Beneficial Bacteria Isolated from Grapevine Inner Tissues Shape Arabidopsis thaliana Roots

We investigated the potential plant growth-promoting traits of 377 culturable endophytic bacteria, isolated from Vitis vinifera cv. Glera, as good biofertilizer candidates in vineyard management. Endophyte ability in promoting plant growth was assessed in vitro by testing ammonia production, phosphate solubilization, indole-3-acetic acid (IAA) and IAA-like molecule biosynthesis, siderophore and lytic enzyme secretion. Many of the isolates were able to mobilize phosphate (33%), release ammonium (39%), secrete siderophores (38%) and a limited part of them synthetized IAA and IAA-like molecules (5%). Effects of each of the 377 grapevine beneficial bacteria on Arabidopsis thaliana root development were also analyzed to discern plant growth-promoting abilities (PGP) of the different strains, that often exhibit more than one PGP trait. A supervised model-based clustering analysis highlighted six different classes of PGP effects on root architecture. A. thaliana DR5::GUS plantlets, inoculated with IAA-producing endophytes, resulted in altered root growth and enhanced auxin response. Overall, the results indicate that the Glera PGP endospheric culturable microbiome could contribute, by structural root changes, to obtain water and nutrients increasing plant adaptation and survival. From the complete cultivable collection, twelve promising endophytes mainly belonging to the Bacillus but also to Micrococcus and Pantoea genera, were selected for further investigations in the grapevine host plants towards future application in sustainable management of vineyards

Effect of plant growth regulators and other selected compounds on the growth of Acremonium coenophialum in vitro

A mutualistic relationship exists between the endophyte Acremonium coenophialum (Morgan, Jones and Gams) and tall fescue Festuca arundenacea (Shreb). The host, tall fescue, provides protection, a source of nutrients and a means of dissemination for the endophyte. The endophyte protects tall fescue from adverse environmental conditions, overgrazing by herbivores and insect and pathogen attack. Changes in the physiology of the fescue plant causes changes to occur in the growth of the endophyte. The purpose of this study was to examine plant growth regulators and carbohydrates to determine their effect on the growth of the endophyte. In liquid and solid media, the synthetic auxins 2,4-D (2,4-dichloro Phenoxyacetic acid) and dicamba (3,6-dichloro 2- methoxybenzoic acid), had no observable effect on growth of A. coenophialum. Abscisic acid also had no observable effect on growth of the endophyte. When A. coenophialum was exposed to an ethylene atmosphere of 9ppm, no observable difference in growth was observed when compared with the control. Gibberellic acid (GA3) had no observable effect on growth of the endophyte after 4 weeks. However, at 6 weeks, a reduction of 40 percent was observed on solid media. In liquid M102 media (Bacon et al. 1988) , growth was consistent with that of the control at concentrations of 0.1, 1 and 10μM; however, 100 percent reduction was observed at 100 μM. The synthetic cytokinin, kinetin, reduced the growth of A. coenophialum at each concentration examined. Growth reductions ranged from 20 percent at 20 μM to 100 percent at 100 μM. Zeatin also reduced the growth of the endophyte. A 50 percent growth reduction was observed at 100 μM. In liquid M102 media, no reduction in growth of the endophyte occurred at 0.1, 1, and 10 μM kinetin, but at 100 μM kinetin, growth was reduced by 95 percent. Growth of A. coenophialum on media containing various carbon sources was investigated. Radial growth was higher on sucrose than on other carbon sources tested. A morphological change was noted on media containing sucrose. The endophyte grown on media containing sucrose exhibited a mucoid-like appearance, while the endophyte grown on the xylose-substituted media had a cottony appearance. In summary, none of the plant growth regulators (PGRs) examined had a stimulatory effect on the endophyte. However, a reduction in growth was noted with cytokinins and GA3. Sucrose was a better carbon source than xylose, but changes in the morphology of the endophyte occurred when grown on media supplemented with sucrose in M102 media. The endophyte took on a mucoid-like appearance when grown on M102 media supplemented with sucrose, while cultures grown on M102 media supplemented with xylose had a white cottony appearance

Identification of candidate plant growth promoting endophytes from Echium plantagineum roots

Magister Scientiae - MSc (Biotechnology)The yearly increase of global population will result in a greater demand for crop production, but with the climates changes and a lack of available agricultural land it will become increasingly more difficult to provide sufficient crops to feed everyone adequately. Application of the PGPE has proven over the past researches to be able enhance growth of plants via various growth promoting mechanisms. To identify suitable growth promoting bacteria candidate, E. plantagineum plant was used to isolate endophytes from the root after surface sterilization. The isolates bacteria were used to inoculate Brassica napus L seeds. The effects of isolate's ability to promote growth were evaluated based on the certain growth parameters after 42 days in the green house. Isolate CP5 produced highest results in all growth parameter. Isolates CP5 was selected as potential candidate as significant improvement was shown by this isolate. This isolate was tested for the ability to produce ACC deaminase, solubilize phosphate, synthesize IAA and siderophore production. Furthermore isolate CP5 growth promotion abilities was tested on Brassica napus L under antimony stress

Investigating the feasibility of light (in)dependent continuous cultivation of an Extremophilic Algae, Galdieria sp. RTK37.1

The extremophilic nature and metabolic flexibility of Galdieria spp. have major potential in several biotechnological applications1. However, limiting research into successful large scale continuous cultivation of Galdieria sulphuraria has restricted industrial application of the species1. This research focused on investigating the feasibility of light dependant and independent continuous cultivation of Galdieria sp. RTK37.1 in various trophic and light conditions. Stable growth of Galdieria sp. RTK37.1 was achieved during photoautotrophic, mixotrophic and heterotrophic conditions, highlighting the ability to achieve submaximal specific growth while continuous collecting biomass for product retrieval. These results have potential industrial ramifications as they demonstrate that the growth of Galdieria sp. RTK37.1 can be manipulated to obtain desired biomass and product yields over long cultivation periods. Continuous cultivation of Galdieria sp. RTK37.1 under various light intensities highlighted that operating chemostats under non-optimal light conditions not only affect the growth of Galdieria sp. RTK37.1 but also the ability to control and achieve desired stable growth. Light intensities greater than ~ 101 mol m-2 s-1 increased wall adhesion and decreased overall photosynthesis rates in photoautotrophically grown Galdieria sp. RTK37.1. Although biomass production increased during cultivation under warm white LED lighting at 191.3 mol m-2 s-1, the presence of immobilised cells is not desired during chemostat cultivation as can lead to non-optimal operation and the inability to obtain steady state growth. Mixotrophic growth is defined as the ability for a cell to combine the mechanisms of photoautotrophic and heterotrophic growth, utilising both inorganic carbons through photosynthesis and organic carbon through respiration simultaneously6. Mixotrophic cultivation of Galdieria sp. RTK37.1 was shown to be an ideal growth condition for obtaining greater biomass production compared to photoautotrophically and heterotrophically grown Galdieria sp. RTK37.1. During steady state mixotrophic growth, Galdieria sp. RTK37.1 achieved a biomass concentration of 1.43 ( 0.12) g L-1, significantly greater than biomass concentrations during photoautotrophic and heterotrophic growth, which were only 0.93 ( 0.01) g L-1 and 0.63 ( 0.02) g L-1 respectively (t-test: p-value < 0.0001). The increased biomass production, along with the decreased net specific oxygen evolution rates and crude protein percentage (which indicated a decrease in photosynthesis compared with photoautotrophy) lead to the conclusion that Galdieria sp. RTK37.1 is a true mixotroph. The results demonstrated a synergistic effect between photosynthesis and aerobic respiration during mixotrophy, indicating both metabolism methods being utilised simultaneously in mixotrophic Galdieria sp. RTK37.1. This research demonstrated that Galdieria sp. RTK37.1 is a promising strain for larger scale production, with evidence towards its ability to be used for large scale continuous cultivation in a range of applications such as phycocyanin production. Biomass production and growth of Galdieria sp. RTK37.1 can be controlled during continuous cultivation by limiting nutrients such as carbon or ammonia, or through various light intensity and wavelength conditions. Additionally, this research highlighted the ability for Galdieria sp. RTK37.1 to adapt to a wide range of conditions, achieving stable growth even under multiply limiting factors