Abstract
Microbial competition for carbon sources is a primary determinant of rhizosphere ecology. We employed the PCR to examine the population fluctuations of a symbiotic nitrogen-fixing bacterium (Rhizobium etli) during the first 11 days following inoculation of Phaseolus vulgaris seedlings grown in the presence or absence of a common asymbiotic rhizosphere resident (Bacillus polymyxa). When B. polymyxa was applied as a co-inoculant, increases in both early rhizobial root populations and final root population densities were observed as compared to single inoculation with R. etli. Modifications to host plant growth (including increased lateral root formation and nodules number) were found concomitant with elevations in R. etli populations on plants co-inoculated with both bacterial genera. In contrast to the in planta results, population enhancements were not observed when R. etli and B. polymyxa were co-cultured in vitro using minimal media in the absence of the seedling. Addition of seed exudate to the growth media also failed to stimulate the population increases observed during co-release in planta. These results suggest that B. polymyxa acts indirectly (i.e., via the plant host) to increase R. etli populations. Our observed synergism among co-resident bacteria supports the hypothesis that microbial communities which colonize the spermosphere may play a significant role in plant development and rhizosphere ecology.
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Claims 6
Claim · model-written summary
B. polymyxa co-inoculation increased early and final R. etli root populations over R. etli alone.
- Taxon
- Phaseolus vulgaris
Phaseolus vulgarise1 - Treatment
- B. polymyxa was applied as a co-inoculante0
- Interactor
- R. etliRhizobium etlie0symbiont
- Second interactor
- B. polymyxa
Paenibacillus polymyxae0symbiont - Outcome
- rhizobial root populations and final root population densitiese0
- Direction
- increasese0
- Comparator
- single inoculation with R. etlie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When B. polymyxa was applied as a co-inoculant, increases in both early rhizobial root populations and final root population densities were observed as compared to single inoculation with R. etli”
e1“Phaseolus vulgaris seedlings”
Claim · model-written summary
Co-inoculation increased lateral root formation in Phaseolus vulgaris.
- Taxon
- Phaseolus vulgarisPhaseolus vulgarise1
- Treatment
- co-inoculated with both bacterial generae0
- Interactor
- R. etliRhizobium etlie0symbiont
- Outcome
- lateral root formatione0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Modifications to host plant growth (including increased lateral root formation and nodules number) were found concomitant with elevations in R. etli populations on plants co-inoculated with both bacterial genera”
e1“Phaseolus vulgaris seedlings”
Claim · model-written summary
Co-inoculation increased nodule number in Phaseolus vulgaris.
- Taxon
- Phaseolus vulgarisPhaseolus vulgarise1
- Treatment
- co-inoculated with both bacterial generae0
- Interactor
- R. etliRhizobium etlie0symbiont
- Outcome
- nodules numbere0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Modifications to host plant growth (including increased lateral root formation and nodules number) were found concomitant with elevations in R. etli populations on plants co-inoculated with both bacterial genera”
e1“Phaseolus vulgaris seedlings”
Claim · model-written summary
Co-culturing R. etli and B. polymyxa without seedlings did not enhance R. etli populations.
- Taxon
- Phaseolus vulgarisPhaseolus vulgarise1
- Treatment
- R. etli and B. polymyxa were co-cultured in vitroe0
- Outcome
- population enhancementse0
- Direction
- not observede0
- Qualifier
- absence of the seedlinge0
- Comparator
- in planta resultse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“population enhancements were not observed when R. etli and B. polymyxa were co-cultured in vitro using minimal media in the absence of the seedling”
e1“Phaseolus vulgaris seedlings”
e2“In contrast to the in planta results”
Claim · model-written summary
Seed exudate added to media did not stimulate the population increase seen with co-release in plants.
- Taxon
- Phaseolus vulgarisPhaseolus vulgarise1
- Treatment
- Addition of seed exudate to the growth mediae0
- Outcome
- population increasese0
- Direction
- failed to stimulatee0
- Comparator
- co-release in plantae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Addition of seed exudate to the growth media also failed to stimulate the population increases observed during co-release in planta”
e1“Phaseolus vulgaris seedlings”
Claim · model-written summary
The authors infer B. polymyxa acts through the plant host to increase R. etli populations.
- Taxon
- Phaseolus vulgarisPhaseolus vulgarise1
- Interactor
- R. etliRhizobium etlie0symbiont
- Second interactor
- B. polymyxaPaenibacillus polymyxae0symbiont
- Outcome
- R. etli populationse0
- Qualifier
- indirectly (i.e., via the plant host)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“B. polymyxa acts indirectly (i.e., via the plant host) to increase R. etli populations”
e1“Phaseolus vulgaris seedlings”
The same questions in other papers
Paenibacillus polymyxa · Rhizobium etli · Phaseolus vulgaris (common bean)Results agree
1 paper in the same direction as this paper
- positive
allelopathy · pest · Phaseolus vulgaris (common bean)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
inoculation · Rhizobium etli · Phaseolus vulgaris (common bean)Positive and negative results
4 papers in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
- positive
2 papers more in this group
See all 6 papers →in vitro · pest · Phaseolus vulgaris (common bean)Results agree
2 papers in the same direction as this paper
- no effect
- no effect
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.