N<sub>2 fixation rates and associated diversity (nifH) of microbialite and mat-forming consortia from different aquatic environments in Mexico

Abstract

The present study describes patterns and rates of N 2 fixation and associated diversity (based on the nifH gene) of microbialite and mat-forming bacterial consortia from different aquatic environments in Mexico. All of the communities shared a diurnal pattern of N 2 fixation with peak activity during the day while showing a unique genetic composition. Our study suggests the importance of heterocystous cyanobacteria as the main diazotrophic organisms, although nifH sequences were also affiliated to Oscillatoriales, Chroococcales, and several Pro-teobacteria. Genetic composition did not relate to the environmental variables analysed, although rates of nitrogenase activity associated to microbial C and N explained 11% of the variation among consortia. KEY WORDS: N 2 fixation · Microbialites · Microbial mats · nifH · Diversity · Community ecology Resale or republication not permitted without written consent of the publisher Aquat Microb Ecol 67: 15-24, 2012 Editorial responsibility: Douglas Capone,

Microbialite genetic diversity and composition relate to environmental variables

“…However, the identification of other bacterial and archaeal taxa associated to microbialites has remained limited (Breitbart et al, 2009;Burns et al, 2009;Bolhuis & Stal, 2011;Mobberley et al, 2012). Microbialites are known to occur in several environments throughout Mexico (Gischler et al, 2008(Gischler et al, , 2011Breitbart et al, 2009;Kazmierczak et al, 2011;Beltrán et al, 2012), a mega diverse country, in which species turnover increases due to strong environmental gradients. Microbialites are known to occur in several environments throughout Mexico (Gischler et al, 2008(Gischler et al, , 2011Breitbart et al, 2009;Kazmierczak et al, 2011;Beltrán et al, 2012), a mega diverse country, in which species turnover increases due to strong environmental gradients.…”

Comparative metagenomics unveils functions and genome features of microbialite‐associated communities along a depth gradient

“…More abundant in surface microbialites (AL‐W and AL‐N‐1), their phylogenetic distribution was generally similar in the different samples, nif genes being mostly affiliated to Cyanobacteria (up to 85%) and to Alphaproteobacteria, Gammaproteobacteria and Betaproteobacteria. This is consistent with previous nifH surveys in Alchichica microbialites (Beltrán et al ., ). AL‐N‐1 displayed a somewhat different profile, with an equivalent proportion of deltaproteobacterial and cyanobacterial genes (Fig.…”

Metabolic potential of microbial mats and microbialites: Autotrophic capabilities described by an in silico stoichiometric approach from shared genomic resources

“…Theoretical rates of CO 2¯x ation calculated with the model, using published N 2¯x ation rates and the availability of dissolved nitrate and phosphate in microbialites of PozasAzules II, Cuatro Cienegas. 59 Reductive tricarboxylic acid cycle (RTCA); dicarboxylate-hydroxybutyrate cycle (D-h); reductive acetylCoA pathway (R Acetyl-CoA). …”

“…[55][56][57][58][59] Nitrogen is a limiting element in aquatic environments 60,61 and it is available to biological systems either through¯xation (N 2 ), and/or assimilation (NH 4 or NO 3 ). In order to couple a measured rate for the pathways identi¯ed in the EFMs analysis, we used the ecophysiological measurements of N 2¯x ation rates estimated by acetylene reduction assays of microbialites from Pozas Azules II in Cuatro Cienegas, Mexico (published by Beltr an et al 59 ) Using the maximum rate of N 2¯x ation (0.1 mol N 2 gC À1 h À1 ) and the availability of dissolved nitrate (1.5 M) and phosphate (1.3 M) in this system as inhomogeneous equalities to determine the elementary°ux vectors 62,63 in the model. Then we obtained and estimated the rates of CO 2¯x ation for each pathway under this constrained condition (see Fig.…”