Genome size and developmental complexity

Haploid genome size (C-value) is correlated positively with cell size, and negatively with cell division rate, in a variety of taxa. Because these associations are causative, genome size has the potential to impact (and in turn, be influenced by) organism-level characters affected by variation in either of these cell-level parameters. One such organismal feature is development. Developmental rate, in particular, has been associated with genome size in numerous plant, vertebrate, and invertebrate groups. However, rate is only one side of the developmental coin; the other important component is complexity. When developmental complexity is held essentially constant, as among many plants, developmental rate is the visibly relevant parameter. In this case, genome size can impose thresholds on developmental lifestyle (and vice versa), as among annual versus perennial plants. When developmental rate is constrained (as during time-limited amphibian metamorphosis), complexity becomes the notable variable. An appreciation for this rate-complexity interaction has so far been lacking, but is essential for an understanding of the relationships between genome size and development. Moreover, such an expanded view may help to explain patterns of variation in taxa as diverse as insects and fish. In each case, a hierarchical approach is necessary which recognizes the complex interaction of evolutionary processes operating at several levels of biological organization.     

Nitrite uptake in Azotobacter chroococcum

Nitrite uptake is made up of two components in Azotobacter chroococcum, a passive diffusion, presumably of nitrous acid, and an active transport of nitrite which uses the nitrate transport system. Only the active component is under regulatory control.     

Azotobacter Genomes: The Genome of Azotobacter chroococcum NCIMB 8003 (ATCC 4412)

The genome of the soil-dwelling heterotrophic N₂-fixing Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 (ATCC 4412) (Ac-8003) has been determined. It consists of 7 circular replicons totalling 5,192,291 bp comprising a circular chromosome of 4,591,803 bp and six plasmids pAcX50a, b, c, d, e, f of 10,435 bp, 13,852, 62,783, 69,713, 132,724, and 311,724 bp respectively. The chromosome has a G+C content of 66.27% and the six plasmids have G+C contents of 58.1, 55.3, 56.7, 59.2, 61.9, and 62.6% respectively. The methylome has also been determined and 5 methylation motifs have been identified. The genome also contains a very high number of transposase/inactivated transposase genes from at least 12 of the 17 recognised insertion sequence families. The Ac-8003 genome has been compared with that of Azotobacter vinelandii ATCC BAA-1303 (Av-DJ), a derivative of strain O, the only other member of the Azotobacteraceae determined so far which has a single chromosome of 5,365,318 bp and no plasmids. The chromosomes show significant stretches of synteny throughout but also reveal a history of many deletion/insertion events. The Ac-8003 genome encodes 4628 predicted protein-encoding genes of which 568 (12.2%) are plasmid borne. 3048 (65%) of these show > 85% identity to the 5050 protein-encoding genes identified in Av-DJ, and of these 99 are plasmid-borne. The core biosynthetic and metabolic pathways and macromolecular architectures and machineries of these organisms appear largely conserved including genes for CO-dehydrogenase, formate dehydrogenase and a soluble NiFe-hydrogenase. The genetic bases for many of the detailed phenotypic differences reported for these organisms have also been identified. Also many other potential phenotypic differences have been uncovered. Properties endowed by the plasmids are described including the presence of an entire aerobic corrin synthesis pathway in pAcX50f and the presence of genes for retro-conjugation in pAcX50c. All these findings are related to the potentially different environmental niches from which these organisms were isolated and to emerging theories about how microbes contribute to their communities.     

Sodium-Dependent Growth of Azotobacter chroococcum

Selected ion-monitoring gas chromatography-mass spectrometry was used for detection of beta-hydroxy fatty acids as an independent assay for the presence or absence of endotoxin in materials claimed to induce nonspecific activation of Limulus amoebocyte lysate. To this end, suspensions of gram-negative and -positive bacteria, one fungal species, cerebrospinal fluid, and hollow-fiber hemodialyzer rinses were assayed for endotoxin by gas chromatography-mass spectrometry and the Limulus amoebocyte lysate assay. Good qualitative agreement was shown for both methods when suspensions of test organisms were assayed. Two false-negative results were obtained by gas chromatography-mass spectrometry assays of cerebrospinal fluid and were shown to be a result of insufficient endotoxin in the cerebrospinal fluid specimens for detection by gas chromatography-mass spectrometry. Hemodialyzer rinses were Limulus assay positive; however, no beta-hydroxy fatty acids were detected by gas chromatography-mass spectrometry. These data were compared with data obtained from USP rabbit pyrogen tests of the rinse materials (nonpyrogenic) and chemical characterization of the Limulus assay-reactive rinses, which showed the rinses to be cellulosic in nature. It is suggested that beta-hydroxy fatty acids, as assayed by selected ion-monitoring gas chromatography-mass spectrometry, be used as chemical marker molecules for the presence or absence of endotoxin in materials reported to cause nonspecific activation of Limulus amoebocyte lysate.     

Nitrate permease from Azotobacter chroococcum

Active transport systems in bacteria can be divided into two groups: those that are osmotic shock-resistant with one single membrane protein, and those that are shock-sensitive and have a membrane-bound protein complex plus a soluble periplasmic protein. Whether the bacterial assimilatory nitrate transport falls into the one or the other of these two groups has not been studied before. We report that nitrate uptake by the strictly aerobic, N₂-fixing heterotrophic bacterium Azotobacter chroococcum is sensitive to osmotic shock. The polypeptide composition of cytoplasmic membranes changes in response to the nitrogen source available to the cells. Incorporation of [³⁵S]-methionine into proteins as well as use of the A. chroococcum TRI mutant, which is defective in nitrate transport, and the A. choococcum MCD1 strain, a mutant unable to use nitrate as a nitrogen source, suggest that nitrate transport into A. chroococcum cells is mediated by a multicomponent system tightly bound to the cytoplasmic membrane.     

Regulation of Azotobacter chroococcum invertase

Synthesis of the Azotobacter chroococcum invertase was found to be dependent on sucrose or raffinose in the growth medium. The activity of this invertase was slightly inhibited by glucose. Fructose, which by itself did not affect the enzyme activity, protected invertase from glucose inhibition. Per cent residual activity plotted against glucose concentration, and Hill plot indicated that this monosaccharide binds to one interacting site of the enzyme. The results show that regulation of this prokaryotic enzyme clearly differs from that of eukaryotic orgnisms.     

Sodium-Dependent Growth of Azotobacter chroococcum

Selected ion-monitoring gas chromatography-mass spectrometry was used for detection of beta-hydroxy fatty acids as an independent assay for the presence or absence of endotoxin in materials claimed to induce nonspecific activation of Limulus amoebocyte lysate. To this end, suspensions of gram-negative and -positive bacteria, one fungal species, cerebrospinal fluid, and hollow-fiber hemodialyzer rinses were assayed for endotoxin by gas chromatography-mass spectrometry and the Limulus amoebocyte lysate assay. Good qualitative agreement was shown for both methods when suspensions of test organisms were assayed. Two false-negative results were obtained by gas chromatography-mass spectrometry assays of cerebrospinal fluid and were shown to be a result of insufficient endotoxin in the cerebrospinal fluid specimens for detection by gas chromatography-mass spectrometry. Hemodialyzer rinses were Limulus assay positive; however, no beta-hydroxy fatty acids were detected by gas chromatography-mass spectrometry. These data were compared with data obtained from USP rabbit pyrogen tests of the rinse materials (nonpyrogenic) and chemical characterization of the Limulus assay-reactive rinses, which showed the rinses to be cellulosic in nature. It is suggested that beta-hydroxy fatty acids, as assayed by selected ion-monitoring gas chromatography-mass spectrometry, be used as chemical marker molecules for the presence or absence of endotoxin in materials reported to cause nonspecific activation of Limulus amoebocyte lysate.     

Reduction of Nitrates by Azotobacter indicum and Azotobacter chroococcum Cultures

The capacity for denitrification was studied in Azotobacter bacteria, which are free-living nitrogen-fixing obligatory aerobes. Data on nitrate reduction to nitrites and nitric oxide by A. indicum under anaerobic conditions were obtained for the first time for genus Azotobacter.     

Zur Kenntnis des Stoffwechselmechanismus in Azotobacter chroococcum

Ohne Zusammenfassung     

Reduction of nitrates by cultures of Azotobacter indicum and Azotobacter chroococcum

The capacity for denitrification was studied in Azotobacter bacteria, which are free-living nitrogen-fixing obligatory aerobes. Data on the nitrate reduction to nitrites and nitric oxide by A. indicum under anaerobic conditions were obtained for the first time for genus Azotobacter.     

Nature and role of plasmids in Azotobacter chroococcum

Summary Heavy metal, antibiotic resistance and hydrocarbon utilization properties were studied inAzotobactor chroococcum to investigate the nature and role of plasmids in different soil isolates. There is wide prevalence of heavy metal resistance, antibiotic resistance and utilization of hydrocarbons; the heavy metal resistance property seems to be conferred by plasmids.