In Azotobacter chroococcum the hydrogenase gene (hup) cluster spans about 14 kb of DNA. In this study about 12 kb of the hup region beginning immediately downstream of the structural genes (hupSL) were sequenced. This revealed 14 additional open reading frames (ORFs) which we designated hupZMNOQRTVABYCDE. All of them are transcribed from the same strand as hupSL and are closely linked. The polypeptides predicted from all these genes are homologous to products of the gene clusters of membrane-bound (NiFe) hydrogenases from other bacteria, including Azotobacter vinelandii, Alcaligenes eutrophus, Rhodobacter capsulatus, Rhizobium leguminosarum and Escherichia coli. The products of hupR and hupZ may be involved in hydrogenase-linked electron transport since they are similar to rubredoxins and b-type cytochromes, respectively. / Site-directed mutagenesis of hupB, hupY, hupD and hupE abolished Hup activity with either O$ sb2$ or methylene blue as the electron acceptor whereas two insertions downstream of the hupE gene had no effect on Hup activity. A 10.5 kb fragment of DNA beginning in hupR was able to complement hupD and hupE mutants, supporting earlier evidence for a promoter downstream of hupSL. / Mutations in hupB, hupY and hupD had little effect on $ beta$-galactosidase activity in a strain also carrying a hupL-lacZ fusion, indicating that hupB, hupY and hupD are probably not involved in regulating the transcription of hupSL. / Adding nickel to the medium restored wild-type Hup activity to a hupB mutant and about half of the activity in a hupA mutant, indicating that the hupB and hupA gene products may be involved in Ni metabolism.

No description available.

No description available.

The purpose of this study is to determine if a strain of Azotobacter chroococcum isolated from the soil in northern Louisiana produces cysts which are as resistant to deleterious agents as those produced by previously reported strains os Azotobacter.

Accessory hydrogen uptake genes have been identified in a region of the Azotobacter chroococcum genome about 5 kb downstream of the hydrogenase structural genes (hupSL). DNA sequencing has revealed six genes (hupABYCDE) in this region. These genes are probably transcribed in the same direction as hupSL but are probably in a different operon. Mutational analysis had shown that disruption of the hupB, hupY, hupD and hupE genes gives a Hup$ sp-$ phenotype. In the present work additional mutational analysis, using Tn5, a Tn5 -derivative containing a promoterless lacZ gene, and a kanamycin resistance gene, confirms the direction of transcription and the separate nature of the hupABYCDE operon, and extends the region known to be necessary for Hup activity to hupA and possibly to 1.6 kb upstream of hupA.

No description available.

No description available.

Olive Mill Wastewater (OMW), by-product of oil industry, is a dark liquid with a characteristic fetid smell, bitter taste and bright appearance / having a high pollution potential, creating serious problems in countries producing olive oil. Azotobacter chroococcum as a Nitrogen-fixing bacteria can bioremediate OMW, by degrading its toxic constituents. With the help of this detoxification process OMW can be used as biofertilizer. In this study, the dynamics of growth and nitrogen fixation at different physiological conditions and nutrient requirements of A. chroococcum in chemically defined N-free medium was determined. These parameters were cultivation conditions such as pH, temperature and aeration and some additives such as inorganic salts, boric acid and nitrogen. Consequently, the maximum cell concentration were obtained when A. chroococcum was grown at neutral pH, 35&amp / #61616 / C, 150 rpm and in medium supplemented with manganese salt at 0.01% concentration. The maximum nitrogen fixation products were attained when A. chroococcum was grown under the same conditions except at pH 8. Further, bioremediation of OMW by A. chroococcum was examined. When A. chroococcum was cultivated in OMW containing basal medium at 10% OMW concentration, a cell density 12 times higher than in the OMW free medium was achieved. Also, it was found to have maximum increase in extracellular protein concentration (112 mg/l) at 10% OMW containing medium and maximum increase in ammonia concentration (9.05 mg/l) at 5% OMW containing medium.

In this study agriculturally important Pseudomonas spp. which may solubilize phosphate and Azotobacter chroococcum which can fix atmospheric nitrogen were grown on waste beer with 4 different concentrations and conditions for best growth were determined. Having potential of use as biofertilizers, they were put in the carrier material peat and survivals of them were observed for 3 months at three different temperatures. Biofertilizer can be defined as a substance which contains living microorganisms which, when applied to seed, plant surface, or soil, colonizes the rhizosphere or the interior of the plant and promotes growth by replacing soil nutrients or making nutrients more available or increasing plant access to nutrients. In order to benefit from the biofertilizers, viable and active microorganisms in high numbers must be present which requires high quality inoculants. The carrier substrate is a critical part of the product formulation and must be capable of supporting high numbers of the intended microbe(s). It was found that Pseudomonas spp. can solubilize phosphate. Furthermore, conditions for best growth for both bacteria were determined as 30 % of waste beer. Peat was found as an appropriate carrier due to preservation of viable cells for 3 months at 0 &ordm / C, 20 &ordm / C and 30 &ordm / C. However, peat couldn&rsquo / t support high numbers of Pseudomonas spp. at 30 &ordm / C.

The work deals with the research of the influence of Free N bacterial preparations (contains selected strains of Azotobacter chroococcum) and Free PK (contains selected strains of Bacillus mulaginosus) and their combinations (Free N + Free PK) on the yield of apples during their intensive cultivation in the orchard. The research took place in 2018 in Agrosad Velké Bílovice on the cultivar 'Super chief', grown in medium-heavy soil and grown-up five-year-old trees. The following indicators were examined: the effect on the amount of five minerals in the fruit (nitrogen, phosphorus, calcium, potassium and magnesium). Comparison with the Control showed that bacterial preparations had no effect on increasing the amount of all five substances studied in fruit. Similarly, it was at examining the amount of titratable acids in fruit, the amount of soluble solids, the amount of vitamin C in the fruit, the strength of the fruit peel, and the antioxidant capacity of the peel and pulp of the fruit. Only with the antioxidant capacity of the fruit peel, Free N exceeded the Control, but the comparison was statistically inconclusive. Further indicators were investigated: the effect of bacterial preparations on average apple weight in t/ha, also on apples below and above 70 mm, on average weight of apples in (g) and number of apples on trees. The check was always on the second, third and last place in the impact indicators. The effect of microbial agents (Free N, Free PK, and their combination) was slightly higher than Control. However, the differences were statistically inconclusive.