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Azotobacter vinelandii
Azotobacter vinelandii is a free-living, Gram-negative soil bacterium. Cells range in shape from rods to coccoid. For bacteria, cells of A. vinelandii are relatively large in size. Large cell size correlates with high DNA content. Cells are usually motile. Under certain conditions, cells undergo encystment. Capsule production is also common in most strains. Pigment production is a common feature of the Azotobacter genus, but A. vinelandii excretes a unique fluorescent pigment. A. vinelandii exhibits chemoheterotrophic growth. Organisms of this species utilize various sugars and alcohols as carbon sources and ammonium, nitrate and urea as sources of nitrogen. A. vinelandii respires aerobically using different organic compounds as electron donors. This species is known to have the highest respiratory rate of all bacteria. The distinguishing characteristic of the genus is their ability to fix atmospheric nitrogen under aerobic or microaerobic conditions. In A. vinelandii, conversion of N2 to ammonia is catalyzed by 1 of 3 distinct, O2-sensitive nitrogenase enzymes. Many different mechanisms and features unique to A. vinelandii work together to carry out this paradoxical diazotrophic growth, including regulatinbg oxygen consumption rates in order to keep the cytoplasmic O2 concentration low. Phylogenetic analysis reveals A. vindelandii is closely related to pseudomonads.

Isolation & enrichment
A. vindelandii was discovered by Lipman in 1903. The organism was isolated from soils in Vineland, New Jersey. . general habitats... enrichment...

Growth/culutral characteristics
Optimal growth pH is 7.0-7.5. Incubation at 37°C in N-free media favors growth of A. vinelandii

Pigments
A. vinelandii can be distinguished from other Azotobacter species upon comparison of differential pigment production. Colonies of A. vinelandii excrete yellow-green, green, or red-violet fluorescent pigments, especially under iron-limiting conditions. These water-soluble pigments diffuse into the agar and cause a color change of the medium.

Metabolism
The ability of A. vindelandii to utilize phenol and rhamnose as sole carbon sources is a distintinguishing characteristic of the species.

nitrogenases
1. molybdenum nitrogenase 2. vanadium nitrogenase 3. iron-only nitrogenase

respiratory protection mechanisms
1. Respiratory proteins: terminal oxidases --> high oxygen consumption (fastest resp rates); ATP synthases --> high cellular levels [ATP]; 2. FeSII-Shenthna protein --> "conformational protection" : forms protective complex with nitrogenase enzyme 3. alginate capsule --> keeps cytoplasm anaerobic: physical O2 diffusion barrier

Morphology
Azotobacter vinelandii are Gram-negative bacteria. The cells of A. vinelandii are realtively large in size; mean cell dimensions are 1.6 -2.5 μm wide by 3-5 μm long. Cells vary from rods to coccoid in shape and can occur singly or in pairs.

Externmal cell wall components
Aside from a few rare nonmotile strains, A. vinelandii cells are motile by means of peritrichous flagella. One strain, A. vinelandii OP, has been measured moving at speeds of 74 μm per second. Chemotaxis...

Capsules/S-layer
PHB deposits serve as carbon and energy reserves.

Genomics
Genomic characteristics vary between different strains in the species. By summing the lengths of restriction fragments found in two separate enzyme digestions, the genome size of A. vinelandii UW was determined to be 4.57 Mb. In addition, six copies of the rrn operon were found to be present. Complete genomic sequencing of A. vinelandii DJ revealed a single circular chromosome with a length of 5,365,318 base pairs. The genome was sequenced using a shotgun sequencing approach. Assembling the genome entailed aligning sequences to optical map generated using restriction enzymes. The molecular guanine to cytosine ratio, as determined in Tm experiments, is 65.7%. A total of 5,051 protein-coding genes exist in the chromosome of this particular strain. high, variable # of chromosomes; up to 80 copies per cell.

Plasmids, ranging in size from 9 to 52 MDa, were found in four lab strains and two isolates of A. vinelandii.

Taxonomy and Phylogeny
The genus name Azotobacter is derived from two Latin nouns: azotum, meaning nitrogen and bacter, meaning rod. The species name, vinelandii, is a derivation of the location where the species was first isolated, Vineland, New Jersey.

P. stutzeri P. aeurginosa

Applications
alginate and PHB cynthesis