TY - JOUR
T1 - Bacterial endophytes enhance competition by invasive plants
AU - Rout, Marnie E.
AU - Chrzanowski, Thomas H.
AU - Westlie, Tara K.
AU - DeLuca, Thomas H.
AU - Callaway, Ragan M.
AU - Holben, William E.
PY - 2013/9
Y1 - 2013/9
N2 - Premise of the study: Invasive plants can alter soil microbial communities and profoundly alter ecosystem processes. In the invasive grass Sorghum halepense, these disruptions are consequences of rhizome-associated bacterial endophytes. We describe the effects of N 2-fixing bacterial strains from S. halepense (Rout and Chrzanowski, 2009) on plant growth and show that bacteria interact with the plant to alter soil nutrient cycles, enabling persistence of the invasive. Methods: We assessed fl uxes in soil nutrients for ~4 yr across a site invaded by S. halepense. We assayed the N 2-fixing bacteria in vitro for phosphate solubilization, iron chelation, and production of the plant-growth hormone indole-3-acetic acid (IAA). We assessed the plant's ability to recruit bacterial partners from substrates and vertically transmit endophytes to seeds and used an antibiotic approach to inhibit bacterial activity in planta and assess microbial contributions to plant growth. Key results: We found persistent alterations to eight biogeochemical cycles (including nitrogen, phosphorus, and iron) in soils invaded by S. halepense. In this context, three bacterial isolates solubilized phosphate, and all produced iron siderophores and IAA in vitro. In growth chamber experiments, bacteria were transmitted vertically, and molecular analysis of bacterial community fingerprints from rhizomes indicated that endophytes are also horizontally recruited. Inhibiting bacterial activity with antibiotics resulted in significant declines in plant growth rate and biomass, with pronounced rhizome reductions. Conclusions: This work suggests a major role of endophytes on growth and resource allocation of an invasive plant. Indeed, bacterial isolate physiology is correlated with invader effects on biogeochemical cycles of nitrogen, phosphate, and iron.
AB - Premise of the study: Invasive plants can alter soil microbial communities and profoundly alter ecosystem processes. In the invasive grass Sorghum halepense, these disruptions are consequences of rhizome-associated bacterial endophytes. We describe the effects of N 2-fixing bacterial strains from S. halepense (Rout and Chrzanowski, 2009) on plant growth and show that bacteria interact with the plant to alter soil nutrient cycles, enabling persistence of the invasive. Methods: We assessed fl uxes in soil nutrients for ~4 yr across a site invaded by S. halepense. We assayed the N 2-fixing bacteria in vitro for phosphate solubilization, iron chelation, and production of the plant-growth hormone indole-3-acetic acid (IAA). We assessed the plant's ability to recruit bacterial partners from substrates and vertically transmit endophytes to seeds and used an antibiotic approach to inhibit bacterial activity in planta and assess microbial contributions to plant growth. Key results: We found persistent alterations to eight biogeochemical cycles (including nitrogen, phosphorus, and iron) in soils invaded by S. halepense. In this context, three bacterial isolates solubilized phosphate, and all produced iron siderophores and IAA in vitro. In growth chamber experiments, bacteria were transmitted vertically, and molecular analysis of bacterial community fingerprints from rhizomes indicated that endophytes are also horizontally recruited. Inhibiting bacterial activity with antibiotics resulted in significant declines in plant growth rate and biomass, with pronounced rhizome reductions. Conclusions: This work suggests a major role of endophytes on growth and resource allocation of an invasive plant. Indeed, bacterial isolate physiology is correlated with invader effects on biogeochemical cycles of nitrogen, phosphate, and iron.
KW - Bacterial endophytes
KW - Biogeochemical cycles
KW - Gramineae
KW - Indole-3-acetic acid
KW - Iron chelation
KW - Microbially enhanced competitiveness
KW - Phosphate solubilization
KW - Plant invasions
KW - Sorghum halepense
UR - http://www.scopus.com/inward/record.url?scp=84884197279&partnerID=8YFLogxK
U2 - 10.3732/ajb.1200577
DO - 10.3732/ajb.1200577
M3 - Article
C2 - 23935109
AN - SCOPUS:84884197279
SN - 0002-9122
VL - 100
SP - 1726
EP - 1737
JO - American Journal of Botany
JF - American Journal of Botany
IS - 9
ER -