Competition for nodulation of field-grown soybeans by strains of Rhizobium fredii

1986 ◽  
Vol 32 (2) ◽  
pp. 183-186 ◽  
Author(s):  
Thomas J. McLoughlin ◽  
Scott G. Alt ◽  
P. Ann Owens ◽  
Corrine Fetherston
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Indigenous Population ◽  
Growing Season ◽  
Indigenous Populations ◽  
First Year ◽  
Antibiotic Resistant ◽  
Rhizobium Fredii ◽  
Glycine Max L ◽  
Resistant Mutants ◽  
Antibiotic Resistant Mutants

Nodulation of Glycine max (L) Merr. by six Rhizobium fredii strains was measured in two Midwestern fields containing high indigenous populations of Bradyrhizobium japonicum (3 × 105/gm soil). The soils were inoculated with antibiotic-resistant mutants using liquid inoculum at two levels on soybean cv. Peking and cv. Jacques 130. Strain establishment was measured 40 days after planting. In the first year, USDA206, USDA217, and USDA257 were the most competitive strains, occupying greater than 50% of the nodules on cv. Peking in both soils. None of the strains were competitive on Jacques 130. In the second growing season, all nodules were formed by the indigenous population on both cultivars, suggesting that these fast-growing strains do not persist in Midwestern soils.

Using spontaneous antibiotic-resistant mutants to assess competitiveness of bradyrhizobial inoculants for nodulation of soybean

1998 ◽  
Vol 44 (8) ◽  
pp. 753-758 ◽  
Author(s):  
Martha E Ramirez ◽  
Daniel W Israel ◽  
Arthur G Wollum II
Keyword(s):  
Parental Strain ◽  
Field Experiments ◽  
Antibiotic Resistant ◽  
Rooting Zone ◽  
Soil Systems ◽  
Yeast Extract Mannitol ◽  
Soil Media ◽  
Resistant Mutants ◽  
Cape Fear ◽  
Antibiotic Resistant Mutants

Spontaneous mutants (3/parental strain) of soybean bradyrhizobia resistant to streptomycin and erythromycin were selected from strains isolated from bradyrhizobial populations indigenous to Cape Fear and Dothan soils. These were used to evaluate (i) the validity of using antibiotic-resistant mutants to make inferences about the competitiveness of parental strains in soil environments and (ii) the recovery of strains in nodules after inoculation of soybeans grown in soils with indigenous bradyrhizobial populations. Streptomycin and erythromycin resistances of all mutants were stable after approximately 27 generations of growth in yeast extract - mannitol medium, but 33% of the mutants lost resistance to erythromycin upon passage through nodules. Only 17% of the mutants were as competitive as their parental strain when inoculated in a ratio near 1:1 in vermiculite. Four of 10 mutants, which differed in competitiveness from their parental strain in vermiculite, had competitiveness against the soil populations equal to that of their parental strain. Therefore, assessment of competitiveness of mutants and parental strains in non-soil media may not accurately reflect their competitiveness in soil systems. For both the Cape Fear and Dothan soils, recovery of a given mutant from nodules of field-grown plants was always lower than from nodules of plants grown in the greenhouse. Inoculation of the entire rooting zone in the greenhouse experiment and of only a portion of the rooting zone in the field experiments may account for this difference in recovery. Techniques that increase the volume of soil inoculated may enhance nodulation by inoculant strains.Key words: Bradyrizobium, antibiotic resistance, competition.

scholarly journals Slow growth determines nonheritable antibiotic resistance in Salmonella enterica

2019 ◽  
Vol 12 (592) ◽  
pp. eaax3938 ◽  
Author(s):  
Mauricio H. Pontes ◽  
Eduardo A. Groisman
Keyword(s):  
Bacterial Population ◽  
Slow Growth ◽  
Large Fraction ◽  
Signaling Molecules ◽  
Antibiotic Resistant ◽  
Phenotypic Changes ◽  
Resistant Mutants ◽  
Persistent Bacteria ◽  
Small Subpopulation ◽  
Antibiotic Resistant Mutants

Bacteria can withstand killing by bactericidal antibiotics through phenotypic changes mediated by their preexisting genetic repertoire. These changes can be exhibited transiently by a large fraction of the bacterial population, giving rise to tolerance, or displayed by a small subpopulation, giving rise to persistence. Apart from undermining the use of antibiotics, tolerant and persistent bacteria foster the emergence of antibiotic-resistant mutants. Persister formation has been attributed to alterations in the abundance of particular proteins, metabolites, and signaling molecules, including toxin-antitoxin modules, adenosine triphosphate, and guanosine (penta) tetraphosphate, respectively. Here, we report that persistent bacteria form as a result of slow growth alone, despite opposite changes in the abundance of such proteins, metabolites, and signaling molecules. Our findings argue that transitory disturbances to core activities, which are often linked to cell growth, promote a persister state regardless of the underlying physiological process responsible for the change in growth.

Competition for nodule occupancy of introduced Bradyrhizobium japonicum strains in a Wisconsin soil with a low indigenous bradyrhizobia population

1990 ◽  
Vol 36 (12) ◽  
pp. 839-845 ◽  
Author(s):  
T. J. McLoughlin ◽  
S. Hearn ◽  
S. G. Alt
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Growing Season ◽  
Field Trials ◽  
Enzyme Linked Immunosorbent Assay ◽  
Nodule Occupancy ◽  
Antibiotic Resistant ◽  
Growing Seasons ◽  
Low Incidence ◽  
One Year ◽  
Successful Inoculation

The population dynamics of six introduced Bradyrhizobium japonicum strains were measured over three growing seasons in a Wisconsin soil with a low incidence of indigenous B. japonicum (10 cells/gm). Four antibiotic-resistant members of the 123 serocluster (which were either spectinomycin resistant or streptomycin resistant), USDA 110, and USDA 138 were inoculated using liquid inoculum, at a rate of 1 × 108 cells per 2.5-cm row, on two soybean cultivars in 1985. Nodule occupants were identified using an enzyme-linked immunosorbent assay (ELISA), fluorescent antibodies, and antibiotic-resistant mutants. In the first growing season, 100% of the nodules were formed by the introduced strains. The nodules from the uninoculated plots were occupied by an indigenous 110 serogroup. In the second and the third season at the same site (without further inoculation), a high percentage (> 60%) of the nodules from all the plots were nodulated by the 123 serocluster (either alone or as mixed infections). However, < 25% of the nodules in the 123-inoculated plots and < 9% in the other plots were formed by any of the antibiotic-marked 123 inoculum strains introduced in 1985. The main conclusions are (i) that it is possible to successfully introduce inoculum strains in soils where the indigenous Bradyrhizobium population is low and to obtain 100% nodule occupancy in the first growing season, and (ii) that successful inoculation in one year in soils with a low incidence of Bradyrhizobium does not ensure that the introduced inoculum strains will form nodules in subsequent years. Key words: Bradyrhizobium japonicum, indigenous bradyrhizobia, interstrain competition, field trials.

Intra- and inter-specific competition in Rhizobium fredii and Bradyrhizobium japonicum as indigenous and introduced organisms

1987 ◽  
Vol 33 (11) ◽  
pp. 990-995 ◽  
Author(s):  
Stephen F. Dowdle ◽  
B. Ben Bohlool
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Nodule Occupancy ◽  
Soybean Field ◽  
Republic Of China ◽  
Rhizobium Inoculation ◽  
Rhizobium Fredii ◽  
History Of ◽  
Competitive Success ◽  
Glycine Max L ◽  
Different Soils

We studied the competition between Bradyrhizobium japonicum and Rhizobium fredii isolates for nodulation of soybean (Glycine max L. Merrill) cultivars Williams and Ai Jiao Zao grown in three different soils in pots. Two of the soils were from People's Republic of China, one from a soybean field in Honghu with no history of Rhizobium inoculation, and one from a rice field in Wuhan with no history of soybean cultivation. The Honghu soil contained B. japonicum and R. fredii (log total number g−1 = 5.82 ± 0.58); whereas the Wuhan soil only contained B. japonicum (log total number g−1 = 2.80 ± 0.52). Inoculation did not result in a significant increase in nodule number on plants in either soil. Uninoculated plants of both cultivars harbored only R. fredii in the Honghu soil and only B. japonicum in the Wuhan soil. Even when B. japonicum were inoculated into the Honghu soil, R. fredii occupied the majority of the nodules on both cultivars. In the Wuhan soil, B. japonicum serogroups USDA110 and USDA136b (= CB1809) occupied the majority of the nodules except when an isolate of R. fredii from the soybean soil was added in high numbers. In a Hawaiian soil devoid of B. japanicum or R. fredii, when soybeans were inoculated with isolates of both species, most of the nodules were formed by B. japonicum. The R. fredii isolate could form up to 20% of nodules in this soil, but only on the Ai Jia Zao cultivar. In the Wuhan but not the Hawaiian soil, peat pelleting of seeds with equal numbers of two B. japonicum and one R. fredii isolates increased nodule occupancy by B. japonicum USDA136b serogroup significantly as compared with when the same isolates were inoculated into the soil. The results reported here highlight the critical importance of being indigenous to the competitive success of B. japonicum and R. fredii in nodulation of their soybean host.

Studies on associative nitrogen fixation by antibiotic-resistant mutants ofAzospirillum brasilensewith genotypes of lentil (Lens culinaris)Rhizobiumstrains in calcareous soil

1985 ◽  
Vol 104 (1) ◽  
pp. 207-215 ◽  
Author(s):  
R. Rai
Keyword(s):  
Nitrogen Fixation ◽  
Azospirillum Brasilense ◽  
Calcareous Soil ◽  
Lens Culinaris ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Antibiotic Resistant ◽  
Uninoculated Control ◽  
Resistant Mutants ◽  
Antibiotic Resistant Mutants

SummaryNitrosoguanidine-induced mutation frequencies for resistance to streptomycin, spectinomycin, erythromycin and novomycin were studied inAzospirillum brasilense.Lentil inoculated withA. brasilenseand its mutants andRhizobiumstrains produced increased nodule dry weight, nitrogenase activity of nodules and roots and grain yield compared with an uninoculated control.

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