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Diversity and expression of nitrogen fixation genes in bacterial symbionts of marine sponges
Author(s) -
Mohamed Naglaa M.,
Colman Albert S.,
Tal Yossi,
Hill Russell T.
Publication year - 2008
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2008.01704.x
Subject(s) - biology , sponge , trichodesmium , nitrogen fixation , cyanobacteria , gene , proteobacteria , diazotroph , bacteria , symbiosis , botany , genetics , 16s ribosomal rna
Summary Marine sponges contain complex assemblages of bacterial symbionts, the roles of which remain largely unknown. We identified diverse bacterial nifH genes within sponges and found that nifH genes are expressed in sponges. This is the first demonstration of the expression of any protein‐coding bacterial gene within a sponge. Two sponges Ircinia strobilina and Mycale laxissima were collected from Key Largo, Florida and had δ 15 N values of c . 0–1‰ and 3–4‰ respectively. The potential for nitrogen fixation by symbionts was assessed by amplification of nifH genes. Diverse nifH genes affiliated with Proteobacteria and Cyanobacteria were detected, and expression of nifH genes affiliated with those from cyanobacteria was detected. The nifH genes from surrounding seawater were similar to those of Trichodesmium and clearly different from the cyanobacterial nifH genes detected in the two sponges. This study advances understanding of the role of bacterial symbionts in sponges and suggests that provision of fixed nitrogen is a means whereby symbionts benefit sponges in nutrient‐limited reef environments. Nitrogen fixation by sponge symbionts is possibly an important source of new nitrogen to the reef environment that heretofore has been neglected and warrants further investigation.