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

The effect of a microbial mixture containing anoxygenic phototrophic bacteria (APB) on the growth of Arabidopsis thaliana ecotype Col-0 under salt stress was investigated. 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 demonstrated that the inoculated plants exhibited increased leaf formation and leafsize. Furthermore, an increase in chlorophyll content was observed in all treatments except treatment4. Quantitative analysis of genes related to early salt stress responses in A. thaliana, including ROS scavenging (APX2), ABA signalling (RD29A and RD29B), and jasmonate synthesis (LOX2), was conducted by RT-qPCR. During the experiment, the metabolic activity of the soil bacteria was determined by measuring the formation of 1,3,5-triphenyl formazan (TFF). 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 Pseudomonas, Variovorax, Azospirillum, Methylophilus, Flavobacterium, Acidovorax, Hydrogenophaga, Mucilaginibacter, and Rhodanobacter. Among all the genera, the proportion of APB genera, including purple non-sulfur bacteria (PNSB), was 15.3% and 18.8% in treatments 2 and 3, respectively.