Full Length Research Paper

Characterization and evaluation of stress and heavy metal tolerance of some predominant Gram negative halotolerant bacteria from mangrove soils of Bhitarkanika, Orissa, India

Mishra R. R.¹, Dangar T. K.², Rath B¹ and Thatoi H.N^1*

¹P.G. Department of Biotechnology, North Orissa University, Takatapur, Baripada, Orissa757003, India.

²Microbiology Laboratory, Crop Production Division, Central Rice Research Institute, Cuttack 753006, Orissa, India.

*Corresponding author. E-mail: hn_thatoi@rediffmail.com. Tel.: 91-9437306696. Fax: 91-6792-255127.

Accepted 27 March, 2009

In the present study both Gram positive and Gram negative bacteria were isolated using enrichment media from five different stations from mangroves soils of Bhitarkanika, Orissa, India. Among the bacterial populations studied, the Gram negative bacterial population was found to be more in all the stations. Out of several Gram negative bacterial isolates, six predominant and morphologically distinct isolates were selected and characterized. Phenotypical the isolates were identified as one each of Pseudomonas aeruginosa and P. alcaligenes and two strains each of Methylococcus sp. and Desulfotomaculum sp. The strain P. aeruginosa and one strain of Methylococcus sp. tolerated up to 13% NaCl and 10% sea salt, respectively. But the other four isolates tolerated 10% NaCl as well as sea salt. Most of the organisms were sensitive to several antibiotics tested except for the antifungal antibiotic Nystatin. The stress tolerant enzyme activities for catalase, peroxidase, polyphenol oxidase, ascorbate peroxidase, ascorbic acid oxidase were found to be variable among the strains. Evaluation of heavy metal tolerance towards the heavy metals; ZnSO₄, CuSO_4, NiCl_2, CdNO₃ and K₂CrO₄ showed that the isolates tolerated 600 - 1000 ppm K₂CrO₄ but only up to 10 - 20 ppm CdNO₃.

Key words: Biochemical characterization, gram negative bacteria, mangroves, stress enzyme, heavy metal, saline ecology.