San Diego State University

About: San Diego State University is a education organization based out in San Diego, California, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 12418 authors who have published 27950 publications receiving 1192375 citations. The organization is also known as: SDSU & San Diego State College.

Seasonal Changes in an Alpine Soil Bacterial Community in the Colorado Rocky Mountains

Abstract: Natural microbial communities are complex and mysterious entities. The advent of culture-independent methods for describing the diversity of bacterial communities has revealed a vast assortment of uncultured bacterial species whose environmental roles are unknown (41). Simultaneously, it is becoming recognized that the composition of microbial communities can have important effects on ecological processes (27, 34, 47). Studies that link microbial community composition to the functioning of ecosystems are needed. The alpine ecosystem of the Colorado Rocky Mountains affords an opportunity for such a study. Our previous work has linked changes in microbial population dynamics to the availability of nitrogen (N) for alpine plants (30). Microbial biomass grows to its highest levels during the winter and early spring, when soils are frozen. Shortly after snow melts in the spring, biomass begins to rapidly turn over, and biomass levels are dynamic throughout the summer. This seasonal turnover of biomass leads to large fluxes of organic N that alpine plants can utilize for growth (33). The biomass dynamics after snowmelt are brought on, in part, by changes in substrate availability and temperature (31) and are accompanied by changes in microbial community composition (34). The winter community has a greater fungal component, differs in its response to temperature, and preferentially degrades cellulose and phenolic compounds, when compared to the summer community. Community DNA hybridization studies showed that the communities differ genetically but did not provide specific information on alpine soil microbial diversity. It has been recently shown that the alpine soil fungal community changes between winter and summer and contains previously undescribed subphylum and class-level diversity (46). Based on these observed seasonal changes in microbial community structure and function, we hypothesize that the bacterial community changes between winter and summer. Furthermore, because microbial diversity is understudied in alpine soils and the fungal diversity has already been shown to be novel, it is likely that the bacterial community contains novel lineages as well. The purpose of the present study was to use culture-based and culture-independent approaches to describe changes in the bacterial community over the ecologically crucial period of time between winter and summer. This information may help explain the physiological characteristics of the microbial community as a whole. Because seasonal changes in ecosystems are generally predictable, recurring phenomena, they are good opportunities to study how microbial communities respond to their environment (3, 6, 50, 57). Seasonal changes in microbial biomass can have important ramifications for nutrient cycling and ecosystem functioning (30, 32, 49, 54, 55). This type of study affords a chance to see how changes in community composition scale up to affect ecosystem processes.