Phosphate solubilizing bacteria: Comparison between coastal and deep sea sediments

Abstract

Phosphate solubilizing bacteria (PSB) play a key role in the phosphate cycle by enzymaticaly hydrolyzing a wide variety of organic phosphorus compounds and solubilizing various major insoluble forms of bound phosphorus. PSB are ubiquitous and are found in intertidal waters, estuaries, coastal beaches and even in offshore regions like deep sea. This study compares the abundance, diversity and enzymatic activity of PSB in the coastal sediments where TOC ranged from 0.6 – 1.3% with that of the deep sea where TOC ranged from 0.1- 0.4%. PSB numbers averaged 1.3x104 cfu g-1 in the coastal sediments while they were 5.0 x103 cfu g-1 in the deep sea sediments. PSB were dominated by γ-Proteobacteria Pseudomonas in the coast and Xanthomonas and β-Proteobacteria Alcaligenes in the deep sea sediments. The average enzyme activity of the PSB in coastal region was twice (0.46 μg P ml-1 h-1) that of their deep sea counterparts (0.24 μg P ml-1 h-1). It related positively to TOC with its variation being more influenced in the CIB sediments (r=0.59) than in the coastal sediments (r= 0.22). It is apparent that the enzyme activity in the coastal sediments could be more for P mobilization and in the oligotrophic deep sea it could be both for P and C mobilization.