Contribution of Cytophaga-Like Bacteria to the Potential of Turnover of Carbon, Nitrogen, and Phosphorus by Bacteria in the Rhizosphere of Barley (Hordeum vulgare L.)

• Published in: Microbial ecology Vol. 43; no. 3; pp. 298 - 306
• Main Authors: JOHANSEN, J. E, BINNERUP, S. J
• Format: Journal Article
• Language: English
• Published: New York, NY Springer-Verlag New York Inc 01.04.2002; Springer
• Subjects: Acid soils; Agricultural soils; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Bacteria; Barley; Biological and medical sciences; Carbon - metabolism; Classification; Cold soils; Cytophaga - physiology; Economic plant physiology; Enzyme Induction; Enzymes; Fundamental and applied biological sciences. Psychology; Hordeum - microbiology; Microbial ecology; Nitrogen - metabolism; Phosphorus - metabolism; Plant Roots - microbiology; Population Dynamics; Rhizosphere; Seasons; Soil bacteria; Soil enzymes; Soil Microbiology; Soil microorganisms; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Various environments (extraatmospheric space, air, water); Barley; Monocotyledones; Cold; Hordeum vulgare; Organic soil; Phosphorus; Nitrogen; Carbon; Substrate; Extracts; Rhizosphere; Cytophagaceae; Gramineae; Angiospermae; Turnover; Bacteria; Nutrient; Spermatophyta; Cytophagales; Cytophaga
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-002-2006-z

The functional potential of bacteria isolated from the rhizosphere of barley (Hordeum vulgare L.) in May, July, and August and cultivated on nutrient-rich substrate (1/10 TSBA) and nutrient-poor substrate (cold soil extract agar) was determined. There was no significant difference in numbers of CFU when counted on nutrient rich or poor substrate. Bacterial numbers increased approximately 3-fold in the rhizosphere soil from May to August but was unchanged in bulk soil over the same period. A total of 4474 randomly isolated bacteria were screened for enzymatic activities involved in carbon turnover (amylase, cellulase, mannanase, xylanase, and chitinase), nitrogen turnover (protease, nitrate and nitrite reductase), and phosphate turnover (phosphatase). In the rhizosphere soil, bacteria carrying C and P turnover enzymes were not stimulated by the growing plant whereas protease and nitrate and nitrite reductase were stimulated by the growing plant. No changes were observed in the bulk soil. Two taxonomic groups were followed: Cytophaga-like bacteria (CLB) and fluorescent pseudomonads, the latter being abundant in the rhizosphere and important contributors to the cycling of organic matter in soil. Unexpectedly in the spring samples, CLB were around 25% of all bacteria isolated, whereas fluorescent pseudomonads made up less than 10%. The relative proportion of these bacterial groups then decreased during the plant growth season but at all times showing a clear rhizosphere effect. Furthermore, up to 70% of the isolates carrying enzymes involved in the turnover of carbon, in the May sample, were identified as CLB, indicating the importance of this group in early colonization of the rhizosphere. The fluorescent pseudomonad group contributed less than 3%.