Biotropica 46(6): Editor’s Choice: Antibiotic bacteria in tropical forest soils may play a role in plant diversity

The November Editor’s Choice article is a fascinating look at spatial variation in the antibiotic-producing bacteria in tropical soils, and the potential role they may play in mediating plant diversity: Kristen K. Becklund, Linda L. Kinkel, and Jennifer S. Powers. 2014. Landscape-Scale Variation in Pathogen-Suppressive Bacteria in Tropical Dry Forest Soils of Costa Rica. Biotropica 46(6): 657-666.

Congratulations to Kristen, who explains a little more about her research below. We also post below the press release the University of Minnesota released about her work.

Streptomyces are diverse soil bacteria known for their prolific production of antibiotics.  Antibiotics can inhibit the growth of diverse plant pathogens in soil.  Each clear area is the “kill zone” of an antibiotic-producing Streptomyces colony (which can be seen in the center) against the specified pathogen target, which has been spread over the surface of the growth medium.  Photo credits: Nuttapon Pombubpa and Kinkel Research Group.

Streptomyces are diverse soil bacteria known for their prolific production of antibiotics. Antibiotics can inhibit the growth of diverse plant pathogens in soil. Each clear area is the “kill zone” of an antibiotic-producing Streptomyces colony (which can be seen in the center) against the specified pathogen target, which has been spread over the surface of the growth medium. Photo credits: Nuttapon Pombubpa and Kinkel Research Group.

Soil bacteria produce the vast majority of antibiotics used in medicine and represent an important source for natural products discovery. In addition to their pharmaceutical importance, antibiotic-producing bacteria are increasingly used in agriculture to promote the biological control of plant pests and pathogens. Despite their importance in medicine and agriculture, very little is known about antibiotic-producing bacteria in natural ecosystems or the consequences these microbes have for plant communities and ecosystems. In soil, antibiotics are believed to act as weapons that allow microbes to kill their competitors and more effectively exploit soil resources. This can lead to declines in populations of plant pathogens and can even result in the development of disease-suppressive soils. Because different plants are susceptible to different pathogens and diseases, variation in the abundance, effectiveness, and specificity of microbially-produced antibiotics has the potential to influence not only plant disease and productivity, but also the composition of tree species in the forest.

As a followup to the study published in this month’s issue of Biotropica, Becklund recently conducted a shadehouse experiment on Barro Colorado Island (BCI), Panama to investigate the links among antibiotic-producing bacteria, soil disease potential, and interspecific seedling performance.   Photo credit:  Lourdes Hernandez.

As a followup to the study published in this month’s issue of Biotropica, Becklund recently conducted a shadehouse experiment on Barro Colorado Island (BCI), Panama to investigate the links among antibiotic-producing bacteria, soil disease potential, and interspecific seedling performance. Photo credit: Lourdes Hernandez.

We found that antibiotic production by soil bacteria in the genus Streptomyces was widespread among seasonally dry tropical forests in Costa Rica. The abundance and activity of antibiotic-producing bacteria varied extensively across the landscape and was related to soil nutrient availability. Our results suggest substantial differences in the capacities of microbial communities to suppress soil-borne diseases in tropical forests. Not only did some soils harbor more antibiotic-producing bacteria than others, but soils differed in which pathogen was killed most effectively. Plant pathogens are predicted to promote the coexistence of diverse tree species, therefore differences in the capacities of soil bacterial communities to inhibit plant pathogens could have significant implications for understanding the mechanisms by which high tree species diversity is maintained in tropical forests. Furthermore, information on antibiotic-producing bacteria in tropical soils could be used to develop more sustainable agricultural practices and promote native plant regeneration efforts in the region.

Kristen Becklund
Dept. of Ecology, Evolution, and Behavior
University of Minnesota

 

Tropical dry forests in the Área de Conservación Guanacaste, Costa Rica.  Unlike rainforests, these forests experience a 5-6 month dry season from December to May, during which the majority of tree species lose their leaves.  Thi photo was taken in the wet season (May–November). Photo credit: Jennifer Powers.

Tropical dry forests in the Área de Conservación Guanacaste, Costa Rica. Unlike rainforests, these forests experience a 5-6 month dry season from December to May, during which the majority of tree species lose their leaves. Thi photo was taken in the wet season (May–November). Photo credit: Jennifer Powers.

Tropical dry forests in the Área de Conservación Guanacaste, Costa Rica.  Unlike rainforests, these forests experience a 5-6 month dry season from December to May, during which the majority of tree species lose their leaves.  . This photo was taken in the dry season (December–May).   Photo credit: Jennifer Powers.

Tropical dry forests in the Área de Conservación Guanacaste, Costa Rica. Unlike rainforests, these forests experience a 5-6 month dry season from December to May, during which the majority of tree species lose their leaves. . This photo was taken in the dry season (December–May). Photo credit: Jennifer Powers.


— FOR IMMEDIATE RELEASE OCTOBER 29 2014 —

Variation in antibiotic bacteria in tropical forest soils may play a role in diversity
Contacts: University News Service, unews@umn.edu, (612) 624-5551, Stephanie Xenos, College of Biological Sciences, sxenos@umn.edu, (612) 624-8723

Minneapolis (10/28/14) — Antibiotic-producing bacteria in soil are the source of many antibiotics used to combat diseases in humans and plants. But, surprisingly little is known about how these microbes impact tropical plant communities and ecosystems, where plant diversity, competition, and pathogen pressures are high.

A study published October 28 in the journal Biotropica represents a step toward a better understanding of the role antibiotic-bacteria play in the ecology of tropical forests. University of Minnesota researchers, led by Kristen Becklund, found that antibiotic production by soil bacteria was widespread, but that the abundance and activity of the microbes varied across the landscape depending, in part, on nutrient availability.

“Our results suggest substantial differences in the capacities of microbial communities to suppress soil-borne diseases in tropical forests,” says Becklund. “The fact that we are seeing all this variation is exciting because it means that these bacteria may be influencing diversity in tropical forests.”

Differences in the capacities of microbial communities to suppress soil-borne diseases in tropical forests could impact the composition of the forest itself. Antibiotics in soil are believed to act as weapons that allow microbes to kill their competitors, including pathogens. This antibiotic inhibition can lead to declines in populations of plant pathogens and can even result in the development of disease-suppressive soils. Because different plants are susceptible to different pathogens and diseases, variation in the abundance, effectiveness and specificity of microbially-produced antibiotics has the potential to influence not only plant disease and productivity, but also the composition of tree species in the forest.

“This study is an initial first step to open the black box of microbial community function in tropical forest soils,” says Powers. Future studies will focus on the causes of the variation in density and activity and the potential consequences for tropical forest communities.

Becklund is a graduate student in the College of Biological Sciences’ Ecology, Evolution and Behavior program. Co-authors include Linda Kinkel, a professor in the Department of Plant Pathology in the College of Food, Agricultural and Natural Resource Sciences, and Jennifer Powers, a professor in the Departments of Ecology, Evolution and Behavior and Plant Biology in the College of Biological Sciences.

 

K. Becklund in the Kinkel lab.  Research in the Kinkel lab focuses on the role Streptomyces play in the structure and function of experimental grasslands and the use of pathogen-suppressive Streptomyces in the biological control of crop diseases in agriculture. Photo credit: Jonathan Pavlica.

K. Becklund in the Kinkel lab. Research in the Kinkel lab focuses on the role Streptomyces play in the structure and function of experimental grasslands and the use of pathogen-suppressive Streptomyces in the biological control of crop diseases in agriculture. Photo credit: Jonathan Pavlica.

K. Becklund in the Kinkel lab.  Research in the Kinkel lab focuses on the role Streptomyces play in the structure and function of experimental grasslands and the use of pathogen-suppressive Streptomyces in the biological control of crop diseases in agriculture. Photo credit: Jonathan Pavlica.

K. Becklund in the Kinkel lab. Research in the Kinkel lab focuses on the role Streptomyces play in the structure and function of experimental grasslands and the use of pathogen-suppressive Streptomyces in the biological control of crop diseases in agriculture. Photo credit: Jonathan Pavlica.

K. Becklund in the Kinkel lab.  Research in the Kinkel lab focuses on the role Streptomyces play in the structure and function of experimental grasslands and the use of pathogen-suppressive Streptomyces in the biological control of crop diseases in agriculture. Photo credit: Jonathan Pavlica.

K. Becklund in the Kinkel lab. Research in the Kinkel lab focuses on the role Streptomyces play in the structure and function of experimental grasslands and the use of pathogen-suppressive Streptomyces in the biological control of crop diseases in agriculture. Photo credit: Jonathan Pavlica.

#####