In recent years, seasonal blooms of the dinoflagellate Noctiluca miliaris have appeared in the open-waters of the northern Arabian Sea (NAS). This study provides the first characterization of bacteria from a seasonal bloom of green Noctiluca of NAS (20 degrees N - 17 degrees N and 64 degrees E - 70 degrees E), during the spring-inter-monsoon cruise of Sagar Sampada 253, in March 2007. Bacterial growth as assessed by most-probable number (MPN) and plate counts, revealed 'variable-physiotypes' over a wide range of salinities (0 percent to 25 percent w/v NaCl), pH levels (5-8.5), and organic nutrient strengths, in comparison to non-bloom waters. MPN indices of bacteria in surface waters of bloom stations DWK and PRB, corresponded to (3.08-4.41)×10 sup(3) cells/mL at 3.5 percent NaCl (w/v), and (2.82-9.49)×10 sup(2) cells/mL at 25 percent (w/v) NaCl in tryptone-yeast extract broth (TYE). Plate counts were (1.12-4)×10 sup(6) CFU/mL at 0 percent (w/v) NaCl, (1.28-3.9)×10 sup(6) CFU/mL at 3.5 percent (w/v) NaCl, and (0.4-7)×10 sup(4) CFU/mL at 25 percent NaCl (w/v) on TYE. One-tenth-strength Zobell's gave (0.6-3.74)×10 sup(5) CFU/mL at pH 5 to (3.58-7.5)×10 sup(5) CFU/mL at pH 8.5. These bacteria were identified to the genera Bacillus, Cellulomonas, Staphylococcus, Planococcus, Dietzia, Virgibacillus, Micrococcus, Sporosarcinae, Leucobacter, and Halomonas. The identity of three strains (GUFBSS253N2, GUFBSS253N30, and GUFBSS253N84) was confirmed through 16S rDNA sequence homology as Bacillus cohnii, Bacillus flexus, and Bacillus cereus. The approx. 2-3 fold higher plate counts of culturable bacteria from the open-waters of the NAS indicate that these bacteria could critically determine the biogeochemical dynamics of the bloom and its milieu. The role of these bacteria in sustaining/terminating the bloom is under evaluation.