Date of Completion

5-17-2026

Degree Type

Honors Thesis - Campus Access

Discipline

Biology (BIOL)

First Advisor

Nancy Fujishige

Abstract

Contemporary agriculture requires sustainable bioinoculants to reduce dependency on synthetic fertilizers. Bacillus simplex, isolated from the Negev Desert rhizosphere of Zygophyllum dumosum (bushy bean caper) has emerged as a potent plant growth-promoting rhizobacterium (PGPR). When co-inoculated with the nitrogen-fixing symbiont Sinorhizobium meliloti, B. simplex significantly increases the biomass, nodule count, and nodule size of its legume host, Melilotus alba (sweet white clover) compared to single inoculation controls. To confirm endophytic colonization, intranodular bacteria were isolated from surface sterilized nodules and validated via 16S rRNA sequencing. However, the intranodular location and colonization pathway of these bacteria remains poorly understood. To visualize the bacterium and investigate the mechanism of colonization, the Bacillus strain is transformed with either pNF8 or ECE152, plasmid vectors which constitutively express green fluorescent protein (GFP). Root colonization is visualized using confocal laser scanning microscopy, providing insights into the attachment patterns and tissue preferences of the strain.. To map these specific tissue preferences and colonization pathways, a wall-weakening protocol utilizing 2% to 3% glycine was optimized to transform the mucoid wild isolates with GFP-expressing plasmid vectors (pNF8 and ECE152). Visualizing these pathways under confocal laser scanning microscopy bridges the gap between controlled microsoil studies and field-scale agricultural applications, establishing B. simplex as a resilient tool for sustainable crop production under shifting climatic conditions.

Download

Available for download on Wednesday, May 19, 2027

Share

COinS