International Journal of Innovations in Engineering and Technology (IJIET) http://dx.doi.org/10.21172/ijiet.142.06 Volume 14 Issue 2 September 2019 033 ISSN: 2319-1058 Diversified collection of novel sponge- associated actinobacteria of Ha Tien sea, Kien Giang province, Vietnam Tran Vu Phuong 1 , Ngo Thi Phuong Dung 2 , Cao Ngoc Diep 3 1,2,3 Biotechnology R&D Institute, Can Tho University, Can Tho City, Vietnam Abstract– Marine actinobacteria are the most economically and biotechnologically valuable prokaryotes receiving much attention for their capacities of antibiotics and enzyme inhibitors. A total of 142 endophytic actinomycetes was isolated from 44 samples of 5 different sponge species in Ha Tien Sea, Vietnam. Due to the antimicrobial activity, 21 isolates were selected for 16S rDNA sequencing. Of identified isolates 13 were characterized as Streptomyces spp. and the remainders belonged to other genera as Microbacterium, Rhodococcus and Gordonia. The antimicrobial activity and the amplifying genes coding for polyketide synthetase (PKS) and nonribosomal peptide synthetase (NRPS) showed that isolates purified from sponges in Ha Tien sea had broad-spectrum antimicrobial activity, mainly against gram-positive bacteria as Bacillus cereus and Staphylococcus aureus. Microbacterium tumbae was also found as a rare actinomycete displayed the antifungal activity. These new cultures can be employed as bioactive resources against pathogens, particularly in relation to food-borne diseases and human health. Keywords: Actinobacteria, antimicrobial activity, marine sponge, nonribosomal peptide synthetase, polyketide synthetase. I. INTRODUCTION Actinobacteria are a diverse group of filamentous Gram-positive soil bacteria with a high G+C (Guanin + Cytosin) content and are abundantly distributed in the environment (such as soil, freshwater, seawater etc.) with strongly biological activities against a majority of phytopathogens including fungi and oomycetes, and thus, actinobacteria have become a sort of potential resource to prevent plant fungal diseases [1]. It has become increasingly difficult to find actinobacteria with a great capacity to produce new antibiotics [2], and as a result, infectious diseases associated with multidrug resistance are rapidly spreading, around the globe. At this juncture, the isolation of new actinobacteria from extreme environments has become a hotspot among researcher a nd scientific community over the past 20 years [3]. These actinobacteria from extreme environments were found to exhibit a unique source of novel biologically active compounds [2]. The rare actinobacteria have the ability to produce active metabolite, which has the property of diverse, unique, unprecedented, and occasionally complicated compounds usually with low toxicity. Among these unusual marine environments to be explored as niches for novel microbes are sponges, which host hundreds of different bacterial groups within their mesohyl tissue. Sponges are constantly filtering bacteria from the water column and are home to a diversity of microbial symbionts [4]. The remarkable biotechnological potential of actinomycetes for drug discovery has been observed since the 1960s, and since that time, actinomycetes have been responsible for more than 70% of all antibiotics discovered [5]. Marine actinobacteria are the most economically and biotechnologically valuable prokaryotes. Representative genera of marine actinobacteria include Actinomadura, Aeromicrobium, Dietzia, Gordonia, Marinophilus, Micromonospora, Nonomuraea, Rhodococcus, Saccharomonospora, Saccharopolyspora, Salinispora, Streptomyces, Solwaraspora, Williamsia, Verrucosispora and several others [6]. New genera within the Streptomycetaceae family continue to be isolated from marine-derived sediments and sponges and have shown as a promising source of novel metabolites [7]; however, few complete genome sequences have been published [8]. Streptomyces, the largest genus of actinobacteria, can produce a variety of beneficial antibiotics, industrial enzymes, and bioactive secondary metabolites including antibacterial, herbicides, and fungicides [9-10]. Approximately, two-thirds of all known natural antibiotics used in medicine and agriculture were belonged to Streptomyces [1]. The production of antibiotics by Streptomyces may play an important role in the bio-control of pathogens [11]. Moreover, Streptomyces spp. have been extensively studied due to their dominance, ease of isolation, enhancement of plant growth, and improvement of crop productivity [12]. The method applied to study the distribution of PKS and NRPS biosynthetic systems was suggested in a collection of wild-type actinomycetes isolated from tropical soil samples [13]. The antimicrobial activity and amplifying genes coding for PKS-I, PKS-II and NRPS showed that endophytic actinomycetes isolated from medicinal plants in Panxi plateau performed as valuable reservoirs of novel bioactive compounds [14].