The Family Azotobacteraceae

Becking, J. H.

doi:10.1007/0-387-30746-x_26

Cited by 26 publications

(25 citation statements)

References 121 publications

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“…But similar results are also known from conventional enrichment cultures. Whereas non-hydrocarbon substrates (compounds with functional groups) such as mannitol in defined nitrogen-free media are known to enrich for rapidly growing cultures of active diazotrophs such as Azotobacter (Becking, 1992), hydrocarbons in such media usually yield poorly growing enrichment cultures unless nitrogen salts are added (F. Musat, unpubl. results).…”

Section: Discussionmentioning

confidence: 99%

Study of nitrogen fixation in microbial communities of oil‐contaminated marine sediment microcosms

Musat

Harder

Widdel³

2006

Environmental Microbiology

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Aerobic microbial degradation of pollutant oil (petroleum) in aquatic environments is often severely limited by the availability of combined nitrogen. We therefore studied whether the microbial community enriched in marine sediment microcosms with an added oil layer and exposure to light harboured nitrogenase activity. The acetylene reduction (AR) assay indeed indicated active nitrogenase; however, similar activity was observed in oil-free control microcosms. In both microcosms, the AR rate was significantly reduced upon a dark shift, indicating that enriched cyanobacteria were the dominant diazotrophs. Analysis of structural dinitrogenase reductase genes (nifH) amplified from both microcosms indeed revealed NifH sequences related mostly to those of heterocystous cyanobacteria. NifH sequences typically affiliating with those of heterotrophic bacteria were more frequently retrieved from the oil-containing sediment. Expression analyses showed that mainly nifH genes similar to those of heterocystous cyanobacteria were expressed in the light. Upon a dark shift, nifH genes related to those of non-heterocystous cyanobacteria were expressed. Expression of nifH assignable to heterotrophs was apparently not significant. It is concluded that cyanobacteria are the main contributors of fixed nitrogen to oil-contaminated and pristine sediments if nitrogen is a limiting factor and if light is available. Hence, also the oil-degrading heterotrophic community may thus receive a significant part of combined nitrogen from cyanobacteria, even though oil vice versa apparently does not stimulate an additional nitrogen fixation in the enriched community.

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Section: Discussionmentioning

confidence: 99%

Study of nitrogen fixation in microbial communities of oil‐contaminated marine sediment microcosms

Musat

Harder

Widdel³

2006

Environmental Microbiology

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“…Azotobacter, a cystforming bacteria, is able to fix nitrogen under aerobic conditions. Interestingly, in some members of this bacterial genus, it has been shown that nitrogen fixation can be performed using up to three different nitrogenase enzymes that use different metal cofactors (Becking et al 2006, Garrity et al 2005). Because many members of Azotobacter exhibit plant-growth promoting features, this genus is included within the PGPB group (Kizilkaya 2008, Krumnow et al 2009, Rojas-Tapias et al 2012.…”

Section: Introductionmentioning

confidence: 99%

Preservation of Azotobacter chroococcum vegetative cells in dry polymers

et al. 2014

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We studied the preservation of Azotobacter chroococcum C26 using three dry polymers: carrageenin, sodium alginate, and HPMC, using a method of accelerated degradation. Bacterial viability, as response variable, was measured at three temperatures in four different times, which was followed by calculation of bacterial degradation rates. Results showed that temperature, time of storage, and protective agent influenced both viability and degradation rates (P;lt;0.05). We observed, using the Arrhenius thermodynamic model, that the use of polymers increased the activation energy of bacterial degradation compared to control. We obtained thermodynamic models for each polymer, based on the Arrhenius equation, which predicted the required time for thermal degradation of the cells at different temperatures. Analysis of the models showed that carrageenin was the best polymer to preserve A. chroococcum C26 since ~ 900 days are required at 4 ºC to reduce its viability in two log units. We conclude, therefore, that long-term preservation of A. chroococcum C26 using dry polymers is suitable under adequate preservation and storage conditions.

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“…Total microbial counts were determined according to Nautiyal (1999), Azotobacter densities were determined by using the most probable number (MPN) method after incubating the tubes at 28 + 2 ˚C for 10 days on modified Ashby's medium (Becking , 2006). Total actinomycetes count was determined on starch nitrate medium (Waksman & lechevalier, 1962).…”

Section: Microbiological Analysismentioning

confidence: 99%

Effect of Some Biofertilizers and Humic Acid Application on Olive Seedlings Growth under Irrigation with Saline Water

El-Shazly

Ghieth

2019

Alexandria Science Exchange Journal

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The present study was conducted to examine the effect of humic acid concentration (0, 0.5, 1 and 1.5 ml/L) and some of biofertilization treatments (control, Azotobacter chroococcum, Mycorrhizae (Glomus macrocarbium) and mix of Azotobacter chroococcum + Mycorrhizae on olive seedling which grown under three levels of saline water (2000, 3000 and 4000 ppm). this experiment was carried out during two successive seasons (2015 and 2016) on Olive seedlings Picual cultivars grown in El-Sheikh Zuwayid station, Desert Research Center North Sinai governorate, Egypt. Based on growth parameters data showed that salinity level (2000ppm) produced the highest significant parameters of the olive seedling; for seedling height, trunk diameter, Branch number., Leaf number., leaf length, leaf width, leaf area, and also the fresh and dry weight of shoot and root system. The lowest values were recorded for salinity level (4000 ppm through the two seasons. Salinity level at 2000 ppm gives the chance of growing plant to complete all of its physiological processes at a proper time than that of high concentration. Highest salinity concentration 4000 ppm caused a decline in all the studied parameters throughout both studied seasons. Increasing humic acid levels from 0.5 to 1.5 ml/L % increased significantly all studied parameters when compared with control (0) in the two studied seasons. Application of biofertilization treatments either singly or mixed enhanced growth and plant biomass of olive seedling under different salinity treatment. Mixed two types of biofertilzer had a significant effect on seedling growth than control and one type of biofertilizer treatments. In addition, Macronutrient content in olive seedling leaf positively affected with humic acid concentration and biofertilization treatments. Mixed biofertilization treatment resulted in higher values of soil microbiological properties, i.e. total microbial counts, Azotobacter densities, Mycorrhizal infection percentage, no. of mycorrhizal spores /gm, microbial enzymes in soil (Dehydrogenase, Nitrogenase and Phosphatase). It can be concluded that, to mitigate the negative impact of salinity of olive seedling we recommend to use humic acid (1.5 ml/L%) with the treatment of biofertilizer (Mycorrhiza and Azotobacter chroococcum).

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The Family Azotobacteraceae

Cited by 26 publications

References 121 publications

Study of nitrogen fixation in microbial communities of oil‐contaminated marine sediment microcosms

Study of nitrogen fixation in microbial communities of oil‐contaminated marine sediment microcosms

Preservation of Azotobacter chroococcum vegetative cells in dry polymers

Effect of Some Biofertilizers and Humic Acid Application on Olive Seedlings Growth under Irrigation with Saline Water

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