This study aimed to isolate and evaluate the antagonistic potential of actinomycetes from mangrove forest of Pahang, Malaysia. Sediment samples from seven different sites were pretreated using wet heat and dry heat methods followed by dilution plating on eight isolation media. In total, 4850 isolates were successfully recovered, with inorganic salt-starch agar displaying the highest percentage of recovery (31.7%), followed by actinomycete isolation agar (24.1%). The wet heat pretreatment was found to be more effective in the enumeration of actinomycetes, since 81.4% of total isolates were yielded using this technique, whereas dry heat treatment was better in the enumeration of spore-forming actinomycetes. After both pretreatments, Streptomyces-like and Micromonospora-like isolates were the most predominant. The antagonistic activities of the representative isolates were evaluated using the cross-streak method. In total, 78 isolates were active against at least one of the test organisms. Among them, 28.2% exhibited antibacterial activity, 23.1% exhibited antifungal activity and 48.7% displayed both. Nine isolates demonstrated broad antagonism by inhibiting the growth of all test organisms. The presence of a relatively large number of bioactive isolates suggests that Pahang mangrove forest is a potential source of actinomycetes with biosynthetic capabilities.

Xylanase is the key enzyme that involves in the hydrolysis of xylan, the main constituent of the complex hemicellulose of the plant cell wall. In this study, forty actinomycetes that were isolated from the sediment of Kuantan Mangrove Forest, Malaysia, were tested for their ability to produce extracellular xylanase. At least 15 isolates were able to degrade xylan in the primary agar-based screening on marine agar containing 0.1% (v/v) azo-xylan (Birchwood). The degradation of xylan was indicated by the formation of halo zone around the colonies and the clear zone index (CZI) was calculated as a ratio of the clearing zones to the colony size. Isolate K2-04 with CZI 3.35 ± 1.91 was identified through 16S rRNA study as Verrucosispora sp. This isolate was further grown in marine broth and incubated at 30 °C, 200 rpm for 20 days. The growth of K2-04 and the xylanase activity was measured at day 2, 4, 6,12 and 18 respectively. The highest enzyme activity of the crude enzyme was recorded at day 18 (1.836 U/mL) and exhibited stability after 20 days storage at 4°C. This study serves as a preliminary study to characterize the properties of Verrucosispora sp. K2-04, rare actinomycete of Kuantan Mangrove Forest, Malaysia.  Index Terms-marine Actinomycetes, xylanase, mangrove, Verrucosispora containing 1 g of dried sediment and 9 ml of sterilized sea water was heated in a water bath at 60°C for 20 min. Morphological differences among the isolates were

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Actinomycetes are biotechnologically important for their unrivalled capacity to produce bioactive secondary metabolites. Although thousands of antibiotics have been discovered from actinomycetes, these represent only a small fraction of the entire reservoir. Thus, screening of actinomycetes from poorly studied environment is a valuable attempt. In the present study, an effort was made to isolate, identify and evaluate the antimicrobial activities of actinomycetes from Tanjung Lumpur Mangrove Forest of Pahang, Malaysia; an underexplored ecosystem. Out of 1366 actinomycetes that were successfully enumerated, a total of 40 representative isolates were selected for further evaluation. The antimicrobial activity of the representative isolates were first assessed using the cross streak method against Bacillus subtilis, Candida albicans, Escherichia coli, Serratia marcescens and Staphylococcus aureus. Twenty five isolates displayed antagonistic potential against at least one of the test organisms. Of this, 40% exhibited antibacterial activity, 24% exhibited antifungal activity and 36% displayed both. The cell–free supernatant of the active isolates were then further evaluated using the agar well diffusion method, in which only 4 isolates displayed inhibitory activity. A total of 13 representative isolates were identified and characterized using 16S rRNA gene partial sequencing. They were further classified into 7 genera namely Streptomyces, Micromonospora, Rhodococcus, Gordonia, Pseudonocardia, Mycobacterium and Actinophytocola. These findings suggested that mangrove of Tanjung Lumpur is a rich source of actinomycetes for the discovery of bioactive secondary metabolites.

Actinomycetes are prolific secondary metabolites producer, and they are sought after for their unparalleled capability. Mangrove forests are among the underexplored locations in search of new resources of actinomycetes. Bioprospecting of actinomycetes in Kuantan mangrove forests has revealed highly diverse actinomycetes with high antimicrobial properties. Members of the rare genera successfully isolated include Micromonospora sp., Pseudonocardia sp., Verrucosispora sp., Nocardiopsis sp., Actinophytocola sp., Dietzia sp., Gordonia sp., Micrococcus sp., Mycobacterium sp., Nocardia sp., Saccharopolyspora sp. And Rhodococcus sp. These rare actinomycetes can also be added to the list of genera isolated from this ecological niche, providing solid evidence that considerable diversity of actinomycetes are distributed within Kuantan mangrove forest. PKS-I and NRPS genes are usually related to the ability to produce secondary metabolites in actinomycetes. Interestingly, several of these rare actinomycetes showed the presence of both PKS-I and NRPS genes or either gene, and this exemplifies the potential of these rare actinomycetes may possess. Further studies conducted on these rare actinomycetes may reveal their true potentials that can be exploited for natural product discovery.

Actinomycetes which abundantly found in nature are renowned for their unique capabilities to produce biologically active metabolites. Poorly studied mangrove ecosystem offers a promising natural resource of new actinomycetes due to their high species diversity. This study aims to assess the diversity of actinomycetes from mangrove forest of Pahang, Malaysia. Various selective isolation media and pre-treatments were employed for maximum isolation of mangrove actinomycetes. A total of 4850 actinomycete isolates had been successfully recovered. It was observed that inorganic-salt starch agar (ISP4) displayed the highest percentage of actinomycetes recovery (31.7 %). Starch-yeast extract (SYE) and starch casein agar (SCA) were found to be more efficient in isolating wide variety of actinomycetes based on their morphological appearance. It was also observed that wet heat pre-treatment was more effective in isolating mangrove actinomycetes as 81.4 % of total isolates were yielded using this technique. On the other hand, dry heat treatment was better in the enumeration of spore-forming actinomycetes despite lower number of isolates recovered. Of both pre-treatments, station 1 which is located within the deep mangrove forest area recorded the highest recovery (23.7 %), with Streptomyces and Micromonospora-like isolates being the most predominant observed from all sampling sites. The presence of relatively large number of isolates suggests that Pahang mangrove forest is a potentially rich source of actinomycetes.