AUTHOR=Barua Niloy , Clouse Kayla M. , Ruiz Diaz Dorivar A. , Wagner Maggie R. , Platt Thomas G. , Hansen Ryan R. 

TITLE=Screening the maize rhizobiome for consortia that improve Azospirillum brasilense root colonization and plant growth outcomes

JOURNAL=Frontiers in Sustainable Food Systems

VOLUME=7

YEAR=2023

URL=https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2023.1106528

DOI=10.3389/fsufs.2023.1106528

ISSN=2571-581X

ABSTRACT=<p>Plant growth-promoting bacteria (PGPB) are valuable for supporting sustainable food production and may alleviate the negative impacts of chemical fertilizers on human health and the environment. While single-strain inoculations have proven unreliable due to poor survival and colonization in the rhizosphere, application of PGPB in multispecies consortia has the potential to improve these outcomes. Here, we describe a new approach for screening and identifying bacterial consortia that improve the growth of corn relative to plants inoculated with a single strain. The method uses the microwell recovery array (MRA), a microfabricated high-throughput screening device, to rapidly explore the maize (<italic>Zea mays L</italic>.) rhizobiome for higher-order combinations of bacteria that promote the growth and colonization of the nitrogen-fixing PGPB, <italic>Azospirillum brasilense</italic>. The device simultaneously generates thousands of random, unique combinations of bacteria that include <italic>A. brasilense</italic> and members of the maize rhizobiome, then tracks <italic>A. brasilense</italic> growth in each combination during co-culture. Bacteria that show the highest levels of <italic>A. brasilense</italic> growth promotion are then recovered from the device using a patterned light extraction technique and are identified. With this approach, the screen uncovered growth-promoting consortia consisting primarily of bacteria from the <italic>Acinetobacter</italic>-<italic>Enterobacter</italic>-<italic>Serratia</italic> genera, which were then co-inoculated with <italic>A. brasilense</italic> on axenic maize seedlings that were monitored inside a plant growth chamber. Compared to maize plants inoculated with <italic>A. brasilense</italic> alone, plants that were co-inoculated with these consortia showed accelerated growth after 15 days. Follow-up root colonization assays revealed that <italic>A. brasilense</italic> colonized at higher levels on roots from the co-inoculated seedlings. These findings demonstrate a new method for rapid bioprospecting of root and soil communities for complementary PGPB and for developing multispecies consortia with potential use as next-generation biofertilizers.</p>