Azotobacter

Abstract

A.zo.to.bac' ter . Fr. n. azote nitrogen; M.L. masc. n. bacter the equivalent of Gr. neut. n. bactrum a rod or staff; M.L. masc. n. Azotobacter a nitrogen rod. Proteobacteria / Gammaproteobacteria / Pseudomonadales / Pseudomonadaceae / Azotobacter Cells range from straight rods with rounded ends to more ellipsoidal or coccoid , depending on the culture medium and age. Cells are up to 2 μm or more in diameter and 4 μm in length . A. paspali cells are usually longer, 5–10 µm in length, and can be filamentous, up to 60 µm long. Cells are usually single but may occur in pairs, irregular clumps (especially with A. paspali ), or, more rarely, in chains of varying length. Encystment occurs during late stationary phase at low frequency or at high frequency after culturing on butanol. Motile with peritrichous flagella or nonmotile. Aerobic, having a strictly respiratory type of metabolism with oxygen as the terminal electron acceptor. Nitrogen is fixed under microaerobic conditions (2% oxygen), under full aerobiosis, or after adaptation in hyperbaric oxygen. N 2 fixation uses Mo‐, V‐, or Fe‐containing nitrogenase enzymes, depending on the environmental metal supply. Water‐soluble and water‐insoluble pigments are produced by some strains of all species . Growth is heterotrophic; sugars, alcohols, and salts of organic acids are used as carbon sources. Ammonium salts, nitrate, and urea are used as sources of fixed nitrogen. Very few amino acids are used, probably due to a general deficiency in amino acid transport. The minimum pH for growth in the presence of fixed nitrogen sources ranges from 4.8 to 6.0 with maximum pH 8.5. The optimum pH for diazotrophic growth is 7.0–7.5. Most isolates are from soil, but a few are from water . One species ( A. paspali ) has been isolated only from roots of the tropical grass Paspalum notatum . The mol % G + C of the DNA is : 63.2–67.5. Type species : Azotobacter chroococcum Beijerinck 1901, 567.

Pseudomonas kirkiae sp. nov., a novel species isolated from oak in the United Kingdom, and phylogenetic considerations of the genera Pseudomonas, Azotobacter and Azomonas

“…Bacteriol ., 1981, 31, 215–218), the classification of Azorhizophilus paspasli [46] is not widely accepted. Consequently, the species was included under the genus Azotobacter as its basonym in the 2005 edition of Bergey’s Manual of Systematics of Archaea and Bacteria [47].…”

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

“…chroococcum have led to fundamental advances in the understanding of the physiology, biochemistry and genetics of N 2 -fixation and H 2 metabolism. Extensive reviews of aspects of the family Azotobacteraceae have been published [13, 14, 15]. …”

Expression of the sRNAs CrcZ and CrcY modulate the strength of carbon catabolite repression under diazotrophic or non-diazotrophic growing conditions in Azotobacter vinelandii

“…Due to the polyploid nature of A . vinelandii [2], the segregation of the generated mutation to all chromosomal copies (and the absence of wild type alleles) was confirmed by PCR. Only one confirmed mutant was chosen for further studies.…”

“…The genus Azotobacter is characterized by its ability to develop a differentiation process under adverse growth conditions. This process culminates in the formation of cysts, which are dormant cells resistant to desiccation [1, 2]. Azotobacter has a strict aerobic metabolism and is characterized by its capacity to fix atmospheric nitrogen to ammonia under aerobic conditions, with the simultaneous protection of the nitrogenase from oxygen inactivation [2].…”

“…vinelandii is a chemo-organotrophic bacterium, that is, it can use many carbohydrates, alcohols and salts of organic acids for growth. However, it is unable to grow using amino acids as the sole carbon source [2]. A .…”