Impact of anoxygenic phototrophic bacteria on the growth of Arabidopsis thaliana under salt stress

This study investigated the effects of a microbial mixture containing anoxygenic phototrophic bacteria (APB) on the growth of Arabidopsis thaliana ecotype Col-0 under salt stress. To induce salt stress, 150 mM NaCl was applied to A. thaliana. Four treatments were employed to assess the impact of APB: 1) control plants, 2) plants inoculated with a mixture of enriched photosynthetic bacteria, 3) plants inoculated with a mixture of enriched photosynthetic bacteria and irrigated with 150 mM NaCl solution, and 4) plants irrigated with 150 mM NaCl solution. The analysis revealed that the inoculated plants exhibited increased leaf formation and leaf size. Furthermore, an increase in chlorophyll content was observed in all treatments except treatment 4. Quantitative analysis of genes related to early salt stress responses in A. thaliana, including genes for ROS scavenging (APX2), ABA signaling ( RD29A and RD29B), and jasmonate synthesis (LOX2), was conducted by RT-qPCR. The metabolic activity of soil bacteria was determined by measuring the formation of 1,3,5-triphenyl formazan. Metagenomic analysis was performed on the soils of the plants in treatments 2 and 3 after 10 days and bacterial diversity was determined. The dominant genera were found to be Pseudomonas, Variovorax, Azospirillum, Methylophilus, Flavobacterium, Acidovorax, Hydrogenophaga, Mucilaginibacter, and Rhodanobacter. Among all genera, the proportion of APB genera, including purple nonsulfur bacteria, was 15.3% and 18.8% in treatments 2 and 3, respectively.