Elevated atmospheric CO2 levels affect community structure of rice root-associated bacteria

Area of Science:

• Microbiology
• Environmental Science
• Plant Science

Background:

• Elevated atmospheric CO2 ([CO2]) influences rice yield and grain quality.
• The impact of elevated [CO2] on rice root-associated bacteria remains largely uncharacterized in large-scale field studies.

Purpose of the Study:

• To investigate the effects of elevated [CO2] on the community structure of rice root-associated bacteria.
• To analyze changes in methane-oxidizing and methanogenic bacteria under elevated [CO2] conditions.

Main Methods:

• A free-air CO2 enrichment (FACE) experiment was conducted with three rice cultivars and two experimental lines.
• Bacterial 16S rRNA gene pyrosequencing was used to analyze microbial DNA extracted from rice roots.
• Quantitative PCR (qPCR) was employed to assess gene copy numbers related to methane metabolism.

Main Results:

• Elevated [CO2] significantly altered the rice root-associated bacterial community structure.
• The relative abundance of methane-oxidizing bacteria (Methylocystaceae) decreased under elevated [CO2].
• Genes involved in methane oxidation (pmoA) decreased, while genes for methanogenesis (mcrA) increased.

Conclusions:

• Elevated [CO2] suppresses methane oxidation and promotes methanogenesis in rice roots.
• These microbial shifts under elevated [CO2] have implications for the carbon cycle in rice paddy fields.