Potential antimicrobial activity of marine molluscs from tuticorin, southeast coast of India against 40 biofilm bacteria

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Date: Jan. 2005
From: Journal of Shellfish Research(Vol. 24, Issue 1)
Publisher: National Shellfisheries Association, Inc.
Document Type: Article
Length: 5,024 words

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ABSTRACT Methanol: water (1:1), methanol: dichloromethane (1:1) and acetone extracts of molluscs comprising 77 whole body, four inks, four opercula, 10 egg masses, and 10 digestive glands were screened for antimicrobial activity on marine biofilm bacteria. The methanol: water (1:1) whole body extracts of Nerita albicilla and Nerita oryzarum showed broad spectral inhibitory activity against 93% and 95% of the 40 biofilm bacteria. The egg masses from 10 gastropods showed activity against more than a quarter of the biofilm bacteria. The methanolic extract of Chicoreus virgineus, Chicoreus ramosus egg masses, and acetone extract of the egg mass of Rapana rapiformis showed broad-spectrum antibacterial activity against all the 40 biofilm bacterial strains. The activity in gastropod egg masses was localized to their internal matrix. Overall screening showed activity in 38.1% of the methanolic extracts followed by 13.3% of methanol: water, 12.4% of methanol: dichloromethane, and 3.8% of acetone extracts. Gastropods showed good activity when compared with bivalves and cephalopods.

KEY WORDS: antifouling, bacteria, biofilm, egg mass, mollusc

INTRODUCTION

The efforts to control marine biofouling are ongoing since humans started venturing into the sea. Among the antifoulants developed to date, organotin compounds are considered as the most effective and have been widely used since the 1970s. It is well established that TBT compounds cause imposex universally (Barroso et al. 2002) and has been documented in over 118 species in 63 genera (Bettin et al. 1996). Organotin pollution has also raised concerns over the accumulation of organotin compounds in the food chain and the associated risks related to the presence of contaminants (Belfroid et al. 2000). International Maritime Organization (IMO) has proposed a complete phasing out of TBT use by the year 2008. The alternative tin free coatings are not only costly, but also their metal constituents may pose environmental problems (Hellio et al. 2004). So, a great deal of research has been focused on finding an alternate nontoxic and eco-friendly antifoulant (De Nys & Steinburg 2002, Fusetani 2004). In this context, marine organisms, especially the sedentary forms have interested researchers very much because they exhibit characteristic chemical defense against the epizooic organisms. More than 100 species of marine organisms have been shown to exhibit antimicrobial activity, as well as the ability to prevent settlement of fouling organisms (Clare 1996, Koh 1997).

Most currently available antifouling compounds are active against barnacles and algae and not against microbes like biofilm bacteria, which cause initial fouling of a submerged surface (Tang & Cooney 1998). Bacteria are the first organisms to foul submerged surfaces in the marine environment. Their subsequent multiplication and production of exopolymers leads to the formation of bacterial biofilms, which attract a large number of secondary fouling organisms (Steinberg et al. 2002). The interaction between bacteria and macrofoulers are dynamic and varied. The resultant biofouling community leads to economic and ecologic implications on both human-made structures and living surfaces.

However, bacteria do not colonize all submerged surfaces in a uniform manner and are influenced by many physical and chemical factors (Fletcher & Marshall...

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Gale Document Number: GALE|A133108179