Enhanced Growth and Contrasting Effects on Arsenic Phytoextraction in Pteris vittata through Rhizosphere Bacterial Inoculations

: This greenhouse study evaluated the effects of soil enrichment with Pteris vittata rhizosphere bacteria on the growth and accumulation of arsenic in P. vittata grown on a naturally As-rich soil. Inoculations were performed with a consortium of six bacteria resistant to 100 mM arsenate and effects were compared to those obtained on the sterilized soil. Selected bacteria from the consortium were also utilized individually: PVr_9 homologous to Agrobacterium radiobacter that produces IAA and siderophores and shows ACC deaminase activity, PVr_15 homologous to Acinetobacter schindleri that contains the arsenate reductase gene, and PVr_5 homologous to Paenarthrobacter ureafaciens that possesses all traits from both PVr_9 and PVr_15. Frond and root biomass significantly increased in ferns inoculated with the consortium only on non-sterilized soil. A greater increase was obtained with PVr_9 alone, while only an increased root length was found in those inoculated with either PVr_5 or PVr_15. Arsenic content significantly decreased only in ferns inoculated with PVr_9 while it increased in those inoculated with PVr_5 and PVr_15. In conclusion, inoculations with the consortium and PVr_9 alone increase plant biomass, but no increase in As phytoextraction occurs with the consortium and even a reduction is seen with PVr_9 alone. Conversely, inoculations with PVr_5 and PVr_15 have the capacity of increasing As phytoextraction.