The aim of this work was to clarify the mechanism related to plant growth promoting of a bacterial strain (L115) isolated from Arachis hypogaea rhizospheres and the effects of high growth temperature and salinity on phospholipids and fatty acids composition. L115 was isolated from peanut rhizospheres and identified according to the sequence analysis of the 16S rRNA gene. Phenotypic, metabolic and plant growth promoting rhizobacteria (PGPR) characteristics of L115 were tested. Inoculation test in plant growth chamber was performed. In addition, L115 was exposed to a 37 °C and 300 mM NaCl and phospholipids and fatty acid composition were evaluated. L115 strain was identified as Ochrobactrum intermedium and was able to increase the peanut shoot and root length as well as dry weight, indicating a PGPR role by being able to produce indole acetic acid and siderophores and present ACC deaminase activity. In addition, L115 showed tolerance to both high growth temperature and 300 mM NaCl. The most striking change was a decreased percentage of 18:1 fatty acid and an increase in 16:0 and 18:0 fatty acids, under high growth temperature or a combination of increased temperature and salinity. The most important change in phospholipid levels was an increase in phosphatidylcholine biosynthesis in all growth conditions. L115 can promote the growth of peanut and can tolerate high growth temperature and salinity modifying the fatty acid unsaturation degree and increasing phosphatidylcholine levels. This work is the first to report the importance of the genus Ochrobactrum as PGPR on peanut growth as well as on the metabolic behaviour against abiotic stresses that occur in soil. This knowledge will be useful for developing strategies to improve the growth of this bacterium under stress and to enhance its bioprocess for the production of inoculants.

This knowledge can be used to develop new Azospirillum brasilense formulations showing an adapted membrane to water deficit.

No abstract

Rhizobacteria are constantly faced with environmental stimuli stresses and should be responding to a wide range of factors through signal transduction pathways that convert extracellular information into intracellular forms. The cytoplasmic membrane of bacteria is permeable to water but forms an effective barrier for most solute present in the cytoplasmic. To survive osmotic stresses, rhizobacteria need to adapt by accumulating specifi c solutes under hyperosmotic conditions and releasing them under hyposmotic conditions. These solutes are referred to compatible solutes and glutamate, K + , trehalose, betaine, among others solutes, are used to response. But new studies to proteins, phospholipids, and polysaccharides and their pattern in response to stress are necessary.

J. curcas and J. macrocarpa are useful for restoring degraded areas and their seeds contain oils for biodiesel production. The aim of the work was to determine the reserve substances in the endosperm and the embryo of J. curcas and J. macrocarpa which is important in understanding the germination process, the establishment of these species and its industrial employment. Seeds were imbibed in distilled water for 24 h, to facilitate removal of seed coat with the aim to separate the embryo and nutritive tissues. In both species, the endosperm contained aleurone grains consisting of a crystalloid and globoid, lipids of red color and the starch was not observed. Four major fatty acids were determined in J. curcas seed: oleic, palmitic, stearic, palmitoleic and oleic fatty acid represents about 70% oil content. Oleic acid was the most abundant in J. macrocarpa seeds, while, there was not palmitoleic acid. Seed with predominantly unsaturated fatty acids is ideal for biodiesel industry. The means of the sugar content were: 14.3 µg/mg in endosperm and 104.76 µg/mg in embryo of J. curcas and 6.48 µg/mg in endosperm and 59.20 µg/mg in embryo of J. macrocarpa. The means of the protein content were: 4.2 µg/mg in endosperm and 45.02 µg/mg in embryo of J. curcas and 3.26 µg/mg in endosperm and 31.08 µg/mg in embryo of J. macrocarpa. Sugar and protein contents of Jatropha seeds were significantly higher in embryo in both species