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Appl Environ Microbiol. 1983 June; 45(6): 1914-1920
Copyright © 1983, American Society for Microbiology. All Rights Reserved.

Enumeration and Localization of N₂-Fixing Bacteria Associated with Roots of Spartina alterniflora Loisel

C. Robertson MCClung, Peter VAN Berkum, Robert E. Davis and Charles Sloger

¹ Department of Plant Pathology, Cook College, Rutgers-The State University of New Jersey, New Brunswick, New Jersey 08903; Agronomy Department, University of Maryland, College Park, Maryland 20742²; and Plant Virology Laboratory³ and Nitrogen Fixation and Soybean Genetics Laboratory, ⁴ Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705

ABSTRACT

Numbers and possible locations of N₂-fixing bacteria were investigated in roots of Spartina alterniflora Loisel, which support nitrogenase activity in the undisturbed native habitat. N₂-fixing bacteria were recovered in cultures both from S. alterniflora roots and from the surrounding sediment, and they formed a greater proportion of the bacteria recovered from root homogenates than from salt-marsh sediment. N₂-fixing bacteria were recovered in high numbers from the rhizoplane of S. alterniflora after roots were treated with 1 or 5% chloramine-T for 1 h or with 1% NaOCl for 1 or 2 h. Immersing S. alterniflora roots in 5% NaOCl for 1 h was more effective in distinguishing bacteria inside the roots since this treatment nearly eliminated N₂-fixing bacteria recoverable from the rhizoplane, although high numbers of N₂-fixing bacteria were recovered from homogenates of roots treated with 5% NaOCl for 1 h. However, this treatment was less effective with roots of Zea mays L. (Funks G4646) and Sorghum bicolor (L.) Moench (CK-60 A), indicating that techniques to surface sterilize roots should be evaluated for different plants. Bacteria were observed by light and electron microscopy inter- and intracellularly in the cortex and in the aerenchyma of S. alterniflora roots. This study clearly shows that bacteria, including N₂ fixers, colonize the interior of roots of S. alterniflora growing in a Chesapeake Bay, Maryland, salt marsh.

Present address: Department of Microbiology and Public Health, Michigan State University, East Lansing, MI 48824.

Mailing address: Nitrogen Fixation and Soybean Genetics Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705.

This article has been cited by other articles:

• Bagwell, C. E., Lovell, C. R. (2000). Persistence of Selected Spartina alterniflora Rhizoplane Diazotrophs Exposed to Natural and Manipulated Environmental Variability. Appl. Environ. Microbiol. 66: 4625-4633 [Abstract] [Full Text]  
• Bagwell, C. E., Piceno, Y. M., Ashburne-Lucas, A., Lovell, C. R. (1998). Physiological Diversity of the Rhizosphere Diazotroph Assemblages of Selected Salt Marsh Grasses. Appl. Environ. Microbiol. 64: 4276-4282 [Abstract] [Full Text]