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Epiphytic cyanobacteria of the seagrass C ymodocea rotundata : diversity, diel nifH expression and nitrogenase activity
Author(s) -
Hamisi Mariam,
Díez Beatriz,
Lyimo Thomas,
Ininbergs Karolina,
Bergman Birgitta
Publication year - 2013
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12031
Subject(s) - diazotroph , biology , cyanobacteria , nitrogenase , seagrass , epiphyte , botany , phyllosphere , diel vertical migration , phylotype , nitrogen fixation , ecology , ecosystem , bacteria , 16s ribosomal rna , genetics
Summary Seagrasses are photoautotrophic, ecologically important components of many globally widespread coastal ecosystems, in which combined nitrogen may limit their production. We examined the biodiversity and diazotrophic capacity of microbial epiphytes associated with the phyllosphere of the seagrass C ymodocea rotundata of the W estern I ndian O cean. Light microscopy, 16 S rRNA and nifH gene analysis revealed the dominance of cyanobacteria in the epiphytic microbial community. Most phylotypes were related to free‐living uncultured benthic cyanobacteria, while some to cyanobacterial endosymbionts of marine diatoms. Novel and potentially diazotrophic species, some of known pantropical distribution, were also discovered. Significant diel nitrogenase activities (acetylene reduction assay) were recorded (up to 358 ± 232 nmol C 2 H 4 g −1 of seagrass FW h −1 ). The nifH gene expression patterns showed that heterocystous phylotypes may be the dominant diazotrophs during the day and non‐heterocystous at night. These data show that C . rotundata is colonized by diverse diazotrophic cyanobacteria species and suggest that these may be beneficial partners of seagrasses in nitrogen‐depleted waters.