepared from the waste husks of M oleifera Pollard et al 1995 Warhurst et al 1997a which could effectively remove up to 98 of the cyanobacterial microcystinLR Warhurst et al 1997b In addition to the strong waterclarifying properties Moringa seeds have also been reported removing more than 90 of cercariae from the water phase Olsen 1987 Bacterial numbers can be reduced drastically due to coagulation Madsen et al 1987 and a pronounced hygienic effect is caused by a strong antibacterial potential against Gramnegative and Grampositive bacteria Suarez et al 2003 2005 However so far no study has examined direct effects of filtrates from crushed M oleifera seeds on growth of cyanobacteria and on their ability in terminating cyanobacterial bloomsThe purposes of this research were to 1 examine in the laboratory the effect of filtrates from crushed M oleifera seeds on the growth and Photosystem II efficiency of the most common bloomforming cyanobacterium in eutrophic freshwater systems worldwide Microcystis aeruginosa Kützing and 2 to test the filtrates on their potential to mitigate high densities of M aeruginosa Inasmuch as M oleifera seed extract exerts bactericidal activity in vitro against Grampositive and Gramnegative bacteria Cáceres et al 1991 Ali et al 2004 Oludoro and Aderiye 2007 Suarez et al 2003 2005 and cyanobacteria are Gramnegative Stanier and CohenBazire 1977 we hypothesize that Moringa seed extracts have an antimicrobial activity against the cyanobacterium M aeruginosaThe cyanobacterium Microcystis aeruginosa NIVACYA 43 was obtained from the Norwegian Institute for Water Research NIVA Norway Stock cultures of this strain were grown in our laboratory in 100mL Erlenmeyer flasks containing 50 mL of slightly modified Woods Hole Chu WC medium Lürling and Beekman 1999 with vitamins added H biotin and B12 cyanocobalamin at 50 ng L−1 and B1 thiamine HCL at 100 ng L−1 The flasks were placed in a Gallenkamp ORBISAFE Netwise Orbital Incubator at 22°C in 40 rpm and in a 186h light/dark cycle The light/dark cycle was programmed that light intensity increased gradually to a maximum of 130 µmol quanta m−2 s−1 and subsequently decreased again to darkness which resulted in a daily average light intensity of ∼57 µmol quanta m−2 s−1 This strain of M aeruginosa is completely uni and bicellular under the given growth conditionsSeeds of M oleifera were obtained from the Miracle Trees Foundation Rotterdam the Netherlands The seed coat was removed and the pulp crushed in a mortar Aliquots of the powder were transferred into preweighed aluminum boats in fivefold Dry weights were determined after 24 h at 105°C and ash weights were determined after placing the boats for 3 h at 550°C

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