Rotten thallus of Red Seaweed, Gracilariopsis heteroclada Zhang et Xia, is Associated with Agar-Digesting Bacillus spp

Joval N,Martinez Martinez,Philip Ian P Padilla

doi:10.21767/1307-234x.1000140

Abstract

Agar-digesting bacteria have been hypothesized to cause rottening of the thalli of economically important marine red seaweeds, Gracilariopsis heteroclada Zhang et Xia (Gracilariaceae, Rhodophyta). However, characterization of these causative agents accompanying seaweeds’ disease in the marine environment has been poorly elucidated. Thus, agar-digesting bacteria associated with ‘rottening thallus’ of red seaweed, were isolated and characterized. Agar-digesters were selected based on their ability to digest agar by forming a clear depression around their colony and/or liquefaction of agar. Selected agar-digesters showed a positive result for gelatinase test and arginine dihydrolase test. 16S rRNA of these isolates was successfully extracted, purified, sequenced and analyzed. Phylogenetic analyses showed that bacterial 16S rRNA sequences from rottening seaweed thalli belong to Bacillus spp (98-99%), suggesting that the isolates were significantly associated with the rottening of red seaweeds in the present investigation.

Highlights

Cultivation of seaweed has been practiced worldwide because of its great ecological and economic importance
In 1990’s, most of the seaweed produced came from the group of brown algae and eventually replaced by red seaweed contributing about 50% of the total seaweed production in the year 2010
Morphological characterization of the isolated bacteria was done based on colony and pigmentation on nutrient (NA+) agar

Summary

Introduction

Cultivation of seaweed has been practiced worldwide because of its great ecological and economic importance. The continuous increase in the farming of these aquatic plants had gained much attention in many parts of the world. These marine species have been widely used as raw materials for the production of commodities in the market such as food, fertilizers, cosmetics and the like. The demands in the world market for the production of raw seaweeds have overwhelmingly contributed to the development of the seaweed of about 99.6% by quantity to the total aquaculture production of the world in 2008 (FAO, 2010). In 1990’s, most of the seaweed produced came from the group of brown algae and eventually replaced by red seaweed contributing about 50% of the total seaweed production in the year 2010

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Results

Conclusion