Evaluation of Spectinomycin Resistance as a Marker for Ecological Studies with Rhizobium spp.

Abstract

ABSTRACT. Resistance to the antibiotic spectinomycin has been examined as a possible marker to supplement streptomycin resistance in ecological or genetic studies with rhizobia. Single step spontaneous mutants resistant to high levels of spectinomycin were isolated from 8 effective strains representing 4 species of Rhizobium. There was no evidence of cross resistance to streptomycin, and streptomycin resistant mutants were not cross resistant to spectinomycin. Minor changes in antigenic characteristics examined by immunodiffusion in agar were detected for mutants from 2 strains but these variants were still identifiable with the parent strains. Partial or full loss of symbiotic effectiveness occurred in only c. 20% of the spectinomycin resistant mutants and the resistance marker was unchanged through one plant passage. It is concluded that spectinomycin resistant mutants properly evaluated for possible pleiolropic effects should provide a useful marker system for use alone or in combination with streptomycin resistance in Rhizobium.

Rhizobiumhost-range extension by introduction ofRhizobium trifolii nodGenes

“…trifolii A TCC 14480 were kindly supplied by the late Prof. Maruyama (The University of Tokyo) and Dr. Garno (Institute of Agrobiological Resources), respectively. Rhizobium fredii USDAI91 Kas r , USDAI92 Kas r , and USDAI93 Kas r , which are resistant to 1,000 mg L -1 kasugamycin, were derived from the parent strains USDAI91, USDAI92, and USDAI93 by the method of Schwinghamer and Dudman (1973). E. coli HB101 and K802 were grown in TY (Beringer 1974) medium.…”

Characterization of Diversity of Bradyrhizobia on Cowpea in Iraq Reveals Unusual Strain Characteristics

“…Resistance of a rhizobial strain to a particular antibiotic is a useful marker (Schwinghamer and Dudman, 1973;Pankhurst, 1977;Beynon and Josey, 1980;Turco et al, 1986). It is important that antibiotic-resistant strains that are selected for inoculation experiments have not lost their infectiveness (i.e.…”

Characterization of Bradyrhizobium japonicum serocluster 123 member isolates native to Iowa soils

“…Antoun (1982) questioned the reliability of genetically marked, resistant mutants for symbiotic properties when used to study rhizobial ecology. Schwinghamer and Dudman (1973) reported no change in the Ngfixation effectiveness of antibiotic-resistant mutants of…”

“…Antibiotic resistance is one method that enables the recovery of the introduced strain from a sterile or non-sterile environment. The use of bacterial strains resistant to high levels of antibiotics to study rhizobial ecology was demonstrated by Danso et al (1973), Dudman (1973), andPankhurst (1977).…”

“…Schwinghamer and Dudman (1973) reported that the frequency of isolation of rhizobial mutants, resistant to 250 ^g/mL of streptomycin, was very low, but that this intrinsic resistance was genetically encoded and was a stable trait in four B_^ iaponicum strains tested.…”