Survival of Azospirillum brasilense in the bulk soil and rhizosphere of 23 soil types

• Published in: Applied and Environmental Microbiology 1995-05, Vol.61 (5), p.1938-1945
• Main Authors: Bashan, Y. (The Center for Biological Research, La Paz, Mexico.), Puente, M.E, Rodriguez-Mendoza, M.N, Toledo, G, Holguin, G, Ferrera-Cerrato, R, Pedrin, S
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; AZOSPIRILLUM; Azospirillum brasilense; Bacteria; Biochemistry and biology; Biological and medical sciences; Biology; Chemical, physicochemical, biochemical and biological properties; CHIMIE DU SOL; Flowers & plants; Fundamental and applied biological sciences. Psychology; ISRAEL; LYCOPERSICON ESCULENTUM; MEXICO; MEXIQUE; Microbial ecology; Microbiology; Physics, chemistry, biochemistry and biology of agricultural and forest soils; QUIMICA DEL SUELO; RHIZOSPHERE; RIZOSFERA; Soil; Soil science; Soils; SOL DE MONTAGNE; SOL DE ZONE ARIDE; SOL TROPICAL; SUELO ARIDO; SUELO DE MONTANA; SUELO TROPICAL; SUPERVIVENCIA; SURVIE; TRITICUM AESTIVUM
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.61.5.1938-1945.1995

The survival of Azospirillum brasilense Cd and Sp-245 in the rhizosphere of wheat and tomato plants and in 23 types of plant-free sterilized soils obtained from a wide range of environments in Israel and Mexico was evaluated. Large numbers of A. brasilense cells were detected in all the rhizospheres tested, regardless of soil type, bacterial strain, the origin of the soil, or the amount of rainfall each soil type received prior to sampling. Survival of A. brasilense in soils without plants differed from that in the rhizosphere and was mainly related to the geographical origin of the soil. In Israeli soils from arid, semiarid, or mountain regions, viability of A. brasilense rapidly declined or populations completely disappeared below detectable levels within 35 days after inoculation. In contrast, populations in the arid soils of Baja California Sur, Mexico, remained stable or even increased during the 45-day period after inoculation. In soils from Central Mexico, viability slowly decreased with time. In all soils, percentages of clay, nitrogen, organic matter, and water-holding capacity were positively correlated with bacterial viability. High percentages of CaCO3 and fine or rough sand had a highly negative effect on viability. The percentage of silt, pH, the percentage of phosphorus or potassium, electrical conductivity, and C/N ratio had no apparent effect on bacterial viability in the soil. Fifteen days after removal of inoculated plants, the remaining bacterial population in the three soil types tested began to decline sharply, reaching undetectable levels 90 days after inoculation. After plant removal, percolating the soils with water almost eliminated the A. brasilense population. Viability of A brasilense in two artificial soils containing the same major soil components as the natural soils from Israel did was almost identical to that in the natural soils. We conclude that A. brasilense is a rhizosphere colonizer which survives poorly in most soils