Isolation of Bacteria with Potential Plant-Promoting Traits and Optimization of Their Growth Conditions

Abstract

This research aimed at investigating the isolation and identification of bacterial strains with biological nitrogen-fixing capability and phosphate, potassium, and zinc solubilization activities from a durum wheat field under two different tillage practices including 10 years of conventional tillage (CT) and no-tillage (NT) practices. Attempts were also extended to estimate their relative abundances in the soil as well as to develop accurate mathematical models in determining the effect of different temperatures, NaCl concentrations and pH on the growth, and activity of selected isolates. Twelve effective bacterial strains, including Pseudomonas, Acinetobacter, and Comamonas genera, were identified with a great potential to solubilize the insoluble forms of phosphate (from 11.1 to 115.5 mg l−1 at pH 8), potassium (from 32.2 to 35.6 mg l−1 at pH 7), and zinc (from 1.11 to 389.90 mg l−1 at pH 9) as well as to fix N2 gas (from 19.9 to 25.2 mg l−1). To our knowledge, this is the first report of the ability of Comamonas testosteroni and Acinetobacter pittii to fix nitrogen and to solubilize insoluble potassium compound, respectively. Three families, Moraxellaceae, Pseudomonadaceae, and Comamonadaceae, showed a higher percentage of abundance in the NT samples as compared to the CT, but only significant difference was observed in the relative abundance of Pseudomonadaceae (P < 0.01). These strains could be definitively recommended as inoculants to promote plant growth in the wide ranges of pH, salinity levels (with maximum growth and complete inhibition of growth from 0.67–0.92% to 3.5–9.3% NaCl, respectively), and temperatures (2.1–45.1 °C).

Biofertilisation with a consortium of growth‐promoting bacterial strains improves the nutritional status of wheat grain under control, drought, and salinity stress conditions

“…The results in Table 2 indicate the changes in nutrient accumulations in durum wheat grains in response to the application of the PGPB bacterial consortium. This finding was reasonably expected, since our beneficial bacteria, including Acinetobacter , and Comamonas genera, had already shown a great ability in converting the insoluble phosphate, potassium, and zinc complexes to soluble forms, biological fixing the nitrogen, and producing indole acetic acid in vitro conditions (Yaghoubi Khanghahi et al, 2021c). Prior studies have proved the importance of PGPB in enriching the harvestable and reproductive parts of the plant with macro and micronutrients in non‐stress (Yaghoubi Khanghahi et al, 2018b) and stress conditions (Meena et al, 2017).…”

“…Also, the differences in starch content between the biofertiliser consortium and other fertilisation levels in salinity were more pronounced than in drought. This result could be related to the greater ability of our beneficial bacteria, particularly N 2 fixer Comamonas testosteroni , to growth in saline conditions in vitro (1% NaCl concentration) (Yaghoubi Khanghahi et al, 2021c), in comparison to the common PGPB strains. This might explain why the grain yield in salinity was higher than that during drought when the PGPB consortium was applied.…”

“…Years ago, we started comprehensive research to advance the knowledge of the relationship between soil biological fertility levels and the communities of beneficial soil bacteria. As a part of this project, we isolated several beneficial bacterial strains from durum wheat fields at Lavello (Southern Italy, Basilicata region, located at 41°03′N, 15°42′E) and identified the four most beneficial among them as Acinetobacter pittii , Acinetobacter oleivorans , Acinetobacter calcoaceticus , and Comamonas testosteroni (Yaghoubi Khanghahi et al, 2021c). These bacterial strains showed a promising ability, not only in transforming the insoluble complexes of phosphate, potassium, and zinc to soluble forms and biological fixing of nitrogen in vitro conditions, respectively (Yaghoubi Khanghahi et al, 2021c), but also in improving some agronomic and physiological parameters of durum wheat plants in a greenhouse experiment (Yaghoubi Khanghahi et al, 2021a).…”

“…As a part of this project, we isolated several beneficial bacterial strains from durum wheat fields at Lavello (Southern Italy, Basilicata region, located at 41°03′N, 15°42′E) and identified the four most beneficial among them as Acinetobacter pittii , Acinetobacter oleivorans , Acinetobacter calcoaceticus , and Comamonas testosteroni (Yaghoubi Khanghahi et al, 2021c). These bacterial strains showed a promising ability, not only in transforming the insoluble complexes of phosphate, potassium, and zinc to soluble forms and biological fixing of nitrogen in vitro conditions, respectively (Yaghoubi Khanghahi et al, 2021c), but also in improving some agronomic and physiological parameters of durum wheat plants in a greenhouse experiment (Yaghoubi Khanghahi et al, 2021a). Also, it was determined how the application of these beneficial bacterial strains, as bio‐inoculant, shaped the rhizosphere and root‐associated bacterial communities under stress (Yaghoubi Khanghahi et al, 2021b).…”

Prokaryote communities associated with different types of tissue formed and substrates inhabited bySerpula lacrymans

“…Other species were Pseudomonas spp. and Acinetobacter spp., taxa which are known for their nitrogen fixing abilities (Liba, Ferrara et al 2006, Wang, Bian et al 2020, Yaghoubi Khanghahi, Strafella et al 2021). Burkholderiales, a class for which a mycophagous lifestyle was suggested (Valášková, de Boer et al 2009, Hervé, Ketter et al 2016, Brabcová, Štursová et al 2018, Starke, Morais et al 2020), was as well quite abundant.…”