Rhodolith holobionts are not sources of fixed nitrogen in a northeastern Gulf of Mexico patch reef

2020 ◽  
Author(s):  
Ethan C Cissell ◽  
Sven A Kranz ◽  
Sophie J McCoy
Keyword(s):  
Nitrogen Fixation ◽  
Gulf Of Mexico ◽  
Nitrogenase Activity ◽  
Patch Reef ◽  
Dry Mass ◽  
Fixation Rate ◽  
Northeastern Gulf Of Mexico ◽  
Local Ecosystem ◽  
Water Column Nutrient ◽  
Functional Analyses

Rhodoliths provide numerous benefits to coastal ecosystems and help support high biodiversity. No study, however, has explored rhodoliths that occupy northeastern Gulf of Mexico patch reefs, and their contributions to local ecosystem function remain uncharacterized. Here, we employed the acetylene reduction assay to assess nitrogen fixation capability in rhodolith holobionts (Lithothamnion spp.; Rhodophyta), sediment, and surrounding seawater from a subtropical patch reef ecosystem in the northeastern Gulf of Mexico. We found no evidence for nitrogenase activity in rhodolith holobionts or seawater from our study site, while nitrogenase activity in sediment underlying rhodoliths was approximately equivalent to a nitrogen fixation rate of 0.521 (SD 0.087) nmol N2 g dry mass−1 hr−1. Our results suggest that rhodoliths in the northeastern Gulf of Mexico rely on sources of nitrogen from sediment nitrogen fixation or water column nutrient availability rather than the activity of symbiotic diazotrophic microorganisms. Functional analyses recognizing rhodoliths as holobionts warrant further investigation to better understand the ecology of rhodoliths.

Seasonal variation in nitrogen fixation, associated microbial populations, and carbohydrates in roots and rhizomes of Typha latifolia (Typhaceae)

1984 ◽  
Vol 62 (9) ◽  
pp. 1965-1967 ◽  
Author(s):  
David D. Biesboer
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Anaerobic Bacteria ◽  
Typha Latifolia ◽  
Root Surface ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Free Sugar ◽  
Fixation Rate ◽  
Reduction Assay

Seasonal changes in nitrogen fixation, numbers of nitrogen-fixing bacteria associated with the roots, and rhizome–root carbohydrates were studied for the broad-leaved cattail, Typha latifolia L. Populations of anaerobic and aerobic diazotrophic bacteria were present on the root surface. Anaerobic bacteria predominated in the diazotrophic association, were more active in the acetylene reduction assay, and generally outnumbered aerobic bacteria by 2 to 1 during maximum rates of seasonal nitrogen fixation. The observed maximum nitrogen fixation rate coincided closely with reproductive development in Typha and peak microbial populations. Starch levels in rhizomes were nearly depleted during the middle of the growing season, whereas free sugar concentrations remained stable. Sugar concentrations in the roots increased rapidly during rhizome–root growth and decreased rapidly prior to peak nitrogenase activity.

scholarly journals Functional Analysis of Multiple nifB Genes of Paenibacillus Strains in Synthesis of Mo-, Fe- and V-Nitrogenase

2021 ◽  
Author(s):  
Qin Li ◽  
Haowei Zhang ◽  
Liqun Zhang ◽  
San-Feng Chen
Keyword(s):  
Functional Analysis ◽  
Nitrogen Fixation ◽  
Gene Cluster ◽  
Biological Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
The Other ◽  
Phylogeny Analysis ◽  
Alternative Fixation ◽  
Functional Analyses ◽  
Biological Nitrogen

Abstract Background: Biological nitrogen fixation is catalyzed by Mo-, V- and Fe-nitrogenases that are encoded by nif, vnf and anf genes, respectively. NifB is the key protein in synthesis of the cofactors of all nitrogenases. Most diazotrophic Paenibacillus strains have only one nifB gene located in a compact nif gene cluster (nifBHDKENX(orf1)hesAnifV). But some Paenibacillus strains have multiple nifB genes and their functions are not known.Results: We have analyzed the genomes of the 116 diazotrophic Paenibacillus strains and found that some Paenibacillus strains have 2-4 nifB genes. Phylogeny analysis shows that all nifB genes in Paenibacillus fall into 4 subclasses: the nifB1 being the first gene within the compact nif gene cluster, the nifB2 being adjacent to anf or vnf genes, the other nifB3 and nifB4 being scattered on genomes. Transcriptional results demonstrate that nifB1 exhibits the greatest increase in expression under Mo-dependent conditions and nifB2 is even more induced under alternative fixation conditions. Functional analyses by complementation of the ∆nifB and ∆nifBHDK mutant of P. polymyxa WLY78 which has only one nifB gene and only Mo-nitrogenase showed that both nifB1 and nifB2 are active in synthesis of Mo-, Fe and V-nitrogenase. The nifB3 and nifB4 genes were not significantly expressed under N2-fixing conditions and could not restore the nitrogenase activity of P. polymyxa ∆nifB mutant, suggesting that nifB3 and nifB4 genes were not involved in nitrogen fixation. In addition, reconstruction of anf system comprising 8 genes (nifBanfHDGK and nifXhesAnifV) and vnf system comprising 10 genes (nifBvnfHDGKEN and nifXhesAnifV) supported synthesis of Fe-nitrogenase and V-nitrogenase in P. polymyxa, respectively. Conclusions: Our data and analysis reveal the contents and distribution of nifB genes in Paenibacillus. We demonstrated that the transcriptions of nifB being adjacent to nif or anf or vnf genes significantly expressed under N2-fixation conditions and are active in synthesis of Mo-, Fe and V-nitrogenase. Our study also provides guidance for engineering nitrogen fixation genes into heterologous hosts for nitrogen fixation.

Studies on compatibility of nitrogen fixation by high-temperature-adapted Rhizobium strains and Vigna radiata genotypes at two moisture levels in calcareous soil

1983 ◽  
Vol 101 (2) ◽  
pp. 377-381 ◽  
Author(s):  
R. Rai ◽  
V. Prasad
Keyword(s):  
Nitrogen Fixation ◽  
High Temperature ◽  
Grain Yield ◽  
Vigna Radiata ◽  
Calcareous Soil ◽  
Nitrogenase Activity ◽  
Summer Season ◽  
Green Gram ◽  
Rhizobium Strains

SUMMARYRhizobium strains adapted to high temperature, and genotypes of green gram, were used to study the symbiotic N2-fixation in a summer season at two moisture levels in calcareous soil. Different interactions between strains and genotypes were observedatthe two moisture levels. At both moisture levels, strain S4 with the green gram genotype S8 showed the greatest grain yield, nitrogenase activity, leghaemoglobin and ethanolsoluble carbohydrate of nodules.

Sediment types determination using acoustic techniques in the Northeastern Gulf of Mexico

2004 ◽  
Vol 8 (1) ◽  
pp. 95-103 ◽  
Author(s):  
Gil Young Kim ◽  
Michael D. Richardson ◽  
Dale L. Bibee ◽  
Dae Choul Kim ◽  
Roy H. Wilkens ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Sediment Types ◽  
Acoustic Techniques ◽  
Northeastern Gulf Of Mexico

High-temperature-adaptedAzospirillum brasilensestrains: growth and interaction response on associative nitrogen fixation, mineral uptake and yield of cheena (Panicum miliaceumL.) genotypes in calcareous soil

1988 ◽  
Vol 110 (2) ◽  
pp. 321-329 ◽  
Author(s):  
R. Rai
Keyword(s):  
Nitrogen Fixation ◽  
High Temperature ◽  
Calcareous Soil ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Cross Resistance ◽  
Mineral Uptake ◽  
Associative Nitrogen Fixation ◽  
Seed Inoculation ◽  
Resistance To Penicillin

SummaryHigh-temperature-adapted strains RAU 1, RAU 2 and RAU 3 ofAzospirillum brasilenseC 7 were isolated from stepwise transfer to higher temperature (30 to 42 °C). One of the strains (RAU 1) showed more growth, greater nitrogenase and hydrogenase activities at 30 and 42 °C than parental and other temperature-adapted strains. This strain also showed growth and more nitrogenase activity from pH 6·5 to 8·0. Strain RAU 1 showed cross-resistance to penicillin (300/µg/ml) but not to streptomycin, kanamycin, viomycin and polymixin B at 30 and 42 °C. It was demonstrated in field plots in calcareous soil that seed inoculation with RAU 1 enhanced mineral uptake of cheena. Inoculation with RAU 1 led to a significant increase in associative nitrogen fixation, dry weight of roots, grain and straw yield of cheena compared with the uninoculated control with or without applied N, but the effect of seed inoculation with high-temperature-adapted strains was variable with different genotypes of cheena.

Assimilation of drifter and satellite data in a model of the Northeastern Gulf of Mexico

2004 ◽  
Vol 24 (9) ◽  
pp. 1001-1013 ◽  
Author(s):  
Shejun Fan ◽  
Lie-Yauw Oey ◽  
Peter Hamilton
Keyword(s):  
Gulf Of Mexico ◽  
Satellite Data ◽  
Northeastern Gulf Of Mexico

Nitrogen fixation (acetylene reduction) by Klebsiella pneumoniae in association with 'Park' Kentucky bluegrass (Poa pratensis L.)

1981 ◽  
Vol 27 (1) ◽  
pp. 52-56 ◽  
Author(s):  
L. V. Wood ◽  
R. V. Klucas ◽  
R. C. Shearman
Keyword(s):  
Nitrogen Fixation ◽  
Klebsiella Pneumoniae ◽  
Ethylene Production ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Poa Pratensis ◽  
Kentucky Bluegrass ◽  
Surface Sterilization ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Turfs of 'Park' Kentucky bluegrass reestablished in the greenhouse and inoculated with Klebsiella pneumoniae (W6) showed significantly increased nitrogen fixation (acetylene reduction) compared with control turfs. Mean ethylene production rates per pot were 368 nmol h−1 for K. pneumoniae treated turfs, 55 nmol h−1 for heat-killed K. pneumoniae treated turfs, and 44 nmol h−1 for untreated turfs. Calculated lag periods before activity was observed were generally very short (less than 1 h).When 'Park' Kentucky bluegrass was grown from seed on soil-less medium of Turface, a fired aggregate clay, inoculation with K. pneumoniae (W6) resulted in 9 of 11 turfs showing nitrogenase activity (mean ethylene producion rate per pot was 195 nmol h−1). Only 3 of 11 turfs treated with heat-killed K. pneumoniae showed any activity and their mean rate of ethylene production (40 nmol h−1 per pot) was significantly lower than that for turfs treated with K. pneumoniae.Using the 'Park'–Turface soil-less model system it was shown that acetylene reducing activity was (i) root associated, (ii) generally highest at a depth of 1–4 cm below the surface, (iii) enhanced by washing excised roots, and (iv) inhibited by surface sterilization of excised roots. Klebsiella pneumoniae was recovered from Turface and roots showing acetylene reducing activity.

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