Annals of Microbiology

, Volume 62, Issue 3, pp 897–904 | Cite as

Occurrence and genetic diversity of phosphate-solubilizing bacteria in soils of differing chemical characteristics in Kenya

  • Keziah W. Ndung’u-Magiroi
  • Laetitia Herrmann
  • John Robert Okalebo
  • Caleb O. Othieno
  • Pieter Pypers
  • Didier Lesueur
Original Article


This study focused on the isolation, identification (sequencing of 16S rDNA gene) and determination of the phosphorus (P)-solubilizing efficiency of native populations of phosphate-solubilizing bacteria (PSB) in 13 Kenyan soils with differing chemical characteristics. Air-dried soil samples were serially diluted and plated on NBRIP media and enumerated. Their phosphate-solubilizing efficiency was assessed on Frioni’s agar. Pearson correlation coefficients were determined between PSB populations and soil properties. The PSB populations varied among the sites tested and had a positive and significant correlation (p ≤ 0.05) with organic carbon (r = 0.76), exchangeable calcium (r = 0.93) and exchangeable magnesium (r = 0.92). A total of 150 isolates were identified to the genus and species level. Among the isolates, Bacillus megaterium, Bacillus sp. and Arthrobacter sp. were the most abundant and well-distributed strains. However, only 5% of the total isolates were efficient in terms of phosphate-solubilizing efficiency. The results indicate that although there were many PSB strains in the soils tested, only a few (5%) were effective in terms of their phosphate-solubilizing ability. It is therefore unlikely that native PSB contribute significantly to solubilizing phosphate in the soils tested, which would ultimately benefit plant growth. Therefore, inoculation with effective strains with a high P solubilization potential is necessary.


Frioni’s agar Phosphorus solubilization efficiency Microbial diversity Kenya 



The authors are grateful to the Bill and Melinda Gates Foundation for their financial support of this study through the commercial products project “COMPRO” coordinated by the Tropical Soil Biology and Fertility Institute of CIAT (TSBF–CIAT). We are also indebted to TSBF–CIAT for providing the laboratory facilities and chemicals for studies and to Leticia A. Fernández for provision of the reference strains.


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Copyright information

© Springer-Verlag and the University of Milan 2011

Authors and Affiliations

  • Keziah W. Ndung’u-Magiroi
    • 1
    • 2
    • 3
  • Laetitia Herrmann
    • 1
  • John Robert Okalebo
    • 3
  • Caleb O. Othieno
    • 3
  • Pieter Pypers
    • 1
  • Didier Lesueur
    • 1
    • 4
  1. 1.Tropical Soil Biology and Fertility Institute of CIAT (CIAT–TSBF)NairobiKenya
  2. 2.Kenya Agricultural Research Institute (KARI–Kitale)KitaleKenya
  3. 3.Department of Soil ScienceChepkoilel University College of Moi UniversityEldoretKenya
  4. 4.Ecologie Fonctionnelle & Biogéochimique des Sols & Agroécosystèmes (SupAgro-CIRAD-INRA-IRD)CIRAD, UMR Eco&SolsMontpellierFrance

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