CIBICI   14215
CENTRO DE INVESTIGACION EN BIOQUIMICA CLINICA E INMUNOLOGIA
Unidad Ejecutora - UE
artículos
Título:
Environmental factors associated with heterotrophic nitrogen-fixing bacteria in water, sediment, and riparian soil of Suquía River
Autor/es:
MERLO, CAROLINA; REYNA, LUCIANA; ABRIL, ADRIANA; AMÉ, MARÍA VALERIA; GENTI, SUSANA
Revista:
LIMNOLOGICA
Editorial:
ELSEVIER GMBH
Referencias:
Año: 2014 vol. 48 p. 71 - 78
ISSN:
0075-9511
Resumen:
In this study we investigated the
environmental factors associated with biological nitrogen (N) fixation (BNF) in
water, sediments, and riparian soil along a polluted river (Suquía River of
Córdoba, Argentina). Here, we screened heterotrophic
nitrogen-fixing bacteria and assessed the magnitude of BNF at different
sites of Suquía River. To this aim, samples of the three habitats (riparian
soil, water, and sediment) were collected from five polluted sites and one
reference site during low and high flow water periods. In all samples the
abundance of N-fixing bacteria was evaluated in solid nitrogen-free medium
and the biological N fixation was measured by nitrogenase
(Nase) enzyme activity using the acetylene reduction method. To identify the heterotrophic N-fixing taxa DNA
of nine cultures isolated from sites with different Nase enzyme activity was extracted
and the 16S rRNA gene was amplified and sequenced. In addition, the ammonia and
organic carbon (C) content in all samples, the dissolved O2 concentration
in water, and the water content in riparian soil were measured. The N-fixing
bacteria were detected in all study sites and habitats. The abundance of them
correlated significantly with organic C content in sediment, and with water and
organic C contents in riparian soil, whereas in water a negative correlation
with dissolved O2 was observed. In addition, the water
and sediment Nase enzyme activity varied among sites during low flow period presenting
significant correlation with ammonia and organic C contents in sediment. The
identified taxonomic groups in the Suquía River are related to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria
although the N-fixing capacity of them was not established.
Altogether these findings demonstrate that
BNF occurs in all habitats of Suquía River, being in sediments influenced
mainly by the higher organic C present in the most polluted sites, while in
riparian soil the organic C and water contents were the major abiotic factors
that control the abundance of N fixing bacteria. In Suquía River water the
density of N fixing bacteria were associated with low dissolved O2
concentration. These data suggest that the BNF in Suquía River is a complex
process that depends on numerous environmental factors that act together.