Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Martínez Hidalgo, María Pilar [1], Khan, Noor [2], HUMM, ETHAN [3], JAYAKARUNAKARAN, AKSHAYA [2], Hirsch, Ann [4].

The Inside Story: Microbes Living Within Plant Tissues.

Numerous studies have shown that microbial symbionts affect the anatomy, physiology, development, and innate/adaptive immunity of legume nitrogen-fixing root nodules and are determinants for the health and productivity of crops. Medicago sativa (alfalfa) root nodules naturally contain an abundant and highly diverse microbial community. We analyzed the nodule microbiome of cultivated alfalfa using metagenomic and culture-based approaches towards identifying the “other” bacteria in the nodule besides rhizobia. The major bacterial taxa from both the alfalfa rhizosphere and within Medicago nodules were cultured, purified to get single colonies, and identified by sequencing; the main nodule inhabitants as expected were the nitrogen-fixing genus Ensifer (formerly Sinorhizobium).  However, numerous non-Rhizobium bacteria are also isolated from surface sterilized alfalfa root nodules. Some of these other alfalfa nodule endophytes were identified as Bacillus species and related genera.  Other Gram-positive bacteria, namely actinomycetes were also detected.  The genus Variovorax (Gram-negative beta-proteobacteria) is particularly interesting not only because of its plant growth-promoting properties, but also because of its bioremediation capabilities. Our data show that Variovorax species grow in the presence of nickel and copper and can also break down acrylamide and other soil contaminants.  Alfalfa plants, when grown together with Variovorax species in metal-contaminated soil, exhibit better growth than the uninoculated, untreated control.

1 - Universidad Rey Juan Carolos, Biology, calle Tulipan s/n, 28933 Mostoles, Madrid, Spain
2 - UCLA, Molecular Cell and Developmental Biology, 621 Charles Young Drive East , Los Angeles, CA, 90095-1606, USA
3 - UCLA, Molecular Cell and Developmental Biology, 621 Charles Young Drive East, Los Angeles, CA, 90095-1606, USA
4 - UCLA, DEPT OF MOL, CELL, & DEVEL BIO, 621 Charles Young Dr., South, Los Angeles, CA, 90095, United States

nodule microbiome
Plant growth-promoting bacteria.

Presentation Type: Oral Paper
Number: SYM1005
Abstract ID:1225
Candidate for Awards:None

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