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

• DOI: 10.1128/aem.70.5.2867-2879.2004
• Publication Date: 2004-05-05T17:48:19Z
• Authors: David A. Lipson; Steven K. Schmidt
• Keywords: DNA, Bacterial; 2. Zero hunger; 0303 health sciences; Colorado; Bacteria; Altitude; Molecular Sequence Data; Sequence Analysis, DNA; 15. Life on land; Culture Media; 03 medical and health sciences; 13. Climate action; RNA, Ribosomal, 16S; Seasons; Ecosystem; Phylogeny; Soil Microbiology; Environmental Monitoring

ABSTRACTThe period when the snowpack melts in late spring is a dynamic time for alpine ecosystems. The large winter microbial community begins to turn over rapidly, releasing nutrients to plants. Past studies have shown that the soil microbial community in alpine dry meadows of the Colorado Rocky Mountains changes in biomass, function, broad-level structure, and fungal diversity between winter and early summer. However, little specific information exists on the diversity of the alpine bacterial community or how it changes during this ecologically important period. We constructed clone libraries of 16S ribosomal DNA from alpine soil collected in winter, spring, and summer. We also cultivated bacteria from the alpine soil and measured the seasonal abundance of selected cultured isolates in hybridization experiments. The uncultured bacterial communities changed between seasons in diversity and abundance within taxa. TheAcidobacteriumdivision was most abundant in the spring. The winter community had the highest proportion ofActinobacteriaand members of theCytophaga/Flexibacter/Bacteroides(CFB) division. The summer community had the highest proportion of theVerrucomicrobiumdivision and of β-Proteobacteria. As a whole,α -Proteobacteriawere equally abundant in all seasons, although seasonal changes may have occurred within this group. A number of sequences from currently uncultivated divisions were found, including two novel candidate divisions. The cultured isolates belonged to the α-, β-, and γ-Proteobacteria, theActinobacteria, and the CFB groups. The only uncultured sequences that were closely related to the isolates were from winter and spring libraries. Hybridization experiments showed that actinobacterial and β-proteobacterial isolates were most abundant during winter, while the α- andγ -proteobacterial isolates tested did not vary significantly. While the cultures and clone libraries produced generally distinct groups of organisms, the two approaches gave consistent accounts of seasonal changes in microbial diversity.