International Journal of Sciences: Basic and Applied Research (IJSBAR) ISSN 2307-4531 (Print & Online) http://gssrr.org/index.php?journal=JournalOfBasicAndApplied -------------------------------------------------------------------------------------------------------------------------------------- Halotolerance of Heterotrophic Bacteria Isolated from Tropical Coastal Waters Ogochukwu Agwu a *, Theresa Oluwagunke b a,b Department of Biological Oceanography, Nigeria Institute for Oceanography and Marine Research, 3 Wilmot Point Street Victoria Island, Lagos 101241, Nigeria a Email: ogoangela@yahoo.com b Email: toks1x@yahoo.com Abstract To initiate an understanding of the halotolerance of indigenous coastal water bacteria, the salt tolerance of a total of one hundred and seventy (170) surface water heterotrophic bacteria isolated from three (Badagry Creek, Ologe Lagoon and Lagos Lagoon) coastal waters in Lagos, Nigeria was evaluated. All isolates proliferated at NaCl concentrations of 0 to 4%, however, as the concentration of salt increased, the percentage of organisms able to grow decreased. At 15% salt concentration, only 10.7, 16.7 and 6.1% of the isolates from Badagry Creek, Ologe Lagoon and Lagos Lagoon respectively grew. Majority (51%) of the isolates grew at salt concentrations of 0 to 8% and were classified as moderately halotolerant, 35% were highly halotolerant growing beyond 8% (10 to 15%) salt concentrations, while 14% which grew between 0 and 4% were grouped as slightly halotolerant. The highest number of highly halotolerant bacteria was isolated from surface water with salinity 0.01 to 0.1‰, meanwhile, none of the organisms isolated at the highest salinity range (30 to 33‰) grew at 15% salt concentration. The widespread of halotolerant bacteria in these water bodies is of great significance for future research and biotechnological development. Keywords: salt tolerance; salinity; Lagos Lagoon; Badagry Creek; Ologe Lagoon 1. Introduction All forms of life require salt for growth and metabolism, and life is known to exist in the diverse salt concentrations encountered in all natural habitats, from fresh water environment to hyper-saline lakes [1]. ------------------------------------------------------------------------ * Corresponding author. E-mail address: ogoangela@yahoo.com. 224