Genome Size and Complexity in Azotobacter chroococcum

• Published in: Journal of general microbiology Vol. 130; no. 7; pp. 1603 - 1612
• Main Authors: ROBSON, ROBERT L, CHESSHYRE, JULIAN A, WHEELER, CARL, JONES, ROBERT, WOODLEY, PAUL R, POSTGATE, JOHN R
• Format: Journal Article
• Language: English
• Published: London Soc General Microbiol 01-07-1984; New York, NY Cambridge University Press
• Subjects: Azotobacter - genetics; Azotobacter chroococcum; Bacteriology; Biological and medical sciences; DNA Restriction Enzymes; DNA, Bacterial; Electrophoresis, Agar Gel; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Genetics; Microbiology; Plasmids; Plasmid; Electrophoresis; Azotobacter chroococcum; Genome; DNA; Size
• ISSN: 0022-1287; 1350-0872; 1465-2080
• DOI: 10.1099/00221287-130-7-1603

ARC Unit of Nitrogen Fixation, University of Sussex, Brighton BN1 9RQ, UK
ABSTRACT
All of eight strains of Azotobacter chroococcum examined contained between two and six plasmids ranging from 7 to > 200 MDal in size. Strain MCC-1, a derivative of NCIMB 8003, was cured of various of the four largest of its five plasmids and the phenotypes of the strains compared. All fixed nitrogen and exhibited uptake hydrogenase activity. No differences were observed in carbon source utilization or antibiotic, heavy metal or UV resistance. The genome sizes of two strains of A. chroococcum were determined by two-dimensional electrophoresis. Strain CW8, an isolate from local soil containing two small plasmids of 6 and 6·5 MDal contained unique DNA sequences equivalent to 1·78 x 10 6 (·20%) bp (1·2 x 10 9 Dal). In strain MCD-1, a derivative of MCC-1, containing a 190 MDal and 7 MDal plasmid, the genome size was 1·94 x 10 6 (·20%) bp. In exponential batch cultures, both contained 20 to 25 genome equivalents per cell. MCD-1 exhibited complex UV kill kinetics with a marked plateau of resistance; CW8 showed a simple response inconsistent with the possibility of organization of its DNA into identical chromosome copies capable of independent segregation.