Effects of Pseudomonas sp. OBA 2.4.1 on Growth and Tolerance to Cadmium Stress in Pisum sativum L

Abstract

Cadmium stress is a barrier to crop production, yield, quality, and sustainable agriculture. In the current study, we investigated the characteristics of bacterial strain Pseudomonas sp. OBA 2.4.1 under cadmium (CdCl₂) stress and its influence on Cd stresses in pea (Pisum sativum L.) seedlings. It was revealed that strain OBA 2.4.1 is tolerant of up to 2 mM CdCl₂, and seed treatment with the bacterium enhanced pea plant growth (length of seedlings) under 0.5 mM cadmium stress. This bacterial strain showed plant growth-promoting properties, including biofilm formation and siderophore activity. An important advantage of the studied strain OBA 2.4.1 is its ability to colonize the plant roots. Moreover, the inoculation with strain OBA 2.4.1 significantly reduced oxidative stress markers in pea seedlings under cadmium stress. These findings suggest that cadmium stress-tolerant strain OBA 2.4.1 could enhance pea plant growth by mitigating stress-caused damage, possibly providing a baseline and eco-friendly approach to address heavy metal stress for sustainable agriculture.

Keywords: PGPR; Pisum sativum L.; Pseudomonas sp.; biofilms; cadmium tolerance; growth stimulation; heavy metals (HMs); malondialdehyde.

Figure 1

Siderophore production of Pseudomonas sp. OBA 2.4.1. The bar in the photograph indicates 1 cm.

Figure 2

A—The growth of the strain Pseudomonas sp. OBA 2.4.1 (1) on LB medium, (2) with the addition of 0.5 mM Cd, (3) with the addition of 1 mM Cd, (4) with the addition of 1.5 mM Cd, (5) with the addition of 2 mM Cd; B—the growth of the strain Pseudomonas sp. OBA 2.4.1 transformed with plasmid pJNTurboRFP (which gives a pink color to the bacteria) (1) on LB medium, (2) with addition of 0.5 mM Cd, (3) with addition of 1 mM Cd, (4) with addition of 1.5 mM Cd, (5) with the addition of 2 mM Cd. The bar in the photograph indicates 1 cm.

Figure 3

Effect of Cd on the growth of pea seeds germinated on filter paper in sterile water (control) and in the presence of Cd: 0.1, 0.2, 0.3, 0.4, 0.5 mM (A); the second variant of the seeds was treated with Pseudomonas sp. OBA 2.4.1 and also grew in the presence of Cd: 0.1, 0.2, 0.3, 0.4, 0.5 mM (B). The bar in the photograph indicates 1 cm.

Figure 4

Effect of Pseudomonas sp. OBA 2.4.1 on the content of H₂O₂ in 7-day-old pea seedlings under normal and Cd stress conditions. The bars indicate the mean values of three replicates ± SEM. Different lowercase letters indicate a significant difference between the means at the level of P < 0.05 (ANOVA, LSD test).

Figure 5

Effect of Pseudomonas sp. OBA 2.4.1 on the content of MDA in 7-day old pea seedlings under normal and Cd stress conditions. The bars indicate the mean values of three replicates ± SEM. Different lowercase letters indicate a significant difference between the means at the level of P < 0.05 (ANOVA, LSD test).

Figure 6

Bacteria transformed with the pJNTurboRFP vector on the surface of pea plant root hairs. Microcolonies of Pseudomonas sp. 2.4.1 formed after 1 day of incubation. Visualization was made using a fluorescent microscope Axio Imager M1 (Carl Zeiss, Jena, Germany). The bar in the photograph indicates 1 mm.