Abstract
Microbial communities that underpin global biogeochemical cycles will likely be influenced by
elevated temperature associated with environmental change. Here, we test an approach to measure
how elevated temperature impacts the physiology of individual microbial groups in a community
context, using a model microbial-based ecosystem. The study is the first application of tandem
mass tag (TMT)-based proteomics to a microbial community. We accurately, precisely and
reproducibly quantified thousands of proteins in biofilms growing at 40, 43 and 46 1C. Elevated
temperature led to upregulation of proteins involved in amino-acid metabolism at the level of
individual organisms and the entire community. Proteins from related organisms differed in their
relative abundance and functional responses to temperature. Elevated temperature repressed
carbon fixation proteins from two Leptospirillum genotypes, whereas carbon fixation proteins were
significantly upregulated at higher temperature by a third member of this genus. Leptospirillum
group III bacteria may have been subject to viral stress at elevated temperature, which could lead to
greater carbon turnover in the microbial food web through the release of viral lysate. Overall, these
findings highlight the utility of proteomics-enabled community-based physiology studies, and
provide a methodological framework for possible extension to additional mixed culture and
environmental sample analyses.
