Isolation and Molecular Identification of Ascomycetes in Sediments and Waters of the Gulf of Aqaba, Red Sea
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Vol.4, No.8, 555-561 (2012) Natural Science http://dx.doi.org/10.4236/ns.2012.48074 Isolation and molecular identification of Ascomycetes in sediments and waters of the Gulf of Aqaba, Red Sea Basem M. Jaber1*, Rola Al-Silawi1, Tariq Al-Najjar2 1Department of Biological Sciences, The University of Jordan, Amman, Jordan; *Corresponding Author: [email protected] 2Department of Marine Biology, Faculty of Marine Sciences, The University of Jordan/Aqaba Branch, Aqaba, Jordan Received 25 June 2012; revised 28 July 2012; accepted 10 August 2012 ABSTRACT marine or facultative. Obligate marine fungi are those that grow and sporulate exclusively in a marine or estua- Using molecular approach, we aimed to identify rine habitat and are permanently or intermittently sub- fungal phylotypes that exist in the Gulf of Aqaba, merged in water. Whereas, facultative marine fungi are Red sea. Several samples were taken from sedi- those that normally occupy freshwater habitats or terres- ments and seawater of three locations along 26 trial surroundings but are able to grow (and possibly to kilometers at 5 m depth. 18S small subunit rRNA sporulate) in the marine environment [9,10]. Currently gene was targeted for PCR amplification and there are 444 known recognized species of obligate and sequencing. Partial sequences introduced as facultative marine fungi. Ascomycota represented by 360 query in BLASTN phylogenetic analysis re- species whereas Basidiomycota are represented by 10 vealed 100% identity with Ascomycota, namely, species and 74 species of mitosporic fungi [11]. Faculta- Aspergillus sp. Penicillium sp. and its closely tive marine fungi can be transferred to seawater by wind, related Eupenicillium sp. The top scorer species rain or runoff soil. Some facultative marine fungi were in this analysis were Aspergillus sydowii, As- able to evolve adaptation to marine environment and pergillus wentii, Aspergillus flocculosus, Peni- eventually became obligate marine [12]. cillium expansum and Eupenicillium javanicum Many reasons have posed the need to examine the ex- with 98% - 100% identity. Phylogenetic analyses tent of marine biodiversity of fungi. For example, the demonstrates close relatedness among isolated emergence marine life diseases to corals, sponges, sea fungi and potential association with Ascomy- fan corals and fish [3,13-15]. Some marine fungi are re- cetes. This study reports a new geographical ported as sources of enzymes used in bioremediation location in which facultative marine Ascomy- [16-18]. New biosynthetic products have been revealed cetes exist in, and sheds some light on fungal in marine-derived fungi [19-21]. Moreover, marine fungi diversity in Gulf of Aqaba. can be exploited for monitoring marine environment pollution [22]. Keywords: Marine Fungi; Ascomycete; 18S ssu Literature search revealed no studies examining fungal rRNA; Gulf of Aqaba; Red Sea biodiversity in Gulf of Aqaba, a semi-enclosed water body located in the most southern part of Jordan and at 1. INTRODUCTION the northern end of the Red Sea. Only one study exam- ined manglicolous fungal diversity in of the Red Sea in Fungi are found ubiquitously in the environment. They the upper Egypt [23]. execute a wide range of important ecological functions The Gulf of Aqaba is a sub-tropical arid area between especially ones associated with decomposition of organic longitude 34˚25' to 35˚00'E and latitude 28˚00' to 29˚33'N substrates in both terrestrial as well as marine environ- (Figure 1). The Gulf is unique for its great depth (about ments, and occasionally in extreme conditions [1-5]. The 1830 m) in proportion to its width (maximum 25 km); magnitude of fungal biodiversity was estimated to be 1.5 the mean depth of the Gulf is about 800 m. Most of the million species [6,7]. However, some estimation ex- rainfall in the region of the Gulf occurs during the period ceeded this number to 5.1 M [8]. Among the estimated November-May. The average rainfall in Aqaba town is 1.5 million, only 5% - 10% has been formally described about 35 mm/yr. Daily temperature ranges between 14˚C [3,8]. Fungi that live in the sea are defined as obligate in January to 45˚C in summer and evaporation rates of Copyright © 2012 SciRes. OPEN ACCESS 556 B. M. Jaber et al. / Natural Science 4 (2012) 555-561 Figure 1. Location of the sampling sites along the coast of the Gulf of Aqaba. seawater between 200 and 365 cm/yr [24]. The aim of The sampling sites are shown in Figure 1. Meanwhile this study is to investigate the existence of fungal life in sediment samples were collected from the same location seawater and sediments of the Gulf of Aqaba and deter- using similar 100 ml sterilized plastic bottle. The sam- mine their phylotypes. Using molecular identification pling was performed twice during 2 months period in the approach, we report the isolation and identification of 5 fall 2010. All samples were transferred to the laboratory Ascomycete sp. Partial sequences of the 18S small sub- by using icebox and cultured within 40 hours of arrival. unit (ssu) rRNA gene were used as queries in BLASTN search that revealed 98% - 100% identity. Phylogenetic 2.2. Fungal Isolation and Culture Conditions analyses revealed close relationship among the isolated Seawater samples were diluted 1/10 using 0.5 M ster- fungi and their potential affiliation with Ascomycetes. We ile NaCl solution, whereas sediment samples were first propose further studies examining fungal biodiversity in washed with sterile NaCl solution to prepare wash off this unique marine environment. solution. From both preparations, 100 μl of either diluted sample or wash off were taken to spread on 2.5% (w/v) 2. MATERIALS AND METHODS Sabouraud Dextrose agar plates containing 50 μg/μl am- 2.1. Sampling Sites picillin. To rule out any possible contamination during manipulation, negative control plates received only ster- Water samples were collected using 100 ml screw-cap ile NaCl washing solution and were exposed to circulat- sterilized bottle, from three selected locations, namely; ing air inside the laminar flow during culturing. All Marine Science Station (MSS); Phosphate Loading Berth plates were incubated for 3 days at 30˚C. After incuba- (PLB) and Industrial Complex area (IC) by snorkeling, tion, cultured plates were screened to select isolated or by SCUBA diving at a depth of 5 m, during Fall 2010. fungal colonies. Each selected colony was sub-cultured Copyright © 2012 SciRes. OPEN ACCESS B. M. Jaber et al. / Natural Science 4 (2012) 555-561 557 several times to ensure obtaining pure culture. Colony and analyzed after staining with ethidium bromide. selection was primarily based on morphological differ- ences between colonies. Although some colonies exhib- 2.5. Sequence Analysis ited only slight differences, yet they were selected for PCR products were sequenced at the Macrogen Com- further analysis. Nine colonies were selected for further pany sequencing facility using Applied Biosystems 3730 identification analysis. Spores were harvested using ster- mXL automated DNA sequencer (Macrogen, Korea). For ile cotton swab pre-wetted with salt-tween [0.1% NaCl identification, sequences were submitted to BLA-STN plus 0.1% tween-80 (vol/vol)] then released in salt-tween (National Center for Biotechnology Information; solution. After that, spores were counted using hemocy- (http://www.ncbi.nlm.nih.gov). The 18S rRNA gene se- tometer. Approximately 6 million spores from each iso- quences from each species and the matched sequences late/colony were inoculated into Erlenmeyer flasks con- from GenBank were aligned using ClustalW2 (EMBL- taining 25 mL of Sabouraud Dextrose Broth 2.5% (w/v) European Bioinformatics Institute-EBI; 50 μg/μl ampicillin. The flasks were incubated for 48 h at http://www.ebiac.uk). Phylogenetic analyses were per- 30˚C and 150 rpm shaking. All inoculations and fungal formed using Phylogeney.fr [25]. Phylogentic tree was handling were done under ClassII BIOAIR Laminar flow reconstructed using the maximum likelihood method (Euroclone division, Italy) to avoid any possible air con- implemented in the PhyML program (v3.0 alRT) and tamination. graphed using TreeDyn (V198.3) [26]. 2.3. Genomic DNA Extraction 3. RESULTS Fungal mycelia of each isolate were collected by cen- 3.1. Phenotypic Characterization trifugation at 10,000 rpm using regular bench-top centri- fuge. Prior to that, microscopic examination was done to Fungi were cultured from form the sediment and sea- test the purity of the culture. Genomic DNA was ex- water of the Gulf of Aqaba, Red seas. tracted from 2 - 3 mg of mycelia using recombinant lyti- All isolates grew equally well on Sabouraud Dextrose case (Sigma, USA) and according to the protocol in wiz- agar plates at 30˚C. Most colonies grew up to 3 - 4 cm in ard genomic DNA purification kit (Promega, USA). diameter after 48 h incubation at 30˚C. No colonies grew on the negative control plates. According to their growth 2.4. Primers and 18S rRNA Gene PCR characteristics and colony morphology, 9 well-isolated Amplification and Sequencing colonies were selected for further characterization and identification. Forward Primer 5’-ATT GGA GGG CAA GTC TGG TG-3’ and reverse primer 5’-CCG ATC CCT AGT CGG 3.2. PCR Amplification of the 18S ssu rRNA CAT AG-3’ bind to conserved regions of the fungal 18S ssu rRNA gene and enclosing containing the variable The primers target a consensus sequence of the 18S regions V7 and V9 as described before [25]. PCR ampli- ssu rRNA gene containing the variable regions V7 and fication was carried out using ReadyMixTM Taq PCR V9. Amplification with the primers described above is Reaction Mix (Sigma, USA) which contains all required expected to yield a 482- to 503-bp fragment, depending reagents except primers. PCR amplification was carried on the fungus tested.