The Family Azotobacteraceae

Abstract

A German zoologist, Ernst Haeckel, coined and defined a new branch of biology, "Oekologie," in 1866 (Egerton 2013). In the later 1800s, four ecological sciences emerged: (terrestrial) plant ecology, (terrestrial) animal ecology, limnology, and marine biology. Plant ecology evolved out of phytogeography and physiology (Billings 1985:5-6), to which was added during the 1890s investigations of plant communities and vegetation succession. Physiology was important, but played a relatively passive role: its significance often depending on how well phytogeographers understood it. European botanists and publications led the way. Phytopathology during the 1800s is discussed in part 44 (Egerton 2012) and omitted here. For phytopathology during the early 1900s, see G. C. Ainsworth, Introduction to the History of Plant Pathology (1981) and C. L. Campbell et al., The Formative Years of Plant Pathology in the United States (1999:225-339). The history of aquatic plant ecology is part of limnology and marine ecology and will be discussed in parts 50 and 51. The ecology of lichens is deferred to part 52 on the history of symbiosis studies. After these exclusions, the remaining plant ecology, about 1870 to mid-1920s, is still vast in scope and detail, and surveys by

Characterization of free nitrogen fixing bacteria of the genus Azotobacter in organic vegetable-grown Colombian soils

“…The primary isolation was made using the grain soil technique (Figure 1A) according to the methodology previously described by Aquilanti et al . (1) and Becking (4) in Ashby-Sucrose agar (Agar 1.5%, Sucrose 0.5%, CaCO 3 0.5%, MgSO 4 0.02%, NaCl 0.02%, KH 2 PO 4 0.02%, FeSO 4 0.0005%). Plates were incubated at 28°C for 7 days until observing sticky and glistening colonies around grains (Figure 1F).…”

“…The genus Azotobacter belongs to the γ-subclass of the Proteobacteria (4, 34) and comprises seven species: A. chroococcum, A. vinelandü, A. beijerinckii, A. paspali, A. armeniacus, A. nigricans and A. salinestri . In 2005 séquences of 16S rDNA were identified that corresponded to a new endemic soil species from Thailand (unpublished data).…”

“…In 2005 séquences of 16S rDNA were identified that corresponded to a new endemic soil species from Thailand (unpublished data). Azotobacter are heterotrophic and aerobic bacteria and their main property is the ability to fix nitrogen non-symbiotically, with a genomic content of G-C of 63–67.5 % (T m ) (4, 32), and distributed in soils, water and sediments (35, 36). Their agronomic importance is due to the capability of synthesizing antibiotics, plant growth promotion substances (21, 24, 25, 30), vitamins, exopolysaccharides and pigment production (8, 28), besides their antagonist effect against pathogens (33).…”

“…For that reason, in the last years authors like Aquilanti et al . (1, 2), and Becking (4), among others, justify the use of molecular techniques and bioinformatics tools allowing fast identification and characterization. This interest is focused towards the validation of fast and reliable molecular methodologies for quality control on agricultural biofertilizers.…”

Isolation and Molecular Characterization of Heavy Metal-ResistantAzotobacter chroococcumfrom Agricultural Soil and Their Potential Application in Bioremediation

“…The genus Azotobacter comprises large, Gram-negative bacteria, mainly found in neutral to alkaline soils, where they constitute a major fraction of the free-living N 2 -fixing population that contributes to nitrogen cycling in the biosphere (Tchan and New 1984). Azotobacter is able to colonize the rhizosphere and root surfaces of many agronomically important plants and establishes nonendosymbiotic root associations that lead to plant growth promotion (Becking 1981), fix nitrogen (Pandey et al 1998), and secrete stimulating hormones, like gibberellins, auxins and cytokinins (Gonzales-Lopez et al 1991). The soil microbial population is under tremendous pressure due to contamination of soil by a variety of toxic substances such as heavy metals, pesticides, and other organic pollutants of wastewater, sewage sludge and environmental origin (Chaudhary et al 1996).…”