Physiological Diversity of Spitsbergen Soil Microbial Communities Suggests Their Potential as Plant Growth-Promoting Bacteria

Abstract

The objective of the study was to assess the physiological diversity and metabolic activity of the soil bacterial communities inhabiting Spitsbergen soils in search of bacterial abilities facilitating plant growth promotion. In the soil, the total number of culturable microorganisms, the number of their individual physiological groups (including Siderophore Synthesizing; SSB and Phosphate Solubilizing Bacteria; PSB), the dehydrogenase (DH) activity, and the ability to utilize sources of C, N, P (EcoPlate) were analysed. In bacterial isolates, siderophores production, ACC (1-aminocyclopropane-1-carboxylate) deaminase (ACCD) activity, IAA (indole-3-acetic acid) synthesis were examined. The isolates were applied to the seeds of Phaseolus coccineus regarding their germination and root length. The results showed differences between copio- and oligotrophic bacteria. A usually high number of SSB was accompanied by the raised number of PSB. A bigger number of SSB was connected with low values of Fe in the soil. High DH activity was assisted by greater number of copio- and oligotrophic bacteria, raised average well color development value, and N and C contents in the soil. Germination index was more alike relative seed germination than relative root growth. IAA concentration and ACCD activity were conversely related. Synthesis of siderophores was matched with ACCD activity and its high level was combined with elevated germination index. In spite of different localization of soil samples, some isolates proved similar traits of activity. Distinct affiliation of isolates and their various localizations were displayed. Among all isolates tested, some possessed one main trait of activity, but most of them had two or more significant features for potential plant growth stimulation. These isolates could be an important source of useful bacteria.

Bacterial Isolate Inhabiting Spitsbergen Soil Modifies the Physiological Response of Phaseolus coccineus in Control Conditions and under Exogenous Application of Methyl Jasmonate and Copper Excess

“…In our previous studies [35], the S17 isolate was biochemically identified as Gram-negative (Figure 1A) Pseudomonas luteola , and characterized by growth on oligotrophic and coptotrophic media, the activity of ACC (1-aminocyclopropane-1-carboxylate) deaminase, the concentration of IAA, and the Minimal Inhibitory Concentration (MIC) for Cu. We also obtained positive results in the following tests: the activity of protease, β-glucosidase, and β-galactosidase; the reduction of nitrate to nitrite ions; the fermentation of d -glucose, the hydrolysis of d -glucose, l -arabinose, d -mannose, d -mannitol, N -acetylglucosamine, d -maltose, gluconate, malate, and citrate; phosphate solubilization on Pikovskaya (PVK) medium (Figure 1B); and the production of siderophores on blue agar with chrome azurol S medium (Figure 1C).…”

“…In our previous study [35], the S17 isolate was biochemically identified using API 20 NE V8.0 tests, and was characterized by ACC (1-aminocyclopropane-1-carboxylate) deaminase activity, MIC for Cu, and the ability to synthesize IAA and produce siderophores (on the chrome azurol S agar medium). A germination test of Phaseolus coccineus plants inoculated with the S17 isolate was carried out as well [35].…”

“…The concentration of IAA was measured as described in Hanaka et al [35]. The phenolic compounds were determined by the modified Folin–Ciocalteau method [72].…”

“…After one day of hydroponic culture, the nutrient solution was supplemented with the bacterial isolate at a concentration of 1 × 10 8 colony-forming units (CFU). The isolate was biochemically identified (API test) as Pseudomonas luteola derived from Spitsbergen soil (N 77°33′55′′ E 14°28′57′′) [35], and designated as S17. After two days of hydroponic culture, MJ (95%) was added at concentrations of 1 or 10 µM (J1 or J10, respectively).…”

“…A source of such strains is Spitsbergen soil. In our previous research, we screened a broad range of isolates from Spitsbergen soils in search of those that are promising in stimulating plant growth [35] and we chose one of them. As bacterial isolates from Spitsbergen seem to have potential for PGP and evoking resistance in stress conditions, it is agriculturally and environmentally valuable to verify their ability to influence the plant status in the presence of exogenously applied J and Cu in excess.…”