© 2015 Gunapati Oinam et al. This is an open access article distributed under the terms of the Creative Commons Attribution License -NonCommercial-ShareAlike Unported License ( http://creativecommons.org/licenses/by-nc-sa/3.0/ ). Journal of Applied Biology and Biotechnology Vol. 3 (06), pp. 001-008, Nov-Dec, 2015 Available online at http://www.jabonline.in DOI: 10.7324/JABB.2015.3601 Identification of diazotrophic nostocalean cyanobacteria of north eastern region of India and evaluation for nitrogenase activity and extracellular ammonium excretion Gunapati Oinam, Wangkhem Indira, O. Avijeet Singh, Th. Indrama, K. Ojit Singh, Laxmipriya Koijam, Chungkham Silvia, A. Subhalaxmi Sharma, Romi Khangembam, Minerva Shamjetshabam, A. Thadoi, K. Sarabati, Th. Bidyababy, O.N. Tiwari* Freshwater Cyanobacterial and Microalgal Repository, Microbial Resources Division, Institute of Bioresources and Sustainable Development (A National Institute of Department of Biotechnology, Govt. of India), Takyelpat, Imphal-795001, Manipur, India. ARTICLE INFO ABSTRACT Article history: Received on: 07/07/2015 Revised on: 25/07/2015 Accepted on: 22/08/2015 Available online: 19/12/2015 In this study, morphological and microscopic observations were performed along with growth measurements, evaluation of extracellular ammonium and nitrogenase activity. A total of 62 diazotrophic nostocalean cyanobacteria belonging to 12 genera viz- Scytonema (2), Anabaena (22), Nostoc (17), Cylindrospermum (2), Anabaenopsis (1), Dichothrix (1), Tolypothrix (2), Calothrix (6), Aulosira (4), Microchaete (3), Wollea (1) and Rivularia (1) which were originally isolated from different niches of north east India were procured from National fresh water cyanobacterial and microalgal repository of DBT-IBSD, Imphal, Manipur, India. Among the different nostocalean cyanobacteria encountered from the various habitats, Anabaena sp. BTA650, an isolate from lithophytes under running water, Moreh, Chandel, Manipur exhibited highest nitrogenase activity of 111.08±13.26 nmole C2H4 μg -1 Chl-a h -1 can be a potential candidate for biofertilizer formulation particularly for terraced hill rice culture condition. Key words: Diazotrophs, cyanobacteria, nitrogenase activity, extracellular ammonium, repository, biofertilizer. 1. INTRODUCTION The North East India is a frontier region with picturesque hills and green meadows which shelters thousand of species of flora and fauna. It is connected to the rest of India by a narrow 20 km wide corridor of land. The lushness of its landscape, geographical and ecological diversity makes the North East India quite different from other parts of the subcontinent. Cyanobacteria are impressive ecosystem engineers since the beginning of the evolutionary history of planet [1]; [2]. They are often referred to as ‘miniature factories’ of the biological world and represent an alternative source of a variety of bioactive compounds, lipids/fatty acids, proteins, enzymes, pigments and compounds of pharmaceutical and nutraceutical value [3]; [4]. According to [5]; [6], the order Nostocales includes filamentous cyanobacteria that are capable of cell differentiation in heterocysts, akinetes or reproductive trichomes (hormogonia). * Corresponding Author E-mail: ontiwari1968@gmail.com The role of nitrogen fixing cyanobacteria in enhancing soil fertility has been long known [7]; [8]. With increasing awareness of their varied potential applications, studies on cyanobacterial diversity have been reported from around the world in recent times [9]; [10]; [11]. Few reports on studies of cyanobacteria from the north eastern region of India are [12]; [13]; [14]; [15]; [16]. Diazotrophic cyanobacterial strains originally isolated from different niches of north eastern region of India were investigated morphologically and biochemically characterized for the biochemical components such as extracellular ammonium excretion, nitrogenase activity and production of chlorophyll-a. 2. MATERIALS AND METHODS 2.1 Preparation of the culture medium BG-11(-N) non nitrogenous culture medium [17] was used for culturing of nostocalean cyanobacteria. Stock solutions of all the ingredients were prepared and stored in screw capped amber colour bottles. A volume of each ingredient was taken accordingly for one litre of the medium.