Daniel Orr

Publication Year



This project sought to investigate the mechanism of disaccharide-induced osmoprotection in S. meliloti. It has been shown that sucrose, trehalose, cellobiose, gentiobiose, palatinose, maltose, turanose and maltotriose can act as non-accumulated osmoprotectants in several strains of S. meliloti (8). Sucrose was shown to provide full recovery of growth in salt shocked cultures of S. meliloti strain 1021, quantified by measuring light scattering at 600 nm. However, cellobiose and maltose were found to be ineffective osmoprotectants for strain 1021. Osmoprotection by sucrose may proceed via a separate pathway than that of cellobiose and maltose. A mutant strain, 307620, which can grow on neither cellobiose nor glucose, was also studied. In preliminary experiments the mutant strain displayed osmosensitivity and was not rescued in 0.45M NaCI by the sucrose, cellobiose, or maltose. In the absence of salt, strain 307620 had significantly stunted growth but recovered with supplemental amounts of sucrose, maltose, or glucose. Further experiments are needed for conclusive identification of strain 307620.