Signaling networks linking bacterial chemotaxis and the general stress response

Designing synthetic, beneficial microbes and microbial communities to inoculate into soil, and manipulation of the microbes around plant roots (the rhizosphere microbiome) to promote plant growth and productivity are current strategies to ensure food security with sustainable agricultural practices. These strategies rely on understanding how bacteria sense and respond to plant hosts. Bacterial signaling networks detect signals, process information, and drive behaviors like movement toward plant roots. These networks allow the bacteria to monitor and adapt to their surroundings with responses such as colonizing a plant surface, exerting beneficial effects on a colonized host plant, or implementing stress responses if conditions worsen. These systems tend to be studied in isolation, a practice needed to understand basic function, but this approach limits the development of effective predictive models and can lead to unexpected challenges for improving bacterial performance in biotechnological applications. This project will investigate a strategy by which beneficial soil bacteria integrate sensing and responses from distinct signaling networks to mediate colonization of plant roots and exert beneficial effects on plant growth. The project will evaluate the implications of its findings for biotechnology by consulting with industry partners. The project will also contribute to workforce development by engaging and training college students and junior scientists in research relevant to biotechnological applications. This project will elucidate molecular mechanisms linking bacterial chemotaxis signaling, flagellum structure and function and general stress responses in a beneficial soil bacterium, Azospirillum brasilense, used as a commercial bio-inoculant. The project will define the general stress response signaling network in this model soil bacterium, elucidate how the general stress response network alters the structure-function of the bacterium’s polar flagellum and identify how the chemotaxis signaling network integrates with the general stress responses network. Examining the molecular signatures that comprise the general stress response will help identify a subset of targets for synthetic engineering applications for the design of next generation bioinoculants. Characterizing how chemotaxis signaling alters the expression of a minor polar flagellin will provide new paradigms that should be applicable to other soil bacteria with similar genome architecture. How chemotaxis signaling intersects with other regulatory networks remains poorly understood, and preliminary data have suggested entirely novel mechanisms and new avenues for producing strains for soil inoculation that have enhanced stress resistance. Characterization of novel molecular pathways that integrate bacterial motility and chemotaxis signaling with regulation of stress responses will advance our understanding of how bacteria adapt in the soil and as part of a rhizosphere. The project will provide research opportunities for undergraduate students who have limited access to research opportunities and provide graduate students and a postdoctoral fellow with opportunities to apply their research communication skills in a breadth of outreach activities, as well as interact with industry partners. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2537644 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Gladys Alexandre | Institution: University of Tennessee Knoxville, KNOXVILLE, TN | Award Amount: $969,275 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2537644 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2537644.html