Presence Of Various Nitrogen Sources Research Articles

Spontaneous Super-Swarming Derivatives of Azospirillum brasilense Sp245 have Different DNA Profiles and Behavior in the Presence of Various Nitrogen Sources

Azospirillum brasilense swims in liquid environments and swarms in semisolid media. Five variants of A. brasilense Sp245, Sp245.P1-Sp245.P5, which swarmed faster than Sp245 in a semisolid malate-salt medium, have been isolated. In Sp245.P1-Sp245.P4, a new megaplasmid was revealed instead of an indigenous 85-MDa plasmid (p85). By polymerase chain reactions (PCR) with primers to the segments of p85 important for proper bacterial motility/flagellation and for dissimilatory nitrite and NO reduction, that DNA of p85 was found retained by all the variants. In ERIC- and RAPD-PCR, microdiversity between the total DNAs of Sp245 and its variants was detected. Interstrain differences in growth characteristics in liquid peptone-succinate-salt medium with KNO3 or KNO2 and in KNO2 production/consumption were revealed. Although all the variants swam and swarmed faster than Sp245 in the medium supplemented with NH4Cl or KNO3, not all of them could do so in MPSS with KNO2.

Production of intracellular β-xylosidase from the submerged fermentation of citrus wastes by Penicillium janthinellum MTCC 10889.

Production of intracellular β-xylosidase was studied in cultures of Penicillium janthinellum grown on citrus fruit waste supplemented cultivation media. Both dried orange peel and sweet lime peel could induce the production of this enzyme. The working strain showed a pronounced optimum pH and temperature for β-xylosidase production at 6.0 and 27 °C, respectively. The enzyme production was found to remain stable for a long period of 120 h. Orange peel and sweet lime peel showed different responses in the presence of various nitrogen sources, probably due to their differences in hemicellulosic contents. This could be further confirmed by the difference in enzyme production after pretreatment with acid and alkali.

Hemagglutinating activity and motility of the bacterium Azospirillum brasilense in the presence of various nitrogen sources

Hemagglutinating activity of the Azospirillum brasilense strain Sp245 grown in liquid media and the swarming motility of those bacteria grown in semisolid media vary significantly depending on the nitrogen source. In media with nitrate or nitrite, an increase in the hemagglutinating activity and a decrease in the swarming circles’ diameter of Sp245 were observed, compared to bacteria grown in the presence of ammonium or N2. A ∼67-kDa hemagglutinin exhibiting affinity to the O-specific polysaccharide, an acidic D-rhamnan (OPS-I), was isolated from the surface of Sp245 cells. Introduction of the hemagglutinin into the media resulted in a decrease in the Sp245 cell motility while not affecting its mutants lacking the acidic D-rhamnan or the Sp245.5 mutant with a different OPS structure. Cells of strain Sp245.5 demonstrated hemagglutinating activity two times higher than that of the parent Sp245 strain and formed “diffuse” colonies, rather than distinct swarming circles Sp245 formed when grown in a semisolid medium. The data obtained demonstrate that intercellular contacts mediated by the interaction between the surface hemagglutinin and OPS-I, which is sensitive to environmental factors, affect the collective motility of cells.

Ultrastructure of the fresh water cyanobacterium Anabaena variabilis SPU 003 and its application for oxygen-free hydrogen production.

Photoproduction of hydrogen has been studied as one of the ways to produce a clean, renewable energy source. Ultrastructure of the selected strain Anabaena variabilis SPU 003, a heterocystous cyanobacterium, has been done to understand the cell structure. The organism was found to be essentially a dark hydrogen producer. While pH had no significant effect on hydrogen production, optimum temperature was found to be 30 degrees C. Various sugars increased the production of hydrogen while the presence of various nitrogen sources inhibits the production. The production of hydrogen is highly sensitive to salinity and micronutrients.

Ultrastructure of the fresh water cyanobacterium Anabaena variabilis SPU 003 and its application for oxygen-free hydrogen production

Photoproduction of hydrogen has been studied as one of the ways to produce a clean, renewable energy source. Ultrastructure of the selected strain Anabaena variabilis SPU 003, a heterocystous cyanobacterium, has been done to understand the cell structure. The organism was found to be essentially a dark hydrogen producer. While pH had no significant effect on hydrogen production, optimum temperature was found to be 30°C. Various sugars increased the production of hydrogen while the presence of various nitrogen sources inhibits the production. The production of hydrogen is highly sensitive to salinity and micronutrients.

Regulation of expression of GLT1, the gene encoding glutamate synthase in Saccharomyces cerevisiae.

Saccharomyces cerevisiae glutamate synthase (GOGAT) is an oligomeric enzyme composed of three 199-kDa identical subunits encoded by GLT1. In this work, we analyzed GLT1 transcriptional regulation. GLT1-lacZ fusions were prepared and GLT1 expression was determined in a GDH1 wild-type strain and in a gdh1 mutant derivative grown in the presence of various nitrogen sources. Null mutants impaired in GCN4, GLN3, GAT1/NIL1, or UGA43/DAL80 were transformed with a GLT1-lacZ fusion to determine whether the above-mentioned transcriptional factors had a role in GLT1 expression. A collection of increasingly larger 5' deletion derivatives of the GLT1 promoter was constructed to identify DNA sequences that could be involved in GLT1 transcriptional regulation. The effect of the lack of GCN4, GLN3, or GAT1/NIL1 was also tested in the pertinent 5' deletion derivatives. Our results indicate that (i) GLT1 expression is negatively modulated by glutamate-mediated repression and positively regulated by Gln3p- and Gcn4p-dependent transcriptional activation; (ii) two cis-acting elements, a CGGN15CCG palindrome and an imperfect poly(dA-dT), are present and could play a role in GLT1 transcriptional activation; and (iii) GLT1 expression is moderately regulated by GCN4 under amino acid deprivation. Our results suggest that in a wild-type strain grown on ammonium, GOGAT constitutes an ancillary pathway for glutamate biosynthesis.