Whether and how whole ecological communities can respond to climate change remains an open question. With their fast generation times and abundant functional diversity, microbes in particular harbor great potential to exhibit community-level adaptation through a combination of strain-level adaptation, phenotypic plasticity, and species sorting. However, the relative importance of these mechanisms remains unclear. Here, through a novel laboratory experiment, we show that bacterial communities can exhibit a remarkable degree of community-level adaptability through a combination of phenotypic plasticity and species sorting alone. Specifically, by culturing soil communities from a single location at six temperatures between 4°C and 50°C, we find that multiple strains well adapted to different temperatures can be isolated from the community, without immigration or strain-level adaptation. This is made possible by the ability of strains with different physiological and life history traits to "switch on" under suitable conditions, with phylogenetically distinct K-specialist taxa favoured under cooler conditions, and r-specialist taxa in warmer conditions. Our findings provide new insights into microbial community adaptation, and suggest that microbial community function is likely to respond rapidly to climatic fluctuations, through changes in species composition during repeated community assembly dynamics.